4.5.2 - Nervous System: 4.5.2.1 - Structure & function

Question 1

What is one of the components of the central nervous system (CNS)?

Answer 1

The brain.

Question 2

What does the CNS do?

Answer 2

It coordinates the response of effectors.

Question 3

What are effectors?

Answer 3

Muscles or glands that act in response to change in the internal or external environment.

Question 4

What is the spinal cord?

Answer 4

The spinal cord is a thick bundle of nerve tissue that carries information about the body to the brain & vice versa. It is important in coordinating the response of effectors to changes in the environment.

Question 5

What do the neurones (nerve cells) do?

Answer 5

They carry out electrical impulses (signals) between receptors, central nervous system (CNS) and effectors..

Question 6

How is the structure of the nervous system is adapted to its functions?

Answer 6

Neurones (nerve cells) are adapted to carry electrical impulses from one place to another:

• They have a long fibre (axon) which is insulated by a fatty sheath
• They have tiny branches (dendrons) which branch further as dendrites at each end.

Question 7

What does the fatty sheath on the axon do?

Answer 7

It allows electrical impulses to travel faster.

Question 8

What do the dendrons and dendrites do?

Answer 8

They increase surface area for more contact with other neurons.

Question 9

What is the use of the nervous system?

Answer 9

It enables humans to react to their surroundings and

to coordinate their behaviour.

Question 10

What happens to the information from receptors?

Answer 10

• Receptors detect a stimulus & send electrical impulses down neurones to the CNS
• The CNS sends electrical impulses down other neurones to effectors
• The effectors bring about a response by muscles contracting or a gland secreting hormones.

Question 11

What is the CNS pathway?

Answer 11

stimulus -> receptor -> coordinator -> effector -> response

Question 12

What systems does homeostasis involve?

Answer 12

Automatic control systems.

Question 13

What does the reflex arc do?

Answer 13

It enables humans to react to their surroundings and coordinate their behaviour.

Question 14

What happens when you touch a hot object?

Answer 14

• First, the stimulus (heat) is detected by the receptor (in the skin)
• Electrical impulses now pass from the receptor along a sensory neurone to the central nervous system (CNS)
• At the end of the sensory neurone there is a junction called a synapse and here a chemical is released
• The chemical diffuses across to a relay neurone in the CNS, which triggers an electrical impulse
• The electrical impulse passes across the relay neurone & reaches another synapse, a chemical is released again.
• The chemical triggers an electrical impulse in a motor neurone
• The electrical impulse passes down the motor neurone to an effector (muscle)
• The muscle contracts & pulls the hand away from the heat, which is the response.

Question 15

What are the stages of a reflex arc?

Answer 15

• Stimulus
• Receptor
• Sensory Neuron
• Relay neuron
• Motor Neuron
• Effector
• Response

Question 16

What are sensory neurones connected to?

Answer 16

Receptors

Question 17

What do receptors allow us to sense?

Answer 17

Our environment.

Question 18

Does the brain make decisions during a reflex action?

Answer 18

No, there is no decision making by the conscious part of the brain, it is automatic and rapid to protect us from danger.