AQA GCSE Biology (8461), Higher tier · Homeostasis and response › The human nervous system
Practise Structure and function. 19 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
A person touches a very hot pan and moves their hand away before they feel any pain.
(a) Describe the pathway taken by nerve impulses in this reflex, from the receptor to the effector.[4]
(b) Explain how a nerve impulse passes across a synapse.[2]
(c) Explain why reflex actions are important.[2]
(d) Reflex actions do not involve the conscious part of the brain. Explain why this makes them faster.[1]
Show the answer and mark scheme
(a)
receptors in the skin detect the heat / stimulus
impulses travel along a sensory neurone to the spinal cord / CNS
impulses pass (across a synapse) to a relay neurone in the spinal cord
impulses travel along a motor neurone to the effector / muscle
the muscle contracts, moving the hand away
(b)
a chemical is released by the first neurone
the chemical diffuses across the gap and causes an impulse in the next neurone
(c)
they are automatic and rapid
(so) they protect the body from harm / damage, e.g. burns
(d)
no time is taken to think / decide / fewer neurones and synapses are involved
Question 3Hard7 marks
A student wants to find out whether practice affects reaction time. The student will use the ruler-drop test and a table that converts the distance the ruler falls into a reaction time.
(a) The person dropping the ruler must not warn the catcher before letting go. Give the reason why.[1]
(b) Plan an investigation to find out whether practice affects reaction time.[6]
Show the answer and mark scheme
(a)
so the catcher reacts to seeing the ruler fall (and does not anticipate / react to a sound)
(b)
one person holds a (30 cm) ruler vertically with the zero mark level with the top of the catcher's thumb
the catcher's forearm rests on the edge of a table / hand is in the same position each time
the ruler is dropped without warning and caught as quickly as possible
record the distance the ruler falls and convert it to a reaction time using the table
test the catcher (e.g. 5 times) before practice to get a starting mean
the catcher then practises, e.g. 20 catches, and is tested again (repeat after more practice)
control variables: same catcher, same hand, same ruler, same person dropping, same starting gap, no distractions
calculate a mean for each stage, ignoring anomalous results
compare the mean reaction times before and after practice / plot a graph of reaction time against number of practice catches
Marked with levels of response: the full level descriptors are in the app.