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24 Cards in this Set
- Front
- Back
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how much larger is threshold than resting membrane potential?
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10-20mV larger than resting potential
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what is the equilibrium potential for sodium?
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+60 mV
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what is the equilibrium potential for potassium?
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-80 mV
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what is the formal definition of the threshold?
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the voltage at which there is 50% probability of evoking an action potential.
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can action potentials be less than full-amplitude?
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no. they are all-or-none
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If we were to apply Ohm's law to membrane potentials, what is the formula for the V we would use?
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Vmembrane-EqVion
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what is g?
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conductance of the ion. g=1/R
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what happens immediately after the voltage-gated Na channels open?
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they begin "inactivation", where the channel becomes impermeable to Na.
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when do the Na channels recover from inactivation into the closed state?
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at negative membrane potentials
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what does activation of the voltage-gated K+ channels do to the membrane potential?
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Drives the potential down towards the equilibrium potential of K+.
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role of voltage-gated K+ channels
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accelerate repolarization by driving the membrane potential down towards Ek
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do voltage-gated K+ channels inactivate?
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no. they close during repolarization
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what is the role of voltage-gated calcium channels in the nerve terminal?
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action potential causes opening of Ca++ channel and influx of Ca++, which is required for release of neurotransmitter.
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what is different about a dendrite action potential?
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the upstroke is longer and the duration of the action potential is longer. the upstroke is longer because Ca++ channels open slowly and also because there are few Na channels. The duration is longer because Ca++ channels inactivate slowly.
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what is the reason for the slow action potentials and slow contraction in smooth muscle cells?
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Ca++ channels
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what is responsible for the very long action potentials in cardiac muscle?
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voltage-gated Ca++ channels
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what causes the upstroke in cardiac pacemaker cells?
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voltage-gated Ca++ channels
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what are the three types of ion flows that propagate action potentials?
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influx of Na, electrotonic conduction of ions inside and outside the cell, efflux of K+ and capacitive ion flow.
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what carries the electrotonic ion flow inside the cell?
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K+
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what carries the electrotonic ion flow outside the cell?
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Na+ and Cl-
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what carries the outward K+ current flow?
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leaky K+ channels
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what are the two ways of increasing action potential speed?
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increase diameter of axon, increase insulation of the axon to allow electrotonic ion flow to travel farther
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in a myelinated axon, what depolarizes the next sodium channel in the propagation chain?
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electrotonic ion flow
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how do local anesthetics block pain perception?
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raise the threshold for sensory neuron depolarization by blocking sodium channels
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