13.8 Reflexes

Question 1

What is the purpose of a reflex?

Answer 1

To protect the body from danger, and prevent serious damage

Question 2

What is a reflex action?

Answer 2

An involuntary response to a sensory stimulus

Question 3

State the movement from stimulus to effector in a reflex arc.

Answer 3

Stimulus –> Receptor –> Sensory neurone –> Relay neurone –> Motor neurone –> Effector

Question 4

What is the spinal cord?

Answer 4

A column of nervous tissues running up the back

Question 5

Describe the movement of impulses from receptor to effector in a reflex arc. (Step-by-step process, not list of neurones)

Answer 5

1- Receptor detects stimulus and creates an action potential in the sensory neurone
2- Sensory neurone carries impulse to spinal cord
3- Relay neurone connects the sensory neurone to the motor neurone within the spinal cord or brain
4- Motor neurone carries impulse to the effector to carry out the appropriate response

Question 6

What is a spinal reflex?

Answer 6

A neural circuit that only goes up to the spinal cord, not the brain

Question 7

Describe how the knee-jerk reflex works.

Answer 7

1- Leg is tapped below the kneecap, stretching the tendon
2- Stimulus initiates a reflex arc, causing the muscle on the thigh to contract
3- Relay neurone inhibits the motor neurone of the hamstring, causing it to relax
4- This combined causes a reflex where the leg kicks

Question 8

What is the knee-jerk reflex used for?

Answer 8

Maintaining posture and balance

Question 9

What does the absence of the knee-jerk reflex indicate?

Answer 9

Nervous problems

Question 10

What is the blinking reflex?

Answer 10

The involuntary blinking of the eyelids

Question 11

When does the blinking reflex occur?

Answer 11

When the cornea is stimulated

Question 12

What is the name for the type of reflex that occurs when the cornea is stimulated/irritated?

Answer 12

Corneal reflex

Question 13

What is the name for the type of reflex that occurs when an over-bright light shines in the eye?

Answer 13

Optical reflex

Question 14

Are blinking reflexes cranial or spinal reflexes?

Answer 14

Cranial, because they only involve the brain and not the spinal cord

Question 15

What are the mechanics of a blinking reflex?

Answer 15

1- Stimulus triggers a response along a sensory neurone
2- Impulse passes through a relay neurone in the brainstem
3- Impulses sent along motor neurone
4- Motor response initiated, eyelids close

Question 16

What is a consensual response?

Answer 16

When both eyes are closed in a blinking reflex

Question 17

What is the blinking-reflex used to test for by doctors?

Answer 17

If a patient is brain-dead

Question 18

What are the key components of a reflex that increase your chances of survival?

Answer 18

• Involuntary responses
• Not having to be learnt out
• Being extremely fast
• Many reflexes are everyday actions

Question 19

Why are reflexes so fast?

Answer 19

Because they have to cross a minimal number of synapses