reflex arc

Question 1

explain the reflex arc of touching a hot object (7 marks)

Answer 1

1. stimulus
   (heat from a hot object)
2. receptor
   (temperature receptors in skin on back of hand generates nerve impulses in sensory neurone)
3. sensory neurone
   (passes nerve impulses to spinal cord)
4. coordinator
   ( intermediate neurone - links sensory neurone to motor neurone in spinal cord)
5. motor neuron
   (carries nerve impulses from spinal cord to muscle in upper arm)
6. effector (muscle in upper arm which is stimulated to contract)
7. response (pulling hand away from a hot object)

Question 2

why are reflex arcs important

Answer 2

rapid - short neuron pathway
(fewer synapses)

involuntary/automatic
doesn’t require decision to be made - so brain free to deal with more complex processes

they are an involuntary response

prevents damage to tissues (e.g: burning)

role in homeostasis (insulin/glucagon)

maintain posture and balance

Question 3

what is the role of a receptor

Answer 3

detection of stimuli

Question 4

what is the role of a sensory neurone

Answer 4

carry electrical impulses from receptor to CNS

Question 5

what is the role of a intermediate neurone

Answer 5

link sensory to motor neurone via spinal cord

Question 6

what is the role of a motor neurone

Answer 6

carry electrical impulses from CNS to effector

Question 7

what is the role of an effector

Answer 7

causes response (muscle contraction/ glands secreting hormones)