nerve elements Flashcards
_________ neurons (aka somatosensory), _________ neurons (aka motor), and __________ nerves are the components of a peripheral nerve
afferent
efferent
autonomic
PNS order of physical size
peripheral nerve > afferent and efferent fibers > fascicles (bundles of axons) > individual nerve fibers (aka axons)
functional unit is the
axon
________ cells surround the axon
schwann
_______ ______ are around the axons and between the axon and schwann cells
myelin sheaths are around the axons (in myelinated nerves) and between the axon and schwann cells
______ of _______ are interspersed among the axon at spaces that are not myelinated
nodes of ranvier
these nodes, or axon intervals, have _______ gated ______ ________ that propagate the nerve conduction and are primary site for LA action
voltage
Na channels
electrical impulses are conducted by localized depolarizations which transmit an electrical signal. resting membrane potential is negative _____ to _____ mV
-60 to -90
_________ gated _______ channels are the primary mediator for influx of ______ which propagates depolarization
voltage gated Na channels
Na
there are three states of the Na channel:
- activated open
- inactivated closed
- rested closed
LAs have the ability to block the channels in the ____ ____ _____ only
first two states only (activated open and inactivated closed)
the inability of the nerve to fire during inactivated state, the refractory period, prevents ______ _______ of the nerve impulses
retrograde conduction
nerve fibers can be _______ or __________
myelinated or unmyelinated
generally, myelinated are _____ fibers, have _______ conduction, and are associated with _______ and ______ function
larger
faster
motor and sensory function
unmyelinated fibers generally have _______ conduction and transmit ________, _______, and ________ impulses
slower
pain
temp
autonomic
nerve fiber size is classified as ___, ____, and _____, with ______ being the largest and _______ being the smallest
A, B, and C
A
C
A fibers have subgroups of _______, ________, _______, and ________ fibers, and are the most myelinated
alpha
beta
gamma
delta
alpha fibers functionality includes ______ _______ and _______-
motor signals
proprioception
beta fibers functionality includes ______, _______, and ______ recognition
motor, touch, and pressure