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Chapter 42 -43 - Coggle Diagram

- - - - gastro vascular cavities
        
        in many cnidarians a central vascular cavity functions it the distribution of material through the body, (keeps inside and outside of body close to environment, also helps with digestion)
        
        planarians have flat bodies along with a gastro vascular cavity flat body maximized surface area in contact with environment and minimizes diffusion distances
      - Open and closed circulatory systems
        
        a circulatory system has 3 parts, fluid, interconnecting vessels (highways) and a muscular pump (heart)
        
        heart powers circulation by using metabolic energy to increase hydrostatic pressure of the fluid in the vessel, then the fluid moves back to the heart
        
        by transporting fluid through the body the circulatory system connects interstitial fluid to the organs involved with gas exchange, absorbing nutrients and disposing of waste
        
        in and animal, and animal breathing O2 has O2 diffused across only 2 layers of cells before reaching the blood, circulatory system then carries oxygen rich blood to all parts of the body through capillaries where they can diffuse over a short distance
        
        open circulatory system
        
        In an open circulatory system, the circulating fluid is called hemolymph. Arthropods and some mollusks have open circulatory systems. The heart pumps hemolymph through short vessels into a body cavity called the hemocoel, where interconnected sinuses ensure that all organs and tissues are bathed in fluid.
        
        heart contracts and pushes interstitial fluid in to hemocoel where it flows until heart relaxes then it goes back up to the heart through pores in heart, the hemolymph does not have back flow because of one way valves called ostia, movement of organism facilitates movement of hemolypm
        
        closed circulatory has a fluid called blood confined to vessels which is distinct from interstitial fluid, the blood is pumped from big vessels into small ones that penetrate organs, and tissues, then chemical exchange happens from blood to interstitial fluid to cells
        
        open circulatory systems use less energy because of lower hydrostatic pressures and can also have different functions like spiders using it to extend their legs
        
        closed circulatory systems have enough blood pressure to effectively deliver O2 and nutrients in other animal, and can also regulate the distribution of blood to different organs
      - Organization of closed circulatory systems in vertebrates
        
        cardio vascular system refers to both the heart and blood vessels in vertebrates, circulating to and from the heart in a network through an extensive network that has twice the size of the earths equator! (on average)
        
        the circulatory system has 3 types of blood vessels Arteries, veins and capillaries each of which only flow in one directions arteries carry blood from the heart to the organs throughout the body
        
        when arteries are in organs they branch out into smaller vessels called arterioles which then carry blood to the capillaries, which are only one cell thick! (network of capillaries are called capillary beds infiltrate tissues and diffuse nutrients across the interstitial fluid)
        
        capillaries then converge into venules which later converge into veins that go to the heart
        
        arteries go away from the heart, and veins go towards the heart with the only exception being portal veins which are like a detour to another capillary bed before going to a vein towards heart
        
        hearts of all vertebrates have at least 2 chambers blood that have blood going into them are called atria and the chambers that have blood going out of them are called ventricles, the amount of chambers in heart and how much they are separated differs a lot between groups of vertebrates as a result of natural selection
      - Single circulation
        
        in single circulation sharks, rays and bony fishes have that blood travels to and from the body in one single loop
        
        , they only have to chambers in their heart an atrium and a ventricle, blood flows from heart to gills where they diffuse oxygen and CO2
        
        blood leaves the hearts and passes through to capillary beds before coming back, but in the capillaries blood pressure dramatically drops decreasing blood flow to the rest of the animals body, which can be helped against with the movement and swimming in the fish
      - Double circulation
        
        there are 2 different circuits are combined into one organ simplyfying pumping cycles
        
        one circuit pumps the right side of the heart pumps oxygen poor blood into capillary beds of gas exchange tissues called the pulmonary circuit (pulmocutaneous circuit for amphibians that can get oxygen from their skin)
        
        another circuit called the systemic circuit ensures that oxygen rich blood is transported into capillary beds of organs and tissues which goes back to the heart following the exchange of O2 and CO2 which completing the circuit
        
        Double circulation boosts blood flow to tissues because blood is re-pressurized after the lungs, creating higher pressure in the systemic circuit than the pulmonary circuit, unlike a single circuit where blood slows down after passing through the lungs.
        
        double circulation in amphibians is slightly less efficient because the blood is not separated by a septum in the heart which causes mixing of deoxygenated blood and oxygenated blood ( they have 3 chambers)
      - Evolutionary variation in double circulation
        
        some vertebrates are intermittent breathers which means they can go along time without breathing, adaptations in intermittent breather allow them to partly or in whole bypass the lungs temporarily
        
        frogs and amphibians have 3 chambers in their heart 2 atria and one ventricle with one ridge that partly separates 90 percent of oxygenated blood into systemic circuit and the rest into pulmonary circuit but underwater in takes advantage of no division in the ventricle by prioritizing blood flow to the skin because their lungs aren't useful under water
        
        In the 3 chambered heart of reptiles like snakes turtles and lizards , there is a incomplete septum or division between oxygenated and deoxygenated blood with left and right chambers in ventricles. 2 major arteries called aortas lead to systemic circulation
        
        in crocodilians the heart is separated by a true septum but pulmonary and systemic circuits connect where arteries exit heart so they can temporarily shunt blood flow away from lungs without varying blood flow of the body parallel when under water
        
        Double circulation in birds and animals are different then other animals, because generally mammals and birds cannot vary their blood flow to the lungs without varying blood flow to their bodies
        
        .Endotherms use 10times as much energy as equal sized ectotherms which means they need 10 times more oxygen and nutrients, and to get rid of ten times for CO2 and other waste which are powered by 4 chambered big hearts and separate systemic and pulmonary circuits
  - - - Contraction of the right ventricle shoots blood to your lungs via the pulmonary trunk
      - blood going through pulmonary trunk goes 3 capillary beds in the lungs to get oxygenated and unload CO2
      - Oxygen rich blood goes back to the heart via the pulmonary vein to the left atrium
      - oxygen rich blood from the left atrium makes it to the left ventricle, which pumps it out to the body with systemic circuit (blood leaves left ventricule through aorta which brings blood through arteries leading throughout the whole body)
      - first branches leading fro the aorta are called coronary branches supply blood to heart muscle it self, while branches further along lead to 7 capillary beds in head and arms
      - Aorta descends to abdomen supplying blood to arteries that lead to 8 capillary beds in abdominal organs and legs
      - Net diffusion of O2 to nearby tissues via interstitial fluid, and net diffusion of CO2 to the blood ( CO2 produced as waste of cellular respiration)
      - Capillaries rejoin into venules which bring blood to veins
      - Oxygen poor blood from head neck and forelimbs is channeled into superior vena cava, while inferior vena cava takes the oxygen poor blood from trunk and legs l hind limbs.
      - the 2 vena cava converge in the right atrium where oxygenated blood flows into the right ventricle
    - - the human heart is about the size of your clenched fist consisteing of mostly cardiac muscle
      - The two atria collect blood returning from the lungs and body, When all four chambers relax, most blood flows passively into the ventricles, with the rest pushed in during atrial contraction. The atria have thin walls, while the ventricles are thicker and contract more forcefully, the left ventricle especially, since it pumps blood throughout the body, unlike right ventricle, which pumps to the lungs.
      - the chambers of heart contract and relax in a cycle when they are relaxed they are filling with blood and when they are contracting it pumps blood, one cycle of filling and pumping is the cardiac cycle (systole for contraction diastole for relaxation)
      - the volume of blood each ventricle pumps in a minute is called cardiac output which is affected by heart rate or how much contractions in a minute, and stroke volume(how much blood you can pump in one contraction), average stroke volume is 70mL, during exercise there is an increase in cardiac output
      - there is 4 valve in the heart that prevent backflow 2 AV valves and 2 semilunar valves, the AV valves close from the high pressure created by ventricle contraction which prevents backflow into atria, the semi lunar valves open with ventricular pressure and semilunar valves in the pulmonary and aortic arteries close when heart relaxes due to blood pressure built up in aortic and pulmonary artery from previous ventricular systole preventing significant back flow
      - you can follow the closing of the heart valves with a stethoscope or listening close with your ear the first lub is caused by the recoil of the blood hitting your closed av valves, and the dub is caused by the vibrations of closing of semilunar valves
      - when there is backflow in the heart valves it may make a abnormal sound called a heart murmur which can be caused by a heart valve defect, if the defect is big enough surgery may be required to replace a valve, but not all heart murmurs are caused by heart defects, and not all reduce efficiency enough to warrant surgery
      - heart muscles can beat without any input from the nervous system with an SA node which is like built in pace maker, it controls the rate and timing at which all cardiac muscle cells contract
      - Impulses from the SA node can be measured when they reach the skin via fluid in a ECG/ EKG, by using electrodes that measure electrical activity
      - Impulses from the SA node make both atria contract in unison but when the signal reaches other autorhythmic cells located in the wall between the left and right atria it is delayed by 0.1 seconds these cells are called the av node this delay ensures there is enough time for atria to finish contracting and fill the ventricles. bundle branches pass signal to bundle branches and signal is spread throughout ventricles via Purkinje fibers
      - physiological cues alter the heart tempo by regulating pacemaker function of SA node, 2 divisions of the nervous system are largely responsible for this, the sympathetic division speeds up your pacemaker when you stand up and start walking or exercise, and parasympathetic slows the pacemaker down when at rest, adrenaline from adrenal gland can also speed up your heart rate, a third input that affects pace maker is temperature, an increase of one degree Celsius can speed up heart rate by as much as 10 beats per minute
    - - blood pressure is usually measure in a artery in the arm at the same height as the heart, for a healthy 20 year old, blood pressure at systole should be 120mm of hg and 70mm at diastole
      - measurement of blood pressure
        
        a sphygmomanometer (inflatable cuff with a pressure gauge) measures blood pressure at an artery, the cuff is inflated until the pressure closes of the artery, when this happen the pressure of the cuff exceed the pressure of the artery
        
        the cuff is slowly deflated until the pressure of the cuff falls just below the pressure of the artery. when you hear the blood start flowing with a stethoscope, you take the pressure on your gauge. this measurement is the systolic blood pressure
        
        when the cuff deflates enough for blood to flow freely and you stop hearing noise, you take your second measurement, the pressure at this point is the diastolic pressure
      - gravity greatly affects blood pressure, for example since your head is roughly 0.35m above your heart it must pump against gravity and blood pressure is slightly decreased, when there is not enough blood flow in your head, your nervous system makes you faint so your heart is level with your head , this makes it easier to get enough blood flow to the brain
      - blood pressure in animals with long necks needs to be significantly higher ((250mmhg near the heart for the giraffe) in order to overcome gravity and get blood to the head, when the head is lowered several mechanisms like one way valves and feedback mechanisms are used reduce cardiac output and reduce blood pressure in the head to avoid brain damage
      - in veins gravity is also important in the veins specially around the legs since veins have relatively low blood pressure to fight gravity, one way valves ensure unidirectional flow of blood in these vessels which is further enhanced by skeletal muscle contractions
      - In some rare cases runners and other athletes can suffer heart failure if they abruptly stop exercise, since when leg muscles are relaxing there is less blood coming back to the heart, if the heart continues to beat rapidly, and there is less blood flow, the heart may malfunction if it is weak or damaged, which is why they need to follow up with lighter exercise to "cool down" until heart rate goes back to resting levels)
    - - at any given time blood is flowing through only 5-10% of the bodies capillaries, each tissues has many capillaries, so blood is supplied to every part of the body, capillaries in brain liver heart and kidney usually remain at capacity but in other part of the body blood can be redirected as needed (blood supply to digestive tract increases after meal. in contrast during exercise blood may go away from the digestive tract)
      - blood flow in the capillaries can be regulates by the vasodilation or constriction of the arterioles and pre capillary sphincters (smooth muscle rings) at the entrance of capillary beds, opening and closing of rings regulates blood flow to particular sets of capillaries. the signals that regulate blood flow include, nerve impulses, hormones in blood stream and chemicals made locally (histamine a chemical produce by cells at a wound site promotes vasodilation increasing blood flow and therefore white blood cells to fight off invaders at wound site)
      - some macromolecules are transported in vesicles across endothelium, small particles like O2 and CO2 simply diffuse across endothelial cells, or in some tissues through microscopic pores in capillary walls, these openings provide transport routes for salts and other solutes like sugar, as well as for bulk flow of liquid into tissues driven by blood preassure
      - Blood pressure tends to push fluid out of capillaries, while plasma proteins pull it back in. Most blood cells and proteins are too large to pass through the endothelium, and these proteins are responsible for much of the blood’s oncotic pressure. This osmotic pressure opposes fluid loss from the capillaries, but at the arterial end, hydrostatic pressure is greater than the osmotic pull, leading to a net movement of fluid out into the interstitial space. At the venous end, hydrostatic pressure drops below the osmotic pressure, allowing some fluid to be reabsorbed, while any remaining fluid is collected by the lymphatic system, maintaining a steady balance in the tissues.
      - each day the average adult loses 4-8L of fluid from the capillaries to the surrounding tissues however the lost fluid and blood proteins that leak are recovered with the lymphatic system
      - Fluid diffuses into the lymphatic vessels via network of tiny vessels intermingled, with capillaries the recovered fluid is called lymph in the circulating in the lymphatic system where the fluid is drained into to large veins at the base of the neck, when the cardio vascular and lymphatic system merge it completes the recovery of fluid lost in the capillaries, as well of transport of lipids from small intestine to blood
      - the movement of lymph is facilitated with smooth muscle contractions, one way valves, and skeletal muscle contractions
      - Disruptions of movement of lymph can come from fluid accumulation or edema, (ex: some parasites lodge in the lymph vessels and cause elephantiasis, condition marked by extreme swelling of limbs and other body parts
      - lymph nodes (lymph filtering organs)serve as check point in the lymphatic system they are filled with honey combs of connective tissue and spaces filed by white blood cells, which function for defense and when there is a infection detected the WBC start multiplying rapidly and the lymph nodes become swollen and tender, lymph nodes may also trap circulating cancer cells, examining lymph nodes of a patient can reveal the spread of the disease
      - evidence has surfaced that Lymphatic system plays a role in harmful immune responses like asthma, this and other findings make the lymphatic system a very active area of bio medical research
  - - - vertebrate blood is connective tissue consisting of cells suspended in a matrix called plasma, blood cells and cell fragments make 45% of volume blood the rest is plasma
      - Plasma 55% of blood volume
        
        ions (sodium, potassium, calcium, magnesium, chloride, bicarbonate,). funtion: osmotic balance , ph buffering, regulation of cell membrane permiability
        
        water. Function: solvent
        
        plasma proteins (albumin, immunoglobulins or antibodies, apolipoproteins, and fibrinogen) function: osmotic balance and ph buffering, defense and immunity, lipid transport, blood clotting respectively
      - cellular elements 45% blood volume
        
        leukocytes (white blood cells) types: basophils, lymphocytes, eosinophils, neutrophils, monocytes, Function: defense and immunity
        
        platelets function: blood clotting
        
        erythrocytes (red blood cells) function transport O2 and some CO2
      - Plasma
        
        Plasma must maintain the concentrations of electrolytes within specific set points because many of these ions are essential components of blood. Some serve as buffers to help maintain pH, while others help maintain osmotic balance. The concentration of ions in plasma directly affects the composition of interstitial fluid, and many of these ions play a vital role in muscle and nerve activity. Together with plasma proteins, ions help the blood carry out functions in osmotic regulation, transport, and defense.
        
        plasma proteins like albumin serve as buffers against pH changes, and help maintain osmotic balance between blood and interstitial fluid, immunoglobulins combat viruses and other foreign agents, apolipoproteins transport lipids (they can only travel in blood when bonded to proteins, fibrinogens act as clotting factors, serum means plasma with no clotting factor
        
        plasma has much higher protein concentration of proteins than interstitial fluid even though they are similar
      - cellular elements
        
        blood contains 2 classes of cells red and white blood cells, also suspended in plasma are platelets (clotting factors)
        
        erythrocytes are the most numerous cells in the blood, they are bi concave and thinner in center than edges (this shape increases surface area) mature erythrocytes lack nucleus so they have more space for an oxygen carrying, iron containing proteins called hemoglobin, erythrocytes lack mitochondria and generate ATP exclusively with a anaerobic metabolism (that way they don't use the same oxygen they are supposed to carry)
        
        despite small size erythrocytes can carry 250 molecules of hemoglobin! that 1 billion O2 molecules 4 per hemoglobin, when erythrocytes pass through capillary bed of respiratory organs O2 diffuses into erythrocytes and binds to hemoglobin, when in systemic capillary beds the O2 is then dropped off and diffuses into body cells
        
        In sickle-cell disease, the hemoglobin inside red blood cells sticks together when oxygen is low, forming long fibers that bend the cells into a sickle shape. This happens because one amino acid in the hemoglobin protein is changed.
        
        Sickle-cell disease significantly impairs circulatory system function because sickle-shaped cells often lodge in arterioles and capillaries, preventing the delivery of oxygen and nutrients and the removal of CO2 and wastes. Blockage of blood vessels and swelling of affected organs cause severe pain. Sickle cells rupture easily, reducing the number of red blood cells available for oxygen transport. The average lifespan of a sickled red blood cell is about one-sixth that of a normal red blood cell, leading to a higher rate of loss than production. Short-term treatment often involves replacement of erythrocytes, while long-term treatments aim to inhibit the aggregation of HbS, (the abnormal form of hemoglobin)
        
        leukocytes , 5 major types, some are phagocytic (swallow and digest micro organisms and debris from bodies own dead cells normally one microliter of blood contains 5k-10k leukocytes , numbers increase temporarily when fighting infection, can be found patrolling interstitial fluid and lymphatic system
        
        platelets, pinched of cytoplasmic fragments of specialized cells in bone marrow, have no nuclei, serve both structural and signaling functions in blood clotting
    - - platelets RBC and WBC all have stem stem cells dedicated to repleneshing the bodies population
        
        stem cells divide via mitosis to make one daughter cell to maintain population and another daughter cell that can specialize
        
        stem cells that produce cellular elements of blood are in re marrow in bone marrow (particularly ribs, vertebrae, sternum and pelvis)
        
        eventually produce progenitors which can still divide limited amount of times
        
        lymphoid progenitors produce lymphocytes (B cells an T cells
        
        Myeloid progenitors make (erythrocytes, Basophils, neutrophils, monocytes, platelets and Eosinophils
      - stem cells replace worn out cell components in blood, erythrocytes are the shortest lived(120 days before being replaced), feedback mechanism senstitive to O2 levels regulate erythrocyte production, low O2=kidneys make and secrete hormone erythropoietin stimulates production of more erythrocytes
      - man made EPO is used now a days to used to treat disorders like anemia, and some athletes use it to get more RBC (although in most sports orgs its banned)
    - - when blood vessels tear, chain of events lead to the quick seal of break, the key event being coagulation which happens when liquid components of blood convert into solid blood clot, minimizing exposure to infection and blood loss
      - if their is no injury then coagulant is in inactive form called fibrinogen
      - Damage to a blood vessel exposes proteins in the vessel wall.
        
        These exposed proteins attract platelets, which gather at the site and release clotting factors.
        
        This starts a cascade of reactions that:
        
        Convert prothrombin into thrombin (active enzyme) that convert fibrinogen to fibrin
        
        fibrin (forms threads to make clot framework)
        
        Mutations that block any step in the process lead to hemophilia, causing excessive bleeding or bruising even from small injuries.
        
        clotting factor trigger cascade of reactions that convert prothrombin into thrombin (active enzyme that converts fibrinogen into fibrin
      - Clotting factors initially convert only a small amount of prothrombin into thrombin. however, thrombin itself triggers the conversion of more prothrombin into thrombin, which drives the clotting process to completion.
      - anticlotting factors in blood normally prevent spontaneous clotting in absence of injury, however sometimes clots can form in blood vessels and blocking flow of blood , these clots are called thrombus
    - - cardiovascular diseases kill more tha 750k people in the U.S a year
      - atherosclerosis, heart attack, and stroke
        
        artherosclerosis
        
        Healthy arteries normally have a smooth lining that reduces resistance to blood flow.
        
        However, when this lining becomes rough or damaged, fatty deposits called plaques can form.
        
        This condition is known as atherosclerosis, and a major contributing factor is high cholesterol.
        
        In atherosclerosis, damage to the arterial lining triggers inflammation, attracting leukocytes that engulf lipids, including cholesterol. Over time, these lipids and immune cells accumulate, forming fatty deposits called plaques.
        
        incorporation of fibrous tissue and even more cholesterol lead lead to growing of the plaque, artery walls become thick and stiff and obstruction increases
        
        if plaque ruptures, a thrombus can form in the artery, potentially causing heart attack or stroke
        
        heart attack
        
        myocardial infarction is the death or damage of cardiac muscle tissue, because of blockage in coronary arteries
        
        coronary arteries supply to heart muscle, however their small diameter they are more vulnerable to obstruction by artheroscloropic plaques or thrombi
        
        blockage can destroy cardiac muscle quickly because it needs a lot of O2 to keep beating, if a large enough portion of the heart is affected then the whole heart will stop beating
        
        Stroke
        
        death of nervous tissue in the brain due to lack of O2
        
        usually results from rupture or blockage of arteries in neck or head
        
        the effects of a stroke and individual survival change largely depend on the extent and location of damaged brain tissue, if stroke was caused by a thrombus rapid administration of clot dissolving drug may limit the damage
        
        even if artherosclerosis isn't detected until major blood flow is disrupted there are warning signs
        
        partial blockage can result in chest pain called angina pectoris
        
        the pain is most likely to be felt when the heart is laboring and it signals that heart isn't getting enough O2
        
        obstructed artery may be treated surgically by inserting mesh tube called a stent to expand the artery, or transplanting a healthy blood vessel from patients chest or limbs to bypass blockage
      - Risk factors and treatment of cardiovascular disease
        
        individuals with high amount of cholesterol (both HDL or LDL) are at substantially increased risk for atherosclerosis
        
        tendency to develop particular cardio vascular disease can be inherited however it is also strongly influenced by lifestyle
        
        exercise decreases HDL and LDL ratio
        
        smoking, and consuming of certain processed vegetable oils called trans fats increase HDL LDL ratio
        
        FOr many individuals at high risk a drugs called statins lower LDL leves and reduce risk of heart attacks
        
        genetic mutation may effect blood LDL level
        
        aspirin inhibits inflammatory responce, as a result aspirin has been found to help prevent recurrance of heart attacks and stroke
        
        hyper tension or high blood is another contributor to heart attack and stroke, high blood pressure damages the endothelium that lines the arteries and promoted plaque formation hyper tension is usuallydefined as 140/90
        
        hypertensioin can be controlled by quitting tobacco products, exercising, and dieting
  - - - partial pressure is the pressure exerted by a specific gas in a mixture of gases, by determining partial pressure helps us predict the net movement of gas at an exchange surface
        
        gas always undergoes net diffusion from region of higher partial pressure to lower partial pressure down pressure gradient
        
        rate of diffusion is directly proportional to size of gradient (increase of higher part pressure or decrease in low part pressure )
      - to calculate partial pressure you need to now the total pressure the mixture of gases exerts and the percent of the specific gas in the mixture, if your gas mixture exerts 100mmhg and O2 is 22% then the partial pressure of O2 is 22mmhg (100x0.22)
      - partial pressures also apply to gases dissolve in liquid, like water, in water an equilibrium state is reached between air out of water and air in the water however their concentrations greatly differ because O2 is much less soluble in water than in air, and the warmer and saltier the water is the less O2 it can hold
    - - the conditions of gas exchange change a lot depending on medium because O2 is a lot more plentiful in air than in water however O2 much less dense and viscous in water so it can move through small passage ways easier
      - water is a much more demanding gas exchange medium than air because O2 dissolved in a given volume of water is always less than equivalent volume of air
        
        water in many places has roughly 30times less concentration of O2 than in air
        
        this means that marine animals have to spend a lot of energy on gas exchange
        
        many adaptations in marine animals allow them to be very efficient with gas exchange to overcome these challenges ( many involve the organization of the surfaces required for exchange
    - - specialization for gas exchange is apparent in structure of the respiratory surface, cells that carry out gas exchange must have their plasma membrane in contact with an (aq) solution (respiratory surfaces are always moist)
      - movement of O2 and CO2 happens through diffusion, gas exchange is fast when area for diffusion is large and the distance traveled is small, so respiratory surfaces tend to be large and thin
      - Some simple animals, such as flatworms, cnidarians, and sponges, have most of their cells in direct contact with the environment, allowing gases to diffuse quickly between any cell and the surrounding water. In more complex animals, however, most cells are not in immediate contact with the environment, so they rely on specialized respiratory surfaces (thin, moist layers of epithelium) that function as dedicated organs for gas exchange.
      - for earth worms and some amphibians their skin serves as a respiratory organ, lots of capillaries just below their skin facilitates exchange of gases between circulatory system and environment
      - for most animals, general body surface lacks sufficient are to exchange gases for the whole organism, the solution to this limitation is dedicated respiratory organs with lots of folds, or branching to increase surface area for gas exchange (Ex: gills lungs and trachea
    - - gills are outfoldings of the body surface that are suspended in water they have a total surface area much greater than the rest of the body's exterior
      - movement of respiratory medium over respiratory surface is called ventilation, in gills water is either moved over the gills or move gills through the water, fish use motion of swimming or coordinated movements of the mouth and gills covers to ventilate their gills in both cases water enters mouth, passes through slits in pharynx flows over gills and exits the body (octopuses and squids ventilate their gills by taking in water and ejecting it giving them jet propulsion)
      - cray fish and lobsters have paddle like appendeges that drive water overt their gills why clams and mussels move water with cilia
      - in fishes gas exchange is maximized by counter current exchange, this is because as blood and water flow opposite to each other each section of blood meats a section water that has a higher PO2 even when the water loses some of the PO2 from the exchange, the next piece of blood in the capillary will still have less O2 than water , because it was already deoxygenated and it just entered the capillary meaning less exposure to water
      - countercurrent exchange insure more than 80% percent of oxygen in dissolved water is removed as it passes the respiratory surface
    - - the most common form of tubes that lead to respiratory surfaces is the insects tracheal system, the largest tubes (tracheae) open to outside the body, where the finest branches are lined with most epithelium for gas exchange, it does not require movement of circulatory system since the tracheal system brings very close to virtually every cell in their body
      - tracheal systems exhibit adaptations for flying animals (they need more oxygen) by flapping their wings those fast muscle contractions force more air into tracheal system bringing more O2 as fuel for flight muscls (with fast muscle)
      - they branch out throughout entire body
    - - localized respiratory organs
      - typically subdivided into numerous pockets. not in contact with the whole body so it needs circulatory system help to bridge the gap (open circulatory organisms have it too)
      - use of lungs does varies among species. Some animals, like mammals and birds, rely entirely on lungs for gas exchange. Others, like amphibians, rely on lungs only partly, supplementing them with gas exchange through their skin. some fish species like lungfish and some catfish have primitive lungs that allow them to breathe air when living in oxygen-poor water.
    - - in lungs air is conveys to them via branching ducts in thoratic cavity enclosed by ribs and diaphragm
      - air enters nostrils, is filtered with hair warmed, humidified and sampled for odor
      - the nasal cavity leads to the pharynx an intersection where paths for food and air cross
      - when food is swallowed the epiglottus covers the glottus (opening in trachea) so food doesnt go down trachea other wise it is open to permit breathing
      - when air passes larynx it goes on to the trachea(larynx and trachea are lined with cartilage so they stay open)
      - in alot of animals exhaled air passes through elastic bands of muscle in larynx called vocal folds (vocal chords in humans) when larynx muscles are stretched they stretch the cords (tight stretch cord=high pitch sound, loose stretch low pitch)
      - air in trachea branches out into 2 bronchi (one for each lung) which then branch repeatedly into finer tubes called bronchioles (looks like inverted tree)
      - epithilial lining the major branches of respiratory tree has microscopic hair called cilia and a thin film of mucus, the mucus traps particle contaminants and the cilia move the mucus out and into the esophagus, called the muscle escalator
      - gas exchange happens in alveoli (air sacs at the tips of the tinies bronchioles) humans lungs contain millions of alveoli and have a surface area of 100m^2 (50times then that of skin)
      - O2 entering alveoli dissolves into the moist thin lining in the inner surfaces and rapidly defuses across epithelium into capillaries, while CO2 diffuses the opposite way from capillaries across epithelium into lining and into the air space
      - if you lack cilia or significant air currents to get rid of particles from their surface makes them more vulnerable for contamination, normally WBC engulf foreign particle but if their is too much the defenses can be overwhelmed leading to inflammation and irreversible damage
      - lungs have surfactant that reduce surface tension so alveoli collapse
      - surfactant in babies typically appears 33 weeks after gestration so premature babies before this don't have surfactant so they need an artificial surfactant to stop their alveoli from collapsing
  - - - when birds breath air passes through respiratory surfaces in one direction
      - air sacks on both side of the lung direct air to the lungs
      - passage of air through the whole system take 2 exhalation and inhalation cycles
      - tiny channels called para bronchi serve as sites for gas exchange
      - 1st inhale air fills the posterior sacks 1 exhale the sacs contract and let air in lungs 2inhale air come out the lungs and into anterior sacs and finally exhale contracts anterior sacs and lets air out the body
      - this system allow the birds lungs to have constant acess to air despite exhaling, this is because even as its exhaling air from posterior sac enters the lungs
      - incoming fresh air never mixes with air that already was used in gas exchange
    - - animals breath with negative pressure breathing, they expand the thoracic cavity to increase volume and decrease pressure making air go into the lungs since air goes from the area of high pressure to low pressure
      - expanding of the thoracic cavity has to do with contraction diaphragm and rib muscles so ribs are expanded and diaphragm expands volume even more
      - inhalation is active (contracting of rib muscles and diaphragm) exhalation is passive (relaxing of diaphragm and ribs)
      - a double membrane surrounds the lungs one sticks to the surface of the lungs and the other to the wall of the thoracic cavity a thin fluid sits between them makes surface tension so the 2 membranes can move in unison, they stick together, you can slide them but they are hard to pull apart
      - when the animal is at rest, rib muscles and diaphragm are enough to change lung volume, but when animal is exercising other muscle in neck, back, chest, etc increase volume of thoracic cavity, further more movement of the animal can make a rhythmic movement of organs in the abdomen, leading to a piston like pumping motion that helps increase volume of air move in and out of lungs
      - tidal volume is the amount of air taken in and exhaled on each normal breath, vital capacity is maximum amount of air in and out and residual volume is the amount of air left when when you try to get as much air out of the lungs as possibly can
      - since lungs in mammals cannot completely empty and use the same pathway for both inhalation and exhalation, fresh air that hasnt been used for exchange is constantly being mixed with old oxygen depleted air
    - - your breathing is mostly regulated by involuntary mechanisms
      - the neruons mainly responsible for regulating breathing are the medulla obloganta, near the base of the brain, neural circuits in the medulla from a pair of breathing control centers
      - The medulla monitors the pH of the cerebrospinal fluid that surrounds it to determine the concentration of CO2 in the blood. Carbon dioxide diffuses from the blood into the CSF, where it reacts with water to form carbonic acid. Because the CSF has little buffering capacity and CO2 continually diffuses in, the fluid is highly sensitive to changes in acidity (because the ph never really settles back to normal). This lack of buffering means that any increase in CO2 quickly lowers the pH, making the CSF an effective medium for detecting CO2 pH changes.
      - when ph lowers sensors in medulla detect the change and in response te medullas control circuits increase the depth and rate of breathing they both remin until excess CO2 is eliminated through exhalled air
      - bood O2 levels have little effect on the breathing control centers, but when o2 levels are very low O2 sensors in the aorta and carotid arteries send signals to breathing control centers
      - a negative feedback system stops your lungs from over expanding, sensors that detect stretching of lung tissue and send nerve impulses to medulla to prevent over exhaling
  - - - gradient of partial pressure between air in the alveoli and blood favors the net diffusion O2 in blood and CO2 out blood
      - after returning to heart blood is pumped to the systemic circuit
      - in systemic capillaries graient of partial pressure favor net diffusion O2 out of blood and CO2 in blood
      - after unloading O2 and loading CO2 the blood is returned to the heart and back to the lungs,
      - in the lungs exchange happens across alveolar capillaries and exhaled air is enriched in CO2 and partially depleted of O2 (becaese there is more CO2 in the blood then CO2 and air and less O2 in blood than air
    - - since O2 has a low solubility in water and animals need alot of oxygen they would need alot of water to just get the oxygen they need
      - To work around this animals transport O2 via proteins called respiratory pigments, they circulate with blood or hemolymph (often contained in specialized cells) the pigments greatly increase the amount of O2 that ca be carried in circulatory fluid
      - there is many different pigments in different animals and each of these molecules have their own distinct color, it is a protein binded to a metal (copper binds to oxygen for blue hemocyanin found in arthropods and a lot of mollusks
      - many invertebrates and almost a vertebrates use hemoglobin (contained in erythrocytes)
      - hemoglobin is made of 4 dubunits which are hemegroup (contains iron) and a polypeptide group each iron carries one oxygen one hemoglobin molecules can carry 4O2 it binds reversiblly ( load O2 in lungs and gills unloads it else where in body)
      - the four subunits go together, when one sub unit bonds to O2 it raises the O2 affinity of the other subunits, but when one sub unit releases, O2 affinity decreases so it releases O2 more readily
      - when a muscle uses O2 PO2 in viscinity decreases since O2 is used in cellular respiration, but because of their cooperativity a slight drop in PO2 causes a relatively large increase in the amount of the blood unloads.
      - the lower the ph in the blood (due to carbonic acid CO2 released from muscles used in exercise) the more blood want to release O2 to ensure that O2 is released to the tissues that need it (this is called the (bohr shift)
    - - Only a small amount of CO₂ is carried in plasma; most is carried in red blood cells. It reacts with water (with the help of carbonic anhydrase) to form carbonic acid, which dissociates into H⁺ ions and bicarbonate. H⁺ ions bind to hemoglobin and other proteins, minimizing changes in blood pH. Most of the bicarbonate diffuses out of the red blood cells into the plasma and is transported to the lungs. The remaining ~5% of CO2 binds to hemoglobin and is transported in red blood cells.
      - When blood flows through the lungs, O₂ diffuses into the blood, which shifts the chemical equilibrium in favor of converting bicarbonate back into CO₂, allowing more CO₂ to diffuse into the alveoli and be exhaled.
    - - mammals vary substanstialy between times they can spend wiothout their normal repiratory medium (seals can survive 20min-1hr underwater)
      - the Cuvier’s beaked whale can reach depths of 2900m and stay submerged for more than 2 hours
      - Adaptations that allow them to do this are an increased ability to store large amounts of O₂ in their bodies. (Seals have a greater blood volume per kilogram of body weight and store much of their oxygen in their muscles as myoglobin.)
      - diving mammals must also swim efficiently, their heart rate and rate of O2 consumption decreases, most blood is routed to vital tissues (brain, spinal cord, adrenal glands, eyes, etc)
      - blood supply to muscles is restricted or during long dives completely shout off, (weddell seal's muscles deplete O2 in myoglobin and get their ATP from anaerobic cellular respiration
      - every mammal has the mammalian diving reflex, when their face hits cold water body processes slow down, blood flow to extremities is reduced, genetic changes that strengthened this reflex may have provided the seal's ancestors with a selective advantage for foraging under water, genetic variations that increased traits of blood volume or myoglobin concentration, would have improved diving ability and become favored during selection over generations.
- - - - to fight of pathogens and foreign particles animals immune system must detect them, a proper immune system can tell between oneself and not oneself
      - immune cells have receptor molecules that bind to molecules from foreign cells or viruses and activate immune response the specific binding of immune receptors to foreign molecules, is a type of molecular recognition, and is the central event that identifies non self cells particles and molecules
      - there are 2 types of reponses innate immunity, (general) and adaptive immunenitiy (special forces for specific threat)
    - - linings in digestive tract or airway provide more barriers to infection
      - the first line of defense is preventing pathogens from entering in the first place. An outer covering like skin, or shell blocks entry to many pathogens but our body cant be completely sealed, so secretions that trap of kill pathogens guard bodies entrances and exits
      - (foreign molecules dont have to be pathonogenic to elicit immune response)
      - these defenses make up the immune system, which enables the animal to avoid or limit infections
      - this situation is bad for animals so they evolved adaptations to protect them selves from pathogens
    - - barrier defenses in insects (exoskeleton around the body, lining in the intestines block infection, and enzyme called lysozyme reaks down bacterial cell walls of many pathogens) allowed for sucess in pathogen rich environments
      - any thing that breaches insects barriers encounters internal immune system, which use recognition proteins to bind to molecules common to different broad classe of pathogens, because these molecules are not normally found in animal cells. once bonded as recognition protein triggers immune response
      - in insects their major immune cells are called hemocytes, they break down microorganisms via phagocytosis (they engulf and digest them) one class of hemocytes makes a defense molecule that helps entrap larger pathogens like plasmodium (blood parasites) . many other hemocytes release anti microbial peptides that circulate throughout the insect and kill bacteria and fungi by disrupting cell their cell membranes
      - innate immune response of insects depends on the class of pathogen, if binding recognition binds to a fungal cell wall, activates a trans protein receptor called toll that makes activates production and secretion of anti microbial peptides that specifically kill fungal cells phagocytic cells in mammals use similar protein receptors to toll to recognize viral, fungal, and bacterial components
      - insects have specific defenses against viruses since they want to make a double RNA template in a cell and cells dont use double starnd RNA
    - - in jawed vertebrates innate immunity works along side adaptive immunity. like insects they use phagocytosis barriers, and antimicrobial peptides as well as vertebrate specific defenses like natural killer cells, interfertons, and inflammatory response
      - barrier defenses
        
        mucous membrane and skin
        
        mucus traps pathogens in respiratoy, digestive tract, etc in trachea the mucus is moved out to prevent lung infections, and tear, saliva, and mucus that coat epithelia provide washing action that inhibits bacteria and fungi colonization
        
        along with preventing entry, body secretions create a hostile environment for many pathogens, lysozyme in tears, saliva etc, destroy cell walls of vulnarable bacteria. most bacteria in food and swallowed mucus gets destoyed by stomach acid
      - cellular innate defenses
        
        toll like rececptors are used to recognize pathogen specific molecular patterns (TLR)
        
        some TLRs detect viral double stranded RNA, while others like TLR 4 detect lipopolysaccharide found in surface of many bacteria, TLR 5 detects flagellin the main protein in bacterial flagella
        
        2 main types phagocytic cells in mammalian body, neutrophils and macrophages, neutrophils, neutrophils circulate in blood and are tattracted to signals from infected tissues, and engulf and destroy pathogens, macrophages are larger phagocytic cells, (some migrate throughout the body and some stay put)
        
        dendritic cells: mainly populate tissues in contact with environment, they stimulate adaptive immunity against the things they engulf
        
        eosinophils: important defense against multicellular envadors like pasasitic worms
        
        natural killer cells: detect abnormal surfacce proteins sometimes found on virus infected cells and and cancerous cells, they release chemicals causing cell death so virus and cancer dont spread
        
        Mast cells:found in connective tisues and contriubte to inflammatory response
    - - starts with activated macrophages discharging cytokines (small peptide signaling molecules) that tell neutrophils to come to the site of injury
      - mast cells release histamine which dilates nearby blood vessels and makes them more permeable
      - increased blood supply makes skin red and hotter
      - cycles of signaling and response continue process of inflammation activated complement proteins activate releasing histamine attracting more phagocytic cells cells to site of injury
      - enhanced blood flow helps deliver antimicrobial peptide, insects kill or inactivate pathogens by disrupting membrane integrity,
      - the result is pus. a fluid rich in white blood cells. dead pathogens, and debris from damaged tissue
      - at the end local inflammatory response excess fluid and pus is taken up by lymph (fluid transported in lymphatic system)
      - Lymph nodes contain macrophages that engulf pathogens entering the lymph. Dendritic cells, which reside outside the lymphatic system, migrate to lymph nodes after encountering pathogens. There, they interact with other immune cells and trigger the adaptive immune response**.
      - lymphatic vessels drain into veins near shoulders via 2 large ducts
    - - lighter injuries or infections cause local inflamatory responses but , if the threat is big enough, it can cause a systemic account, cells in infected tissue secrete hormones that promote release of more neutrophils from bonemarrow. in sever infection number of white blood cells may increase several fold in a few hours
      - systemic response sometimes includes fever, substance release by certain macrophages increase body's temperature set point, its hypothesized that it may speed up phagocytosis and speed up metabolism, helping cell repair
      - certain viral, bacterial, and fungal infections can caused sepsis which is a overwhelming inflamatory response that damages organs, increased blood vessel leakiness allows fluid to leak out of blood and into tissues. this results in low blood pressure.
      - if allowed to progress it can progress to septic shocl where blood pressure keeps lowering and blood supply to organs ins significantly reduced. it has a mortality rate of 40%
      - chronic inflammation threatens human health with diseases like Crohn's disease which are unregulated inflammatory responses that disrupt intestinal function
    - - pathogen recognition triggers production and release of proteins and peptides that attack pathogens, interferons and complement proteins are unique to mammals
      - interferons are proteins that provide innate defense against viruses, by making surrounding uninfected cells produce substances that inhibit viral replication, reducing cell to cell spread, some white blood cells have a different type of interferons that help activate macrophages
      - infection fighting compliment system is made of roughly 30 proteins in blood plasma, they circulate in blood plasma until activated by things on surface of pathogens
    - - outer capsule of certain bacteria interferes with cellular recognition and phagocytosis
      - some bacteria are recognized but simply resist breakdown after being engulfed by a host cell, instead of being destroyed it grows and reproduces in host cells, hiding from bodies defenses (tuberculosis)
      - some visuses block innate immune response at a cellular level by encoding proteins that generally inhibit protein synthesis in host cell, or suppress production of defensive proteins like interferons (viral infection can become well established before host can mount an effective immune response)
  - - - vertebrates have both innate and adaptive immunity (arsenal of receptors detect feature only found in one part of one molecule of one pathogen, very specific)
      - relies on T cells and B cells types of WBC called lymphocytes. some lymphocytes migrate to the thymus and mature into T cells while the ones that stay in bone marrow mature into B cells, a third type in bone marrow are natural killer cells in innate immunity
      - antigens as triggers for adaptive immunity
      - any substance that triggers T and B cells is a antigen, recognition happens when T or B cells bind to the antigen via protein called antigen receptor each of them is highly specific for each virus or bacteria
      - immune system cells produce millions of antigen receptors, a huge arsenal like a library of many bacteria viruses or fungi that the lymphocytes can react to and know specifically what they are dealing with
      - antigens are typically big and foreign, many antigens protude out of surfaces of viruses or foreign cells however some antigens like toxics secreted by bacteria are released into extra cellular fluid
      - the part of the antigen that binds to the antigen receptor is called the epitope, a single antigen has several epitopes, B and T cells have similar receptors so they each recognize one epitope this gives them high specificity
    - - each antigen b receptor is a Y shaped protein made of 4 poly peptide chains 2 heavy chains and 2 light chains, they are linked by disulfiede bridges
        
        each B cell antigen receptor has 2 identical antigen binding sites
        
        the binding of B cells to an antigen is an early step in B cell activation, it eventually leads to formation of cells that make soluble receptors called anti bodies or immunoglobulin (they are direct defense to pathogens in body fluids)
        
        binding is highly specific because the antigen binding site for a receptor has a unique shape, like a key and lock fit at a specific epitope. even small changes in amino acids change the shape of the binding site
        
        antibodies and b cell receptors can bind to whole antigens either on surface of pathogens or in body fluids
    - - the host protein that displays antigen fragment on cell surface are MHC by displaying the fragments MHC molecules are important for antigen recognition by T cells
      - unlike B receptors, T receptors only recognize antigen fragments presented on other cells, variable regions of both chains are what form the site that binds to antigen
      - display of antigen happens when pathogen infects a cell or is engulfed by and immune cell, in the cell the pathogen is cleaved into fragments which bind to a MHC molecule, this MHC molecule transports the antigen fragment to the cell surface resulting in antigen presentation
      - the display of these fragments advertises that the cell has been infected and if a T cell comes along that can bind with it, it triggers and adaptive immune response increase in number of cells for that pathogen, precious exposure leads to faster and stronger response
    - - diverse lymphocyte arsenal allows for detection of new antigen and pathogens, adaptive immunity normally does not attack the bodies own cells, activation of B or T cells leads to
        
        lymphocytes develop receptor diversity and self tolerance as they mature, cell proliferation and immunological memory occur after encountering specific antigen, diversity tolerance proliferation and memory develop in that sequence
        
        we generate millions of different antigen receptors despite only having 20l protein encoding genes in the human genome with combinations or combinatorial assembly
        
        receptor diversity starts at gene level like in immunoglobulin light chains however it also applies to B cell receptor and antibodies, B and T cell receptor genes go through similar gene rearrangement processes for diversity
        
        the light chain contains on C segment 40 V segments and 5 J segments that all get arranged along the gene in a sequence, they can be combined in 200 different ways, number of combinations i heavy chains is even greater
        
        DNA rearrangement is needed to make functional ig gene, recombinaze joins V and J segments, this eliminates long stretch of DNA between fragments and forms a new single exon =part V and J
        
        recombinase acts randomly linking any 40 V segments to any 5 J segments, only one allele of the the ligh chain and heavy chain are rearranged and the rearrangements are permanent passed down on to daugher cells when lymphocyte divides
        
        after both chains are rearranged antigen receptors can be made, each pair of randomly rearranged heavy and light chains results in different antigen binding sites
        
        mutations during recombination add more variation, making the number of antigen bind specificities even greater.
        
        self tolerance originates when lymphocytes antigen receptors test for self reactivity while in thymus or in bone marrow, B and T cells that have receptors specific to the own body are destroyed via apoptosis (programmed cell death) other ones are rendered non functional, leaving only lymphocyte that react to foreign molecules
        
        match between an antigen receptor and an epitope initiates events that activate the lymphocyte bearing the receptor., once activated B and T cells go through multiple divisions making a clone, some cells from clones become effector cells (mostly shortly lived cells that take effect immediately against antigen or pathogen, producing the antigen)
        
        effector cells for B cells form plasma cells which secrete antibodies, for T cells the effectors form helper T cells or cyotoxic T cells, remaininf cells in clones become memory cells
        
        clonal selection: encounter with antigen selects the lymphocyte that will divide and produce clonal population of cells specific for a paricular epitope
    - - responsible for long term protection against pathogens form prior infection
      - prior exposure to antigen alters the speed, strength and duration of immune response (secondary immune response is faster than primary immune response by effector cells formed by clones of lymphocytes)
      - secondary immune response relies on resevoirs of T and B memory cells, these cells are longed lived and provide basis for immunological memory
      - the 2 classes of lymphocytes fight infection inn different ways and different settings
  - - - Helper T cells: activating adaptive immunity
        
        helper T cell activates humoral and cell mediated immune responses.
        
        2 conditions must be met
        
        Foreign molecule (antigen) must bind the T cell’s receptor.
        
        Antigen must be presented on an antigen-presenting cell (APC
        
        infected cells can display foreign particle on surface with MHC molecules most body cells have type 1 but antigenpresenting cells have both class 1 and class 2 MHC molecules.
        
        Dendritic cells or macrophages present antigen to naïve helper T cells, activating them and triggering clonal expansion, B cells present antigen to already activated helper T cells, which then activate B cells for antibody production.helper T cells stimulate cytotoxic T cells
      - B Cells and Antibodies: A Response to Extracellular Pathogens
        
        secretion of antibodies is the hall mark of humoral immune response
        
        B cell activation requires signals from helper T cells and direct protein binding of pathogen surface proteins, Stimulated by an antigen and cytokines, B cell proliferates and turns into memory B cells and antibody secreting plasma cells
        
        Macrophages and dendritic cells can present fragments from many protein antigens, B cell presents only antigen it specifically binds to. When a B cell binds an antigen, it internalizes a few molecules by receptor-mediated endocytosis and then displays an antigen fragment on its class II MHC to a helper T cell, with this direct contact being critical for B cell activation.
        
        B cell activation leads to robust hormone response a singe activated B cell gives rise to thousands of identical plasma cells, plasma cells start producing and secreting antibodies
        
        anti bodies dont directly kill pathogens they disrupt their processes by binding to them
        
        in opsonization antibodies promote phagocytosis
        
        phagocytosis lets macrophages and dendrites present antigens to stimulate T cells which stimulates, the B cells to make more antibodies that contribute to phagocytosis, positive feedback loop ensures effective, coordinated immune response
        
        antibodies can work together with proteins of complement system Binding of a complement protein to an antigen antibody complex on foreign cell triggers events leading to formation of pore that makes Ions and water rush into the cell, making it explode
        
        antibodies can bring about death of infected body cells, when viral products from using cell machinery to replicate show up on the surface of the cell, antibody can recruit natural killer cell for it to come and destroy infected cell
        
        there is 5 types of B cells but have a distinct heavy chain C region lgD is extremely membrane bound, unlike other 4 that have soluble forms, such as anti bodies found in blood, saliva, breast milk etc
      - Cytotoxic T Cells: A Response to Infected Host Cells
        
        pathogens can reproduce in and kill host cells
        
        cytotoxic T cells use toxic proteins to kill cells infected by pathogens before pathogens fully mature
        
        pathogens can replicate in cells kill them. Cytotoxic T cells prevent this replication by using toxic proteins to kill cells infected with intracellular pathogens. To activate, they require signals from helper T cells and interaction with MHCs Infected cells display foreign protein fragments which are recognized by cytotoxic T cells. The accessory protein CD8 binds to class 1 MHC, directing the cytotoxic T cell to target the infected cell.
        
        targeted destruction is done with proteins that disrupt membrane integraty and trigger cell death
      - both humoral and cell mediated immune responses have both primary and secondary response the combination and cooperation of all the immune system cells and memory B and helper T cells enable better secondary response
      - immunization
        
        the better protection provided by second immune response is the basis for immunization
        
        artificially produced weak version of antigens introduced in body can generate an adaptive immune response in order to fight of the real deal later (example: covid 19 vaccine)
        
        vaccination programs have ben successful against many infectious diseases, that once incapacitated or even killed people,
        
        vaccine hesitancy is fueled by misinformation about safety and disease risk
        
        active immunity: defenses that arise when pathogen elicits a immune response from own body
        
        passive Immunity gained by receiving pre-formed antibodies rather than producing them through your own immune response like that of a mothers antibodies crossing placenta and into fetus
  - - - allergies
        
        hyper sensitive responses to certain antigens called allergins
        
        hay fever: Allergen exposure activates B cells to produce IgE antibodies, IgE binds to mast cells in nasal passages, eyes, and airways, mast cells release histamine and other chemicals, causing sneezing, itching, watery eyes, and runny nose
      - auto immunediseases
        
        Autoimmune diseases occur when the immune system attacks own body due to low self tolerance
        
        Lupus : Antibodies target histones and DNA, causing skin rashes, fever, arthritis, kidney dysfunction.
        
        Type 1 diabetes: Immune system attacks insulin-producing beta cells, causing insulin deficiency
        
        Multiple sclerosis: Immune system attacks myelin sheaths of neurons causing impaired nerveous system signal transmission
        
        Heredity, sex, and environment can affect risk of autoimmune disease, Certain families show increased susceptibility to specific autoimmune disorders.
      - Exertion, Stress, and the Immune System
        
        Moderate exercise improves immune system function, making common cold and other upper respiratory tract infections less common
        
        Exhaustive exercise (too much exercercise) weakens immunity, and increases frequency and severity of infections.
        
        low sleep: adults who get less than 7 hours of sleep get sick 3 times more often than adults who average 8 housr
    - - latency
        
        some viruses can avoid triggering immune response with a argely inactive state called latency
        
        typically persists until either favorable conditions for the virus occur or unfavorable conditions for host surival occur
      - antigenetic variation
        
        Some pathogens escape immune defenses by changing their appearance to the immune system.
        
        a pathogen with Altered epitopes allows for reinfection or persistance without triggering triggering rapid and robust response mediated by memory cells.
        
        antigenic variation is the reason you need a yearly flu shot ( it undergoes frequent mutations as it replicates from host to host
      - HIVs attack on the immune system
        
        HIV RNA is integrated into the host genome, allowing production of more viruses.
        
        HIV can escapes adaptive immune response because of high mutation, altered proteins on the surface of some mutated viruses reduce antibodies and cytotoxic T cells recognition and on going replication and evolution in host
        
        Viral replication and cell death triggered by virus lead to loss of helper T cells, impairing both humoral and cellmediated immune responses. eventually resulingt in AIDS an impairment in immune response that leaves body vulnerable to infections and cancers it could usually defeat