Anatomy

PNS Part I

Monday, November 17, 2014

8:14 AM

Introduction

Peripheral NS

Divides into:

Autonomic

Somatic

Ganglia- groups of cell bodies

Nerves- fiber tracts

Nerve Structure

Axon covered by Endoneurium-connective tissue wrappings around axon

Fascicle- collection/bundle of axons.

Perineurium- surrounds fasicle

Epineurium- surrounds bundles of perineurium

Blue - Sensory (Afferent) neuron- sense nerve impulse to CNS. Enters through dorsal root.

Red- Motor (efferent) neuron- exits from ventral root. It exits to effector organ.

Mix- Spinal nerve- mixed nerves. It’s a combo of sensory and motor neurons.

Dorsal ramus- serves the back

Ventral rams- serves the chest, the front, and the arms and legs

These nerves are also mixed.

Regeneration of Nerve Fibers

The further away the damage is from the cell body, the more likely it is to regenerate.

Also if the damage was little, it will be able to regenerate.

1. (Wallerian degeneration)

* The axon becomes fragmented at the injury site ..

* Everything distal to the damage will degenerate - axon starts to shred. (known as Wallerian degeneration)

1. Macrophages

* clean out the dead axon distal to the injury.

* They don’t not phagocize the schwann cells. They clean everything else. They stimulate growth factor of schwann cells.

1. Regeneration tube

* Axon sprouts or filaments, grow through a regeneration tube formed by schwann cells.

1. New myelin sheath forms

-schwann cells wrap around axon and produces a new myelin sheath

Chromatolysis- occurs in the soma of the neuron. Super duper Protein production by the Nissl bodies (rough er)- increased protein synthesis.

When nerve is damage, the protein synthesis increases!

Regeneration of Nerve Fibers

CNS

Oligodendrocytes

* Growth-inhibiting proteins

* Neurite outgrowth inhibitor (Nogo A)- inhibits axonal regeneration

Astrocytes

* Glial scar tissue

*...