Reflexes

Question 1

What is a reflex?

Answer 1

An involuntary response to a sensory stimulus.

Question 2

What is a reflex action?

Answer 2

The fast response to a situation which prevents or minimizes damage to the body.

Question 3

What is a reflex arc?

Answer 3

The pathway of neurones involved in a reflex action.

Question 4

What is the role of a receptor in the reflex arc?

Answer 4

Detects the stimulus and creates an action potential in sensory neurone.

Question 5

What is the role of a sensory neurone in the reflex arc?

Answer 5

Carries impulses to the spinal cord.

Question 6

What is the role of a relay neurone in the reflex arc?

Answer 6

Connects the sensory neurone to the motor neurone within the spinal cord or brain.

Question 7

What is the role of a motor neurone in the reflex arc?

Answer 7

Carries impulses to the effector to carry out the appropriate response.

Question 8

Describe step by step the reflex arc involved in the withdrawal of your hand from a fire/hot pan.

Answer 8

1) Thermoreceptors in skin detect the heat coming off the stimulus.
2) Sensory neurone passes nerve impulses to the spinal cord
3) Relay neurone passes impulses across the spinal cord
4) Motor neurone passes impulse to the muscles
5) Effector muscles contract
6) The hand is moved away from the flame quickly

Question 9

What is the spinal cord?

Answer 9

A column of nervous tissues running up the back and is surrounded by the spine for protection.

Question 10

What is the knee-jerk reflex?

Answer 10

A spinal reflex that is commonly used by doctors to test a person’s reflex action.

Question 11

Describe step by step the knee-jerk reflex.

Answer 11

1) Patella is tapped (part of the knee just below the kneecap) This is the stimulus
2) Patellar tendon is stretched
3) Extensor muscle on top of the thigh contracts
4) At the same time, a relay neurone inhibits the motor neurone of the flexor muscle, causing it to relax.
5) The contraction with the relaxation of the antagonistic flexor hamstring muscle causes the leg to kick.

Question 12

How is the knee-jerk reflex used by the body?

Answer 12

To help maintain posture and balance, so we stay balanced without thought.

Question 13

What is the blinking reflex? What type of reflex is it?

Answer 13

An involuntary blinking of the eyelids. A cranial reflex.

Question 14

What is the purpose of the blinking reflex?

Answer 14

Keep the cornea safe from damage due to foreign bodies such as dust or flying insects entering the eye.

Question 15

What is the corneal blinking reflex?

Answer 15

Reflex in response to physical foreign bodies entering the eye.

Question 16

What is the optical blinking reflex?

Answer 16

Reflex in response to over-bright light

Question 17

Describe step by step the blinking reflex.

Answer 17

1) Cornea of eye is irritated by a foreign body
2) This triggers an impulse along a sensory neurone (the fifth cranial nerve)
3) Impulse passes along relay neurone in the lower brain stem
4) Impulses are sent along the motor neurone (seventh cranial nerve)
5) A motor response of closing the eyelids occurs

Question 18

Why do doctors test unconscious patients with the blinking reflex?

Answer 18

To make sure the lower brain stem is still functioning.

Question 19

How do reflexes increase your chance of survival?

4 ways

Answer 19

1) By being involuntary
2) Not having to be learnt
3) By being extremely fast
4) They keep us upright and help with daily actions we don’t think about.