Peripheral nervous system terminology

What does the peripheral nervous system consist of

12 pairs of cranial nerves, 31 pairs of spinal nerves, and all associated ganglia and sensory receptors

motor, sensory, and autonomic neurons that innervate end-organs that include sensory receptors, muscles and glands

sensory nerves originate in the ___ root

dorsal

motor nerves originate in the _____ horn

anterior

autonomic neurons are divided into the

sympathetic and parasympathetic nerves

where does sympathetic nerves originate?

latearl horn of the throacic spinal cord

where does parasympathetic nerves originate

the latearl gray matter of the sacral level of the spinal cord and the brain itself

Name the 5 cutaneous sensory end-organ receptors

thermoreceptors

nociceptors

mechanoreceptors

chemoreceptors

photoreceptors

what is an axon

a projection of a nerve away from the cell body that conducts impulses

what is a dendrite

an extension of the cell body that receives signals from other neurons

what is the endoneurium

the innermost covering of a peripheral nerve that surrounds each individual axon

what is the epineurium

the outermost covering of a peripheral nerve that surrounds the entire nerve and provides a buffer for the peripheral nerve

what is a motor unit

a single motor neuron and all of the muscle fibers that it innervates

what is myelin

proteins and lipids that form to create a sheath around particular nerves, increases conductivity of the nerve impulse

what is nerve conduciton velocity

measures the speed of a nerve impulse along the axon of a nerve

what is a neuron

nerve cells that receive and send signals to other nerve cells, comprised of a cell body, axon and dendrites

what are nodes of ranvier

brief gaps in myelination of an axon, serves to facilitate rapid conduction of a nerve impulse via jumping from gap node to gap node

what is the perineurium

the middle layer of covering surround the peripheral nerve that envelopes fascicles or groups of axons and maintains the blood-nerve barrier

what is saltatory conduction

an action potential moving along an axon in a jumping fashion from node to node, decreases the use of sodium potassium pumps and increases speed of conduction

what is a schwann cell

cells that cover the nerve fibers within the peripheral nervous system and form the myelin sheath

characteristics of A fibers

large, myelinated, high conduction rate

what are the subsets of A fibers?

alpha, beta, gamma, delta

what are alpha motor neurons

muscle spindle primary endings, golgi tendon organs, touch

what are beta neurons

touch, kinesthesia, muscle spindle secondary endings

what are gamma neurons

touch, pressure,, gamma motor neurons

what are delta neurons

pain, touch, pressure, temperature

characteristics of B fibers

medium fibers, myelinated, reasonably fast conduction rate, preganglionic fibers of the autonomic system

characteristics of C fibers

small, poorly myelinated or unmyelinated, slowed conduction rate, postganglionic fibers of the sympathetic system, exteroceptors for pain, temperature and touch