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?

Action potentials Signup and view all the answers

Which ion channels are used to create graded potentials?

Ligand-gated and mechanically gated ion channels Signup and view all the answers

Where are mechanically gated ion channels primarily found?

Sensory neurons including touch and pressure receptors Signup and view all the answers

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

Action potentials are created using voltage-gated channels Signup and view all the answers

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

Non-gated channels Signup and view all the answers

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

They open due to mechanical vibration or pressure stimuli. Signup and view all the answers

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

It opens the gates of the potassium channel when pulled. Signup and view all the answers

What causes voltage-gated ion channels to open?

Changes in membrane potential. Signup and view all the answers

What is the resting membrane potential mentioned in the content?

Negative 70 millivolts Signup and view all the answers

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

From high concentration to low concentration. Signup and view all the answers

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

The membrane potential increases and moves towards zero. Signup and view all the answers

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

By physically opening in response to sound vibrations or body movements. Signup and view all the answers

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

They can trigger the channels to open. Signup and view all the answers

What initiates an action potential in a neuron?

A sufficient change in voltage near a voltage-gated ion channel Signup and view all the answers

Where do graded potentials typically occur in a neuron?

In the cell body and dendrite regions Signup and view all the answers

How do action potentials propagate along the axon?

By triggering nearby voltage-gated channels to open in sequence Signup and view all the answers

What distinguishes graded potentials from action potentials?

Graded potentials are localized and can vary in magnitude, while action potentials are uniform and propagate along the axon. Signup and view all the answers

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

Ligand-gated and mechanically gated ion channels Signup and view all the answers

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

It triggers the subsequent opening of other voltage-gated ion channels. Signup and view all the answers

What is a key characteristic of action potentials?

They are always triggered by the same amount of voltage. Signup and view all the answers

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

They propagate along the axon without weakening. Signup and view all the answers

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

Graded potential reaches threshold Signup and view all the answers

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

Increases positive charge inside the cell Signup and view all the answers

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

Once initiated, the action potential cannot be stopped Signup and view all the answers

During the repolarizing phase, what is primarily occurring?

Return of membrane potential to resting conditions Signup and view all the answers

What happens if a hyperpolarizing graded potential occurs?

Decreases the likelihood of reaching threshold Signup and view all the answers

What occurs during the after potential or hyperpolarizing phase?

Membrane potential dips below resting potential Signup and view all the answers

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

Sufficiently large graded potential Signup and view all the answers

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

They must be large enough to reach threshold Signup and view all the answers

What initiates the depolarizing phase in the membrane potential?

Sodium rushing into the cell Signup and view all the answers

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

Positive 35 millivolts Signup and view all the answers

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

It decreases the membrane potential Signup and view all the answers

What role do sodium-potassium pumps have during repolarization?

They help restore resting membrane potential Signup and view all the answers

Which phase occurs immediately after depolarization?

Repolarization Signup and view all the answers

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

Slow efflux of potassium Signup and view all the answers

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

Due to potassium moving out Signup and view all the answers

What happens when the membrane potential approaches threshold during repolarization?

Activation gate of sodium channel re-closes Signup and view all the answers

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

A suprathreshold stimulus Signup and view all the answers

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

It requires a larger stimulus to reach the threshold Signup and view all the answers

Which statement about the absolute refractory period is correct?

No action potential can occur regardless of stimulus strength Signup and view all the answers

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

By observing the frequency of action potentials Signup and view all the answers

What occurs to sodium channels during the relative refractory period?

They return to resting state Signup and view all the answers

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

It results in a single action potential only Signup and view all the answers

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

Graded potentials must reach a higher threshold than resting state Signup and view all the answers

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

They contribute to hyperpolarization Signup and view all the answers

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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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.