neuron transmitters Flashcards
central nervous system
brain and spinal cord
peripheral nervous system
sensory (afferent) and motor (efferent)
afferent
arrives at the central nervous system
efferent
exit the central nervous system
-motor: outgoing
-effect treatment
autonomic
sympathetic and parasympathetic
-involuntary to viscera
somatic
voluntary to skeletal muscles
alpha motor neuron
sympathetic
stress
fight or flight
parasympathetic
peace
rest and digest
neuron
the basic structural unit of the nervous system
3 autonomical regions of a neuron
dendrites, cell body, axon
axon terminals
NMJ (ach is released here)
dendrites
receivers
-beginning of neuron
cell body
contains nucleus
-cell processes radiate out
axon
axon terminals
-senders/ transmitters
end of neuron
motor neuron (efferent, somatic)
dendrites (spinal cord) cell body (soma) axon (spinal cord), axon terminals (NMJ)
NMJ formation
- motor neuron axon
- axon terminal
- synapse
- motor end plate
- sarcolemma
motor end plate
receives ach
-initiates an AP
ICF
greater amounts of potassium than sodium
ECF
greater amounts of sodium than potassium
resting membrane potential
the difference in electrical between outside and inside of cell (polaried)
- more positive charges (Na + & K+) in ECF)
what means it is polarized
-70 mV
what causes the resting membrane potential
caused by the uneven separation of positively charged ions
at rest, K and NA channels allow more K outside and combined with Na already there, big (+) charge _____
relative to the inside (-70 mV)
how is RMP maintained
greater membrane K+ permeability
-K+ channels are open at rest allowing it to leak out causing a higher (+) charge outside than inside
how is RMP maintained?
greater membrane K+ permeability
-K+ channels are open at rest allowing it to leak out causing a higher (+) charge outside than inside
Na+ channels are ____ open at rest
NOT
-these channels allow more K+ outside and combined with Na+ already there, big + charge relative to inside
sodium-potassium pump
3 Na+ OUT of cell for every 2 K+ INTO the cell
-uses ATPase to perform job
what is the most active in bringing re-polarized cell back to RMP
sodium-potassium pump
polarization
changes in membrane permeability to Na and K+
rmp = -70mV
depolarization
to get the muscle contraction
characteristics of depolarization
More Na+ channels open
-greater + charge collecting in ICF
-relative difference between ECF and ICF becomes increasingly less negative and then positive
-70 mV —- 0 mV —- +20 mV
depolarization
threshold of _____ must be reached for
-55 for action potential to happen
hyperdepolarization
more K channels open
-greater (+) charge collecting in ECF
-relative difference between ECF and ICF increasingly negative
polarized membrane =
Na+ inside cell and K+ outside of cell (-70)
repolarization membrane
k+ outside of the cell and Na+ inside of the cell (-70)
neural impulse order
polarized membrane (-70) to -55 to + number depolarization threshold (Na+ rushes in then K+ begin to open) repolarization (back to threshold then K+ channels close, then hyperpolarization
graded potential
A change in the electrical potential on the membrane of an excitable cell (e.g. a nerve cell) in response to a stimulus, and where the magnitude of change is proportional to the strength of the stimulus
-70 to -55 mV: depolarizing GP, =
Na+ influx
-55 to +30 mV: depolarizing AP,
Na+ influx
after repolarization K+ and Na+ have to be re-distributed
Na+ - K+ pump
how do we get back from repolarized to RMP
have to get K+ back into ICF and Na+ into ECF
absolute refractory period
-during depolarization
-neuron unable to respond to another stimulus
-Na+ channels already open
relative refractory period
during repolarization
-neuron responds only to very strong stimulus
-K+ channels open (Na+ closed)
speed of propagation down an axon is due to
- myelin - fatty sheath around an axon (Schwann cells)
- axon diameter = larger =faster
axon diameter
type 11x is the largest
type 11a is moderate
type 1 is smallest
pre-synaptic cell = motor neuron
ap arrives at axon terminal
ap causes influx voltage-gated Ca+ channels to open
Ca+ accumulates in ICF causing ACH efflux
Postsynaptic cell = muscle fiber
ach binds to the receptor at the motor end plate
causes depolarization
ap moves along plasmalemma
down tubules
repolarization of plasmalemma
return to RMP of plasmalemma
atp is used in 3 different ways during muscular contraction
- myosin
- Na+ K+ pump
- SR and Ca+ pump
mechanisms size and strength
increase in muscle size and altered neural control
neural factors affecting the strength (SCARR)
- synchronizing of motor units
- coactivation of agonist and antagonist muscles
- autogenic inhibitions
- recruitment of motor units
- rate coding of motor units
synchronizing of motor units
may allow strength gains
coactivation of agonist and antagonist muscle
reduced coactivation may lead to strength gains
autogenic inhibitions
reflex inhibition of a motor neuron in repone to excessive tension in the muscle fiber supplies
-can override in emergency
recruitment
more motor units are recruited due to increased neural drive to alpha motor neuron
