NMJ Flashcards
What is involved in postural reflexes?
What else does this structure do?
Cerebellum!
Takes info from motor and sensory and compares them…
Learned movements!
What happens after ACh binds to a nicotinic receptor on a muscle cell??
Binds to this non-selective cation channel…
Na+ goes IN
K+ goes OUT
This causes a depolarization and an END PLATE POTENTIAL (EPP)
The EPP then moves out to the adjacent membrane and opens voltage gated Na+ channels. This causes an AP to go along the muscle cell!
What part of ACh after it is degraded by ACH esterase is reuptaken and reused?
Choline!
Do EPP’s summate? Do they always reach threshold?
they don’t need to summate. They ALWAYS reach threshold.
Threshold is -55 and EPP goes to -15.
So there is a large safety factor!
What does nerve gas do?
What are 2 other names for nerve gas?
Names = organophosphate pesticides, VX Sarin
Inhibits ACh esterase
Therefore it causes EPP to occur once and then no repolarization can occur… this causes paralysis because there is no more AP
Myotatic reflex?
Alpha, gamma, extrafusal muscle fibers, muscle spindle, intramural muscle fibers, 1a sensory afferent, inhibitory interneuron!
Stretch reflex
Alpha motor neuron goes to = extrafusal muscle fibers - causes contraction
1a sensory afferent goes from stretch receptor on muscle spindle to spinal cord and activates alpha motor neuron.
ALSO activates inhibitory interneuron to inhibit antagonist muscle.
Gamma motor neuron goes to intramural muscle fibers to stretch the stretch receptor to allow for proprioception.
Synapse vs NMJ
Synapse = neuron to neuron, many NT’s, summate required, inhibitory and excitatory
NMJ = neuron to skeletal muscle, only ACh, no summation, 1ap, 1 EPP, 1 AP, always excitatory!
EPP to -15mV
