PNS

Question 1

What is the PNS?

Answer 1

Peripheral Nervous System
- Nerves (cranial and spinal) and ganglia

Question 2

What are the 2 divisions of the PNS?

Answer 2

1. Sensory - afferent
2. Motor - efferent
   —> Somatic
   —> Autonomic —> Sympathetic
   —> Parasympathetic

Question 3

What are the 12 cranial nerve pairs?

Answer 3

I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlea
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal

Question 4

What are the 31 spinal nerve pairs?

Answer 4

C8
T12
L5
S5
Co1

Question 5

What are somatic nerves?

Answer 5

Nerves for voluntary control
- afferent —> sensory
- from skin, skeletal muscles, joints
- spinal ganglia
- efferent —> motor
- to skeletal muscles

Question 6

What is a dermatome?

Answer 6

Area of skin supplied by a single spinal nerve

Question 7

What is a myotome?

Answer 7

Group of muscles innervated by a single spinal nerve

Question 8

What are visceral nerves?

Answer 8

Nerves for involuntary control of viscera (internal organs) —> ANS
- afferent —> sensory
- spinal ganglia
- efferent —> motor
- peripheral gangli
- sympathetic —> viscera + periphery
- parasympathetic —> viscera

Question 9

What is a ganglion, nucleus and plexus?

Answer 9

Ganglion = collection of cell bodies outside the CNS
Nucleus = collection of cell bodies inside the CNS
Plexus = network of interconnecting nerves

Question 10

What is the structure of peripheral nerves?

Answer 10

Axons —> fascicle —> nerve
- endoneurium covers axon
- perineurium covers fascicle
- epineurium covers nerve

Question 11

How are peripheral nerves classified? (2)

Answer 11

1. Conduction velocity —> A (fastest), B, C (slowest)
2. Axonal diameter —> I (largest), II, III, IV (smallest)
   - sensory only

Question 12

How are sensory receptors classified? (2)

Answer 12

1. Source - external —> exteroceptors
   eg. pain, temp, touch
   - internal —> proprioceptors
   eg. movement, joint position
   —> enteroceptors
   eg. gut movement, blood pH
2. Detection - chemoreceptors
   - photoreceptors
   - thermorecepetors
   - mechanoreceptors
   - nociceptors

Question 13

What are the 5 types of sensory receptors based on detection?

Answer 13

1. Chemoreceptors —> chemicals eg. smell
2. Photoreceptors —> light
3. Thermorecepetors —> temp
4. Mechanoreceptors —> ion channel opens eg. touch
5. Nociceptors —> tissue damage —> pain

Question 14

What are the 3 proprioceptors?

Answer 14

1. Muscle spindles —> detect length
2. Golgi tendon organs —> detect tension
3. Joint receptors —> detect start/end of movement

Question 15

What is a motor unit?

Answer 15

Motor neurone with all the muscle fibres it innervates

Question 16

How are sympathetic nerves organised?

Answer 16

Thoracolumbar —> T1-L2
- Pre-ganglionic all from T1-L2 lateral horns —> all to
sympathetic trunk
- Ganglia - skin/heart —> in sympathetic trunk
- other —> pre-aortic ganglia

Question 17

How are parasympathetic nerves organised?

Answer 17

Craniosacral
- Cranial III —> lacrimal gland
VII —> pupillary constriction
—> submandibular salivary gland
—> sublingual salivary gland
IX —> parotid gland
X —> heart
—> abdominal viscera
- S2-S4 —> abdominal viscera
—> pelvic viscera