Nerves + Ganglia + Regeneration

What is a nerve

a bundle of axons myelinated and unmyelinated covered by connective tissue in the PNS

What are the three connective tissue coverings of a nerve from superficial to deep

epineurium, perineurium, endoneurium

Epineurium

Outermost tissue covering

dense fibrous connective tissue that covers entire nerve

Perineurium

Middle tissue covering layer

course connective tissue around fascicles (bundles of axons)

Endoneurium

inner most layer

Loose connective tissue around individual axons and myelin sheaths

Do nerves have blood vessels and why

Yes - nerves also need oxygen and nutrients

Most nerves are _______ (afferent/efferent)

mixture of efferent and afferent

• somatic afferent and somatic efferent

• visceral afferent and visceral efferent

Peripheral nerves are classified as ______ or _____ nerves

cranial or spinal nerves

SA/ME and DA/VE acronym

sensory afferent/ motor efferent

dorsal afferent/ ventral efferent

Difference between somatic and visceral nerves

somatic nerves are voluntary → skin, muscles etc

visceral nerves are involuntary → organs glands smooth muscles

Ganglia

bundle of cell bodies in the PNS

(nuclei in the CNS)

What are the two main ganglias in the pns

dorsal root ganglia and autonomic ganglia (sympathetic and parasympathetic that carries post ganglionic fibers)

Dorsal root ganglia

Sensory afferent neuron cell bodies

somatic (based on slides but based on chat it has visceral as well)

Autonomic ganglia

motor neurons + visceral

Mature nerves are ____

amitotic → don’t divide

How does nerve fibers (axons) regenerate in the PNS

If the soma / cell body is intact, the axons will regenerate

guided by shwann cells

Can the CNS regenerate fibers

really poorly because oligodendrocytes have growth inhibiting proteins that block regeneration