Module 10 - Structure of a neuron

What are the 2 types of cells in nervous system

Neurons, Neuroglia cells

Neuroglia cells

Non neural (no action potential)
Supports and protects neurons
More than 50% of brain weight
4 types in CNS, 2 types in PNS

Trigger zone

Where electrical signal/action potential is created
Consists of axon hillock and Initial segment

Axon terminals

End of axon

Presynaptic terminal/Synaptic end bulb

End of axon terminal
Start of synapse

Axoplasm/axolemma

Axons cytoplasm and cell membrane

Collateral axon

Branching out of an axon

Schwann cells

Supports neuron
Wraps PNS
Form myelin sheath

Node of ranvier

Spaces on axon with no myelin sheath

Axon diameter and length specialty

Diameter stays the same in each axon, length varies

Why do axons have vesicles that store neurotransmitters in presynaptic terminal and dangers that can occur

To send info to next muscle
Can cause a stimulation or inhabitation
Vesicles move up and down axon, if disease gets in, could get to CNS

How can neurons be classified

Function or structure

Function classification of neuron

Motor/efferent neuron - Action potential away from CNS
Sensory/afferent neuron toward CNS
Interneurons - Connects sensory to motor neuron in CNS

Structure classification of neurons

Multipolar - Many dendrites, 1 axon (most neurons in CNS and most motor neurons)
Bipolar - 1 dendrite, 1 axon (Sensory organs, eyes, nose)
Unipolar neuron - Cell body stuck off onto side, 1 axon, 1 cell body, (touch, pressure receptors)

Astrocytes

Most numerous
Star shaped
Releases chemicals to form tight junctions
Helps maintain blood brain barrier
Has foot processes that branch off and cover blood vessel surfaces

What are the 4 CNS neuroglia

Astrocytes
Ependymal cells
Microglial
Oligodendrocytes

Ependymal cells

Lines ventricles of brain and central canal
Makes Choroid plexus which produces cerebral spinal fluid
Contains cilia

Micorglial cells

Floats around and digests foreign objects
Clean up crew

Oligodendrocytes

Forms myelin sheath for CNS
Surrounds axon
Can form myelin sheath for many axons

What are the 2 neuroglial cells for PNS

Schwann cells
Satellite cells

Schwann cells

Wraps around axon multiple times
Forms myelin sheath
Helps speed up action potential
Can only wrap 1 axon

Satellite cells

Protects cell bodies in ganglia

Unmyelinated sheath

Does not wrap around fully but still wraps around a little
Can do multiple axons

Tract/Nerve tract

Bundle of myelinated axons in CNS

Nucleus

Collection of cell bodies in CNS

White matter

Regions in spinal cord/brain with groups of myelinated axons

Gray matter

Regions in brain/spinal cord consisting of neuron cell bodies, dendrites, unmyelinated axons and neuroglia
Processes info
In brain, is on outside and some on inside - In spinal cord, gray is inner