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Chapter 42 and Chapter 44 (Chapter 42 Circulation and Exchange (Gas…
Chapter 42 and Chapter 44
Chapter 42 Circulation and Exchange
Circulatory system (ch. 42.1)
Diffusion
random thermal motion
the molecular trade that an animal carries out with its environment
gaining O2 and nutrients while releasing carbon dioxide and other waste products
very slow for distances of more than over a few millimeters
the time it takes from for a substance to diffuse from one place to another is proportional to the square of the distance
Gastrovascular Cavities
enables organisms to live without a distinct circulatory system
the body wall is only bout two cells thick which diffuses nutrients a short distance
Example: Planarians and other flatworms
fluid bathes both the inner and outer layers, facilitating exchange of gases and cellular waste
cells lining the cavity are the only ones that have direct access to nutrients released by digestion
Open and Closed Circulatory systems
composed of three basic components
a circulatory fluid
a muscular pump, the heart
the heart powers circulation by using metabolic energy to elevate the circulatory fluid's hydrostatic pressure
the pressure the fluid exerts on surrounding vessels
the lower hydrostatic pressures allows the organism to use less energy than closed systems
interconnecting vessels
functionally connects the aqueous environment of the body cells to the organs that exchange gases, absorb nutrients, and dispose of wastes
Open circulatory system
the circulatory fluid called hemolymph is also called interstitual fluid that bathes the body cells
Examples of animals: Grasshoppers, and some molluscs including clams
contraction of the heart pumps the hemolymph through the circulatory vessels into interconnect sinuses, spaces surrounding the organs
the hemolymph and body cells exchange gases and other chemicals
relaxation of the heart draws hemolymph back in through pores which have valves that close when the heart contracts
Closed circulatory system
a circulatory fluid called blood is confined to vessels and is distinct from the interstitual fluid
one or more hearts pump blood into large vessels that branch into smaller ones that infiltrate the tissues and organs
the benefits of a closed circulatory system includes blood pressure high enough to enable the effective delivery of oxygen
chemical exchange occurs between the blood and the interstitual fluid as well as between the interstitual fluid and the body cells
Example: Annelids (including earthworms), cephalopods ( including squids and octopuses), and all vertebrates have closed circulatory systems
found in the largest and most active species , squids and octopuses
Organization of Vertebrate Circulatory System
Cardiovascular system
the heart and blood vessels in the vertebrates
the hearts of all vertebrates contains two or more muscular chambers
the chambers the receive blood entering the heart is called the atria
the chambers responsible for pumping blood out of the heart are called ventricles
blood circulates to and from the heart through amazingky extensive network of vessels
there are three major types of blood vessels
capillaries
Arteries
carry blood from the heart to organs throughout the body
arteries branch into arterioles
these small vessels convey blood to capillaries
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Veins
the vessels that carry blood back to the heart
arteries and veins are distinguished by the direction in which they carry blood, not by the oxygen content or other characteristics of the blood
arteries carry blood away from the heart
veins carry blood to the heart
Single Circulation
blood travels through the body and returns to its starting oint in a single circuit
the heart consists of two chambers
an atrium and a ventricle
blood entering the heart collect in the atrium before transfer to the ventricle
contraction of the ventricle pumps blood to a capillary bed in the gills here there is net diffusion of oxygen into the blood anf of carbon dioxide out of the blood
capillaries converge into a vessel that carries oxygen-rich blood to the capillary beds throughout the body
blood enters and returns to the heart
when blood flows through the capillary beds, blood pressure drops
the drop in pressure in the gills limits the rate od blood flow in the rest of the animal's body
when the animals swims, the contraction and relaxtaion its muscles help accelerate the relatively sluggish pace of circulation
Double circulation
two circuits of blood flow
the pumps for the two circuits are combined into a single organ, the heart
in one circuit, the right side of the heart pumps oxygen-poor blood to the capillary beds of the gas exchange tissues
pulmonary circuit
gas exchange takes place in the capillaries of both the lungs and the skin
Systemic circuit
begins with the left side of the heart pumping oxygen-enriched blood from the gas exchange tissues to capillary beds in organs and tissues throughout the body
provides vigorous flow of blood to the brain , muscles, and other organs because the heart repressurizes the blood after it passes through the capillary beds of the lungs or c=skin
Chapter 42.2 Coordinated cycles of heart contraction drive double circulation in mammals
mammalian circulation
Contraction of the right ventricle pumps blood to the lungs via the pulmonary arteries
as the blood flows through the capillary beds in the left and right lungs, it loads oxygen and unloads carbon dioxide
oxygen-rich blood flows into the heart's left ventricle via the aorta
the aorta conveys blood to arteries leading throughout the body
the branches lead capillary beds in the head and arms
the aorta descends into the abdomen, supplying oxygen-rich blood to arteries leading to the capillary beds in the abdominal organs and leg
the mammalian heart
located behind the sternum, the human heart is about the size of a clenched fist and consists mostly of cardiac muscle
the two atria have relatively thin walls and serve as collection chambers for blood returning to the heart from the lungs or other body tissues
the blood that enters the atria then flows into the ventricles while all four of the chambers are relaxed
the remainder is transferred by contraction of the atria before the ventricles begin to contract
the ventricles have a much thicker wall than that of the atria and it contracts much more forcefully
the left ventricle has a thick wall and pumps blood throughout the body via the systemic circuit
although the left ventricle contracts with greater force than the right ventricle, it pumps the same volume of blood as the right
ventricle during each contraction
The heart contracts and relaxes in a rhythmic cycle
when the heart contracts, it pumps blood
when the heart relaxes, it fills with blood
a complete sequence of pumping and filling is referred to as the cardiac cycle
systole
the contraction phase of the cycle
diastole
the relaxation phase
the four valves in the heart prevents backflow and keeps blood moving in the correct direction
the valves open when pushed from one side and close when pushed from the other
atrioventricular valve
lies between each atrium and ventricle
anchored by strong fibers that prevent them from turning inside out during ventricular systole
pressure generated by the contraction of the ventricles closes the AV valves , which keeps the blood from flowing back into the atria
semilunar valves
located at the two exits of the heart: where the pulmonary artery leaves the right ventricle and where the aorta leaves the left ventricle
If blood squirts backward through a defective valve, it may produce and abnormal sound called a heart murmur
Cardiac Output
the volume of blood each ventricle pumps per minute
two factors determine cardiac output
the rate of contraction ,or heart rate ( number of beats per minute)
the stroke volume, the amount of blood pumped by a ventricle in a single contraction
the average stroke volume is about 70 ml
Sinoatrial node
pacemaker can help control the rhytmic beat of the heart
Electrocardiogram
electrodes placed on the skin record the currents thus measuring electrical activity of the heart
Atrioventricular node
a relay point formed by cells
Chapter 42.3 Patterns of Blood pressure and flow reflect the structure and arrangement of blood vessels
Blood vessel structure and function
all blood vessels contain a central lumen ( cavity) lined with an endothelium, a single layer of flattened epithelial cells
the smooth endothelial layer minimizes resistance to fluid flow
surrounding the endothelial are tissue layers that differ among capillaries, arteries, and veins, reflecting distinct adaptations to the particular functions of these vessels
capillaries
the smallest blood vessels
have very thin walls that consists of just an endothelial and a surrounding extracellular layer called basal lamina
the exchange of substances between the blood and interstitial fluid occurs
Arteries and veins
each have walls that consist of to layers of tissue surrounding the endothelium
the layer is maintained by unidirectional flow of blood despite the low blood pressure in these vessels
Blood Pressure during the Cardiac Cycle
Systolic Pressure
arterial blood pressure is highest when the heart contracts during ventricular systole
each ventricular contraction causes a spike in blood pressure that stretches the walls of the arteries
Pulse
the rhythmic bulging of the artery walls with each heart beat
Blood Pressure
vasoconstriction
increases blood pressure upstream in the arteries
when smooth muscles in the arteriole walls contract, the arterioles narrow
Vasodilation
an increase in diameter that causes blood pressure in the arteries to fall
Diastolic pressure
the elastic walls of the arteries snap back
lower substantial blood pressure when the ventricles are relaxed
Capillary Function
Provides blood to all parts of the body at the same time
they are not very big because each tissue has many capillaries
How is blood flow in capillary beds altered?
Can be altered by the constriction and dilation of the arterioles that supply capillary beds
Precapillary sphincters
rings of smooth muscle located at the entrance to capillary beds
Fluid Return by the Lymphatic System
Lymphatic System
recovers lost fluid and returns it into the blood via a network of tiny vessels intermingled with capillaries
the recovered fluid is called lymph
circulates within the lymphatic system before draining into a pair of large veins of the cardiovascular system at the base of the neck
lymph nodes
play an important role in the body's defense
honeycomb of connective tissues with species filled by white blood cells which function in defense
when a body is fighting an infection, the white blood cells multiply rapidly, and the lymph nodes become swollen and tender
Ch 42.4 Blood components function in exchange, transport, and defense
Blood composition and Function
vertebrates blood is a connective tissue consisting of cells suspended in a liquid matrix called plasma
Cellular Element
makes up 45% of the blood
Erthrocytes (red blood cells)
main function is to transport oxygen
human erthrocytes are small disks that are biconcave and has a thinner center than the edges
the shape increase the surface area, enhancing the rate of diffusion of oxygen across the plasma membrane
the space leaves room for hemoglobin
the iron-containing protein that transports oxygen
an abnormal form of hemoglobin
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lack nuclei and mitochondria but generate their ATP exclusively by anaerobic metabolism
Life span of 120 days on average before replaced
A feedback mechanism sensitive to O2 levels control erythrocyte production
if oxygen levels fall, the kidneys synthesize and secrete a horomone called erythopoietin (epo) that stimulates the generation of more erythrocytes
Leukocytes (white blood cells)
fight against infections
phagocytic
engulfing and digesting microorganisms and debris from the body's own dead cells
Basophils
Lymphocytes
mount immune responses against foreign substances
Eosinophils
Monocytes
Neutrophils
Platelets
pinched-off cytoplasmic fragments of specialized bone marrow cells
about 2-3m in diameter and have no nuclei.
Platelets serve both structural and molecular functions in blood clotting
Blood clotting
when blood vessels are broken by and injury, a chain of events ensues that quickly seals the break, halting blood loss and exposure to infection
the exposed proteins then attracts platelets which gather at the site of the injury and release clotting factors
the clotting factors trigger cascade of reactions leading to the formation of an active enzyme. thrombin
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the key mechanical event in this response is coagulation
the conversion of the liquid components of blood into a solid-a blood clot
the coagulant, or sealant, circulates in an inactive form called fibriogen
positive feedback loop
Plasma
makes up 55% of the blood
Water
Solvent
Ions (blood electrolytes)
Sodium
potassium
Calcium
Magnesium
Chloride
Bicarbonate
Osmotic balance, pH buffering, and regulation of membrane permeability
Plasma Proteins
Albumin
Osmotic balance, pH bufferring
Immunoglobulins (antibodies)
Defense
Apolipoproteins
Lipid transport
Fibrinogen
Clotting factor
Transport nutrients such as glucose, fatty acids, vitamins, waste products of metabolism, respiratory gases (oxygen and carbon dioxide) and horomones
Stem cells and the Replacement of Cellular Elements
stem cell
can reproduce indefinitely, dividing mitotically to produce one daughter cell that remains a stem cell and another that adopts a specialized function
located in the red marrow inside bones
pelvis
ribs
vertebrae
sternum
as they divide and self-renew, these stem cells give rise to two sets of progenitor cells
Lymphoid progenitors
produce lymphocytes
Myeloids progenitors
produces all other white blood cells, red blood cells,and platelets
Cardiovascular Disease
Atherosclerosis
the hardening of the arteries by accumulation of fatty deposits
affected by cholesterol which is a steroid that is important for maintaining normal membrane fluidity in animal cells
cholesterol travels in blood plasma mainly in particles that consists of thousands of molecules and other lipids bound to a protein
low density lipoprotein
delivers cholesterol to cells for membrane production
high density lipoprotein
scavenges excess cholesterol for return to the liver
Heart Attack
Myocardial infarction
the damage or death of cardiac muscle tissue resulting from blockage of one or more coronary arteries
supply oxygen rich blood to the heart muscle
coronary arteries are small in diameter and therefore vulnerable to obstruction by atherosclerotic plaque or thrombi
Stroke
the death of nervous tissue in the brain due to a lack of oxygen
result from rupture or blockage of arteries in the head
Gas exchange occurs across specialized respiratory surfaces ( Ch 42.5)
Partial Pressure Gradients in Gas Exchange
partial pressure
the pressure exerted by a particular gas in a mixture of gases
determining partial pressure enables us to predict the net movement of a gas exchange surface
a gas always undergoes net diffusion from region of higher partial pressure to a region of lower partial pressure
Respiratory Media
Oxygen is plentiful in air making up about 21% of the atmosphere by volume
air is less dense and less viscous than water so it is easier to move and to force through small passageways
breathing air is relatively easy and need not be particularly efficient
water is much more demanding gas exchange medium than air
the amount of oxygen present in water varies but is less than in an equivalent volume of air
has a lower oxygen content, greater density, and greater viscosity
aquatic animals must expend considerable energy to carry out gas exchange
Respiratory surfaces
the part of an animal's body where gas exchange occurs
movement of oxygen and carbon dioxide across respiratory surfaces takes place by diffusion
the rate of diffusion is proportional to the surface area across which it occurs and inversely proportional to the square of the distance through which molecules move
almost always moist
Gills in Aquatic Animals
gills are outfoldings of the body surface that are suspended in the water
have a total surface area much greater than that of the rest of the body's exterior
ventilation
movement of the respiratory medium over the respiratory surface
maintains the partial pressure gradients of O2 and carbon dioxide across the gills
gas exchange
countercurrent exchange
the exchanges of substance or heat between two fluids flowing in the opposite direction of each other
Tracheal System in Insects
a network of air tubes that branch throughout the body
the largest tube is the trachea
opens to the outside
at the tips of the branches are moist epithelial lining that enables gas exchanges by diffusion
the efficient exchange of oxygen and carbon dioxide does not require the participation of the animal's open circulatory system
Lungs
localized respiratory organs
subdivided in numerous pockets
have evolved in a few aquatic vertebrates as adaptations to living in oxygen-poor water or spending part of their time exposed to air
Mammalian Respiratory Systems: A closer Look
The trachea branches into two bronchi, one leading to each lung
Bronchi branches into fiber tubes called bronchioles
gas exchange occurs in alveoli, air sacs clustered at the tips of the tiniest bronchioles
oxygen dissolves in the limning of the alveoli while carbon dioxide occurs in the opposite direction
Surfactant surface
active agent, coats the alveoli and reduces surface tension,
mucus
traps dust, pollen , and other particulate contaminants
Chapter 42.6 and 42.7 Breathing ventilates the lungs and Adaptation for gas exchange
Breathing
the process that ventilates lungs
the alternating inhalation and exhalation of air
Positive Pressure breathing
inflating the lungs with forced airflow
inhalation begins when muscles lower the floor of an amphibian's oral cavity , drawing the air through its nostrils
the nostrils and mouth close, the floor of the oral cavity rises . forcing air down the trachea
Exhalation
air is expelled by the elastic recoil of the lugs and by compression of the muscular body wall
How a Mammal Breathes
Negative pressure breathing
pulling rather than pushing air into the lungs
using muscular contraction to actively expand the thoracic cavity, mammals lower air pressure in their lungs below that of the air outside their body
Tidal Volume
the volume of air inhaled and exhales with each breath
Vital capacity
the tidal volume during maximal inhalation and exhalation
after forced exhalation, residual volume is what's left
gas flows from a region of higher pressure to a region of lower pressure
the lowered air pressure in the lungs causes air to rush through nostrils and mouth and down the breathing tubes to the alveoli
Diaphragm
a sheet of skeletal muscle taht forms the bottom wall of the cavity
contracting the rib muscles pulls the ribs upwards and the sternum outward
when the diaphragm contracts, it expands the thoracic cavity
inhalation
active and requires work
Exhalation
passive
the muscles controlling the thoracic cavity relax, and the volume of the cavity is reduced
Chapter 44 Osmoregulation and Excretion
Osmoregulation balances the uptake and loss of water and solutes (CH 44.1)
Osmoregulation
the general term for the processes by which animals control solute concentrations and balance water gain and loss
Excretion
ridding the body of nitrogenous metabolites and other metabolic waste products
if water uptake is excessive , animal cells swell and burst
if water loss is substantial then cells shrivel and die
Osmosis and Osmolarity
water enters and leaves cells by osmosis
the movement of water across a membrane from a higher concentration to a lower concentration
Osmolarity
the number of moles of solute per liter of solution
two solutions with the same osmolarity are said to be isoosmatic
there is no net movement of water by osmosis between two isoosmotic solutions
to solutions differ in osmolarity, the solution with the higher concentration of solutes is said to be hyperosmotic and the more dilute solution is said to be hypoosmotic
Osmoregulatory challenges and Mechanisms
Osmoconformer
to be isoosmotic with its surroundings
marine animals
their bodies have no tendency to gain or lose water
Osmoregulator
to control internal osmolarity independent of that of the external environment
osmoregulation enables animals to live in environment s that are uninhabitable for osmoconformers
allows many marine animals to maintain and internal osmolarity different from that of sea water
must discharge excess water in a hypoosmotic environment
Marine Animals
actively transport specific solutes that establish levels in hemolymph deifferent from those in the ocean
Freshwater Animals
body fluids must be hyperosmotic because animal cells cannot tolerate salt concentrations as low as that of lake or river
water balance relies on excreting large amounts of very dilute urine and drinking almost no water
salt lost in urine are replenished by eating and by salt uptake across their gills
Animals that live in Temporary Waters
Dehydration
desiccation
fatal for most animals
Anhydrobiosis
a dromant state when animals' habitats dry up
Land Animals
waxy layers , shells, and keratin help prevent the body from becoming dehydrated
lose water through urine and feces, and from the surfaces of gas exchange organs
maintain water balance by drinking and eating moist foods and by producing water metabolically through cellular respiration
Energetics of Osmoregulation
osmoregulators must expend energy to maintain the osmotic gradients that cause water to move in and out
active transport to manipulate solute concentrations in their body fluids
accounts for 5% or more of the resting metabolic rate of many fishes
minimizing the osmotic difference between body fluids and the surrounding environment decreases the energy cost of osmoregulation
Ch. 44.2 An animal's nitrogenous wastes reflect its phylogeny and habitat
Nitrogenous breakdown products of proteins and nucleic acids are the most significant waste products
when proteins and nucleic acids are broken apart for energy or converted to carbohydrates or fates, enzymes remove nitrogen in the form of ammonia
Ammonia
very toxic because its ion, ammonium can interfere with oxidative phosphorylation
animals that secretes ammonia need to drink a lot of water in order to keep the level at a low concentration
Urea
the product of an energy-consuming metabolic cycle that combines ammonia with carbon dioxide in the liver
very low toxicity
energy cost is a huge disadvantage though
animals spend part of their lives in water and part on the land would switch between excreting ammonia and excreting urea
Uric Acid
relatively nontoxic and does not readily dissolve in water
can be excreted as semisolid paste with very little water loss
more energetically expensive than urea, requiring considerable ATP for synthesis from ammonia
The influence of Evolution and Environment on Nitrogenous Wastes
The availability of water is a key factor
Examples:
terrestrial trutles excrete mainly uric acid, where as aquatic turtles excrete urea and ammonia
amphibian egg, which lacks a shell, ammonia or urea can simply diffuse out of the egg
Endotherms
use energy at high rates and eat more food and produce more nitrogenous waste than ectotherms
Diverse excretory systems are variations on a tubular theme (44.3)
How urine is produced
Filtration: the excretory tubule collects a filtrate from the blood.
Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule
Reabsorption: The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids
3 Secretion: other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule
Excretion; The altered filtrate (urine) leaves the system and the body
Protonephridia
consists of a network of dead-end tubules that branch throughout the body
caped with cellular units called flame bulbs
each flame bulb consists of a tubule cell and cap cell that has a tuft of cilia projecting into the tubule
performs different functions in different organisms
ex: in freshwater flatworms,most metabolic wastes diffuse out of the animal across the body surface or are excreted into the gastrovascular cavity and eliminated through the mouth
parasitic flatworms that are isoosmotic have protonephridia that primarily function in disposing of nitrogenous wastes
Metanephridia
organs that collect fluid directly from the coelem
a paair found in each segment of an annelid, where they are immersed in coelomic fluid and enveloped by a capillary network
surrounded by ciliated funnels that draws fluid into a collective tubule which includes a storage that opens to the outside
Earthworms experiene uptake of water through their skins where the metanephridia balances the water influx by producing urine that is dilute
Malpighian Tubules
removes nitrogenous wastes and that also function in osmoregulation
extend from dead-end tips immersed in hemolymph to openings into the digestive tract
the lining of the tubules secretes certain solutes, including nitrogenous wastes from the hemolymph into the lumen of the tubule
The excretory system of humans
consists of kidneys
a pair of organs each about 10 cm in length that transports and stores urine
urine produced by each kidney exits through the ureter
the ureteres then drain into a common sac called the urinary bladder
during urination, urine is expelled from the bladder through a tube called the urethra
has an outer renal cortex
has an inner renal medulla
Renal pelvis
where remaining fluids are collected and then excreted out as urine
Ch.44.4 The nephron is organized for stepwise processing of blood filtrate
Nephrons
weave back and forth across the renal cortex and the medulla
the functional units of the vertebrate kidney
roughly 1 million nephrons are in a human kidney, 85% are cortical nephrons
reach only a short distance into the medulla
15 % is made of juxtamedullary nephrons
extend deep into the medulla
essential for production of urine that is hyperosmotic to body fluids, a key adaptation for water conservation in mammals
Nephron Organization
each neprhon consists of a single long tubule as well as a ball capillaries called the glomerulus
the blind end of the tubule forms a cup-shaped swelling, called Bowman's capsule
surrounds the glomerulus
Three major regions of the nephron
Proximal Tubule
reabsorption in the proximal tubule is critical for the recapture of ions, water and valuable nutrients from the huge volume of intial filtrate
helps maintains a relatviely constant pH in body fluids
Loop of Henle
Descending Loop of Henle
further reduces filtrate volume via distinct stages of water and salt movement
numerous water channels formed by aquaporin proteins make the transport epithelium freely permeable to water
Ascending limb of the loop of Henle
filtrate returns to the cortex in the ascending limb
the epithelial membrane that faces the filtrate in this limb is permeable
in the thin segment, NaCl becomes highly concentrated in the descending limb, diffuses out of permeable tubule into the interstitial fluid
Distal Tubule
regulates the K+ and NaCl concentration of body fluids
involves variation in the amount of potassium ions secreted into the filtrate as well as the amount of sodium chloride
contributes to pH regulation by the controlled secretion of H+ and reabsorption of HCO3-
Collecting Duct
processes the filtrate into urine and carries to the rental pelvis
as filtrate passes along the transport epithelium of the collecting duct
hormonal control permeability and transport determines the extent to which the urine becomes concentrated
Concentrating Urine in the Mammalian Kidney
Countercurrent multiplier systems
expend energy to create concentration gradients
44.5 Hormonal circuits link kidney function, water balance, and blood pressure
Antidiuretic Hormone
Vasopressin
ADH molecules released from the posterior pituitary bind to and activate membrane receptors on the surface of collecting duct
hypothalamus
increase released of ADH from the posterior pituitary
the resulting increase in water re absorption in the collecting duct concentrations urine, reduces urine volume
The renin-angiotensin-Aldosterone System
regulates kidney function
responds to the drop in blood volume and pressure by increasing water and sodium and reabsorption
involves juxtaglomercular apparatus
a specialized tissue consisting of cells of and around the afferent arteriole, which supplies blood to the glomerulus
when blood pressure or volume drops in the afferent arteriole, the JGA releases the enzyme renin
renin initiates a sequence of steps that cleave a plasma protein called angiotensinogen , ultimately yielding a peptide called angiotensin II
Angiotensin ii triggers vasocontriction, increasing blood pressure and decreasing blood flow to capillaries in the kidney
stimulates the adrenal glands to release a horomone called aldosterone
Aldosterone causes the nephrons' distal tubules and collecting duct to reabsorb more Na+ and water which increases the blood volume and pressure
Coordinated Regulation of Salt and Water Balance
Atrial Natriuretic peptide
opposes the RAAS
the walls of the atria of the heart release ANP in response to an increase in blood volume and pressure
inhibits the release of renin from JGA, inhibits NaCl reabsorptions by the collecting ducts and reduces aldosterone release adrenal glands