Chapter 9- The nervous system (2)

Question 1

Why can’t axons rely on passive diffusion to get elements where they are needed to be?

Answer 1

Because axons are very long

Question 2

What method of transport do axons rely on?

Answer 2

Axonal transport

Question 3

What does axonal transport contain?

Answer 3

Contains various cytoskeleton components and motor proteins which act as locomotives, pulling essential elements down the tracks.

Question 4

What is anterograde?

Answer 4

Transporting substances away from the nucleus

Question 5

What is retrograde?

Answer 5

Transporting substances towards the nucleus.

Question 6

What is an axon terminal?

Answer 6

This is where the signal is transmitted to another neuron, or to a muscle.

Question 7

How does an axon terminal transmit its signal?

Answer 7

It transmits the signal by releasing a chemical called a neurotransmitter.

Question 8

What is a nerve?

Answer 8

Is a collection of neurons in the PNS

Question 9

What can a single nerve contain?

Answer 9

Both efferent and afferent fibres.

Question 10

What is a nerve called in the CNS?

Answer 10

A tract

Question 11

What are some neutron corrections and clarifications?

Answer 11

1- Not all electrical activity arrives at dendrites

2- Not all neurons have multiple dendrites.

3- Not all neurons have an axon.

Question 12

Only around half of the cells of the nervous system are neurons. What are the other half?

Answer 12

Neural support cells called glia.

Question 13

What are the key functions of the glia?

Answer 13

1- Helping to hold neurons in place

2- Supplying oxygen and nutrients to neurons

3- Removing pathogens and dead neurons

Question 14

CNS glia include:

Answer 14

1- Oligodendrocytes
2- Microglia
3- Ependymal cells

Question 15

PNS glia include:

Answer 15

1- Schwann cells

2- Satellite cells

Question 16

In the PNS, what do Schwann cells produce?

Answer 16

Myelin

Question 17

What does a Schwann cell do?

Answer 17

The Schwann cell membrane repeatedly wraps itself around an axon.

Then it squeezes tight to form a myelin sheath and making it largely non conductive.

Question 18

A single Schwann cell provides myelin for how many PNS neurons?

Answer 18

Only one PNS neuron

Question 19

What is the Nodes of Ranvier?

Answer 19

Gaps in the myelin sheath that occur between individual Schwann cells.

This is where the electrical signal is regenerated.

Question 20

What is an oligodendrocyte?

Answer 20

The functional equivalent to Schwann cells but in the CNS

Question 21

Unlike Schwann cells, a single oligodendrocyte can do what?

Answer 21

Myelinate multiple axons.

Question 22

What are astrocytes and what do they do?

Answer 22

Star shaped structures that cover blood vessels in the CNS

They store nutrients

Question 23

What are satellite cells and what do they do?

Answer 23

Coat the soma of nerve cells in the PNS.

Similar in function to astrocytes in the CNS in that they supply nutrients.

They also act as a protective barrier

Question 24

What are the microglia and what do they do?

Answer 24

Involved in the CNS.

Involved in injury. They will move to the damage site and will engage in phagocytosis and consume debris and pathogens which will destroy any unwanted substances.

Question 25

What are the ependymal cells and what do they do?

Answer 25

Line the ventricles of the brain and line the central canal of the spinal cord.

Involved in secretion of cerebrospinal fluid (CSF)- provides a degree of mechanical support. It cushions the spine and brain against trauma.