exam Q's

Question 1

fill the gap
Reflexes are very fast as they only involve one or two …………………………. , which are the slowest parts of nerve
transmission. This is one reason why reflexes give a survival advantage.

Answer 1

synapses

Question 2

Aldosterone and ADH are hormones that act on the kidney.
Aldosterone causes sodium ions to be pumped from the collecting duct cells into tissue fluid.
Describe how the endocrine and nervous systems work together to increase water reabsorption from the
collecting duct.

Answer 2

Endocrine system
* hypothalamus causes release of ADH from
pituitary aldosterone released from adrenal
cortex
* ADH released from pituitary gland
* ADH binds to receptors on the cell
membranes of collecting duct cells …
* … and this increases permeability to water
(regulated by aquaporins)

Nervous system:
* hypothalamus is part of nervous system
* osmoreceptors in the hypothalamus …
* … detect a low water potential in the blood
* ADH is produced in the hypothalamus
* posterior pituitary is extension of
hypothalamus

Aldosterone:
* sodium ions pumped out of collecting duct
cells (into tissue fluid) (and potassium ions
pumped in)
* lowers water potential in tissue fluid
* concentration gradient established
* sodium ions reabsorbed from the collecting
duct lumen
* water diffuses into collecting duct cells / out
of lumen via osmosis.

Question 3

Explain why glucose is required for the contraction of skeletal muscle

Answer 3

(glucose) for respiration /
as respiratory substrate /
to release energy ✓
to produce ATP ✓
ATP needed (in muscle
contraction) for breaking
cross-bridges between
myosin and actin / AW ✓
ATP , hydrolysed / to ADP
and Pi , to reset myosin
heads ✓
ATP for active transport of
calcium ions (back) into
sarcoplasmic reticulum ✓