First order neurons

Question 1

An afferent neuron is?

Answer 1

A neuron that carries sensory information from the PNS to the CNS.

Question 2

A pseudounipolar afferent neuron is named for the order of what?

Answer 2

In which the neurons are located:

• First-order afferent neuron
• Second-order neuron
• Third-order neuron

Question 3

Order for second-order and third-order neurons?

Answer 3

Second-order neuron - Brain/brainstem

or

Second-order neuron - third-order neuron - brain

Question 4

First-order afferent neuron is?

Answer 4

Located in the PNS

-Conveys the action potential from the sensory receptor to the CNS.
Once in the CNS, subsequent interneurons bring the information to the brain and/or brainstem.

Question 5

First-order neuron size?

Answer 5

Vary in diameter and amount of myelination

• Larger diameter = faster NCV
• Thicker myelination = faster NCV

The larger the axon diameter, the thicker the myelin sheath, (thus unmyelinated neurons will also have the smallest axon diameter)

Question 6

Cutaneous Neurons (Largest to smallest)

Answer 6

A-Beta
A-Delta
C

Question 7

Nociception (pain) is what neurons?

Answer 7

A-Delta and C afferents

Question 8

Temperature (non-noxious) is what neurons?

Answer 8

A-Delta and C afferents

Question 9

Light touch (includes vibration) is what neurons?

Answer 9

A-Beta afferent

Question 10

Muscle and Joint Neurons (largest to smallest)

Answer 10

Ia
Ib
II (same size/myelination as A-Beta)

Question 11

What type is annulospiral-ending?

Answer 11

Type Ia afferent

Question 12

What type is flower spray ending?

Answer 12

Type II afferent

Question 13

What type is Golgi Tendon Organ ending?

Answer 13

Type Ib afferent