Lecture 11: nerve types

Factor that determines the type of first-order sensory neuron

The stimulus modality (such as touch, pain, or temperature), which dictates which receptors and sensory fibres carry the information.

Receptors and nerve fibres that mediate proprioception

Muscle spindles, Golgi tendon organs, and other mechanoreceptors; conducted mainly via $\text{A-}\alpha$ and $\text{A-}\beta$ fibres.

Receptors and nerve fibres that mediate touch

Mechanoreceptors; conducted mainly via $\text{A-}\beta$ fibres.

Receptors and nerve fibres that mediate temperature

Cold and warmth receptors; conducted via $\text{A-}\delta$ and C fibres.

Receptors that detect pain and their associated nerve fibres

Nociceptors (free nerve endings); signals travel via $\text{A-}\delta$ and C fibres.

Nerve fibres responsible for fast, sharp pain

Mainly $\text{A-}\delta$ fibres, which are myelinated and conduct signals relatively quickly.

Nerve fibres responsible for slow, aching pain

Mainly C fibres, which are unmyelinated and conduct signals slowly.

Receptors and nerve fibres that mediate itch

Pruritic receptors; conducted mainly via C fibres.

Sensory nerve fibre order from fastest to slowest conduction speed

$$\text{A-}\alpha \rightarrow \text{A-}\beta \rightarrow \text{A-}\delta \rightarrow \text{C}$$

Effect of myelination on nerve conduction speed

Myelin increases signal conduction speed; myelinated $\text{A-}\delta$ fibres conduct significantly faster than unmyelinated C fibres.