15.1: Neurones and nervous coordination

Question 1

What are the two forms of coordination

Answer 1

1. Nervous system
2. Hormonal system

Question 2

Features of the nervous systerm

Answer 2

• Uses nerve cells to pass along electrical impulses
• Stimulate target cells by secreting neurotransmitters directly on them
• This results in rapid communication between parts of an organism
• The responses produced are often short-lived and restricted to a localised region of the body e.g hand withdrawal from a fire

Question 3

Features of the Hormonal system

Answer 3

• Produces hormones that are transported in the blood plasma to target cells
• The target cells have specific receptors on their cell surface membrane, and the change in concentration of hormones stimulates them
• This results in a slower, less-specific form of communication between parts of an organism
• The responses are long-lasting and widespread. e.g. Control of blood glucose (insulin and glucagon)

Question 4

Differences between the nervous system and hormonal system

Question 5

What is a neurone (nerve cell)

Answer 5

A specialised cell adapted to rapidly carrying electrochemical changes called nerve impulses from one part of the body to the other

Question 6

General Structure of a mammalian motor neurone

Answer 6

1. Cell body

• contain all normal organelles. Associated with protein synthesis and neurotransmitters

2. Dendrons (split into Dendrites)

• Extensions of the cell body which divide into smaller dendrites, these carry nerve impulses towards the cell body

3. Axon

• Single long-fibre that carries nerve impulses away from the cell body

4. Schwann cells

• Surround the axon, protecting it and providing electrical insulation. Carry out phagoytosis and play a role in nerve generation. Wrap many times = membranal layers

5. Myelin Sheath

• Forms a covering to the axon and is made up of Schawnn cells. Rich in myelin - Myelin sheath = myelinated neurones

6. Nodes of raviner

• Constrictions between schwann cells where there is no myelin sheath

Question 7

Features of a Neurone

Answer 7

1. Cell body
2. Dendrons (dendrites)
3. Axon
4. Schwann cells
5. Myelin sheath
6. Nodes of Raviner

Question 8

Types of neurones

Answer 8

Sensory neurones

Motor neurones

Intermediate/relay neurones

Question 9

Neurone classification

Answer 9

Neurones are classified according to their function.

Question 10

Sensory Neurones

Answer 10

Transmit nerve impulses from a receptor to an intermediate or motor neurone

They have one dendron that is very long. It carries the impulse towards the cell body and one axon that carries it away

Question 11

Motor Neurones

Answer 11

Transmit nerve impulses from an intermediate/relay neurone to an effector, e.g. muscle or gland. Motor neurones have a long axon and many dendrites

Question 12

Intermediate/Relay neurones

Answer 12

Transmit nerve impulses between neurones, for example, from a sensory to a motor neurone. They have multiple short processes.