Membrane Potential Flashcards by britt rank

Nerves and muscles are ______________

excitable tissues

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They use membrane potential to propagate an action potential (spark).

excitable tissues

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In nerves, action potentials are used to ____________

transmit nerve impulses

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In muscles, action potentials _________________

trigger muscle contractions.

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are propagated from the axon hillock to the axon terminal

action potentials (nerve impulses)

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are initiated at the axon hillock, and conducted throughout a nerve fiber (axon)

action potentials (nerve impulses)

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are highly irritable

neurons

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electrical impulses carried along muscle cell membranes and neuron axons

action potentials

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only generated by muscle cells and neurons

action potentials

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the underlying functional feature of the nervous system

action potentials,

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an action potential in the axon of a neuron is a _______

nerve impulse

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they do not decrease in strength over distance

nerve impulse (action potentials )

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are always the same voltage, regardless of the stimulus (all-or-none)

action potentials

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the potential difference (–70 mV) across the membrane of a (voltage)

resting neuron

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it is generated by different concentrations of Na+, K+, Cl, and protein anions (A)

Resting Membrane Potential

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ionic differences are the consequence of

differential permeability of the neurilemma to Na+ and K+

operation of the sodium-potassium pump

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type of transport protein

pumps

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pumps move substances against _________

concentration gradient

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Do pumps require ATP energy?

yes

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e.g., sodium-potassium______ in plasma membrane

pumps

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the inside of the membrane becomes less negative

depolarization

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the membrane returns to its resting membrane potential

repolarization

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the inside of the membrane becomes more negative than the resting potential

hyperpolarization

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Changes in Membrane Potential are caused by _________

hyperpolarization, repolarization, depolarization

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closed in the resting state

activation gates

open in the resting state

inactivation gates

Na+ and K+ channels are closed

Action Potential: Resting State

leakage accounts for small movements of Na+ and K+

Action Potential: Resting State

each Na+ channel has two voltage-regulated gates ________

activation & inactivation gates | Action Potential: Resting State

example: Na+ channel

Voltage-Gated Channel

closed when the intracellular environment is negative Na+ cannot enter the cell

Voltage-Gated Channel

ions move quickly across the membrane

open gated channel

open when the intracellular environment is positive Na+ can enter the cell

Voltage-Gated Channel

movement is along their electrochemical gradients

open gated channel

an electrical current is created

open gated channel

voltage changes across the membrane

open gated channel

(Na+ enters cell); only occurs if threshold is reached in cell body

depolarization

(K+ exits cell or Cl- enters cell)

repolarization

(excessive efflux of K+); ionic redistribution is then restored by Na+-K+ pump

hyperpolarization

at threshold, depolarization becomes _____________

self-generating

a critical level of depolarization (-55 to -50 mV)

threshold

Na+ gates are opened;

K+ gates are close

Na+ permeability increases;

membrane potential reverses

membrane is depolarized by 15 to 20 mV

threshold

established by the total amount of current flowing through the membrane

Threshold and Action Potentials

stimuli are not relayed into action potentials

weak (subthreshold)

stimuli are relayed into action potentials

strong (threshold)

action potentials either happen completely, or not at all

all-or-none phenomenon

sodium inactivation gates close

Repolarization Phase

membrane permeability to Na+ declines to resting levels

Repolarization Phase

as sodium gates close, voltage-sensitive K+ gates open

Repolarization Phase

K+ exits the cell and internal negativity of the resting neuron is restored

Repolarization Phase

Phases of the Action Potential

1 – resting state 2 – depolarization phase 3 – repolarization phase 4 – hyperpolarization

restores the resting electrical conditions of the neuron

sodium-potassium pump

ionic redistribution back to resting conditions is restored by the __________

sodium-potassium pump

potassium gates remain open, causing an excessive efflux of K+

Hyperpolarization

efflux causes______of the membrane (undershoot)

Hyperpolarization

the neuron is insensitive to stimulus and depolarization during this time

Hyperpolarization

ions of the extracellular fluid move toward the area of ____________________

greatest negative charge

is created that depolarizes the adjacent membrane in a forward direction

a current

propagates away from its point of origin

the impulse

the action potential moves away from the _______

stimulus

where sodium gates are closing, potassium gates are open and create a _________

current flow

time from the opening of the Na+ activation gates until the closing of inactivation gates

the absolute refractory period

prevents the neuron from generating another action potential

the absolute refractory period

ensures that each action potential is separate

the absolute refractory period

enforces one-way transmission of nerve impulses

the absolute refractory period

rapid conduction in myelinated fibers

saltatory conduction

impulse jumps over sections of the fiber covered with insulating myelin

saltatory conduction

more potassium on the ____ of the cell

inside

more sodium on the _____ of the cell

outside

_____ use active transport

pumps

_______ use passive transport

leak channels

only go in one direction

action potentials

instigates axon hillock to start action potential (k+ leaves the cell & takes positive charge with it)

threshold

nerve cell membrane

neurilemma

2 items share a transport protein and move in the same direction

symport

2 items share a transport protein and move in the opposite direction

antiport

bundle of beurons inside brain/spinal cord

tract

neuron

single nerve cell

bundle of neurons outside the brain and spinal cord

nerve

calcium

potential

charge

concentration

tonic

dissolves

solvent

trying to dissolve

solute

excitable tissue use membrane potential to ________

propagate an action potential (spark).