Electrophysiology II Flashcards
What is a level of depolarization which when exceeded always results in an action potential?
Threshold
What are voltage changes common to excitable cells?
Action potentials
Action potentials are always what?
All or nothing
What gates in Na+ (and sometimes Ca+) channels open upon depolarization?
M (activation) gates
What gates in Na+ (and sometimes Ca2+) channels close upon depolarization?
H (inactivation) gates
K+ channels with what type of gates open upon depolarization?
N(activation) gates
The following gates are characteristic of what: M open, n open, h close?
Depolarization
The following gates are characteristic of what: m close, n close, h open?
Repolarization
What are the orders in gates from fastest to slowest?
M,h,n
Positive feedback interaction of depolarizing activation of m gates and the resulting depolarization of inward Ina is known as what?
Hodgkin cycle
What is the period of which h gates are closed and it’s not possible to generate another action potential?
Absolute refractory period
What occurs because because the resulting depolarization closes h gates on muscle Na channels keeping them in the equivalent of an absolute refractory period?
Hyperkalemic periodic paralysis
What is the period in which n gates are open and it takes an increased stimulus current to generate another action potential?
Relative refractory period
What is the term referring to action potentials that are recorded extracellularly and are recoded together simultaneously?
Compound action potentials
What are the 2 kinds of local circuit currents?
Resistive current and capacitive current
What current flows by actual movement of ions through channels and inward IR depolarization?
Resistive current
What current flows because of charge displacement across the lipid bilayer of the membrane and outward Ic depolarizes?
Capacitive current
What is determined by stimulating a periphery nerve and recording the compound action potential at a known distance?
Conduction velocity
Conduction velocity is proportional to what?
Fiber diameter
What is the general conduction velocity in unmyelinated fibers?
2m/s
Conduction is characterized by what?
Inflow of resistive current, out flow of capacitive current
What type of fibers propagate action potentials by saltatory conduction?
Myelinated fibers
The myelin decrease capacitance of what region preventing out flow of capacitive current?
Intermodal region
The area in a myelinated axon where the axon membrane is exposed and the capacitive current can flow out is known as what?
Node of Ranvier
What is the conduction velocity of myelinated fibers?
Between 5 and 120 m/s
The resistive current of the excited node produces enough capacitive current to bring the next two nodes to threshold is known as what?
Safety factor
What fiber type has a velocity of 120 m/s, found in spindle afferents for proprioception and alpha motor neuron efferents?
Large myelinated
What fiber type travels 15-70m/s, has touch/ pressure afferents and gamma motor neuron efferents?
Intermediate myelinated fibers
What type of fibers travel at 1 m/s, have pain/temperature afferents and autonomic efferents?
Small unmyelinated
Demyelination results in what?
Capacitive current leaking out and a block of propagation
