PNS Revision

Question 1

Are motor neurones multipolar or unipolar?

Answer 1

Multipolar

Question 2

Are sensory neurones multipolar or unipolar?

Answer 2

Unipolar

Question 3

Where do motor neurones go to and from?

Answer 3

Efferent neurones i.e. towards body wall/ cavity/ organ
FROM upper motor neurone within a motor tract in CNS
TO lower motor neurone within cranial or spinal nerve

Question 4

Where do sensory neurones go to and from?

Answer 4

Afferent neurones i.e. to brain
FROM primary afferent or visceral neurone within cranial or spinal nerve
TO 2nd order neurone within a sensory tract in the CNS

Question 5

What are nerve cell bodies called in the CNS vs in the PNS?

Answer 5

CNS - nucleus

PNS - ganglion

Question 6

What are bundles of axons called in the CNS vs in the PNS?

Answer 6

CNS - tract

PNS - nerve

Question 7

How many spinal nerves are there vs how many vertebrae are there?

Answer 7

C1-C8 but ONLY 7 CERVICAL VERTEBRAE
T1 - T12  
L1 - L5
S1 - S5
Co1
for the rest - same number of spinal nerves as vertebrae

Question 8

What are the nerve plexuses?

Answer 8

Networks of intertwinned anterior rami
Cervical - C1- C4
Brachial - C5 - T1
Lumbar - L1 - L4
Sacral - L5 - S4

Question 9

What is a dermatome?

Answer 9

Area of skin supplied by both the anterior and posterior ramus of that spinal nerve

Question 10

What is a myotome?

Answer 10

Skeletal muscles supplied with motor innervation by both anterior and posterior ramus of that spinal nerve

Question 11

Where does sympathetic outflow originate?

Answer 11

From autonomic centres in brain

Question 12

Where does the sympathetic outflow exit the spinal cord?

Answer 12

From levels T1 - L2

Question 13

What does the sympathetic outflow supply?

Answer 13

Skin sweat glands
Skin arrector muscles
All arterioles (sympathetic tone)

Question 14

Where do nerves to and from the heart pass?

Answer 14

Presynaptic axons synapse in T1 or cervical para-vertebral ganglia
Postsynaptic axons pass in cardiopulmonary splanchnic nerves to SA and AV nodes and myocardium

Question 15

Where do nerves to and from the lungs pass?

Answer 15

Presynaptic - upper thoracic paravertebral ganglia

Postsynaptic - pass in cardiopulmonary splanchnic nerves to bronchiolar smooth muscle and mucous glands

Question 16

Where do nerves to and from the abdominal organs pass?

Answer 16

Presynaptic - one of the prevertebral ganglia e.g.
celiac ganglion of celiac plexus (foregut)
aorticorenal ganglia (kidney)
Superior mesenteric ganglion of SM plexus (midgut)
inferior mesenteric ganglion of IF plexus (hindgut and pelvic/ perineal organs)

Question 17

Where do nerves to and from the adrenal medulla pass?

Answer 17

Presynaptic - aorticorenal ganglion

Synapse directly with adrenaline/noradrenaline secreting cells of adrenal medulla i.e. no postsynaptic ganglia

Question 18

What causes Horner’s syndrome?

Answer 18

Damage to sympathetic trunk e.g.
trauma
arch of aorta dissection 
internal jugular vein engorgement
goitre
deep cervical node metastases
lung apex malignancy (pancoast tumour)

Question 19

What are the signs of horner’s syndrome?

Answer 19

Facial ptosis - due to lack of sympathetic innervation of smooth muscle in levator palpebrae superioris
Miosis - pinpoint pupil due to lack of sympathetic innervation of dilator papillae
Reduced sweating - due to lack of sympathetic innervation of skin sweat glands

Question 20

Where do presynaptic parasympathetic axons leave the CNS?

Answer 20

Via CNIII, VII, IX, X and sacral spinal nerves

Question 21

Where do parasympathetic axons travel to?

Answer 21

Eye via ciliary ganglion
Lacrimal gland and salivary glands via parasympathetic ganglion
Organs of neck, chest and abdomen via vagus nerve
Hindgut, midgut and perineum via sacral spinal nerves