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TOPIC 6: Human Physiology, muscle contractions --> pressure changes -…

- - - - SMSM
        1) Serosa = Outer coat of connective tissue
        2) Muscle layer = longitudinal muscle with inside circular muscle
        3) Sub mucosa = tissue layer containing blood and lymph vessels
        4) Mucosa = lining of the small intestine, with a surface epithelium
        
        link to www.google.com
      - PERISTALSIS. The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut.
        
        peristalsis is the involuntary contraction and relaxation of longitudinal and circular muscles through the digestive tract.
        
        Contraction of circular muscle prevents food from being passed backwards towards the mouth.
        contraction of longitudinal muscle moves food along the gut.
        
        swallowed food moves down the esophagus in one persitaltic wave. peristalsis only occurs in one direction: away from the mouth.
        
        MAIN FUNCTION: churning of the semi-digested food to mix it with enzymes, speeding the process of digestion.
    - - Enzymes digest most macromolecules in food into monomers in the small intestine.
        enzymes secreted by the pnacreas into the smlal intenstine carry out hydrolysis of food molecules.
        
        starch is digested to maltose by amylase
        
        triglcyerides and phospholipids are digested to fatty acids and glycerol by lipase and phospholipase
        
        proteins digfested into peptides by protease
        
        sucrase digestes sucrose into fructose and glucose
        
        nucleases digests dna into nucleotides
        
        lactase digests lactose into glucose and galactose.
    - - the inner epithelium lining of the intestine is highly folded into finger-like projections called vili.
        Vili are small finger-like projections of the mucosa on the inside of the intestinal wall. Vili increases the the SA:V available for absorption
        absorption is the process of taking substances into cells.
        nutrietns are mainly absorbed in the S.Intestine
        rate of absorption depends on vili surface area.
      - MR.SLIM
        Microvilli – Ruffling of epithelial membrane further increases surface area
        Rich blood supply – Dense capillary network rapidly transports absorbed products
        Single layer epithelium – Minimises diffusion distance between lumen and blood
        Lacteals – Absorbs lipids from the intestine into the lymphatic system
        Intestinal glands – Exocrine pits release digestive juices
        Membrane proteins – Facilitates transport of digested materials into epithelial cells
        
        get your marks
        
        large surface area by microvilli / protrusion of exposed parts
        
        epithelium only one layer thick
        
        protein channels allow facilitated diffusion and active transport
        
        mitochondria provide ATP
        
        blood capillaries close to epithelium/ surface
        
        absorption of glucose/ amino acids
        
        lacteal / lymphatic vessel in center to absorb fats
      - Villi absorb monomers formed by digestion as well as mineral ions and vitamins.
        
        the epithelium lining is permable enough to allow useful nutrients to pass through. howrever the lining mainly absorbs the producsts of digestion/monomers of food
        harmful substances abrosrbed by epithelium is removed by the liver. unwanted substances are removed in urine.
      - lymph vessel
        arteriole
        venule
        (central) lacteal
        capillary network
        epithelial layer/ lining/ epithelium
        microvilli
        goblet cells
    - - during absorption, nutrietnts must pass from the lumen of the small intestine into the capillaries or lacteals of the vili.
        1) Co-transport (active transport): Glucose and amino acids are co-transported across the epithelial membrane by the active translocation of sodium ions (Na+)
        2) facilitated diffusion: monosaccharides (Channel proteins help hydrophilic food molecules pass through the hydrophobic portion of the plasma membrane)
        3) simple diffusion: triglycerides (Hydrophobic materials (e.g. lipids) may freely pass through the hydrophobic portion of the plasma membrane)
        6) Osmosis: Water molecules will diffuse across the membrane. water is absrobed mostly in large intestine but also in the small intestine.
    - - Starch digestion involves catalysis, enzyme specificity and membrane permeability.
        starch is a macromolecule composed of alpha glucose monomers linked in condesation reactions.
        2 types of starch digestion depending on amylose (unbranced)(only amylase) or amylopectin (branched) which is digested by amylose AND dextrins.
        amylase in salive begins the digestion of starch in the mouth. main digestion occurs in the small intestine
    - - a. contraction of muscle «layers»/peristalsis helps move food
      - OR
      - circular muscle contraction prevents backward movement of food
      - OR
      - longitudinal muscle contraction moves food along gut
      - b. peristalsis/muscle contractions mix food with intestinal enzymes
      - c. enzymes digest macromolecules into monomers
      - d. pancreatic enzymes/amylase/lipase/endopeptidase «chemically» digest food in«lumen of» small intestine
      - e. «pancreatic» amylase digests starch
      - OR
      - lipases digest lipids/fats/triglycerides
      - OR
      - endopeptidases/dipeptidases digest proteins/polypeptides
      - f. bile/bicarbonate secreted into the small intestine creates favorable pH for enzymes
      - OR
      - bile emulsifies fat
      - g. some final digestion into monomers is associated with epithelial cells/epithelium «of small intestine»
      - h. mucosa layer/inside surface/lining of small intestine contains villi/finger-like projections
      - i. villi/microvilli increase surface area for better absorption
      - j. villi absorb products of digestion/monomers/mineral «ions»/vitamins
      - k. glucose/amino acids enter blood «capillaries»
      - OR
      - lipids enter lymph vessels/lacteals
      - l. absorption involves active transport/diffusion/facilitated diffusion
      - m. different nutrients are absorbed by different transport mechanisms
      - Accept an example for mp c
- - - - Blood pressure in veins is very low so blood can flow backwards. to mantain circulation pocket valves are found in veins, consisting of a 3 cup-shaped flaps of tissue.
      - if blood starts to flow backwards it gets caught on the flaps of the pocket valve. these fill with blood, blocking the lumen of the vein.
        blood flow towards the house pushes the flaps to the side. pocket valve is open to mantain a constant and unidirectional blood flow towards the heart.
  - - - myogenic muscle contraction;
      - contracts without stimulation;
      - pacemaker/sino-atrial node/SAN in (wall of) right atrium;
      - pacemaker/sino-atrial node/SAN initiates contraction;
      - nerves (from brain) transmit messages to pacemaker;
      - to alter/increase/decrease the rate of the pacemaker;
      - medulla of the brain controls heart rate/beat;
      - epinephrine/adrenaline is hormone produced by adrenal gland;
      - epinephrine/adrenaline accelerates heart rate/beat;
  - - - at 0.0-0.1 seconds: Sn sends electrical singal to atria. atria contracts. atrioventricular valve opens pumping blood to ventricle
        at 0.1-0.15 seconds: ventricle receives electrical signal and contracts, rapid pressure build up. AV valve closes
        at 0.4 seconds: semilunar valves open and blood is pumped to the arteries.
        at 0.45 seconds: closes Semilunar valve to prevent backflow.
    - - the sinoatrial node sets up the rythm for the beating of the heart and a responds to singals from outside the heart
      - these signals come from the medulla
        
        signals from one of the nerves cause the pacemaker to increase the freqyency of heartbeats
        
        signals from the other nerve causes the pacemaker to decrease the heart rate.
      - the brain (medulla) receives input from receptors that mantain blood pressure, sugar cells, oxygen conc, and pH.
        
        the pH of the blood reflects co2 conc. the lower the pH, the greater the co2 conc.
        1) low BP, low oxygen, low ph = high co2 = heart rate must increase
        2) high o2 conc and high ph = low co2 = heart rate must decrease
      - Epinephrine increases the heart rate to prepare for vigorous physical activity.
        
        the sinoatrial node responds to epineprhin (adreanlin) in the blood by increasing heart rate.
        it is secreted by the adrenal glands and its secretion is controleld by the hypothalamus; it increases when vigorous physical activty may be necessary or in response to the fight or flight response (used when hunting preys)
- - - - When the skin is cut = blood vessels are severed and bleed = the bleeding stops by blood clotting.
      - clotting functions to prevent blood loss from the body and prevent the entry of pathogens.
      - the blood emerging from a cut changes from liquid to a semi-solid gel that dries with air to form a scab.
      - Clotting factors are released from platelets.
        
        The process by which blood clots involves a cascade of reactions, each of which produces a catalyst for the next reaction. 1) clotting occurs only if platelets release clotting factors
        
        PROCESS:
        when a cut occurs, platelets aggregate at the site forming a temporary plug called a coagulation cascade --> then they release clotting factors that trigger the clotting process --> thrombin catalyses the conersion of fibrinogen into insoluble fibrin
        
        The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin
        
        the coagulation cascade and the clotting factors produces an enzyme called thrombin, thrombin converts the soluble fibrinogen into insoluble fibrin.
        the fibrin traps blood cells to form a temporary clot.
        the clot is a gel, but in contact with air it dries to form a scab.
    - - patients with CHD form blood clots in the coronary arteries, these carry blood and nutrients to the heart.
      - a blood clot is a thrombus. coronary thrombosis is the formation of blood clots in the coronary arteries. if the coronary arteries become blocked/occluded by a blood clot due to the rupture of fatty deposits by LDL, the heart is deprived of oxyge and nutrients
        = cardiac muscles cannot produce suffiecnt ATP
        = weak and irregualr contractions
        = fibrilation
        = coronary occlusion leads to the hardening of the arteries and increased risk of coronary thrombosis
      - Coronary artery disease refers specifically to the narrowing of the arteries that supply the heart with blood, whereas atherosclerosis refers to narrowed arteries anywhere in the body.
  - - - lymphocytes are white blood cells that provide specific immunity to disease by producing antibodies that bind to antigens on pathogens
      - microorganisms are recognised by proteins on the surface of pathogens stimualting a specific immune response.
        any chemical that stimulates a specific immune resposne is called an antigen.
        antigens are proteins found in the surface of foreign cells that cause an immune response.
        
        the specific immune reponse is the production of antibodies in response to a pathogen.
        
        the antibodies will bind to the antigen on the pathogen.
        
        antibodies are produced by specfici lymphocutes. each lymphocyte produces different antibodies that bind to specific antigens.
        
        there are limited antibodies due to limited lymphocytes = antigens on the pathogen sitmulate the division and differentiation of lymphocytes.
        
        Plasma cells are specialized B lymphocytes that secrete a large amount of antibodies during a selective immune response. they simply secrete a lot of antibodies to control a pathogen
        
        Antibodies are proteins that defend the body against pathogens by binding to antigens on the surface of these pathogens and stimulating their destruction.
        antibodies have two regions:
        
        hypervariable region that binds to specific antigens
        
        a second region that helps the body fight the pathogen:
        1- makes the pathgen more recognisable to phagocytes
        2- prevents viruses from docking to host cells.
        
        some lymphocytes become memory cells = these remaon inactive unless the same pathogen reinfects the body again.
        
        Immunity to an infectious disease involves either having antibodies against the pathogen or memory cells that allow rapid production of antibodies
    - - the human immunodefiency virus (HIV) is a retrovirus that destroys helper T-cells, casuing the loss of antibody production. if antibodies are detected that act against HIV the person is HIV positive.
        a reduction in t cells reduces antibodie numbers leading to weakedn immune response. the persdon will eventually develop AIDS which is acquired immmune defiency syndrome.
        AIDS spreads by HIV infection.
        CAUSES: unprotected sexual intercouse/sharing needles/transfusion of infected blood
  - - - Virus are non-living and can only reproduce when they are inside living cells. they use the chemical processes of a living host cell, so they lack a metabolism.
        these processes cannot be targeted by drugs as the host cell would be damaged as well.
        PENICILLIN AND OTHER ANTIBIOTICS CONTROL BACTERIAL INFECTIONS AND ARE NOT EFFECTIVE AGAINST VIRUSES.
      - Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance.
        
        multiple resistant genes in bacteria are a problem as they are resistant to more than one antibiotic. MRSA is a multiple resistant bacteria that has infected people and cannot be treated by antibiotics.
        bacteria can reproduce rapidly and exchange resistant strains
        
        avoiding antibiotic resistance: high hygiene standards; limit prescription: avoid use by farmers: complete course of antibiotics
- - - - respiratory muscles must contract to change the volume and pressure of the thorax cavity. pressure changes will cause ventilation.
      - muscles work when they contract by exerting a pulling force that causes movement = become shorter.
        muscles lengthen when they relax while the other contracts
      - muscles that increase the volume of the chest cause inspiration
        
        muscles that decrease the volume of the chest cause expriation
      - When in a pair of muscles one contracts and the other relaxes, they are antagonistic muscle pairs: inspiration and expiration require opposite muscle movements, therefore respiratory muscles is antagonistic
        
        ventilation involves two pairs of opposite movements that change the volume and pressure inside the thorax:
        INSPIRATION:
        
        Diaphgram (1) = moves downwards and flatterns (lets air in) CONTRACTS
        
        Abdomen wall muscles (1.5) relax
        
        Ribcage = moves upwards and outwards:
        
        external intercoastal muscles contract ribcage upwards
        
        internal intercoastal muscles relax and pull back into elongated state
        
        volume increases, pressure decreases
        
        EXPIRATION:
        
        diaphrgam relaxes, letting air out and moving upwards into a doomed shaped
        
        abdomen wall muscles contract pushing the abdominal organs and the diaphrgam upwards
        
        ribcage = moves downards and inwards
        
        external intercoastal muscles relax and go into elongated state
        
        internal intercoastal contract pulling ribcage downward
        
        pressuren cinreases and volume decreases
    - - Emphysema is a lung condition whereby the walls of the alveoli lose their elasticity due to damage to alveolar walls. = leads to thick alveolar walls = decreases surface area for gas exchange = degradation of the alveolar walls can cause holes to develop --> pulmonary bullae
        loss of elasticity means that ventilation is more difficukt, damage to alveolar cells is irreversible and it causes a low oxygen saturation in the blood
- - - - Some neurons have the axon covered by a fatty substance called myelin which functions as an insulating layer.
        
        nerve fibres insulated with myelin have layers of phospholipids
        
        specialised cells called Schwann cells deposit the myelin by growing around the nerve fibre.
        
        the gap betwen the myelin deposited by Schwann cells is the node of Ranvier.
        
        in myelinated nerve fibres, the nerve impulse can jump from one node to another by saltatory conduction.
        
        saltatory conduction is the jumping of the action potential between nodes of ranvier in myelinated axons. allow action potential to travel at faster rates.
    - - a resting potential is the difference in charge across the membrane when a neuron is not firing.
        a neuron that is not transmitting a signal has a potential difference across its membrane, this is the resting potential.
        resting potential is due to an imbalance of positive and negative charges across the membrane.
        when resting potential, more sodiums otuside (negative relaitve to the outside)
      - b. Explain how an impulse passes along the membrane of a neuron.
        
        a. resting potential is –70mV / relatively negative inside in comparison to the outside;
        
        b. Na K pumps maintain/re-establish (the resting potential);
        
        c. more sodium ions outside than inside (when at the resting potential);
        
        d. more potassium ions inside than outside (when at the resting potential);
        
        e. nerve impulse is an action potential that stimulates a (wave of) depolarization along the membrane/axon;
        
        f. if neuron is stimulated/threshold potential/–50mV is reached sodium ion channels open;
        
        g. sodium ions diffuse/move in;
        
        h. (Na move in) causing depolarization;
        
        i. potassium ion channels open / potassium ions diffuse/move out;
        
        j. (K move out) causing repolarization;
        
        k. local currents / description of Na ion diffusion between depolarized region and next region of axon to depolarize;
      - sodium and pottasium is pumped in and out of the mebrane to mantian a resting potential.
        if more sodium inside = the membrane inside is positive, if more pottasium inside = membrane negative
        creates charge imbalance
      - An action potential consists of depolarisation and repolarization of the neuron: it is a rapid change in memrbane potential consisting of
        
        depolarisation = due to opening of sodium channels in the memrbane: charge chnage from - to +, by diffusing (3) sodium ions into the neuron
        
        repolarization = occurs after depol, opens pottasium channels: charge change from + to - by diffusing sodium ions out of the neruon and (2) pottasium in
    - - refractory period occurs after an action potential, the sodium pottasium pump put the voltage back to resting so another action potential can be initiated.
  - - - an action potential is a nerve impulse that will only be initiated if a threshold potential is reached. this potential volatge is reached when voltage gated sodium channels open causing depolarisation.
  - - - the synaptic cleft is a gap where neurotrnamistters travel across
  - - - synapse is gap between adjacent neurons;
      - (arriving) action potential depolarizes pre-synaptic membrane;
      - opens (voltage-gated) calcium channels in membrane;
      - causes influx of calcium ions;
      - causes synaptic vesicles to fuse with pre-synaptic membrane;
      - vesicles release/exocytose neurotransmitter into the synaptic cleft;
      - neurotransmitter diffuses/moves across synaptic cleft;
      - neurotransmitter binds to receptors on post-synaptic membrane;
      - opens channels allowing sodium ions/potassium ions to diffuse;
      - initiation of action potential/depolarization in post-synaptic membrane;
      - removal/breakdown of neurotransmitter stops effect on post-synaptic membrane;
  - - - choline will be reasbrobed by the presynaoptic neuron
      - acetylcholine only remains bound to receptors for a short time.
        
        acetylcholine receptor sites on post synaptic neuron recognise it. in the synaptic cleft the enzyme acetycholinase is present so it breaksdown the neurotransmitter into choline and the acetyl group
    - - neonicotinoids are synthetic compounds that bind to acetylcholine receptors in cholinergic synpases (a synapse that uses acetylcholine as a neurotransmitter) in the nervous sytem of insects.
        this blocks the receptors for acetylcholine, preventing synaptic transmission = causing death of insects
        they use this drug as a pesticide as they are not toxic to humans
- - - - because leptin supresses appetite, it was considerd as a form of treatment for indivualds with clincal obesity
        
        leptin injections would supress hunger and lead to weight loss
        
        leptin trials was conducted on mice by fusing the blood ciruclation of healthy and obese mice:
        
        leptin in the blood of the healthy mice was transferred to the obese mice.
        
        the obese mice responded to leptin and lost weight
        
        however, when the obese mice had a deffective leptin receptor it did not loose weight as it did not respond to high leptin concenteratinos.
        
        Most cases of obesity are caused by an unresponsiveness to leptin and not leptin defiency. humasn have high leptin levels: clinical trials of leptin injectinos showed that patients remained the same and other adverse effects were experienced
    - - Circadian rythms are the bodys physiological response to the 24 hour day-night cycle
      - circadian rythms depend on 2 groups of cells in the hypothalamus called the suprachiasmitc nuclei
        
        these cells set a daily rythm
        
        in the brain the SCN controls the secretion of melatonin by the pineal gland
      - melatonin is the hormone resposible for synchronising circadian rythms and regulating the body's slee ping schedule
      - melatonin is regulated in response to periods of darkness, higher concs at night. high melatonin levels promotes sleep and a drop in body temperature.
      - Retinal cells detect light and passes impulses to cells in the suprachiasmatic nuclei
      - Causes of jet lag and use of melatonin to alleviate it.
        
        jet lag is a common experience for people who cross more than 3 different time zones in air travel.
        symtomps are fatigue: headache: interrupted sleeping schedule
        cause = the SCN and pineal gland continue to set a circadian rythm for the old timeznone, so sleeping schedule is not synchronised to the new timezone
        melatonin tablets is used to treat jet lag by promoting sleep
  - - - testes develop from embryonic gonands and develop testoterone-secreting cells that produce testosterone during pregancy.
        testosterone cuases male genitalia to develop prenatally
        at puberty testosterone concetrations increase to stimulate sperm production and the development of male secondary sexual charactersitics such as (1) pubic hair (2) ENLARGement of penis
    - - in the absence of the SRY gene = embryonic gonands develop as ovaries which secrete estrogen and progrestorone
        these will initate the development of female reproductive organs
        in puberty estrogen and progrestrone production will increase to develop female secondary sexual charactersitics: (1) breast enlargemnt (2) menstruation (3) pubic hair
  - - - A. FSH is secreted at the start of the cycle / early in the cycle / days 1 to 5 / when progesterone / estrogen is low;
      - B. FSH stimulates the development of follicles;
      - C. FSH stimulates estrogen secretion (by the developing follicle);
      - D. estrogen stimulates the repair of the uterus lining;
      - E. rapid increase in estrogen stimulates LH production, (positive feedback);
      - F. low levels of estrogen initially inhibit FSH (and LH) secretion;
      - G. LH is secreted in the middle of the cycle / before ovulation / days 10 to 14;
      - H. LH causes ovulation;
      - I. LH causes the development of the corpus luteum;
      - J. LH causes secretion of progesterone;
      - K. LH stimulates less estrogen;
      - L. progesterone causes thickening of the uterus lining / prepares uterine lining for implantation;
      - M. progesterone / estrogen inhibits the secretion of LH / FSH;
      - N. falling progesterone levels at the end of the cycle allow FSH production / menstruation;
      - O. lower concentrations of estrogen and / or progesterone allow disintegration of endometrium / menstruation occurs;
      - the corpus leteum (by LH) produces estrogen and progresterone, thickening the endometrium
    - - a. FSH stimulates estrogen secretion by follicle cells;
      - b. at start of menstrual cycle;
      - c. leading to development of endometrium;
      - d. (FSH and) LH (rise to a peak and) causes egg to be released/ovulation;
      - e. causes follicle cells to secrete less estrogen/more progesterone;
      - f. progesterone maintains endometrium/uterine lining
      - g. LH promotes change of follicle to corpus luteum;
      - h. secretion of LH and FSH regulated by negative feedback;
      - i. regulated/inhibited by high estrogen and progesterone levels;
      - j. low progesterone levels cause menstruation;
  - - - A. (IVF) is fertilization outside body
      - B. (drug) stops normal menstrual cycle;
      - C. (inject FSH) to stimulate ovaries / stimulate production of eggs;
      - D. (HCG) matures the follicles;
      - E. eggs are removed from follicles / ovaries / mother;
      - F. male provides sperm / sperm donor;
      - G. washing / capacitation of sperm;
      - H. eggs are mixed with sperm;
      - I. 2–3 embryos are implanted into uterus;
      - J. pregnancy test is done to see if implantation / pregnancy has occurred;
    - - pros/positive considerations: [3 max]
      - chance for infertile couples to have children;
      - decision to have children is clearly a conscious one due to difficulty of becoming pregnant;
      - genetic screening of embryos could decrease suffering from genetic diseases;
      - spare embryos can safely be stored for future pregnancies/used for stem cell research;
      - cons/negative considerations: [3 max]
      - IVF is expensive and might not be equally accessible;
      - high risk of failure/low success rate
      - it is not natural/cultural/religious objections;
      - could lead to eugenics/gender choice;
      - could lead to (unwanted) multiple pregnancies with associated risks;
      - M. allows for surrogate mothers;