MAJOR DIVISIONS OF THE PERIPHERAL NERVOUS SYSTEM

Question 1

Cranial and spinal nerves consist of

Answer 1

bundles of nerve fibres supported by connective tissue

Question 2

How many pairs of cranial nerves are there?

Answer 2

12

Question 3

12 pairs of cranial nerves leave the brain and pass through

Answer 3

foramina in the skull

Question 4

How many pairs of spinal nerves?

Answer 4

31

Question 5

31 pairs of spinal nerves leave the spinal cord and

Answer 5

pass through the intervertebral foramina in the vertebral column

Question 6

Spinal nerves are associated with regions of the spinal cord:

Answer 6

8 cervical (but only 7 cervical vertebrae)
12 thoracic
5 lumbar
5 sacral
1 coccygeal (but 4 coccygeal vertebrae)

Question 7

Question 8

Spinal nerves are connected to the spinal cord by 2 roots:

Answer 8

Anterior (ventral) root
Posterior (dorsal) root

Question 9

Question 10

The anterior (ventral) root consists of what nerve fibres?

Answer 10

Efferent fibres:
bundle of nerve fibres that carry nerve impulses away from the CNS

Fibres going to skeletal muscle and cause contraction = motor fibres

Neuron cell bodies of these fibres are located in the anterior gray horn of the spinal cord

Question 11

The posterior (dorsal) root consists of what nerve fibres?

Answer 11

Afferent fibres:
bundles of nerve fibres that carry nerve impulses to the CNS

Fibres carry information about sensations of touch, pain temperature, and vibration = sensory fibres

Neuron cell bodies of these fibres are located in a swelling on the posterior root = posterior (dorsal) root ganglia (DRG)

Question 12

Spinal nerve roots pass from the spinal cord to the level of their respective intervertebral foramina, where they unite to form a spinal nerve

Question 13

Spinal nerve contains a mix of both motor and sensory fibres

Question 14

Question 15

Each spinal nerve divides into large anterior and smaller posterior ramus
after emerging from the intervertebral foramen
Each ramus contain both motor and sensory fibres

Question 16

Posterior ramus

Answer 16

Pass posteriorly around the vertebral column Supply muscle of the skin and back

Question 17

Anterior ramus

Answer 17

Pass anteriorly
Supply the muscles and skin over the anterolateral body wall and all muscles and skin of the limbs
Anterior rami join one another at the root of the limbs to form complicated nerve plexuses
- Cervical and brachial plexuses are located
at the root of the upper limbs
- Lumbar and sacral plexuses are located at
the root of the lower limbs

Question 18

Question 19