14.3 A reflex arc

Question 1

What are the two major divisions of the nervous system

Answer 1

1. The central nervous system

2. The peripheral nervous system

Question 2

What is the central nervous system made up of

Answer 2

The brain and spinal cord

Question 3

What is the peripheral nervous system made up of

Answer 3

Pairs of nerves that originate from either the brain or the spinal cord

Question 4

What is the peripheral nervous system divided into

Answer 4

1. Sensory neurones, which carry nerve impulses from receptors towards the CNS
2. Motor Neurones, which carry nerve impulses away from the CNS to effectors

Question 5

How is the motor nervous system further divided

Answer 5

1. The voluntary nervous system, nerve impulses to muscles under concious control
2. The autonomic nervous system, nerve impulses to subconciously controlled effectors

Question 6

What is the Spinal Cord

Answer 6

A column of nervous tissue that runs along the back and lies inside the vertebral column for protection

Question 7

What emerges at intervals along the spinal cord

Answer 7

Pairs of nerves

Question 8

Describe the main stages of a spinal reflex arc

Answer 8

1. The stimulus - heat from a hot object
2. A receptor - Temperature receptors in the skin on the back of the hand, which generates nerve impulses in the sensory neurone
3. A sensory neurone - Passes nerve impulses to the spinal cord
4. A coordinator - Links the sensory neurone to the motor neurone in the spinal cord
5. A motor neurone - Carries nerve impulses from the spinal cord to a muscle in the upper arm
6. An effector - the muscle in the upper arm, which is stimulated to contract
7. The response - pulling the hand away from the object

Question 9

Why are reflex actions important

Answer 9

1. They are involuntary, and therefore down require the decision-making powers of the brain, thus leaving it free to carry out more complex responses
2. They protect the body from harm
3. They are fast, because the neurone pathway is short with very few synapses where neurones communicate
4. The absence of decision-making means the action is RAPID