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Biology > 9.3 > Flashcards

9.3 Flashcards

1
Q

define homeostasis

A

the maintenance of a state of dynamic equilibrium through response of the body to internal and external stimuli

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2
Q

state the main homeostatic systems

A

control of heart rate
maintenance of pH
osmoregulation
thermoregulation

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3
Q

what is the equation for cardiac output

A

cardiac volume(dm^3) x heat rate (beats per min)

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4
Q

what is the average heart beat per minute and volume of blood per minute

A

70 times
4-6dm^3

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5
Q

how are fit people adapted to be good at exercise

A

they have a slower resting heartbeat and heart rate begins to increase when anticipating exercise

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6
Q

where is the cardiac control centre

A

medulla oblongata

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7
Q

where are baroreceptors found

A

sinuses in the carotid arteries and on the aorta

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8
Q

what are baroreceptors

A

mechanoreceptors that are sensitive to pressure changes

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9
Q

what are chemoreceptors

A

sensory nerve cells which respond to changes in CO2 levels in the blood

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10
Q

how do nerve impulses travelling down the sympathetic nerve from the cardiac center increase heartrate

A

release noradrenaline which stimulates the SAN which increases the frequency of signals from the pacemaker so the heart beats more quickly and the sympathetic nerve which passes into the ventricles increase the force of contraction

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11
Q

how do nerve impulses travelling down the parasympathetic nerve from the cardiac center decrease heartrate

A

release acetylcholine which inhibits SAN therefor slows down heart rate

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12
Q

what do baroreceptors do at rest

A

send a steady stream of signals back through sensory neurons to the cardiac center

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13
Q

what happens when exercise starts (involving baroreceptors)

A

blood vessels dilate (vasodilation) in response to adrenaline and blood pressure falls which reduces the stretch on the baroreceptors which reduces the stimulation from the baroreceptors to the cardiac control center which as a result sends signals along the sympathetic nerve to stimulate heart rate and increase blood pressure by vasoconstriction

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14
Q

how are baroreceptors involved in lowering blood pressure after exercise

A

when exercise stops blood pressure continues to increase so baroreceptors are stretched so send more impulses to the cardiac center which then sends impulses through the parasympathetic system to slow down heart rate and widen blood vessels in order to lower bloop pressure

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15
Q

where are chemoreceptors found

A

walls of aorta and carotid arteries

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16
Q

what happens when CO2 levels in the blood increase (involving chemoreceptors)

A

blood pH decreases and is detected by chemoreceptors
send impulses to cardiac center which increases impulses down the sympathetic nerve which increases heart rate, increasing blood flow to the lungs so more CO2 is removed

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17
Q

what happens when CO2 levels in the blood decrease (involving chemoreceptors)

A

blood pH rises and is detected by chemoreceptors which respond by reducing the number of impulses to the cardiac center which then reduces the number of impulses in the sympathetic nerve so heart rate returns to its intrinsic rhythm

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18
Q

where is adrenaline release from

A

adrenal medulla

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19
Q

what does adrenaline do

A

binds to receptors on target organs and SAN to increase frequency of excitation to increase heart rate
stimulates cardiac center to increase impulses to sympathetic neurons to increase heart rate

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20
Q

why is adrenaline needed to increase heart rate

A

to supply you with extra oxygen and glucose for the muscles and brain in case you need to fight or flight

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21
Q

define osmoregulation

A

the maintenance of a constant osmotic potential in the tissues of a living organism by controlling water and salt concentrations

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22
Q

what is deamination

A

the removal of the amino group from excess amino acids in the ornithine cycle in the liver which is then converted to ammonia then urea which can be excreted at the kidneys

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23
Q

what is the ornithine cycle

A

series of enzyme controlled reactions that convert ammonia from excess amino acids to urea in the liver

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24
Q

what are the main organs involved in osmoregulation

A

kidney and liver

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25
Q

where does deamination occur

A

the liver

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26
Q

what cells are involved in deamination

A

hepatocytes

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27
Q

summarise the ornithine cycle

A

ammonia, water and CO2 in
water and urea out

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28
Q

describe the kidneys

A

pair of dark reddish brown organs attached to the back of the abdominal cavity surrounded by a thick layer of fat involved in controlling the water potential of the blood that passes through them, removing substances that would affect the water balance

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29
Q

why are the kidneys surrounded by a thick layer of fat

A

to protect them from mechanical damage

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30
Q

what is the renal vein

A

carries blood away from the kidney after the removal of excess solutes and water

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31
Q

what is the renal artery

A

carries blood to the kidney

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32
Q

what is the ureter

A

carries urine from the kidney to the bladder

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33
Q

what is the urinary bladder

A

stores urine before micturition

34
Q

what is the cortex of the kidney

A

rich capillary network making it a dark red colour containing Malpighian bodies of all the nephrons

35
Q

what is the renal medulla

A

contains the loop of Henle from the nephrons

36
Q

what is the pelvis of the kidney

A

the central chamber where urine arrives from the collecting duct

37
Q

what is the juxtamedullary nephron

A

the long loop penetrates right through the medulla

38
Q

what is the pyramid in kidneys

A

a collection of tubules, collecting ducts and blood vessels

39
Q

what is the cortical nephron

A

loop which only just enters the medulla

40
Q

what are the two main roles of the kidney

A

excretion (removal of urea)
osmoregulation

41
Q

what is ultrafiltration

A

the process by which fluid is forced out of the capillaries in the glomerulus of the kidney into the kidney tubule through the epithelial walls of the capillary and the capsule

42
Q

what is selective reabsorption

A

the process by which substances needed by the body are reabsorbed from the kidney tubules into the blood

43
Q

what is tubular secretion

A

the process by which inorganic ions are secreted into or out of the kidney tubules as needed to maintain the osmotic balance of the blood

44
Q

what are nephrons

A

microscopic tubules that make up most of the structure of the kidney

45
Q

where are the cortical nephrons found

A

mainly in the renal cortex but they have a short loop of Henle which only just reaches into the medulla

46
Q

where are juxtamedullary nephrons found

A

they have a long loop of Henle that penetrates right through the medulla

47
Q

what is formed in ultrafiltration

A

tissue fluid

48
Q

what do the bowmans capsule and glomerulus make up

A

Malpighian body

49
Q

what material cannot pass through the pores in the glomerulus capillaries

A

blood cells and large plasma proteins

50
Q

what is the bowmans capsule made up of and how are they adapted to their function

A

podocytes
they have extensions called pedicels that wrap around the capillaries forming slits that ensure any cells, platelets or large plasma proteins that have left the capillary do not get into the tubule

51
Q

how does ultrafiltration work

A

high bp in the glomerulus capillaries because the diameter of the blood vessels coming into the glomerulus are larger than the blood vessels leaving
this high pressure squeezes blood out through pores in the capillary wall
bowmans capsule contains pedicels that ensure any cells, platelets or large plasma proteins do not enter the tubules
filtrate then enters the capsule containing the same concentration of substances as the blood plasma

52
Q

does ultrafiltration require energy

A

no

53
Q

what is removed from the blood in ultrafiltration

A

urea, water, glucose, salt, other substances

54
Q

what is the proximal convoluted tubule

A

the first region of the nephron after the Bowmans capsule where over 80% of the glomerular filtrate is absorbed back into the blood

55
Q

what adaptations does the proximal convoluted tubule have

A

covered in microvilli to increase surface area for reabsorption
lots of mitochondria for active transport of substances out of the nephron back into the blood

56
Q

what is moved out of the nephron in selective reabsorption

A

glucose, vitamins, hormones, 85% of water and NaCl

57
Q

how does selective reabsorption work

A

glucose, vitamins and 85% of Na+ are moved out of the tubule by active transport
water and Cl- moves out of the tubule passively into the intracellular spaces which then pass by diffusion into the extensive capillary network
the blood is constantly moving which maintains the concentration gradient
an isotonic solution with the tissue fluid is made in the tubule when it reaches the loop of henle

58
Q

what is a countercurrent multiplier

A

a system that produces a concentration gradient in a living organism using energy from cellular respiration

59
Q

what is the permeability of the descending limb

A

freely permeable to water but not permeable to sodium and chlorine

60
Q

does active transport occur in the descending limb

A

no

61
Q

what happens in the descending limb

A

water moves out of the descending limb via osmosis and into the blood because there is a low osmotic potential in the medulla as theres a high concentration of Na+ and Cl- ions when it reaches the hairpin the loop is very concentrated and hypertonic to the arterial blood

62
Q

what is the permeability of the first section of the ascending limb

A

very permeable to Na+ and Cl-
not permeable to water

63
Q

what happens in the ascending limb

A

first thin ascending limb, Na+ and Cl- move out of the tissue fluid into the medulla down the concentration gradient
second thicker ascending limb Na+ and Cl- are actively pumped out giving a high concentration of Na+ and Cl- in the medulla for the descending limb
water cannot move out of the ascending limb so fluid becomes less concentrated

64
Q

what affects permeability of the distal convoluted tubule

A

ADH

65
Q

what is the distal convoluted tubule

A

the section of the nephron after the loop of henle that leads into the collecting duct where balancing water needs of the body takes place

66
Q

what is ADH

A

hormone produced in the hypothalamus stored in the posterior pituitary which increases permeability of the distal convoluted tubule and the collecting duct to water

67
Q

what happens in the distal convoluted tubule if theres not enough salt in the body

A

sodium is actively transported out of the tubule and chlorine ions follow
water also moves out by osmosis if walls are permeable to water

68
Q

what is the collecting duct

A

takes urine from the distal convoluted tubule to be collected in the pelvis of the kidney, the region of the kidney where most water balancing needed for osmoregulation occurs

69
Q

how do kangaroo rats survive without drinking water

A

they produce water by oxidative reactions in their cells

70
Q

how are desert animals adapted to reduce water lost in urine

A

large proportion of juxtamedullary nephrons
long loops of henle - long thin descending loop so more water is reabsorbed into the blood
more infoldings in the cell membranes of epithelial cells lining the tubules which increases surface area for a steeper concentration gradient to increase water reabsorbed
lots of mitochondria with densely arranged cristae to maximise cellular respiration for active transport of ions in or out of tubules

71
Q

how does ADH work

A

binds to receptors on the membrane of tubule cells triggering reactions to form cAMP that acts as a second messenger to cause vesicles (containing water channels) within the cell lining to be inserted into the membrane making it permeable to water

72
Q

what happens to the water channels when ADH levels decrease

A

levels of cAMP fall and water channels are withdrawn from the membrane and repackaged in vesicles making it impermeable to water

73
Q

what could cause the blood to become more concentrated (decrease in water potential)

A

water shortage, sweating, salty food

74
Q

what could cause blood to become less concentrated (increase water potential)

A

water loading

75
Q

what happens when the blood becomes more concentrated (decrease in water potential)

A

detected by osmoreceptors in the hypothalamus
more ADH released from posterior pituitary
second convoluted tubule and collecting duct become more permeable to water
water potential restored back to normal

76
Q

what happens when the blood becomes less concentrated (increase in water potential)

A

detected by osmoreceptors in the hypothalamus
less ADH released from posterior pituitary
second convoluted tubule and collecting duct become less permeable to water
water potential restored to normal

77
Q

what type of feedback system does ADH have

A

negative feedback loop

78
Q

what are osmoreceptors

A

sensory receptors in the hypothalamus that detect a change in the concentration of inorganic ions and therefor changes in osmotic potential of the blood

79
Q

how does an increase in blood pressure affect the release of ADH

A

increase in blood pressure detected by baroreceptors in aortic and carotid arteries
resulting in less ADH being released from the posterior pituitary therefor second convoluted tubule and collecting duct are less permeable to water so increased volume of water lost in urine to reduce blood volume and pressure

80
Q
A

Biology (33 decks)

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