9.3

Question 1

SAN

Answer 1

• Cells in SAN are more permeable to sodium ions entering the cells than potassium leaving cell.
• This depolarises cell.
• Build up of NA ions make cell reach action potential threshold.

Question 2

changing heart rate

Answer 2

• Cardiovascular centre in the medulla oblongata can affect heart rate.
• Stretch receptors in the muscles detect movement of limbs - impulse sent to cv center and heart rate increase.
• Chemoreceptors in caroited artery, aorta and brain detect decrease in pH of blood. - Increase production of CO2 impulse sent Cv heart rate increase.
• Impulses pass along sypathetic nervous system.
• Accelerans nerve connects SAN with CV centre.

Question 3

Exercise

Answer 3

• Blood pressure increases.
• Strech receptors in wall of corotid dected.
• Receptors send impulse to cv centre and this sends impule to SAN to reduce heart rate.
• Vagus nerve connects CVC with SAN.

Question 4

Adrenaline

Answer 4

• Binds to receptors in cardiac muscle.
• Increases permeability of cells to calcium ions.
• More rapid depolarisation.
• Action potential is reached more quickly - heart rate speeds up.

Question 5

baroreceptors

Answer 5

• Found in sinuses of carotid arteries.
• Blood vessels dialate in response to adrenaline released - blood pressure slightly falls.
• Reduces stretch on baroreceptors.
• CVC sends signals along sympathetic nerve to stimulate heart rate and increase blood pressure by vasoconstriction.
• Opposite occurs.
• Baroreceptors are stretched.
• Send nerve impulse to cardiac centre.
• Which sends impulses to parasympathetic system to slow down heart rate and cause widening of blood vessels.

Question 6

Chemoreceptors

Answer 6

• Walls of carotid arteries.
• When blood has higher CO2 conc. than Normal the pH is lowered.
• Chemoreceptors detect this and send impulses along sensory neurons to the CVC.
• Increases impulses traveling down sympathetic nerve to the heart.
• HR increases - increased blood flow to lungs - more CO2 removed - pH increases.
• Chemoreceptors reduce no. of impulses.
• Reduces impulses to sympathetic.
• Reduces acceleration of heart.
• FReturns to intrinsic rhythm.

Question 7

hormones

Answer 7

sympathetic nerve stiulates the adrenal medulla to release adrenaline

Question 8

osmoconformers

Answer 8

osmotic concentration of their surroundings

Question 9

osmoreulators

Answer 9

main the osmotic potential of their cells
kindeys and the liver

Question 10

liver

Answer 10

the liver cells deaminate excess amino acids
remove amino group and convert it to ammonia which is toxic
then converted to urea by a series of enzyme controlled reaction called the ornithine cycle
then filtered out the blood in the kidneys

Question 11

kindeys

Answer 11

control water potential of the blood
fine filter removing waste product as urine
-urea
-ions
-water
reabsorb
-glucose
-disolved ions
-some water

Question 12

gross structure of the kidney

Answer 12

sourounded by fibrous captule
outer region - cortex, darker
inner region - medulla, lighter
ureter - carrier urine
renal artery - supplies kidney with oxygenated blood
renal vein - returns blood to heart

Question 13

nephron structure

Answer 13

tiny microscopic tubes making up kidney
2 main types:
-cortical nephrons
found in renal cortex
have short loop of henle that just reaches medulla
-juxtamedullary nephrons
long loop of henle that penetrates through the medulla
good at producing concentrated urine

Question 14

nephron order

Answer 14

bowmans capsule -mass of blood capilaries
proximan convulated tubial - links bowmans capsule and loop of henle surrounded by blood capillary
loop of henle - extends into the medulla of the kidney
distal convulated tubial -between loop of henle and collecting duct
collecting duct - dct empties into it

Question 15

cardiac output

Answer 15

cardiac output = cardiac volume x heart rate

Question 16

ultrafiltration

Answer 16

• High blood pressure develops in the glomerula capillaries.
• Diameter of blood coming in is greater than blood leaving.
• High pressure squeezes blood out the capillary wall.
• Cells of bowmans capsule (podocytes) act as additional filter.
• These have extensions (pedicels) that wrap around capilaries forming slits so any cells, platlets or plasma proteins that have left capillary do not get through tubule.
• The filtrate that does get through contains:
  -urea
  -glucose
  -salt

Question 17

selective reabsorbiton

Answer 17

kidney tuble returns most of what has been removed
eg glucose

Question 18

proximal convoluted tubule

Answer 18

80% of filtrate is reabsorbed back into the blood in the proximal convoluted tubule
cells covered in microvilli which increase surface area
large no of mitochondria
reabsorbed by active transport
amount of reabsorbition always same

Question 19

loop of henle

Answer 19

in medulla of kidney
create water potential between filtrate and medullary tissue fluid
-water reabsorbed from dct and cd
has a countercurrent multiplier
-formed from flow of fluid in opposite directions in the adjacent limbs and diff permeabilities of sections to water
- a system that uses active transport to set up and maintain conc grads
-this allows the kidney to concentrate the urine in dpt and cd

Question 20

accending limb

Answer 20

• First section very perm. to Na+ and Cl- ions but not water.
• No active transport.
• Na + and Cl- move out of conc. fluid in loop into tissue fluid down conc. grad.
• Second thicker section is also imperm. to water but Na+ and Cl- are actively pumped out of tubule into tissue fluid.
• Tissues have very high Na+ and Cl- ion conc.
• Water pass out of descending limb by osmosis.
• But water cannot follow as ascending is impermeable.
• So becomes less conc.

Question 21

decending limb

Answer 21

• Freely perm. to water.
• Not to Na+ and Cl-.
• No active transport.
• Fluid entering is isotonic with blood.
• External conc. of Na+ and Cl- in tissue fluid is higher further down.
• Water moves out into tissue fluid by osmosis down conc. grad.
• Then into blood of vasa recta.
• By the time the fluid reaches hairpin bend at bottom of blood it is very conc. and hypertonic to arterial blood.

Question 22

distal convoluted tubial

Answer 22

permable to water
but varies with adh

Question 23

collecting duct

Answer 23

permability affected by adh
water moves out and down water potential gradient as passes through medulla (high conc of sodium and chloride ions) then urine becoming more concentrated

Question 24

osmoregulation

Answer 24

osmotic potential of the blood maintained
detected by osmoreceptors
balancing water and salts taken in and lost
controlled by anti diuretic hormone

Question 25

adh

Answer 25

produced in hypothalamus secreted into posterior lobe of pitutiary where stored increases permeability of the distal convulated tubule and collecting duct to water

Question 26

mechanism of adh

Answer 26

- Does not cross membrane as primary messenger. - Binds to specific receptors triggering reactions that result in the forming of cAMP as second messenger. - Sets up series of reactions casuing vesicles in cell lining the tubules to move to and fuse with cell membranes. - Water channels inserted into membrane. - Making it permable to water which moves through channels out of tubules and into blood capillaries by osmosis. - When adh levels fall cAMP fall and water channels withdrawn and packaged back in vesicles.

Question 27

high water potential

Answer 27

high water potential in the blood detected by the hypothalamus release of adh from pituitary is inhibited walls of collecting duct and dct remain impermeable to water no water reabsorbed into capillaries large volume of dilute urine produced

Question 28

low water potetial in blood

Answer 28

-low water potential in blood detected by hypothalamus -posterior pituitary releases more adh -adh travels in the blood to the kidney -it attaches to receptors on the collecting duct and dct making them more permeable to water -water leaves tubule by osmosis and moves into capilaries -small volume of conc urine is produced

Question 29

rise in blood pressure

Answer 29

detected by baroreceptors in arteries adh release is inhibited increased water loss in ruine blood volume decrease and blood presure falls

Question 30

fall in blood pressure

Answer 30

detected by baroreceptors in arteires adh realease is stimulated from pituatry water is reabsorbed into blood capilaries blood volume increase and raises blood pressure

Question 31

diabetes insipidus

Answer 31

produce large volumes of very dilute urine when people don't produce any/little ADH or the kidneys don't respond to it collecting ducts and dcts are permanently impermeable to water patients feel very thirsty and have to drink large amounts of water treaded with chemical that replaces adh

Question 32

kangaroo rats adaptations

Answer 32

dont drink water but produce small amounts of very concentrated urine -large proportion of juxtamedullary nephrons -long loops of henle (thin descending loop longer ) -higher number of unfolding in cell membranes (increased surface area for diffusion) -high numbers of mitochondria (densly arranged cristae for max respi providing more energy for active pumping of ions)

Question 33

endotherms

Answer 33

relies on own metabolic processes higher body temp conserve heat e.g mammals and birds can cope with high and low external temps metabolic rate has to be high 5x ecotherm of same mass need to eat more

Question 34

ecotherms

Answer 34

rely on external enviroment modifacations to take advantage of the enviroment e.g bask in sun areas to maximise absorbtion modify behavior to aid thermoregulation less food required

Question 35

warming of organisms

Answer 35

metabolism -waste energy conductions from surroundings convection from surroundings radiation from surroundings

Question 36

cooling of organisms

Answer 36

evaportation of water conduction to surroundings convection to surroundings radiation to surroundings

Question 37

cold environment -endotherms

Answer 37

reduce surface area to volume ratio - rate of cooling decrease thick layer of fat beneath skin insulation against cooling small extremities countercurrent exchange system -venous blood warmed hibernation