Neuroscience Chapter on Ion Channels
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Questions and Answers

Which type of ion channels are primarily responsible for creating action potentials?

  • Chemically gated ion channels
  • Voltage-gated ion channels (correct)
  • Mechanically gated ion channels
  • Ligand-gated ion channels

What are graded potentials also known as?

  • Synaptic potentials
  • Electrical impulses
  • Action potentials
  • Local potentials (correct)

In which region of neurons are voltage-gated ion channels predominantly located?

  • Synaptic terminals
  • Cell body
  • Dendrites
  • Axon (correct)

Which type of signal allows for communication over both short and long distances?

<p>Action potentials (D)</p> Signup and view all the answers

Which ion channels are used to create graded potentials?

<p>Ligand-gated and mechanically gated ion channels (C)</p> Signup and view all the answers

Where are mechanically gated ion channels primarily found?

<p>Sensory neurons including touch and pressure receptors (A)</p> Signup and view all the answers

What is a key difference between graded potentials and action potentials?

<p>Action potentials are created using voltage-gated channels (B)</p> Signup and view all the answers

Which type of ion channel is not typically involved in generating electrical signals in neurons?

<p>Non-gated channels (B)</p> Signup and view all the answers

What is the primary function of mechanically-gated ion channels?

<p>They open due to mechanical vibration or pressure stimuli. (D)</p> Signup and view all the answers

In the inner ear, what role does the gating spring play in potassium ion movement?

<p>It opens the gates of the potassium channel when pulled. (A)</p> Signup and view all the answers

What causes voltage-gated ion channels to open?

<p>Changes in membrane potential. (A)</p> Signup and view all the answers

What is the resting membrane potential mentioned in the content?

<p>Negative 70 millivolts (C)</p> Signup and view all the answers

What is the typical direction of ion movement through mechanically-gated channels?

<p>From high concentration to low concentration. (A)</p> Signup and view all the answers

What happens to the membrane potential when ions move through voltage-gated ion channels?

<p>The membrane potential increases and moves towards zero. (D)</p> Signup and view all the answers

How do mechanically-gated channels facilitate the sense of hearing and balance?

<p>By physically opening in response to sound vibrations or body movements. (B)</p> Signup and view all the answers

What is the effect of small changes in membrane potential on voltage-gated ion channels?

<p>They can trigger the channels to open. (D)</p> Signup and view all the answers

What initiates an action potential in a neuron?

<p>A sufficient change in voltage near a voltage-gated ion channel (A)</p> Signup and view all the answers

Where do graded potentials typically occur in a neuron?

<p>In the cell body and dendrite regions (D)</p> Signup and view all the answers

How do action potentials propagate along the axon?

<p>By triggering nearby voltage-gated channels to open in sequence (B)</p> Signup and view all the answers

What distinguishes graded potentials from action potentials?

<p>Graded potentials are localized and can vary in magnitude, while action potentials are uniform and propagate along the axon. (B)</p> Signup and view all the answers

What kind of channels are primarily involved in the generation of graded potentials?

<p>Ligand-gated and mechanically gated ion channels (D)</p> Signup and view all the answers

What role does ion movement play in the generation of action potentials?

<p>It triggers the subsequent opening of other voltage-gated ion channels. (C)</p> Signup and view all the answers

What is a key characteristic of action potentials?

<p>They are always triggered by the same amount of voltage. (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of graded potentials?

<p>They propagate along the axon without weakening. (C)</p> Signup and view all the answers

What occurs first during the process of generating an action potential?

<p>Graded potential reaches threshold (B)</p> Signup and view all the answers

What is the primary effect of depolarization on the membrane potential?

<p>Increases positive charge inside the cell (A)</p> Signup and view all the answers

What defines the all-or-none principle in action potentials?

<p>Once initiated, the action potential cannot be stopped (D)</p> Signup and view all the answers

During the repolarizing phase, what is primarily occurring?

<p>Return of membrane potential to resting conditions (A)</p> Signup and view all the answers

What happens if a hyperpolarizing graded potential occurs?

<p>Decreases the likelihood of reaching threshold (A)</p> Signup and view all the answers

What occurs during the after potential or hyperpolarizing phase?

<p>Membrane potential dips below resting potential (D)</p> Signup and view all the answers

What triggers the opening of the first voltage-gated channels?

<p>Sufficiently large graded potential (B)</p> Signup and view all the answers

What is the role of graded potentials in the context of action potentials?

<p>They must be large enough to reach threshold (D)</p> Signup and view all the answers

What initiates the depolarizing phase in the membrane potential?

<p>Sodium rushing into the cell (D)</p> Signup and view all the answers

At what membrane potential does the inactivation gate of the sodium channel close?

<p>Positive 35 millivolts (D)</p> Signup and view all the answers

What is the effect of potassium moving out of the cell during repolarization?

<p>It decreases the membrane potential (C)</p> Signup and view all the answers

What role do sodium-potassium pumps have during repolarization?

<p>They help restore resting membrane potential (C)</p> Signup and view all the answers

Which phase occurs immediately after depolarization?

<p>Repolarization (B)</p> Signup and view all the answers

What primarily occurs during the opening of potassium channels in the depolarization phase?

<p>Slow efflux of potassium (B)</p> Signup and view all the answers

How does the inside of the cell become less positive during repolarization?

<p>Due to potassium moving out (B)</p> Signup and view all the answers

What happens when the membrane potential approaches threshold during repolarization?

<p>Activation gate of sodium channel re-closes (B)</p> Signup and view all the answers

What is required to generate an action potential during the relative refractory period?

<p>A suprathreshold stimulus (A)</p> Signup and view all the answers

What happens to the graded potential during the relative refractory period compared to the resting condition?

<p>It requires a larger stimulus to reach the threshold (B)</p> Signup and view all the answers

Which statement about the absolute refractory period is correct?

<p>No action potential can occur regardless of stimulus strength (A)</p> Signup and view all the answers

How does the brain differentiate between a strong stimulus and a mild stimulus?

<p>By observing the frequency of action potentials (B)</p> Signup and view all the answers

What occurs to sodium channels during the relative refractory period?

<p>They return to resting state (D)</p> Signup and view all the answers

What is the effect of increasing the stimulus strength beyond the threshold?

<p>It results in a single action potential only (C)</p> Signup and view all the answers

What is the relationship between graded potentials and threshold in the context of action potentials?

<p>Graded potentials must reach a higher threshold than resting state (B)</p> Signup and view all the answers

What is the primary role of potassium channels during the relative refractory period?

<p>They contribute to hyperpolarization (D)</p> Signup and view all the answers

Flashcards

Mechanically-gated channels

Ion channels that open in response to physical forces such as vibration or pressure.

Gating Spring

A structure attached to a mechanically-gated channel that responds to movement between cells, opening the channel.

Voltage-gated channels

Ion channels that open in response to changes in the electrical charge across a cell membrane.

Resting membrane potential

The typical resting electrical charge across a cell membrane, usually around -70 millivolts.

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Ion movement

The movement of ions across a membrane, which can change the membrane potential.

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Membrane potential change

A change in the membrane potential that triggers the opening of voltage-gated channels.

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Electrical signal creation

The process by which voltage-gated channels open and allow ion movement, contributing to electrical signals within cells.

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Potassium movement in the inner ear

The movement of potassium ions through mechanically-gated channels in the inner ear, which is important for hearing and balance.

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Mechanically gated ion channels

Specialized receptors found in sensory neurons, like touch, pressure, pain, and special senses, that open in response to physical stimuli.

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Voltage gated ion channels

Ion channels found specifically in the axon region of all types of neurons, responsible for generating electrical signals.

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Graded potentials

Electrical signals that occur over short distances, primarily used for local communication within a neuron.

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Action potentials

Electrical signals that can travel long distances, enabling communication between neurons.

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Depolarization

The change in membrane potential that triggers the opening of voltage-gated channels, leading to action potentials.

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Repolarization

The process of restoring the membrane potential to its resting state after an action potential.

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How do gated channels differ between graded potentials and action potentials?

Ligand-gated and mechanically-gated channels are used in creating graded potentials, while voltage-gated channels are used in action potentials.

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What is the key difference between graded potentials and action potentials?

Graded potentials are localized and short-distance, while action potentials are long-distance and allow for communication over great distances.

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Threshold Potential

The initial change in membrane potential that triggers an action potential.

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Frequency Coding

A strong stimulus generates a frequent stream of action potentials, while a weak stimulus results in a less frequent firing rate.

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Refractory Period

The period of time following an action potential where a neuron cannot generate another action potential.

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Propagation of Action Potential

The process by which an action potential travels along the axon, relying on the opening and closing of voltage-gated channels.

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Saltatory Conduction

The jumping of an action potential from one node of Ranvier to the next along a myelinated axon.

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Threshold

The specific membrane potential that triggers the opening of voltage-gated channels, initiating an action potential.

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Hyperpolarization

A brief period after repolarization where the membrane potential dips below resting membrane potential, making it harder to initiate another action potential.

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All-or-None Principle

The principle that an action potential either occurs fully or not at all, there's no partial action potential.

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Voltage-gated Channel Activation

The process where voltage-gated channels are triggered to open, allowing ion movement, which generates the action potential.

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Peak of depolarization

The point at which the membrane potential reaches its most positive value, typically around +35 millivolts.

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Inactivation gate

A gate associated with voltage-gated sodium channels that closes when the membrane potential reaches the peak of depolarization, preventing further sodium influx.

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Threshold during repolarization

The point during repolarization when the membrane potential crosses the threshold, causing the activation gate of the sodium channel to close again.

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Sodium-potassium pump

An active transport protein responsible for pumping sodium ions out of the cell and potassium ions into the cell, helping to maintain resting membrane potential.

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Membrane potential

The difference in electrical charge across the cell membrane, typically measured in millivolts.

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Suprathreshold stimulus

A stimulus that is stronger than the typical threshold needed to initiate an action potential, generating a larger graded potential to reach the new threshold.

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Relative refractory period

The period after an action potential during which another action potential can be generated, but only with a much stronger stimulus.

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Absolute refractory period

The period directly after an action potential during which another action potential cannot be generated, regardless of the stimulus strength.

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Threshold stimulus

The minimum amount of stimulation required to trigger an action potential in a neuron.

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Study Notes

Lecture 16 - Changing Membrane Potential

  • Neurons and muscle cells are electrically excitable due to resting membrane potential
  • Gated ion channels allow for changing membrane potential, creating electrical impulses
  • Three types of gated ion channels: ligand-gated, mechanically-gated, and voltage-gated

Slide 2

  • Neurons are excitable due to resting membrane potential
  • Gated ion channels change membrane potential, creating signals
  • Three types: ligand-gated, mechanically-gated, and voltage-gated

Slide 3

  • Ligand-gated ion channels respond to chemical stimuli (ligands)
  • Ligands bind to receptors, opening channels, allowing ion movement
  • Example: sodium channel, ligand is acetylcholine
  • Ions move down their concentration gradient (high to low)

Slide 4

  • Mechanically-gated channels respond to pressure or vibration
  • Example: inner ear
  • Movement opens channels, allowing ion movement

Slide 5

  • Voltage-gated channels respond to changes in membrane potential
  • Found primarily in axons
  • Important in creating electrical signals
  • Found in axon terminals and presynaptic terminals
  • Also in cardiac and smooth muscle

Slide 6

  • Table summarizing different ion channels and their locations
  • Leak channels maintain resting membrane potential, throughout all parts of the neuron

Slide 7

  • Two types of signals in neurons: graded potentials (local potentials) and action potentials
  • Graded potentials use ligand-gated and mechanically-gated channels, affecting a localized area
  • Action potentials use voltage-gated channels, propagating signals over long distances

Slide 8

  • Summary of graded potentials and action potentials (table)

Slide 9

  • Graded potentials: small, localized changes in membrane potential
  • Depolarization: membrane potential becomes less negative
  • Hyperpolarization: membrane potential becomes more negative
  • Example: sodium ions cause depolarization; potassium ions cause hyperpolarization

Slide 10

  • Graded potential strength depends on stimulus strength and frequency
  • Summation: multiple graded potentials can be added together for a larger response
  • Graded potentials, are localized and cannot travel far

Slide 11

  • Action potential: large, rapid change in membrane potential
  • Threshold: specific voltage change initiating an action potential
  • All-or-none principle: action potential either occurs fully, or not at all

Slide 12

  • Action potentials use voltage-gated channels
  • Two main types: sodium and potassium voltage-gated channels

Slide 13

  • Depolarization phase: sodium channels open, sodium rushes in
  • Membrane potential becomes more positive

Slide 14

  • Repolarization phase: potassium channels open, potassium rushes out
  • Membrane potential returns to resting level;sodium channels close

Slide 15

  • After-hyperpolarization: membrane potential briefly becomes more negative than resting level
  • Sodium-potassium pumps maintain resting membrane potential

Slide 16

  • Sodium-potassium pumps maintain resting membrane potential

Slide 17

  • Refractory periods: periods where the neuron is less sensitive to stimulation
  • Absolute refractory period: no action potential can occur
  • Relative refractory period: a stronger-than-usual stimulus is needed for an action potential

Slide 18

  • Stimulus strength determines action potential frequency
  • High frequency = strong stimulus

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Lecture 16 -Changing Membrane Potential PDF

Description

Test your knowledge on the types of ion channels involved in neuronal action potentials and graded potentials. This quiz covers their locations, functions, and key differences. Challenge yourself with questions on how these channels contribute to neuronal signaling.

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