3.6 : Organisms respond to changes in the environment

Question 1

NERVOUS COORDINATION AND MUSCLES:

What is a nervous system? (A01)

Answer 1

1. Communication is by nerve impulses.
2. Transmission is by neurones.
3. Transmission is very rapid.
4. Nerve impulses travel to specific parts of the body.
5. Response is localised.
6. Response is rapid.
7. Response is short-lived.
8. Effect temporary and reversible.

Question 2

NERVOUS COORDINATION AND MUSCLES:

What is a hormonal system? (A01)

Answer 2

1. Communication is by chemicals called hormones.
2. Transmission via blood stream.
3. Transmission slow.
4. Hormones travel to all parts of the body but only target cells respond.
5. Response is widespread.
6. Response is slow.
7. Response is long-lasting.
8. Effect permanent and irreversible.

Question 3

NERVOUS COORDINATION AND MUSCLES:

What are neurones? (A01)

Answer 3

1. Specialised cells that are adapted to rapidly carrying electrochemical changes called nerve impulses from one part of the body to the other.

Question 4

NERVOUS COORDINATION AND MUSCLES:

Define cell body. (A01)

Answer 4

1. Contains the usual cell organelles, nucleus and large amounts of RER.
2. Associated with production of protein and neurotransmitters.

Question 5

NERVOUS COORDINATION AND MUSCLES:

Define dendrons.(A01)

Answer 5

1. Extensions of the cell body that are subdivided into smaller branched fibres called dendrites.
2. Dendrites carry nerve impulses to cell body.

Question 6

NERVOUS COORDINATION AND MUSCLES:

Define axon. (A01)

Answer 6

1. A single long fibre that carries nerve impulses AWAY from cell body.

Question 7

NERVOUS COORDINATION AND MUSCLES:

Define Schwann cells. (A01)

Answer 7

1. Surrounds axon, protecting it and providing electrical insulation.
2. Carry out phagocytosis.
3. Wrap themselves around axon many times, so that layers of their membrane build around it.

Question 8

NERVOUS COORDINATION AND MUSCLES:

Define myelin sheath. (A01)

Answer 8

1. Forms covering the axon.
2. Made up of Schwann cells.
3. Swchann cells rich in lipid known as myelin.
4. Neurones with myelin sheath called myelinated neurones.

Question 9

NERVOUS COORDINATION AND MUSCLES:

Define nodes of Ranvier. (A01)

Answer 9

1. Constrictions between adjacent swchann cells when there is no myelin sheath.
2. Constrictions are 2-3 micrometres long.
3. Occur in every 1-3 mm in humans.

Question 10

NERVOUS COORDINATION AND MUSCLES:

Define sensory neurones.

Answer 10

1. Transmit nerve impulses from receptor to intermediate or motor neurone.
2. Have 1 dendron that is long.
3. Carriers impulses towards the cell body and 1 axon that carries it away from the cell body.

Question 11

NERVOUS COORDINATION AND MUSCLES:

Define motor neurone.

Answer 11

1. Transmit nerve impulses from intermediate or relay neurone to effector such as glands / muscles.
2. Long axon.
3. Many short dendrites.

Question 12

NERVOUS COORDINATION AND MUSCLES:

Define intermediate or relay neurone.

Answer 12

1. Transmit nerve impulses between neurones i.e. from sensory to motor neurones.
2. Have numerous short processes.