homeostasis

Question 1

Describe what is meant by negative feedback.

Answer 1

where a change triggers a response which reduces the effect of a change;

Question 2

Water is removed from the body via the kidneys. Give two other ways in which
water is removed from the body.

Answer 2

1. sweating
2. breathing

Question 3

explain how ADH increases the movement of
water from the lumen of the collecting duct into the blood.

Answer 3

• ADH binds to collecting ducts
  stimulates vesicles containing aqua porins and phospholipids to bind to collecting duct
• water enters aquaporins by osmosis down water potential gradient
  -and is reabsorbed into the capillaries.

Question 4

what symptoms would be experienced with no ADH

Answer 4

thirst

Question 5

Synapses are unidirectional. Explain how acetylcholine contributes to a synapse
being unidirectional.

Answer 5

vesicles containing acetylcholine are only found in presynaptic membrane so can only be released form presynaptic membrane
receptors only found on post synaptic membrane

Question 6

Describe the evidence from the graph that curve A represents the volume of
gastric juice produced by nervous stimulation.

Answer 6

-rapid
- sort duration

Question 7

Explain
how a decrease in the availability of calcium ions could disrupt the contraction
mechanism in muscles.

Answer 7

• tropomsyin doesnt move so binding site on actin filament is not exposed
  myosin head cant bind to binding site on actin
  ATPase does not activated so ATP and ADP and Pi cannot form power stroke
  -

Question 8

why is the ATPase essential in muscle contraction

Answer 8

hydrolysis ATP into ADP +Pi for power stroke when myosin head binds to binding site on actin filament