Neurones 13.2

Question 1

Why do we have a nervous system?

Answer 1

So that our body can respond to stimuli or changes in the environment. It is fast and targeted which will produce a rapid response as opposed to the hormonal system.

Question 2

Neurones

Answer 2

These are specialised nerve cells that transmit electrical impulses rapidly around the body. They will carry information from the sensory receptors to the effectors for actions to be carried out and a response to be produced.

Question 3

Structures within a neurone

Answer 3

Cell body, dendron, axon

Question 4

Cell body

Answer 4

This contains the nucleus surrounded by cytoplasm. There are many endoplasmic reticulum and mitochondria which will produce neurotransmitters from one neurone to the next

Question 5

Dendron

Answer 5

These are extensions of the cell body and can branch off into smaller branches called dendrites. This transmits impulses from the receptor to the cell body.

Question 6

Axon

Answer 6

Singular elongated nerve fibres which are very thin, cylindrical and have narrow cytoplasm. They transmit impulses away from the cell body towards the places it needs to go.

Question 7

Neurotransmitters

Answer 7

Special chemicals that pass signals from one neurone to another

Question 8

Types of neurones

Answer 8

Sensory, relay, motor

Question 9

Sensory Neurones

Answer 9

These carry impulses from a sensory receptor to the relay or motor neurone. They have one dendron that carries the impulse to the cell body in the middle and one axon that carries the impulse away.

Question 10

Relay Neurones

Answer 10

These transmit impulses between sensory and motor neurones. They have very small axons and dendrons. Their cell body is in the middle.

Question 11

Motor Neurones

Answer 11

These transmit impulses from the sensory or relay neurones to an effector which could be a muscle or a gland. They have short dendrites and one long axon. The cell wall is on the left end.

Question 12

Nervous Transmission Pathway

Answer 12

Sensory Receptor -> Sensory Neurone -> Relay Neurones -> Motor Neurone -> Effector Cell

Question 13

Myelin Sheath

Answer 13

This is made up of multiple phospholipid bilayers on top of each other which acts as an insulated layer. This covers the axons of some neurones and allows their impulses to be a lot faster. Schwann cells produce the myelin sheath by growing and producing these layers around their cells. Each time it grows, it puts a double phospholipid bilayer. A myelinated neurone has an impulse of 100m per second compared to unmyelinated which has 1m per second

Question 14

Nodes of Ranvier

Answer 14

These are the small gaps between the myelinated sheaths on an axon. The electrical impulse will jump from one node to the next and will not pass through the myelin sheath as it is insulated. This allows the impulse to travel much faster than if it were to travel continuously.

Question 15

Multiple Sclerosis

Answer 15

This is an autoimmune disease where the body will attack its own tissue and results in the damage of the myelin sheath and the breakdown of neurones. This means either the impulses will be a lot slower or there won’t be any impulses