The Basic Anatomy & Functioning of the Peripheral Nervous System

Question 1

Which type of neurone (no. of poles) is most common in the ANS and motor nervous system?

Answer 1

Multipolar

Question 2

Which type of neurone (no. of poles) is most common in the sensory nervous system?

Answer 2

Unipolar (or pseudounipolar)

Question 3

How many tracts are in the motor pathway?

Answer 3

2: Lower Motor Neurone (LMN) and Upper Motor Neurone (UMN)

Question 4

How many tracts are in the sensory pathway?

Answer 4

3: 1st Order neurone, 2nd order neurone, 3rd order neurone.

Question 5

What is the name for a group of nerve cell bodies in the CNS?

Answer 5

Nucleus

Question 6

What is the name for a group of nerve cell bodies in the PNS?

Answer 6

Ganglion

Question 7

What is the name for a bundle of axons in the CNS?

Answer 7

A tract (usually single modality)

Question 8

What is the name for a bundle of axons in the pNS?

Answer 8

A nerve (often mixed)

Question 9

How many pairs of spinal nerves are there?

Answer 9

31

Question 10

Where can spinal nerves be found?

Answer 10

Intervertebral foramina

Question 11

What kind of information is carried in the posterior roots and rootlets?

Answer 11

Sensory (towards cord)

Question 12

What kind of information is carried in the anterior roots and rootlets?

Answer 12

Motor (away from cord)

Question 13

What location does the smaller posterior rami serve?

Answer 13

Posterior body wall

Question 14

What location does the larger anterior rami serve?

Answer 14

Anterolateral body wall

Question 15

What information travels in the Spinothalamic Tract (STT)?

Answer 15

Sensory (afferent)

Question 16

What information travels in the Corticospinal Tract (CST)

Answer 16

Motor (efferent)

Question 17

Where do tracts decussate (cross) in the STT?

Answer 17

They crossover in the spinal cord, usually 1-2 spinal nerve segments above their point of entry. The second order neurone travels to the thalamus and synapses with a 3rd order neurone.

Question 18

Where do tracts decussate (cross) in the CST?

Answer 18

Around 90% of the tract decussates in the medulla, forming the lateral corticospinal tract. The remaining 20% form the ventral corticospinal tract and cross at the appropriate spinal level

Question 19

Which spinal nerve corresponds to dermatome covering the male nipple?

Answer 19

T4

Question 20

Which spinal nerve corresponds to the dermatome covering the umbilicus?

Answer 20

T10

Question 21

Which spinal nerves correspond to the upper limb dermatomes?

Answer 21

C5-T1

Question 22

Which spinal nerves correspond to the lower limb dermatomes?

Answer 22

L2-Co1

Question 23

What is a plexus?

Answer 23

A network of intertwined anterior rami.

Question 24

What are the roots of the cervical plexus?

Answer 24

C1-C4

Question 25

What are the roots of the brachial plexus?

Answer 25

C5-T1

Question 26

What are the roots of the lumbar plexus?

Answer 26

L1-L4

Question 27

What are the roots of the sacral plexus?

Answer 27

L5-S4

Question 28

What is a dermatome?

Answer 28

The area of skin supplied by the anterior and posterior rami of a specific spinal nerve.

Question 29

What is a myotome?

Answer 29

The skeletal muscles supplied with motor innervation by both the anterior and posterior rami of a specific spinal nerve. NB - dos not always correspond to dermatome (e.g. diaphragm)

Question 30

Sympathetic outflow occurs at which spinal levels?

Answer 30

T1-L2 into sympathetic chains (paravertebral ganglion)

Question 31

How do sympathetic nerves reach the body wall?

Answer 31

They pass into all spinal nerves from anterior rootlets and then synapse in the paravertebral ganglion.

Question 32

How do sympathetic nerves reach the organs?

Answer 32

They hitch a ride with arteries to all head an neck organs.

Question 33

What is different about sympathetic outflow to the abdominopelvic organs?

Answer 33

Axons synapse in the pre vertebral ganglia (beyond sympathetic trunk). All the others synapse in the paravertebral ganglia (within sympathetic trunk)

Question 34

What is different about sympathetic innervation to the adrenal glands?

Answer 34

Axons synapse directly onto the organ.

Question 35

How do parasympathetic nerves reach the organs? | NB - no parasympathetic supply to body wall

Answer 35

CN III, VII, IX, X and sacral spinal nerves.

Question 36

What is different about the Vagus nerve (CN X) and the sacral spinal nerves?

Answer 36

These synapse in ganglia on or very close to the organs themselves. The others synapse in ganglia distant to their target organs e.g. ciliary ganglion