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Phisiology Hope > Electrophysiology > Flashcards

Electrophysiology Flashcards

1
Q
  • integrated proteins that span the cell membrane

* When open, permit the passage of certain ions

A

Ion Channels

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2
Q

• Ion channels permit the passage of some ions, but not others
• Selectivity is based:
o channel size
o distribution of charges that line it
o size and charge of ions
o how much water the ion attracts and holds around it

A

Ion Channel Selectivity

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3
Q
  • ion channels have gates controlled by voltage (differences in membrane potential)
  • location: axon hillock, unmyelinated axons, along the nodes of Ranvier in myelinated axons
  • responsible for generation and propagation of action potentials (outgoing signals from neurons)
A

Voltage-gated

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4
Q
  • ion channels (chemically-gated channels) are opened or closed by hormones, second messengers, or neurotransmitters
  • location: dendrites, cell body
  • responsible for synaptic potentials (incoming signals to neurons)
A

Ligand-gated

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5
Q
  • ion channels (leakage channels) are always open
  • location: cell membrane on dendrites, cell body and axon
  • responsible for resting membrane potential
A

Non-Gated

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6
Q
  • Potential difference generated across a membrane because of a concentration difference of an ion
  • Can be generated only if the membrane is permeable to the ion
  • SIZE depends on the size of the concentration gradient
  • SIGN depends on whether the diffusing ion is positively or negatively charged
  • Created by the diffusion of very few ions
  • Do not result in changes in concentration of the diffusing ions
A

Diffusion Potential

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7
Q

• Diffusion potential that exactly balances (opposes) the tendency for diffusion caused by a concentration difference

A

Equilibrium Potential

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8
Q
  • Chemical and electrical driving forces that act on an ion are equal and opposite
  • No net diffusion of the ion occurs
A

Electrochemical Equilibrium

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9
Q

• In the presence of a nondiffusible ion, diffusible ions distribute themselves so that at equilibrium their concentration ratios are equal

A

Gibbs-Donnan Equilibrium

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10
Q

• Used to calculate the equilibrium potential at a given concentration difference of a permeable ion across a cell membrane

A

Nernst Equation

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11
Q

• Calculates membrane potential on the inside of a membrane when a membrane is permeable to several different ions

A

Goldman-Hodgkin-Katz Equation

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12
Q
  • Measured potential difference across the cell membrane in millivolts (mV)
  • Expressed as the intracellular potential relative to the extracellular potential
  • A resting membrane potential of -70 mV means 70 mV, cell negative
A

Resting Membrane Potential (RMP)

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13
Q

• Any change in which membrane voltage shifts to a less negative value

A

Depolarization

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14
Q

generation of a nonpropagated response

A

Local potential

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15
Q

generation of a propagated response

A

Action potential

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16
Q
  • Vary in magnitude (voltage) according to the strength of the stimulus
  • A more intense or prolonged stimulus opens more ion gates than a weaker stimulus
A

Local potentials are GRADED

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17
Q
  • Get weaker as they spread from the point of stimulation
  • As Na spreads out under the plasma membrane and depolarizes it, K flows out
  • Prevents local potentials from having any long-distance effects
A

Local potentials are DECREMENTAL

18
Q

• if stimulation ceases, K diffusion out of the cell quickly returns the membrane voltage to its resting potential

A

Local potentials are REVERSIBLE

19
Q
  • Alteration in the membrane potential of a cell resulting from activation at the synapse
  • If the intracellular voltage increases, it is called an excitatory post-synaptic potential (EPSP)
  • If the intracellular voltage decreases, it is called an inhibitory post-synaptic potential (EPSP)
A

SYNAPTIC POTENTIALS

20
Q
  • Transmembrane potential difference produced in sensory receptors
  • Occurs generally as depolarization resulting from inward current flow
  • Influx of current will often bring the membrane potential of the sensory receptor towards threshold for triggering an action potential
A

GENERATOR/RECEPTOR POTENTIALS

21
Q
  • Passive spread of charge inside a neuron due to local changes in ionic conductance
  • Ionic charge enters in one location and dissipates to others, losing intensity as it spreads (graded response)
A

ELECTROTONIC POTENTIALS

22
Q
  • Rapid changes in the membrane potential that spread along the nerve fiber
  • To conduct a nerve signal, the action potential moves along the nerve fiber until it comes to the fiber’s end
A

Action Potential

23
Q
  • If a stimulus depolarizes the neuron to threshold, the neuron fires at its maximum voltage
  • If threshold is not reached, the neuron does not fire at all
  • Above threshold, stronger stimuli do not produce stronger action potentials (not graded)
A

Action potentials follow ALL-OR-NONE LAW.

24
Q
  • Action potentials do not get weaker with distance
  • An action potential at the end of a nerve fiber will be just as strong as an action potential in the trigger zone up to a meter away
A

Action potentials are NON DECREMENTAL.

25
Q
  • If a neuron reaches threshold, the action potential goes to completion
  • Action potentials cannot be stopped once it begins
A

Action potentials are IRREVERSIBLE.

26
Q
  • Resting membrane potential before the action potential begins
  • Membrane is polarized because of the -90 mV membrane potential
A

Resting Stage

27
Q
  • When the threshold potential (-65 mV) is reached, the voltage-gated Na+ channels overwhelm K+ and other channels
  • Membrane suddenly becomes permeable to sodium ions
A

Depolarization

28
Q

• in large nerve fibers, the great excess of positive sodium ions causes the membrane potential to overshoot beyond the zero level

A

Overshoot

29
Q

o Necessary actor in both depolarization and repolarization of the nerve membrane

A

Voltage-Gated Sodium Channel

30
Q
  • Sodium channels begin to close and the potassium channels open more than normal
  • Rapid diffusion of potassium ions to the exterior re-establishes resting membrane potential
A

Repolarization

31
Q

o also plays an important role in increasing the rapidity of repolarization of the membrane

A

Voltage-Gated Potassium Channel

32
Q
  • K+ conductance remains higher than at rest after closure of the Na+ channels
  • Membrane potential is driven very close to the K+ equilibrium potential
A

After hyperpolarization (undershoot)

33
Q

• Depolarization process travels over the entire membrane if conditions are right, or it does not travel at all if conditions are not right

A

All-or-Nothing Principle

34
Q

Factors Affecting Conduction Velocity

A
  1. Fiber Size
    - Increasing the diameter of a nerve fiber results in decreased internal resistance and faster conduction velocity
  2. Myelination
    • Myelin acts as an insulator around nerve axons and increases conduction velocity
    • Myelinated nerves exhibit saltatory conduction
35
Q

• Time periods after an action potential, during which a new stimulus cannot be readily elicited

A

Refractory Periods

36
Q
  • Another action potential cannot be elicited, no matter how large the stimulus
  • Coincides with almost the entire duration of the action potential
A

Absolute Refractory Period

37
Q
  • inactivation gates of the Na+ channel are closed when the membrane potential is depolarized and remain closed until repolarization occurs
  • No action potential can occur until the inactivation gates open
A

Ionic Basis of Absolute Refractory Period

38
Q
  • Begins at the end of the absolute refractory period and continues until the membrane potential returns to the resting level
  • Action potential can be elicited only if a larger than usual inward current is provided
A

Relative Refractory Period

39
Q
  • K+ conductance is higher than at rest
  • Membrane potential is closer to the K+ equilibrium potential and farther from threshold
  • More inward current is required to bring the membrane to threshold
A

Ionic Basis of Relative Refractory Period

40
Q
  • Cell membrane is held at a depolarized level such that the threshold potential is passed without firing an action potential
  • Occurs because depolarization closes inactivation gates on the Na+ channels
A

Accommodation

Phisiology Hope (7 decks)

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