Peripheral Nervous System

Question 1

What are the basic units of the Nervous System?

Answer 1

Neurones

Question 2

What produces the myelin sheath in the PNS?

Answer 2

Schwann cells.

(Oligodendrocytes in the CNS).

Question 3

Describe a multipolar neuron.

Answer 3

• 2 or more dendrites.
• Majority of CNS neurones.
• All the motor neurons of skeletal muscle and ANS.
• Cell body found in the CNS.

Question 4

Describe a unipolar neuron.

Answer 4

• Double process.
• Cell body found in the PNS.
• AKA sensory / pseudounipolar.

Question 5

Another way to describe an Efferent neuron?

Answer 5

Motor neuron.

Question 6

The impulse of an efferent neuron moves towards?

Answer 6

The body wall, body cavity or organ.

Question 7

The impulse of an afferent neuron moves towards?

Answer 7

The brain.

Question 8

Another way to describe an Afferent neuron?

Answer 8

Sensory neuron.

Question 9

What is a nerve?

Answer 9

Collection of axons surrounded by connective tissue and blood vessels.

Question 10

Most nerves exist in which modality?

Answer 10

Mixed i.e. somatic motor, somatic sensory and sympathetic.

Question 11

How many pairs of spinal nerves are there?

Answer 11

31 pairs.

Question 12

Where are spinal nerves found?

Answer 12

The intervertebral foramina.

Question 13

Spinal nerves connect structures of the soma via what?

Answer 13

Rami

Question 14

Spinal nerves connect via rami to what?

Answer 14

Structures of the soma.

Question 15

Spinal nerves connect with the spinal cord segment of the same number via what?

Answer 15

Roots and rootlets.

Question 16

Spinal nerves connect via roots and rootlets to what?

Answer 16

The spinal cord segment of the same number.

Question 17

Describe the posterior rami of spinal nerves.

Answer 17

Small and innervate the posterior body wall.

Question 18

Describe the anterior rami of spinal nerves.

Answer 18

Large and innervate the anterolateral body wall.

Question 19

Describe the transmission of sensory axons in relation to the spinal nerves.

Answer 19

ALL sensory axons pass from spinal nerve > posterior root > posterior rootlets > posterior horn of spinal cord.

Question 20

Where are the cell bodies of primary afferent neurones located?

Answer 20

Dorsal root ganglion.

Question 21

Describe the transmission of motor axons in relation to the spinal nerves.

Answer 21

ALL motor axons pass from anterior horn of spinal cord > anterior rootlets > anterior root > spinal nerve.

Question 22

How does segmental innervation of the body wall arise?

Answer 22

Each spinal nerve supplies innervation to a unilateral area of the body.

Question 23

Each spinal nerve pair supplies all structures in a segment of the body with what?

Answer 23

• General sensory supply to all structures.

Question 24

Each spinal nerve pair supplies skeletal muscles in a body segment with what?

Answer 24

• Somatic motor supply to skeletal muscles.

Question 25

Each spinal nerve pair supplies the skin and smooth muscles of arterioles in a body segment with what?

Answer 25

- Sympathetic nerve supply to skin and smooth muscle of arterioles.

Question 26

What is a dermatome?

Answer 26

Area of skin supplied with sensory innervation from a single spinal nerve. NB there is overlap by adjacent spinal nerves.

Question 27

What is a myotome?

Answer 27

Skeletal muscles supplied with motor innervation from single spinal nerve. NB myotome sometimes deep to dermatome of same spinal nerve, but not always e.g. diaphragm.

Question 28

Male nipple found in which dermatome?

Answer 28

T4

Question 29

Umbilicus found in which dermatome?

Answer 29

T10

Question 30

C2-C4 of the dermatome map cover which areas?

Answer 30

Posterior scalp, neck and shoulder.

Question 31

C5-T1 of the dermatome map cover which areas?

Answer 31

The upper limb.

Question 32

L2-Co1 of the dermatome map covers which areas?

Answer 32

The lower limb, gluteal region and perineum.

Question 33

What spinal nerves contribute to the cervical plexus?

Answer 33

C1-C4

Question 34

The cervical plexus (C1-C4) supplies what?

Answer 34

- The posterior scalp. - Neck. - Diaphragm.

Question 35

What spinal nerves contribute to the brachial plexus?

Answer 35

C5-T1.

Question 36

The brachial plexus supplies what?

Answer 36

The upper limb.

Question 37

What spinal nerves contribute to the lumbar plexus?

Answer 37

L1-L4.

Question 38

The lumbar plexus supplies what?

Answer 38

The lower limb.

Question 39

What spinal nerves contribute to the sacral plexus?

Answer 39

L5-S4.

Question 40

The sacral plexus supplies what?

Answer 40

- The lower limb. - Gluteal region. - Perineum.

Question 41

Where does sympathetic outflow originate from?

Answer 41

Control centres in the brain > then passes down spinal cord.

Question 42

What segments of the spinal cord have lateral horns for cell bodies?

Answer 42

T1 to L2.

Question 43

Through which root/rootlets does "presynaptic" sympathetic axons (motor innervation) pass through?

Answer 43

Anterior rootlets/roots.

Question 44

Where do presynaptic axons destined for the heart synapse?

Answer 44

T1 or cervical PARAverterbral ganglia.

Question 45

Through what do postsynaptic axons to the SA & AV nodes + the myocardium pass?

Answer 45

Cardiopulmonary splanchnic nerves.

Question 46

Where do presynaptic axons of the lungs synapse?

Answer 46

In the upper thoracic PARAvertebral ganglia.

Question 47

Where do postsynaptic axons of the lungs pass to reach the bronchiolar smooth muscle and mucous glands?

Answer 47

Cardiopulmonary splanchnic nerves.

Question 48

Presynaptic axons of the abdominopelvic organs synapse where?

Answer 48

In one of the PREvertebral ganglia.

Question 49

Give an example of a PREvertebral ganglia in which presynaptic axons of the abdominopelvic organs synapse?

Answer 49

- Coeliac ganglion of coeliac plexus (foregut). - Aorticorenal ganglion (kidney). - Superior mesenteric ganglion of SM plexus (midgut). - Inferior mesenteric ganglion of IF plexus (hindgut + pelvic/perineal organs).

Question 50

Presynaptic axons of the adrenal medulla pass through the aorticorenal ganglion to synapse where?

Answer 50

Directly onto the adrenaline/noradrenaline secreting cells of the adrenal medulla.

Question 51

Presynaptic parasympathetic axons leave the CNS via which cranial nerves?

Answer 51

- CN III. - CN VII. - CN IX. - CN X.

Question 52

Presynaptic parasympathetic axons leave the CNS via cranial nerves and what other nerves?

Answer 52

Sacral spinal nerves.

Question 53

Presynaptic parasympathetic axons leave the CNS and reach the eye via what?

Answer 53

The ciliary ganglion and CN III (oculomotor).

Question 54

Presynaptic parasympathetic axons leave the CNS and reach the lacrimal gland and salivary glands via what?

Answer 54

Parasympathetic ganglia in the head.

Question 55

Presynaptic parasympathetic axons leave the CNS and reach the organs of the neck, chest, and abdomen (to mid-gut) via what?

Answer 55

CN X - vagus.

Question 56

Presynaptic parasympathetic axons leave the CNS and reach the hindgut, pelvis and perineum via what?

Answer 56

Sacral spinal nerves.

Question 57

Name the ipsilateral symptoms of Horner's Syndrome?

Answer 57

- Miosis. - Ptosis. - Anhydrosis. - Increased warmth and redness.

Question 58

Impaired innervation to the head and neck of what kind is responsible for Horner's Syndrome?

Answer 58

Impaired sympathetic innervation.

Question 59

What may cause compression of the cervical parts of the sympathetic trunk, leading to Horner's Syndrome?

Answer 59

- Root of neck trauma. - Carotid dissection. - Internal jugular vein engorgement. - Deep cervical node metastases. - Pancoast tumour (lung apex).

Question 60

What causes ptosis in Horner's Syndrome?

Answer 60

A lack of sympathetic innervation of the smooth muscle within levator palpebrae superioris.

Question 61

What causes miosis in Horner's syndrome?

Answer 61

A lack of sympathetic innervation to dilator pupillae.

Question 62

What causes a reduction in sweating in Horner's syndrome?

Answer 62

Lack of sympathetic innervation to sweat glands of the skin.

Question 63

What causes increased warmth in Horner's syndrome?

Answer 63

Dilation of the skin arterioles.