Top answers

How do muscle fibres contract?

Contraction occurs when an impulse from a motor neurone reaches the synapse at the junction with the muscle, the neuromuscular junction (NMJ). At the presynaptic membrane of the NMJ, depolarisation results i...
EB
Answered by Emily B. • Biology tutor
4544 Views

Describe the different roles of aldosterone and cortisol in the body

Both aldosterone and cortisol are produced in the adrenal cortex of the adrenal gland (which are situated above the kidneys on either side of the body). Aldosterone is a mineralocorticoid and helps to contro...
AJ
Answered by Aiman J. • Biology tutor
11883 Views

Describe the roll of kupffer cells in the liver

Kuppfer cells are a specialised type of macrophage. They travel within the sinusoids of the liver and breakdown and recycle old red blood cells. Red blood cells contain heamoglobin, and when haemoglobin is b...
AJ
Answered by Aiman J. • Biology tutor
9448 Views

Why may a rise in testosterone above normal cause a subsequent decrease in the hormone?

This is a question from the AQA June 15 Biology A level past paper. Short answer: Raised testosterone causes a physiological decrease in GnRH as well as LH and FSH via negative feedback. Detailed answer: To ...
DK
Answered by Dhiluni K. • Biology tutor
4414 Views

Outline some of the evidence for evolution

The fossil record provides a comprehensive array of evidence for evolution. For example Darwin studied Brachiopods, and within rocks you can see the clear change in the Brachiopods through time. The fossil r...
KT
Answered by Kelly T. • Biology tutor
3777 Views