B10. The Nervous System

Question 1

What is homeostasis?

Answer 1

Homeostasis in the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
e.g. control of blood glucose concentration

Question 2

What are the 2 automatic control systems of the body?

Answer 2

1) The Nervous System
2) Endocrine system

2) The Endocrine System

Question 3

What type of messages travel via the nervous system?

Answer 3

Electrical impulses

Question 4

What is a neuron?

Answer 4

A neuron is a nerve cell along which an electrical impulse can travel.

Question 5

Name 3 types of neuron.

Answer 5

1) Sensory neuron
2) Relay neuron
3) Motor neuron

Question 6

The nervous system is made up of 2 parts. What are these 2 parts?

Answer 6

The central nervous system (brain and spinal cord) and the peripheral nervous system (all other nerve cells).

Question 7

Describe how a neuron is adapted for it’s function.

Answer 7

• Thin projections called dendrites extend from the cell body and connect with other neurones, allowing electrical impulses to pass from one to the other.
• The axons of most neurones are insulated by a layer called the myelin sheath. This ensure the impulses travel rapidly along the axon.

Question 8

What happens if the myelin sheath degenerates?

Answer 8

The electrical impulse can not travel as smoothly down the axon. The person may experience tremors.

Question 9

Describe the pathway of an electrical impulse during a conscious action e.g. putting up your hand to answer a question.

Answer 9

Stimulus –> Receptor –> Sensory neuron –> CNS (brain) –> Motor neuron –> Effector (muscle/gland) –> response.

Question 10

What is a stimulus?

Answer 10

A change in your environment e.g. hearing a loud bang.

Question 11

What parts of the body detect stimuli.

Answer 11

Sense receptors in the sense organs i.e. ears, eyes, nose, mouth, skin.

Question 12

What is a synapse?

Answer 12

A synapse is a gap between two neurons. Electrical impulses can not cross the synapse.

Question 13

Describe how electrical impulses can cross the synapse.

Answer 13

1) Electrical impulse reaches the end of the first neuron.
2) This stimulates the release of neurotransmitter chemicals.
3) The neurotransmitter chemicals diffuse across the synapse.
4) They bind to receptors on the next neuron.
5) This binding of the neurotransmitters to the receptors stimulates the second neuron to transmit an electrical impulse (same message) along its axon.

Question 14

What are the names of the chemicals that diffuse across the synapse?

Answer 14

Neurotransmitter chemcials.

Question 15

Describe the pathway of an electrical impulse during a reflex action.

Answer 15

Stimulus –> Receptor –> Sensory neuron –> CNS (spinal cord) –> Motor neuron –> Effector (muscle/gland) –> response.

Question 16

What is the difference between a voluntary action and a reflex action.

Answer 16

We can choose the response for a voluntary action, whereas reflex actions are ‘inbuild’ responses in our spinal cord. They are INVOLUNTARY responses which are not controlled by the brain.

Question 17

Why are reflex actions important to humans.

Answer 17

They are:

• Fast
• Automatic
• Protective responses.

Question 18

Where are neurotransmitter chemicals stored?

Answer 18

In vesicles in the pre-synaptic neuron.

Question 19

Give an example of a reflex action?

Answer 19

• touching a very hot object
• looking into bright light

Question 20

Describe how the structure of a sensory neuron to a motor neuron?

Answer 20

The cell body of a motor neuron is at the beginning of the cell whereas it is more central in a sensory neuron.

Question 21

Which part of the CNS controls reflex responses?

Answer 21

The spinal cord

Question 22

Why is the brain not involved (initially) in a reflex repsonse?

Answer 22

It would take too long and the person may be harmed