Module 5: Reflexes

Question 1

A reflex is an …

Answer 1

involuntary response to a sensory stimulus

Question 2

Most reflexes follow the same steps between the stimulus and the response , state and briefly describe the 4 steps

Answer 2

Receptor-detects stimulus and generates an action potential in sensory neuron
Sensory neuron-carries impulse to spinal chord
Relay neuron-connects sensory and motor neurons by the spinal chord or brain
Motor neuron-carries impulse to the effector to carry out appropriate response

Question 3

What are the 2 main reflexes ?

Answer 3

the knee jerk reflex
the blinking reflex

Question 4

What kind of reflex is the knee jerk reflex , why?

What kind of reflex is the blinking reflex , why?

Answer 4

knee jerk-spinal reflex as neural circuit only goes through the spinal chord

blinking-cranial reflex as neural circuit passes through the brain

Question 5

Describe the knee jerk reflex step by step …

5 steps

Answer 5

1)When the patella is tapped this stretches the patella tendon and acts as a stimulus
2)stimulus initiates an action potential which travels down sensory neuron until reaching a motor neuron
3)impulse travels along motor neuron and reaches extensor muscle causing it to contract
4)At the same time , a relay neuron inhibits the motor neuron causing the flexor muscle to relax
5)The combined contraction and relaxation of this antagonistic muscle pair causes the leg to kick

Question 6

What is the name given to a pair of muscles that contract/relax together to allow movement?

Answer 6

antagonistic pair

Question 7

Describe the blinking reflex step by step …

4 steps

Answer 7

1)the cornea of the eye becomes irritated by a foreign body , this acts as a stimulus
2)this stimulus triggers an impulse along a sensory neuron
3)the impulse then passes through a relay neuron in the lower brain stem
4)impulses are then sent along branches of the motor neuron to initiate contraction of both eyelid muscles , causing both eyelids to close

Question 8

Reflexes are essential for survival as they …

Answer 8

avoid the body being harmed or reduce the severity of any damage

Question 9

Explain how the fact that reflexes are involuntary responses increases our chance of survival

Answer 9

reflexes don’t involve decision making areas of the brain , preventing the brain becoming overloaded with situations where the response is always the same

Question 10

Reflex responses are innate , how does this increase our chance of survival?

1 point

Answer 10

it means they provide immediate protection as they don’t have to be learnt

Question 11

State how reflexes are so much more rapid compared to other responses

Answer 11

because they only involve one or two synapses , which are the slowest part of nerve transmission