Peripheral Nerve Flashcards
The majority of neurons are shaped
Multipolar
Ganglion cells of statoacoustic nerves and retinal are shaped
bipolar
Examples of Unipolar cells
Posterior root ganglion neurons
Cranial nerve ganglion neurons
Pain, touch, temperature and position
sense
Somatic Afferent
Motor signals that control striated
muscles
Somatic Efferent
“Visceral sensibility” - peristaltic
activity, blood pressure, bladder fullness, etc.
Visceral Afferent
Autonomic nervous system. Two
neurons linked together
Visceral Efferent
Nerve cell body in CNS; axon extends to
autonomic ganglion
Preganglionic
Nerve cell body in autonomic ganglion;
axon extends to visceral target
Postganglionic
Posterior Roots are
Sensory
Posterior Root ganglions are ________ neurons with two axon-like processes
Unipolar
Anterior Roots are
Motor
Posterior Rami serve
the back
Anterior Rami serve
anterior body
Nerve Trunks may contain
myelinated axons, unmyelinated axons, Schwann cells
Myelin
Spiral wrapping of glial membrane, covers up to 1 cm of axon, insulates and increases velocity of action potentials
Myelin is created by _______ in the CNS? in the PNS?
Oligodendroglia cells = CNS
Schwanna cells = PNS
Space between internodal segments
Node of Ranvier
Local anesthetics are able to act where?
Nodes of Ranvier
What kind of axons are important in pain transmission?
Unmyelinated
Saltatory Conduction
Membrane depolarization takes place at nodes
Wave of depolarization is renewed at next node
Conduction can take place in either direction
If an axon is crushed, the axon ______ to the crush will degenerate
distal
The axon _______ to the crush will die back a short distance
proximal
A cell body with a crushed axon will react by
becoming more metabolically active (chromatolysis)
When axons and myelin degenerate, ____________ engulfs the debris
Macrophages
More Schwann cells =
Shorter internodal distance
Slower conduction time
A - Alpha afferent velocity and function
70-120 m/sec, myotatic reflex
A- Beta velocity and function
60-80 m/sec, deep touch
A - Delta velocity and function
10-30 m/sec, light touch/fast pain
C velocity and function
0.5-2.5 m/sec, slow pain
Pathway of Motor Nerves to Striated muscles
Anterior horn of spinal cord, anterior root, spinal nerve, striated muscles
Neurotransmitter of the PNS
Acetylcholine
This structure lies parallel to muscle fibers within striated muscles
Neuromuscular spindle
Nuclear Bag contains:
Annulospiral ending - senses stretch
A - alpha sensory fiber which conducts stretch signal back to spinal cord
Adjacent to the Nuclear Bag is:
Intrafusal muscle fibers
Innervated by gamma motor neurons
Function to increase tension on nuclear bag
(do not move limb)
Extrafusal muscle fibers:
Move limb
Innervated by Alpha motor neurons
the nerve cell body (located in the CNS) and its axon (located in the PNS) that innervates a striated muscle.
Lower Motor Neuron
A lesion of the Lower motor neuron leads to
Flaccid paralysis Atonia Areflexia Fasciculations Muscle atrophy
Atonia
Loss of muscle tone
Areflexia
Loss of the stretch (myotatic) reflex
Fasciculations
Spontaneous contraction of bundles of muscle fibers
Lower Motor Neuron lesions result from lesions of:
Peripheral nerve
Anterior root
Anterior horn motor neurons
Myasthenia Gravis
Most common primary disorder of neuromuscular
transmission.
Patients complain of weakness.
Drooping eyelids (ptosis) is the first symptom in most cases.
Oropharyngeal muscle weakness is common.
