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topic 6 (organims respond to change their environment) Flashcards

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1
Q

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

A

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

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2
Q

what are the two main forms of coordination in animals?

A

the nerve system

the hormonal system

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3
Q

describe how the hormone system works

A

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.

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4
Q

describe how the nerve system works

A

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

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5
Q

difference between hormonal system and neurone system

A

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

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6
Q

describe the components of a mammalian motor neurone?

A

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

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7
Q

describe how sensory neuron works?

A

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.

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8
Q

describe how motor neuron works?

A

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

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9
Q

what are the 4 stages of an action potential?

A

resting potential
depolarisation
repolarisation
hyperpolarisation

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10
Q

describe how intermediate/relay response works?

A

transmits impulses between neurones e.g sensory-moto neuron

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11
Q

how are ions movement controlled in Axons

A

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

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12
Q

describe resting potential?

A

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

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13
Q

describe depolorisation?

A

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

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14
Q

describe depolarisation

A

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

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15
Q

describe hyperpolarisation

A

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

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16
Q

what stimuli do plants respond to?

A

light
gravity
water

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17
Q

what is a tropism?

A

a growth in response to a directional stimuli

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18
Q

what hormones usually react to stimuli?

A

plant growth factor e.g IAA

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19
Q

how does light affect root and shoots regarding IAA

A

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

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20
Q

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

A

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

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21
Q

aside from elongation what other affects does IAA have on plants

A

It causes the cell walls to have plasticity and stretch

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22
Q

what is taxis? with example

A

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

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23
Q

what are the different types of taxis?

A

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

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24
Q

what is kinesis?

A

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

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25
Q

what is a stimulus?

A

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

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26
Q

what is a receptor and what do they lead to

A

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

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27
Q

what is the structure of a perciunun corpisal?

A 
capsule on the outer layer
layers of connective tissue with viscous gel inbetween
neuron
neuron ending
capillary
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28
Q

what is the paciniun corpuscle specific too?

A

mechanical pressure

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29
Q

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

A

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

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30
Q

what are the two types of photoreceptors?

A

rods and cones

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31
Q

describe the features of rods?

A

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

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32
Q

how is a generator potential produced in the rod?

A

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

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33
Q

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

A

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

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34
Q

Describe the features of cones?

A

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

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35
Q

where are cones and rods distributed in the eye?

A

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

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36
Q

what is the autonomic nervous system and its 2 divisions?

A

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

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37
Q

what does myogenic mean?

A

its contractions are initiated from the muscle itself

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38
Q

What is SAN

A

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

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39
Q

what sequence of events control the basic heart rate?

A

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

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40
Q

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

A

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)

41
Q

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

A

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

42
Q

how due pressure receptors

A

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

43
Q

what are the 2 divisions of the nervous system?

A

CNS-central nervous system inclued spinal cord and brain

PNS-peripheral nervous system includes nerves originating from brain/spinal chord

44
Q

what can the peripheral nervous system be divided into?

A

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

45
Q

what are the 2 divisions of the motor neurone

A

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

46
Q

what is a reflex?

A

a rapid involountary response to a sensory stimulus

47
Q

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

A 
stimulus
receptor
sensory neurone
coordinator
motorn neurone
effector
receptor
48
Q

what is the importance of reflex arcs?

A

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

49
Q

how does an action potential pass across mylineated axon?5

A

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

50
Q

how does action potential move across unmylineated axon?

A

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.

51
Q

what affects the speed at which action potential travels at?

A

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

52
Q

what is the all or nothing principle?

A

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

53
Q

how can organism percieve size of stimulus

A

different neurones have different threshold values

the number of impulses at a given time

54
Q

what is the refractory period?

A

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

55
Q

how does transmission at synapse occur

A

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+

56
Q

what is the purpose of the refractory period?

A

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

57
Q

what is the purpose of the refractory period?

A

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

58
Q

structure of the synapse?

A

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

59
Q

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

A

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

60
Q

how do inhibitory synapses work?.

A

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

61
Q

what is a cholinergic synapse?

A

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

62
Q

what are the three types of muscles and their differences?

A

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

63
Q

what is myofibril?

A

small muscle fibres which can be combined together to form muscles

64
Q

what is myobrils made up of ?

A

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

65
Q

why do myofibrils seem striped?

A

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

66
Q

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

A

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

67
Q

ddescribe fast twitch fibres and the adaptations they have

A

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

68
Q

what are neuromuscular junctions?z

A

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

69
Q

what are 3 stages of sliding filament theory?

A

stimualtion
contraction r
relaxation

70
Q

describing stimulation in sliding filament theory

A

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

71
Q

describe contraction in filament thory

A

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

72
Q

describe relaxation in filament theory?

A

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

73
Q

what is homeostasis?

A

maintenance of constant internal environment

74
Q

what is control mechanism?

A

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

75
Q

what is positive/negative feedback?

A

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

76
Q

why is their several negative feedback mechanisms?

A

to regulate departure from the norm in several directions

77
Q

how do hormones travel ?

A

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

78
Q

how is the second messenger model used by adrenaline?

A

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

79
Q

what are three things that affect blood glucose level?

A

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

80
Q

what role does the pancreas play in blood glucose

A

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

81
Q

what are the three process in liver which regulate blood sugar

A

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)

82
Q

how does insulin affect body cells

A

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

83
Q

how does insulins production reduced glucose blood concentration

A

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

84
Q

how does glucagon affect blood concetration

A

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

85
Q

what are the 2 types of diabetes?

A

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

86
Q

~

how is type 1 and type 2 diabetes treated?

A

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

87
Q

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

A

osmoreguation and it involves the kidney

88
Q

describe the structure of the kidney?

A

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

89
Q

describe structure of nephron?

A

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

90
Q

what is associated with each nephron

A

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

91
Q

what are the steps of osmoregulation

A

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

92
Q

describe the formation of glomerular filtrate by ultafiltration?

A

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

93
Q

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

A

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

94
Q

adaptatations of proximal convolute tubule

A

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

95
Q

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

A

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

96
Q

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

A

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

97
Q

how is their osmoisis throughout the whole collecting duct?

A

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

98
Q

how does the body respond to low water potential in blood

A

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

99
Q

how does body react to increase in water potential ?

A

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

Biology (9 decks)

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