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31

events that occur at a chemical synapse

chemical synapses allow the release and reception of chemical neurotransmitters. They are more common than electrical synapses and are usually made up of two parts: the axon terminal and a neurotransmitter receptor region.

the axon terminal is a knob like structure of the pre synaptic neuron. The axon terminal contains many synaptic vesicles containing neurotransmitters.

The electrical current from the pre synaptic neuron dissipates into the synaptic cleft. Therefore chemical synapses prevent nerve impulses being directly transmitted between neurons.

32

Major types of neurotransmitters

Acetylcholine
Amino acids (GABA, glutamic acid)
Monoamines (dopamine, histamine, norepinephrine, serotonin)
Neuropeptides (endorphins, enkephalins, substance P)
Gases (nitric oxide)

33

What is an action potential

An action potential is the basis for a nerve impulse.

It is based on the cell membrane reaching its threshold potential, and is a brief reversal of membrane potential with a change in voltage of 100mv

34

Classifications of nerve fibers

They are classified by their diameter, degree of myelination, and speed of conduction.

Group A fibers mostly serve joints, skeletal muscles and skin. They are primarily somatic sensory and motor fibers, with the largest diameter of all types of fibers and thick myelin sheaths. These fibers conduct impulses at speeds as high as 300mph.

Group be fibers are of intermediate diameter, with light myelination. They conduct impulses at speeds averaging approx. 20mph.

Group C fibers are non-myelinated, with the smallest diameter, and cannot create saltatory conduction. They conduct impulses at 2mph or less.