Organisation of the Nervous System

Question 1

What are the two divisions of the nervous system?

Answer 1

1. CNS - the brain and spinal cord

2. PNS - axons, ganglia and supporting cells

Question 2

What are the two types of cells found in neural tissue?

Answer 2

1 = neurons or nerve cells which transmit electrical impulses along their cell membranes
2 = neuroglia which are responsible for supporting the neuron, regulating interstitial fluid and bringing nutrients

Question 3

Why do neural cells have no capacity for cell division and what does this mean for the cells?

Answer 3

They are highly differentiated and this means they have limited capacity to repair themselves after injury.

Question 4

What on a neuron allos them to communicate with each other?

Answer 4

Synapses on the dendrites.

Question 5

What are neuroglia and what are the 4 types?

Answer 5

These are non nervous support cells. The four types are, astrocytes, oligodendrocytes, microglia and ependymal cells

Question 6

What are the functions of astrocytes?

Answer 6

Maintenance of the blood-brain barrier (separates circulating blood in the brain and extracellular fluid in the CNS).
Contain microfilaments which give strength to the CNS.
Stabilise structure after injury and produce scar tissue.
Direct neural growth during development.
Controlling interstitial environment including neurotransmitters.

Question 7

What is the function of a oligodendrocyte?

Answer 7

They wrap together or form myelin to improve the conducting velocity of the axons. The section they wrap around is the axon.

Question 8

What does a microglia cell do?

Answer 8

They are immune cells which have a similar function to macrophages but they work in the brain.

Question 9

What does an ependymal cell do?

Answer 9

Lines the passageways of the CNS. They are epithelial cells that make branching processes with other glial cells.

Question 10

Where are cell bodies found in the PNS?

Answer 10

In the ganglia, supported by satellite cells.

Question 11

How many pairs of cranial severs leave the brain? How many pairs of spinal nerves go to the PNS?

Answer 11

12

20

Question 12

What do somatic nerves contain?

Answer 12

Motor and sensory fibres

Question 13

All sensory axons whether somatic or autonomic have their cell bodies — the CNS in — where there are — synapses?

All motor ganglia belong to the — nervous system and —- contain synapses.

Answer 13

outside, ganglia, no

autonomic, always

Question 14

What is the shape of the cell bodies in the spinal cord? What matter is this? What two sides run together?

Answer 14

In a H shape (grey matter). The motor and sensory side which run together.

Question 15

Why does the anterior ramus of the vertebrae contain more axons than the posterior one?

Answer 15

The anterior one supplies all the thoracic region but the posterior only supplies sin on the back.

Question 16

What sample can be taken from the vertebrae to look for damage?

Answer 16

A sample of the fluid in the spinal cord.

Question 17

What neuron goes in and what neuron leaves the spinal cord? What are the two branches coming off each vertebrae?

Answer 17

The sensory neuron comes in and the motor neuron leaves.

There is a posterior branch towards the back and the anterior branch towards the front.

Question 18

What is a dermatome?

Answer 18

An area of skin that is mainly supplied by afferent nerve fibres from the dorsal root.

Question 19

What is a nerve plexus? Explain details on this.

Answer 19

A nerve plexus is a branching network of intersecting nerves. The anterior rami of all spinal nerve rejoin to form plexuses. These networks occur in the cervical, brachial, lumbar and sacral regions of the vertebrae. Fibres from different anterior roots crisscross and are redistributed so each plexus contains fibres from different nerves.

Question 20

Where do sensory fibres have their ganglia?

Answer 20

In the posterior root ganglia of the spinal nerves or in the sensory ganglia of the cranial nerves.

Question 21

Where do the cell bodies of the motor neurons lie?

Answer 21

In ganglia outside the CNS.

Question 22

Autonomic motor pathways consist of two neurons in series. Explain this.

How does this differ from the somatic pathway?

Answer 22

The first has its cell body in the CNS with the axon extending to the autonomic ganglion where it synapses. From here, the axon from the cell body travels to the effector organ.

The somatic pathway has no synapses.

Question 23

What is the distribution and innervation of the sympathetic nervous system?

Answer 23

Distribution: All parts of the body wall and viscera
Function: Innervation of all skin sweat glands, the arrector pili muscles of the hairs, muscular wall of blood vessels

Question 24

What are typical effects that the sympathetic nervous system has on the body?

Answer 24

Staring eyes, cold, clammy skin, dry mouth, hair standing on end.

Question 25

What is the distribution and function of the parasympathetic nervous system?

Answer 25

Distribution: head and trunk only
Function: localised response used to conserve energy e.g. slowing heart rate

Question 26

What is the length of the preganglionic (CNS) and postganglionic (PNS) for the sympathetic and parasympathetic divisions/

Answer 26

Sympathetic = short preganglionic and long postganglionic
Parasympathetic = vice versa