topic 6 (organims respond to change their environment)

Question 1

what are the problems of cells becoming specialised and what has to occur as a response?

Answer 1

they lose the ability to perform other functions and become dependent on other cells. So different functional systems must work coordinately

Question 2

what are the two main forms of coordination in animals?

Answer 2

the nerve system

the hormonal system

Question 3

describe how the hormone system works

Answer 3

the hormonal system- produces chemical hormones that are transported in the blood plasma to their target cell. The target cell has specific receptors on the cell surface membrane the change in hormone concentration stimulates them. this results in slower less specific forms of communication between parts of the body.The response is long lasting and widespread.

Question 4

describe how the nerve system works

Answer 4

the nerve system- uses nerve cells to pass electrical impulses through them. They stimulate target cells by secreting neurotransmitters. This results in rapid communication between parts of an organism. The response is short and specific to certain region in the body

Question 5

difference between hormonal system and neurone system

Answer 5

in HS communication is by hormones ,transmission is by blood and slow,hormones travel throughout body but only target cells respond, response is wide spread, response is slow and longlasting,effect may be permenant and irreversble
in NS communication is by nerve impulses,transmission is by neurones and quick,Nerve impulses travel to specific parts of the body, response is localised rapid and short lived,effect may be temporary and reversible

Question 6

describe the components of a mammalian motor neurone?

Answer 6

cell body- normal organelles large amount of rough endoplamic reticulum associated with protein production and neurotransmitters
dendrons- extensions from the cell body that subdivide into dendrites that carry nerve impulses to the cell body
axon- carries nerve impulses away from the cell body
Schwann cells- protects axon and acts as electrical insulation. Carry out phagocytosis and help nerve regeneration
myelin sheath- covers axon and is made up of the membranes of the schwann cell. Membranes are rich in lipid called myelin
nodes of ranvier-constrictions between adjacent schwann cells where there is myelin sheath

Question 7

describe how sensory neuron works?

Answer 7

Sensory neuron transmit nerve impulses from a receptor to an intermediate or motor neuron.They have one dendron that is long.this carries the impulse to the body cell and the axon sends it away from the body cell.

Question 8

describe how motor neuron works?

Answer 8

transmit neuron impulses from an immediate or relay neuron to an effector (gland,muscle).Motor neurons have a long axon and many short dendrites

Question 9

what are the 4 stages of an action potential?

Answer 9

resting potential
depolarisation
repolarisation
hyperpolarisation

Question 10

describe how intermediate/relay response works?

Answer 10

transmits impulses between neurones e.g sensory-moto neuron

Question 11

how are ions movement controlled in Axons

Answer 11

phospholipid bilayer prevents ions from moving in and out
Na/k pump actively transports Na+ out the axon and K+ into the axon
channel proteins which have gates allow for na+ and k+ to facillitate diffusion into and out the axon

Question 12

describe resting potential?

Answer 12

the axon is negatively charged -50/-90.
Na+ is actively transported out the axon by pump
k+ is actively transported into the axon by the pump
this happens in the ration 3Na+/2k+
this creates an electrochemical gradient
some of Na+ and k+ is facilitated diffusion back in and out
more k+ is diffused out
more k+ ion channels , more open k+ ion channels
It is polarised

Question 13

describe depolorisation?

Answer 13

energy of stimulus causes some Na voltage gated channels to open in the axon membrane.
Na+ Fac diffuses back into axon via electrochemical gradient.
As they are posistively charged they trigger a reversal of potential difference across membraene.
As more Na+ Fac diffuses in more na voltage gated channels open so even more Na+ fac diffuses in
this continues until max voltage of 40 mv

Question 14

describe depolarisation

Answer 14

once 40mv has been reached the na voltage gate channels shut and the k voltage gated channels open
k+ fac diffuses out axon through eleectrochemical gradient
opening more k voltage gated channels.
this repolarises the axon

Question 15

describe hyperpolarisation

Answer 15

the outward diffusion of k+ causes a temporary overshoot of the electrical gradient
this makes the inside of the axon more negative than usual
this is good as it allows the axon to not become overloaded and prevents immediate action potentials
the resting potential is re established via k/na pump

Question 16

what stimuli do plants respond to?

Answer 16

light
gravity
water

Question 17

what is a tropism?

Answer 17

a growth in response to a directional stimuli

Question 18

what hormones usually react to stimuli?

Answer 18

plant growth factor e.g IAA

Question 19

how does light affect root and shoots regarding IAA

Answer 19

IAA is produced in the tip of the shoot and travels down to the rest of the plant.It is evenly distributed.When light hits the shoot it causes them to move from light side to shade side.The high concentration of IAA on the shade side cause elongation faster than the other side hencce and the shoot to bend towards the light.
At the root IAA acts the opposite and inhibits elongation this causes the root to bend away from the light

Question 20

how does gravity affect the the shoot and root regarding IAA?

Answer 20

IAA is produced in the tip of the root. It spreads evenly throughout the root.
Due to gravity acting downwards it begins to gather on the lower side. As IAA inhibits growth at the root. The upper side goes through elongation while the lower side does not this produces a bend downwards to gravity.
In shoots the high concentration of IAA on the lower side causes cell elongation and hence the shoot grows againsy gravity

Question 21

aside from elongation what other affects does IAA have on plants

Answer 21

It causes the cell walls to have plasticity and stretch

Question 22

what is taxis? with example

Answer 22

a directional response to a stimulus. Either moving towards or away from it
e.g earthworms move away from light. Bacteria may mpve towards a high conc of glucose

Question 23

what are the different types of taxis?

Answer 23

geotaxis - response to gravity
phototaxis - response to light
chemotaxis- response to chemical

Question 24

what is kinesis?

Answer 24

A form of response where the organism does not move towards or away from the stimulus. Instead it increases speed or chages the rate at which changes directions.
E.g A woodlouse favours damp conditions If it ends up in a dry condition it will change directions various times in order to find damp conditions but not immediately find it. Once it arrives back at its favoured conditions it will stop moving at changing direction at a fast rate

Question 25

what is a stimulus?

Answer 25

A change in the enviroment internally or externally that can be detected and usually triggers a response

Question 26

what is a receptor and what do they lead to

Answer 26

chemical structures mostly proteins that respond to specific stimulus and can lead to generator response which can lead to a response

Question 27

what is the structure of a perciunun corpisal?

Answer 27

``` capsule on the outer layer layers of connective tissue with viscous gel inbetween neuron neuron ending capillary ```

Question 28

what is the paciniun corpuscle specific too?

Answer 28

mechanical pressure

Question 29

how does a pressurea at the porcinian corpusal prodruce a generator potential?

Answer 29

there are stretch mediates sodium channels. normally at resting potential na+ cannot go through them as they are too thin.However under pressure these widen and allow na+ to flood into the neurone. This influx of na+ changes the potential of the membrane producing a generator potential which in turn can produce an action potential

Question 30

what are the two types of photoreceptors?

Answer 30

rods and cones

Question 31

describe the features of rods?

Answer 31

cannot detect between the difference in wavelength and therefore can only be used to used to see in black and white Can detect very low intensities as many connected to a single bipolar cell As a certain potential has to be produced to cause a generator potential it is more likely to happen

Question 32

how is a generator potential produced in the rod?

Answer 32

the chemical rhodopsin is broken down their is enough energy for this to happen at low light intesities

Question 33

what is a consequence of many rods being attached to a single bipolar cell

Answer 33

as the rods share the same neuron it will only generate one potential no matter how many neurones are stimulated. This means that the brain cannot distinguish between the different source of lights and hence rods give low viscual activity

Question 34

Describe the features of cones?

Answer 34

attached to one bipolar cell and one neurone hence if two neurones are stimulate 2 impiulses are seen seen seperately however higher light intesities are required to get an action potential contain 3 pigments R,G,B allowing us to see in colour Iodopsin can only be broken down by high light intesities meaning only they produce a generator potential has high viscual activity

Question 35

where are cones and rods distributed in the eye?

Answer 35

cones focussed at the fovea as they have the highest light intesity rods distributed evenly can be found at the peripherals where light intesity is lowest

Question 36

what is the autonomic nervous system and its 2 divisions?

Answer 36

autonomic nervous system controls the internal muscles and glands subconsciously i sympathetic: stimulates effectors and speeds up any activity parasypathetic;inhibits effectors and slows down any activity they usually work against each other and are therefore antagonistic

Question 37

what does myogenic mean?

Answer 37

its contractions are initiated from the muscle itself

Question 38

What is SAN

Answer 38

the sinoatrial node based in the wall of the right atrium it has the initial stimulus where contraction occurs it has a basic rhythm of stimulation that determines the beat of the heart essentially it is the pacemaker

Question 39

what sequence of events control the basic heart rate?

Answer 39

a wave of electrical excitation spreads from the sinoatrial node across the atria causing them both to contract Atrioventricular septum stops it from crossing over to the ventricles the wave of excitation enters the atrioventricular node which is between atria after a short delay the atrioventricular node spreads this electrical node to the ventricles via the purkyne tissue (specialised muscle fibre) which is made of the bundle of his the bundle of his travels across the atrioventricular septum to the base of ventricles where the bundle branches into smaller fibres of purkyne the wave is released from the purkyne causing both the ventricles to contract quickly

Question 40

how is heart rate modified i.e increased/decreased?

Answer 40

it is controlled by the medulla obloganta which is connected to the Sinoatrial node via the sympathetic (increases heart rate) and parasympathetic nerve (decreases heart rate)

Question 41

how do chemoreceptors affect heart rate (in regards to CO2)?

Answer 41

high concentrations of CO2 produce acidic conc and hence lower pH the chemoreceptors detect this change and send more nerve impulses to the medulla obloganta that increase heart rate this in turn sends more nerve impulses to the sinoatrial node via the sympathetic nerve this increases the electric wave production at the SAN hence increasing heart rate this increases blood flow hence more co2 is removed the chemoreceptors detect the increase in pH and sends less nerve impulses to the medulla oblagante which in turn sends less impulses to the SAN reducing heart rate

Question 42

how due pressure receptors

Answer 42

pressure receptors in the cartoid arteries detect if the pressure is too low/high if high send less nervous impulse to medulla oblagante from here send impulse via parasympthateic nerve to san to reduce heart rate

Question 43

what are the 2 divisions of the nervous system?

Answer 43

CNS-central nervous system inclued spinal cord and brain | PNS-peripheral nervous system includes nerves originating from brain/spinal chord

Question 44

what can the peripheral nervous system be divided into?

Answer 44

motor neurone - carry electrical impulse from CNS to effectors sensory neurone - carry electrical impulses from receptors to CNS

Question 45

what are the 2 divisions of the motor neurone

Answer 45

volountary nervous system- happens under conscience control which carries impulses to body muscles autonomic nervous system- happens under subconscience control nerve impusles carried to smooth muscles,glands and cardiac muscles

Question 46

what is a reflex?

Answer 46

a rapid involountary response to a sensory stimulus

Question 47

what are the steps in a reflex arc?????

Answer 47

``` stimulus receptor sensory neurone coordinator motorn neurone effector receptor ```

Question 48

what is the importance of reflex arcs?

Answer 48

They allow for the brain to not be overflowed they are rapid as they only have to travel through a few neurones they do not have to be learned

Question 49

how does an action potential pass across mylineated axon?5

Answer 49

mylinated sheath stopping action potentials from forming.The only gaps is at the nodes of ranvier where the action potential can occur.This means that the action potential basically jumps from node to node in a process called saltatory conduction.This makes it quicker than the unmylineated axon

Question 50

how does action potential move across unmylineated axon?

Answer 50

Action potentials move along an unmyelinated axon by continuous propagation , in which the moving action potential affects one segment of the axon at a time. A local current depolarizes the next segment to threshold, and the cycle repeats, propagating the action potential along the axon in 1 direction only.

Question 51

what affects the speed at which action potential travels at?

Answer 51

myelin sheath temperature axon diamteter- the bigger the diamteter the faster it travels

Question 52

what is the all or nothing principle?

Answer 52

their is a threshold for an action potential to occur | if this not met an action potential will not occur and it will just reset

Question 53

how can organism percieve size of stimulus

Answer 53

different neurones have different threshold values | the number of impulses at a given time

Question 54

what is the refractory period?

Answer 54

the short period where sodium ion vaulted gates are blocked preventing sodium from diffusing from coming inside axon. therefore no further action potential can be produced

Question 55

how does transmission at synapse occur

Answer 55

pre synaptic membrane is depolarised by action potential this causes calcium channels to open and ca2+ to move into synaptic cleft by facillitated diffusion this triggers synaptic vesicles to move fuse with presynaptic membrane and release neurotransmitters neurotransmitters diffuse accross synaptic cleft neurotransmitters attach to receptors on post synpatic membrane Na+

Question 56

what is the purpose of the refractory period?

Answer 56

it ensures action potentials only move forward as action potential can be propogated at a reigon that is refractory It allows action potential to be seperate and not one after the other It limits the amount of action potentials and thus limits the strength of stimulus that can be detected

Question 57

what is the purpose of the refractory period?

Answer 57

it ensures action potentials only move forward as action potential can be propogated at a reigon that is refractory It allows action potential to be seperate and not one after the other It limits the amount of action potentials and thus limits the strength of stimulus that can be detected

Question 58

structure of the synapse?

Answer 58

synapses transmit information through chemicals (not impusles) via neurotransmitters neurones are seperated by synaptic cleft the neurone that releases the neurotransmitter is called the presynaptic neurone the axon of this neurone ends in a a synaptic knob neurotransmitter is stored in a vesicle once released it travels across to the postsnaptic neurone which has receptors on its membrane to recieve it

Question 59

what does a low voltage action potential often lead to? and what 2 things can be done to combat this?

Answer 59

not enough neurotransmitters released to the postsynaptic neurone to trigger a new action potential if this occurs their are 2 types of summation to ensure an actino potential is fired by the post synaptic neurone spatial summation-lots of presynaptic neurones release neurotransmitters at the same time to exceed the threshold value of the post synaptic neurone which can trigger a new action potential temporal summation- a single presynaptic neurone releases lots of neurotransmitters in a fixed period of time eventually reaching the threshold value for the action potential

Question 60

how do inhibitory synapses work?.

Answer 60

the presynaptic neurone releases a type of neutotransmitter that binds to chloride ions protein channels on the postsynaptic neurone this causes the chloride protein channel to open and Cl- move into the po the binding of the neurotransmitter causes k+ channels to open k+ leaves and cl- enters the post synaptic neurone this causes it to become more negative e.g -80mv when it is usually -65mv this is called hyperpolerisation and makes an action potential less likely to occur unless their is a large influx of sodium ions

Question 61

what is a cholinergic synapse?

Answer 61

where the neurotransmitters are made up of acetylcholine | they are present in vertebrates where they occur at the cns and juctions between nerves and muscles

Question 62

what are the three types of muscles and their differences?

Answer 62

smooth moved involountarily is on the blood vessel walls cardiac moved involountarily surrounding hear skeletal (moved volountarily under conscience)

Question 63

what is myofibril?

Answer 63

small muscle fibres which can be combined together to form muscles

Question 64

what is myobrils made up of ?

Answer 64

2 protein filaments actin - thinner 2 stranded twist wrapped around each other myosin - thicker made of long rod shaped tails with bulbous heads

Question 65

why do myofibrils seem striped?

Answer 65

they contain 2 lines I line this is light as the myosin and actin do not overlap A line this is darker as the myosin and actin do overlap at the centre of each a line is the h zone the a line is cut in half by the I line which is lighter the distance between 2 z lines is known as a sacromere

Question 66

describe the features of slow twitch fibres and the adaptations they have?

Answer 66

do not have as powerful contractions but can contract for long better suited for endurance and are found in muscles such as the calf muscle they are adapted for aerobic respiration by: a large store of myoglobin a rich blood supply to vessels lots of mitochondira to produce ATP

Question 67

ddescribe fast twitch fibres and the adaptations they have

Answer 67

contract faster and stronger for a short amount of time used in intense sports such as weight lifting they are common in biceps its adaptations are: thicker and more myosin filaments high concentration of glycogen a high conc of enzymes used in anaerobic respiration to produce atp a high store of phosphocreatine which can convert ADP to ATP IN anaerobic conditions

Question 68

what are neuromuscular junctions?z

Answer 68

where a skeletal muscle fibre joins a motor neurone it is the end of the action potential acetylcholine binds wih receptors on muscle fibre

Question 69

what are 3 stages of sliding filament theory?

Answer 69

stimualtion contraction r relaxation

Question 70

describing stimulation in sliding filament theory

Answer 70

stimulation action potetnail reaches neuromuscular junctions causing ca2+ channels to open and ions to move into the synaptic knob this caues vesicles to bind with presynaptic membrane releasing acetylcholine into the cleft the acetylcholine can then diffuse across to the muscle fibre binding with its receptors depolarisiing it

Question 71

describe contraction in filament thory

Answer 71

action potential from sarcoplasmic reticulum which actively transport Ca2+ Ca2+ causes tropomyosin to stop blocking binding sides on the actin myosin head attaches to actin form cross bridge at a specific angle causing tension the myosin head changes angles releasing ADP + Pi New ATP attaches to each myosin head changing shape of head so it is no longer complementary to actin ca2+activate atpase which hydrolyse atp to adp providing the energy for the myosin head to get back into position the myosin with the ADP reattaches further along the actin cauing the cyle to continue as myosin is joined tail tail facing away from each other the movement of myosin also causes the movement of actin this causes the shortening of the adjacent z lines and hence contraction

Question 72

describe relaxation in filament theory?

Answer 72

when stimulation stops the ca2+ are actively transported back into the endoplasmic reticulum using atp the reabsorption of ca2+ allow tropomyosin to move back into place blocking myosin from attaching to actin this stops contraction

Question 73

what is homeostasis?

Answer 73

maintenance of constant internal environment

Question 74

what is control mechanism?

Answer 74

stages that allow for homeostasis optimum point - the point where system works the best receptor - detects any deviation from the optimum point coordinator - coordinates information from receptors and carries it on effector - muscle or gland which allows system to get back to original point feedback mechanisms - receptors respond to change by effector

Question 75

what is positive/negative feedback?

Answer 75

negative feedback- when the receptors detect that the conditions are back to its optimum after a change from the effector hence turning of the control mechanism positive feedback- when the receptors detect that conditions deviated from the optimum and the effectors increase the deviation

Question 76

why is their several negative feedback mechanisms?

Answer 76

to regulate departure from the norm in several directions

Question 77

how do hormones travel ?

Answer 77

produced in the gland travel in blood plasma to target cell which have specific receptors on their cell surface membrane which are complementary

Question 78

how is the second messenger model used by adrenaline?

Answer 78

adrenaline binds to transmembrane protein recepetors in cell surface membrane of liver cell this causes the protein to change shape in inside of membrane this change leads to activation of enzyme adenyl cyclase which converts atp to cyclase amp this acts as the second messenger that binds to protein kinase enzyme changing its shape and activating it kinase catalyses the reaction of glycogen to glucose which moves out of the liver cell by faciliated diffusioninto the blood by channel proteins

Question 79

what are three things that affect blood glucose level?

Answer 79

diet- e.g absorbed from hydrolysis of lactose,maltose,sucrose glycogenlysis glucogenesis

Question 80

what role does the pancreas play in blood glucose

Answer 80

has the islets of langerhans this has alpha cells which produce glucagone has beta cells that produce insulin

Question 81

what are the three process in liver which regulate blood sugar

Answer 81

glycogenisis - when glucose level is too high the liver takes it and converts it into glycogen glycogenolysis - when glucose level is too low liver breaks down glycogen to form glucose gluconeogenesis - production of glucose from other sources other than carbohydrates. (when supply of glycogen is finished)

Question 82

how does insulin affect body cells

Answer 82

beta cells in islets of langerhans receptors detect the stimulus of rise in blood glucose and release into blood plasma. all body cells apart from red blood cells have glycoprotein receptors when they combine : it changes tertiary structure of glucose transport carrier proteins causing them to open and allow more glucose to enter the cell by fac diffusion increase in the number of glucose transport channels activation of enzymes that convert glucose to glycogen and fat

Question 83

how does insulins production reduced glucose blood concentration

Answer 83

increase the rate of absorption into cells increases breakdown from glucose to glycogen increases break down from glucose to fat increases the respiratory rate of cells therefore using more glucose increasing its uptake

Question 84

how does glucagon affect blood concetration

Answer 84

islet of langerhan detect reduced blood glucose level Alpha cells secrete glucagon into blood plasma these attach to specific protein receptors on cell surface membrane of liver activate enzymes that convert glycogen into glucose activate enzymes that convert amino acids and glycerol into glucose gluconeonesis

Question 85

what are the 2 types of diabetes?

Answer 85

type 1: body does not produce insulin due to autoimmune response where body attacks islets of langerhan beta cells type 2: lack of response to insulin due to glycoprotiens receptors on cells losing response. Also can be due to an insufficient supply of insluin from the pancreas

Question 86

~ | how is type 1 and type 2 diabetes treated?

Answer 86

type 1 :insulin injenctions (cannot be taken orally as it is a protein that will be digested).Right dose has to be calculated to prevent glucose conc from becoming to small type 2:regular intake of carbohydrates and regular exercise

Question 87

what is the homeostatic control of water potential called and what does it involve?

Answer 87

osmoreguation and it involves the kidney

Question 88

describe the structure of the kidney?

Answer 88

fibrous capsule- outer membrane protects the kidney cortex - made up of renal capsule medulla -made of loops of henle renal pelvis - collects urine into ureter ureter - carries urine to bladder renal artery supplies the kidney with blood from the aorta renal vein- returns blood to the heart via vena cava

Question 89

describe structure of nephron?

Answer 89

Renal (Bowmans) capsule - start of nephron surrounds blood capillaries(known as glomerulus) inner layer is made of podocytes proximal convoluted tubule-loops surrounded by blood capillaries walls are made of epithilial cells loop of henle - loop extends from cortex to medulla distal convoluted tubule loops surrounded by blood capillaries walls made of epithilial cells collecting duct- number of distal convoluted tubes from a number of nephrons empty

Question 90

what is associated with each nephron

Answer 90

afferent arteriole - tiny vessel comes from renal artetery supplues nephron with blood glomerulus- many branched knots of capillaries where blood fluid is forced out to efferent arteriole- tiny vessel carries blood away from renal capsule smaller diamter so higher pressure

Question 91

what are the steps of osmoregulation

Answer 91

formation of glomerular filtrate by ultrafiltration reabsorption of glucose and water by proximal convoluted tubule maintenence of gradient Na+ in the medulla by loop of henle reabsorption of water by distal conoluted tubule and ducts

Question 92

describe the formation of glomerular filtrate by ultafiltration?

Answer 92

blood enters kidney through afferent arteriole. this leads on to the glomerulus (small capillaries ). This then leads on to the efferent arteriole. The afferent arteriole has a smaller diameter than the efferent arteriole. This leads to a build up hydrostatic pressure within the glomerulus causing water, glucose and mineral ions to be forced out forming the glomerular filtrate.Blood cells and proteins are too large and therefore do not move out

Question 93

how is water and glucose reabsorbed by the proximal convoluted tubule?

Answer 93

Na+ actively transported out the cell lining the proximal convoluted tubule lowering the conc Na+ can then diffuse down a conc gradient from lumen of proximal convoluted tubule into lining of proximal convuluted tubule cells through carrier proteins which bring glucose aswell (cotransport ) glucose can then diffuse from proximal convuluted tubule into blood stream ALL GLUCOSE IS REABSORBED

Question 94

adaptatations of proximal convolute tubule

Answer 94

microvillii large SA for reabsorption from filtrate infoldings at base for large SA to transfer reabsorbed substance into blood capillaries lots of mitochondira for ATP productoin

Question 95

what are the reigons of the loop of henlethe loop of henle?

Answer 95

descending limb, narrow thin walls that are highly permeable to water ascending limb wider ans thicker walls that are impermeable to water

Question 96

how is the gradient of sodium ions maintained by the loop of henle?

Answer 96

loop of henle extends into medulla of kidney and ensures water is reabsorbed from collecting duct,concentrating urine so it has a lower potential than the water Na+ actively transported out of ascending limb of the loop of henle using ATP this creates a low water potential in interstitial reigon the walls in descending limb are permeable and allow water to move out of filtrate into intersatital space by osmosis. the water enters blood capillaries in the area and is travelled away the filtrate continues to lose water as it moves down the descending limb lowering its water potential at the base of ascending limb Na+ diffuse out the filtrate as it moves up Na+ is pumped out his increases water potential In the intersatial space between the ascending limb and collecting duct there is a gradient of water potential with the highest water potential at the cortex and increasingly lower further down the medulla the collecting duct is permeable so the filtrate moves down it and water moves out into blood vessels this causes the filtrate to be lower in water potential aswell as the intersatial space meaning water can move out across the whole duct

Question 97

how is their osmoisis throughout the whole collecting duct?

Answer 97

their is a counter current flow the filtrate in the collecting duct has a low water potential and interstitial fluid has even lower water potential this allows for a concentration gradient through out the whole collecting duct

Question 98

how does the body respond to low water potential in blood

Answer 98

osmoreceptors in hypothalamus detect change water is lost from these osmoreceptors cells by osmosis making them shrink which causes them to produce antiduiretic hormone (ADH) ADH passes into pituarity gland where where it is secreted into capillaries it reaches kidneys where it increases permeablility of water of cell surface membrane of collecting duct and distal convoluted tubule specific protein receptors on the membrane of these cells bind to ADH activating phosphorylase this causes the vesicles within the cell to move to and fuse with its cell membrane these veiscles contain aquaporins (water channel proteins) increasing the permeability of cell surface membranes ADH increases permeability of collecting duct to urea further deccreasing water potential the water that leaves travels down a conc gradient and is reabsorbed the osmoreceptors detect the increase and send fewer impulses to pituitary gland

Question 99

how does body react to increase in water potential ?

Answer 99

osmoreceptors detect change hypothalamus send less ADH less permeable cell surface membrane at collecting duct & distal convoluted tubules less water is reabsorbed and hence more diulute urine is produced water potential is decreased osmoreceptors detct and produce more ADH