Nerve Structure

Question 1

What is a nerve?

Answer 1

A nerve is a bundle of axons in the PNS

Question 2

Afferent Division in PNS (to the CNS)

Answer 2

Sensory Receptors:
•Special Sensory: 5 senses (smell, taste, vision, balance, hearing)
•Somatic Sensory: skeletal muscles, joints, skin surface (pressure, touch, pain, temp., position)
Visceral Sensory: internal organs

Question 3

Efferent Division in PNS (from the CNS)

Answer 3

Somatic Nervous System:

• Effector: Skeletal Muscle

Autonomic Nervous System:

• Effector: Smooth muscle, Cardiac muscle, glands

•Parasympathetic division (rest & digest)

•Sympathetic division (fight & flight)

Question 4

PNS divided into 2 groups …

Answer 4

Cranial Nerves
Spinal Nerves

Question 5

Cranial Nerves

Answer 5

12 pairs of cranial nerves

• pass into face and neck through foramina in the skull
• nerves are entirely sensory or mixed

Question 6

Spinal Nerves

Answer 6

31 pairs of spinal nerves

• join the spinal cord at intervertebral foramina
• pass either into the upper and lower limbs or into the body wall
• are mixed nerves (carry sensory, motor & autonomic)
• formed by dorsal and ventral roots

Question 7

Node of Ranvier

Answer 7

unmyelinated gaps in the axon myelin sheath (Schwann cell membrane)

Question 8

Neurilemma

Answer 8

• outer layer of the Schwann cell
• covers the axolemma at the myelinated internodes

Question 9

3 Connective tissue membranes around a nerve

Answer 9

1. Epineurium: layer enclosing a variable number of fascicles (bundles of neurons)
2. Perineurium: layer enclosing each fascicle
3. Endoneurium: layer enclosing each axon within the fascicle

Question 10

Vasa nervorum

Answer 10

• small arteries that provide blood supply to peripheral nerves