NERVE PHYSIOLOGY Flashcards
coordinates the activities of the other organs in response to signals from the external and internal environment
functions as activation of muscles for movement, control of glandular secretion, regulation of heart rate and blood pressure, and maintenance of body tempt
nervous system
brain and spinal cord enclosed in bony coverings
central nervous system
cranial and spinal nerves
peripheral nervous system
supportive cells
non excitable
regulation, support physical and and metabolic needs of neurons
neuroglia
excitable cells
specialized for communication and signaling
mostly amitotic, with a high metabolic rate
neurons
neuroglia in the CNS
microglia
ependymal cells
astrocytes
oligodendrocytes
neuroglia in the PNS
satellite cells
schwann cells
myelinating cell in the PNS
schwann cells
encapsulate dorsal root and cranial nerve ganglion
satellite cells
in the CNS
most abundant
controls the chemical environment
aids in synapse formation; buffer the extracellular environment
connects neurons to blood vessels
Astrocytes
in the cns it is a myelinating cell
oligodendrocytes
in the cns
phagocytic cell
important role in immune responses
microglia
ciliated
forms the epithelium lining the ventricular spaces of the brain, contains CSF
ependymal cells
functional unit
interconnected neurons
coded by action potentials
neurons
axon hillock
area where the action potentials are created
axon terminal
presynaptic terminal; where neurotransmitters are located, majority of NTAs are acetylcholine
increases the speed of nerve impulses transmission
dendrites are unmyelinated
myelin sheath
requires metabolic energy and involves calcium ions
guided by microtubules (kinesin and dynein)
axonal transport
membrane bound organelles and mitochondria
rate:400mm/day
fast axonal transport
substances dissolved in plasma
rate 1mm/day
transports proteins such as actin, neurofilaments and microtubules
rate limiting for the regeneration of axons
slow axonal transport
transport from soma toward the axon terminals
kinesin
anterograde axonal transport
transport from axon terminal to the soma
involves dynein
retrograde axonal transport
when a peripheral nerve is cut the part of the nerve separated from the cell body (distal part shows a series of chemical and physical degenerative changes
axon swells, myelin sheath form bead like structures
wallerian degeneration
electrical potential across the cellular membrane of nerve cells
membrane potential
unequal electrolytes distribution between ECF/ICF
diffusion ions down their concentration gradients
selective permeability of plasma membrane
electrical attraction of cations and anions
resting membrane potential
when gated ion channels open ions, diffuse across the membrane following their ______________
this movement of charge is an electrical current and create voltage change across the membrane
electrochemical gradient
inside the membrane becomes less negative (or even reverses)
increases the probability of producing nerve impulses
depolarization
membrane returns to its resting membrane potential
repolarization
inside of the membrane becomes more negative than the resting potential
reduces the probability of producing nerve impulses
hyperpolarization
local disturbances in membrane potential
depolarization decreases potential across cell membrane due to opening of gated Na+ channels
Na+ rushes in down concentration and electrical gradients
graded or local potential
amplitude is proportional to the size of the stimulus
graded
decremental
does not spread
short distance signals
additive effect of several subthreshold stimuli in the regeneration of nerve impulses
summation
the same presynaptic neuron stimulates the postsynaptic neuron multiple times in a brief period
temporal summation
multiple neurons all stimulate postsynaptic neuron
spatial summation
rapid all or none change in the membrane potential following of the nerve by a suitable threshold stimulus
voltage dependent ion channels
action potential
during the time when Na+ activation channels are open and inactivation channels are closed, the membrane cannot respond to another stimulus
(Na+ channels must be in their resting state to respond to another stimulus)
Absolute refractory period
for a time after the absolute refractory period (when Na+ channels are in their resting state) the K+ channels are still open
during this time the threshold to start another action potential is increased
Relative refractory period
depolarization only at nodes of ranvier (areas along the axon that are unmyelinated and where there is high density of voltage-gated ion channels)
current carried by ions flows through extracellular fluid from node to node
saltatory conduction
an action potential spreads (propagates) over the surface of the axolemma
an action potential must pass through each point along the neuron cell membrane which makes the conduction of the nerve impulse relatively slow
continuous conduction
