Impulse Transmission in Neurons
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Questions and Answers

What is the significance of the threshold level in the context of action potentials?

  • It regulates the speed of repolarisation in the neuron.
  • It dictates whether an action potential will be generated or not. (correct)
  • It determines the amplitude of the action potential.
  • It ensures the action potential propagates bidirectionally.

Which of the following is a characteristic of the 'all or nothing' principle associated with action potentials?

  • Once the threshold is reached, a full action potential will occur. (correct)
  • The neuron gradually depolarizes in response to increasing stimulus strength.
  • The action potential only occurs partially if the stimulus is weak.
  • The strength of the stimulus determines the speed of the action potential.

In myelinated neurons, what role do the nodes of Ranvier play in the propagation of action potentials?

  • They slow down signal transmission to ensure accurate processing of information.
  • They increase the resistance of the axonal membrane to prevent ion leakage.
  • They produce myelin to insulate the axon, thus speeding up transmission.
  • They serve as sites where the action potential jumps from one node to the next. (correct)

What would be the most likely effect of a drug that blocks potassium channels in a neuron?

<p>Prolonged depolarisation of the neuron. (A)</p> Signup and view all the answers

How does repolarisation contribute to returning the neuron to its resting state?

<p>By restoring the negative charge inside the neuron. (A)</p> Signup and view all the answers

What ionic event is directly responsible for the repolarisation phase of an action potential?

<p>Efflux of potassium ions (K+) out of the neuron. (D)</p> Signup and view all the answers

During hyperpolarisation, the membrane potential becomes:

<p>More negative than the resting potential. (B)</p> Signup and view all the answers

What is the primary mechanism that leads to hyperpolarisation in a neuron?

<p>Prolonged opening of potassium channels. (A)</p> Signup and view all the answers

What is the primary mechanism by which a neuron returns to its resting potential after an action potential?

<p>The sodium-potassium pump actively transporting ions. (B)</p> Signup and view all the answers

Which part of the neuron is primarily responsible for receiving information from other neurons?

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

What event directly triggers the release of neurotransmitters into the synaptic cleft?

<p>The action potential reaching the axon terminals. (A)</p> Signup and view all the answers

How do neurotransmitters facilitate communication between two neurons?

<p>By crossing the synaptic cleft and binding to receptors on the next neuron. (B)</p> Signup and view all the answers

What is the role of the axon in neuronal communication?

<p>To transmit information over long distances to other cells. (C)</p> Signup and view all the answers

Which of the following best describes how the sodium-potassium pump helps to maintain the resting membrane potential?

<p>By transporting sodium ions out of the neuron and potassium ions into the neuron. (D)</p> Signup and view all the answers

The relative refractory period corresponds to

<p>The period when a strong stimulus can generate another action potential (A)</p> Signup and view all the answers

Where does the neuron process the information it receives?

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

What crucial role do sodium channels play during the depolarization phase of an action potential?

<p>They open and allow sodium ions to rush into the neuron, making the inside more positive. (C)</p> Signup and view all the answers

A neuron's resting membrane potential is typically around -70 mV. What does this negative value indicate about the charge distribution across the cell membrane?

<p>The inside of the neuron is more negatively charged compared to the outside. (D)</p> Signup and view all the answers

What is the primary function of the resting membrane potential in a neuron?

<p>To provide the neuron with a baseline electrical charge, enabling it to respond rapidly to stimuli. (C)</p> Signup and view all the answers

Which event is most directly triggered when a neuron receives a stimulus strong enough to exceed its threshold?

<p>Initiation of an action potential. (C)</p> Signup and view all the answers

A neurobiologist is investigating a neuron that fails to initiate action potentials despite receiving consistent stimuli. Which of the following scenarios could explain this phenomenon?

<p>All of the above. (D)</p> Signup and view all the answers

Imagine a hypothetical scenario in which the sodium channels in a neuron open, but the sodium ions are unable to enter the cell. What immediate effect would this have on the neuron's ability to generate an action potential?

<p>The neuron would be unable to depolarize, preventing the action potential. (B)</p> Signup and view all the answers

If a certain drug causes the resting membrane potential of a neuron to become more negative (e.g., -90 mV instead of -70 mV), how would this affect the neuron's excitability?

<p>The neuron would become less excitable, as a larger stimulus would be required to reach the threshold for action potential generation. (C)</p> Signup and view all the answers

During an action potential, why is it essential for the inside of the neuron to become more positive compared to the outside?

<p>To create an electrical gradient that drives the signal down the axon. (C)</p> Signup and view all the answers

Which of the following accurately describes the role of dendrites in a neuron?

<p>To receive incoming signals from other neurons. (B)</p> Signup and view all the answers

What is the crucial factor that determines whether a neuron will transmit a signal?

<p>The strength of the incoming stimulation. (A)</p> Signup and view all the answers

What is the term used to describe the phenomenon of signal transmission along the entire length of the axon?

<p>Action potential. (B)</p> Signup and view all the answers

Which of the following is most directly involved in the transmission of a neuronal signal?

<p>The movement of charged particles. (B)</p> Signup and view all the answers

A scientist is studying a neuron and observes that it fails to transmit any signals, regardless of stimulation. Which component of the neuron is most likely malfunctioning?

<p>The axon, preventing the action potential from propagating. (C)</p> Signup and view all the answers

A researcher discovers a new drug that blocks the movement of ions across the neuronal membrane. What direct effect would this drug have on neuronal function?

<p>Inhibit the neuron's ability to transmit signals. (C)</p> Signup and view all the answers

If a neuron's dendrites are damaged, what is the most likely immediate consequence for the neuron?

<p>Inability to receive incoming signals effectively. (D)</p> Signup and view all the answers

How would a longer axon affect the action potential?

<p>It would allow the neuron to transmit signals across longer distances. (B)</p> Signup and view all the answers

Which of the following best describes the distribution of sodium and potassium ions in a neuron at rest?

<p>Sodium concentration is higher outside the cell, while potassium concentration is higher inside. (D)</p> Signup and view all the answers

What is the primary factor that establishes the chemical gradient for ions across a neuron's cell membrane?

<p>Unequal distribution of ions inside and outside the cell. (A)</p> Signup and view all the answers

How does the electrical gradient contribute to the electrochemical gradient in a neuron?

<p>By creating a difference in charge across the membrane due to unequal ion distribution. (D)</p> Signup and view all the answers

A neuron is at rest. Which of the following scenarios would cause the electrical gradient to decrease?

<p>A decrease in positively charged ions outside the cell. (A)</p> Signup and view all the answers

Which combination of gradients (chemical and electrical) drives sodium ions into the cell when ion channels open?

<p>Chemical gradient pushing sodium in, electrical gradient attracting sodium in. (C)</p> Signup and view all the answers

If the cell membrane were equally permeable to both sodium and potassium ions at rest, what would likely happen to the resting membrane potential?

<p>The resting membrane potential would become more positive. (D)</p> Signup and view all the answers

A researcher introduces a substance that selectively blocks potassium channels in a neuron. How would this affect the neuron's resting membrane potential?

<p>The resting membrane potential would become more positive. (C)</p> Signup and view all the answers

Which of the following ions primarily contributes to establishing the resting membrane potential by leaking out of the neuron?

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

What is the approximate change in membrane potential (in mV) required to trigger an action potential, assuming a resting membrane potential of -70mV and a threshold voltage of -55mV?

<p>15 mV (D)</p> Signup and view all the answers

Which of the following is NOT a state of voltage-gated sodium channels during an action potential?

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

Which event directly triggers the opening of voltage-gated sodium channels during the initiation of an action potential?

<p>Depolarization of the membrane to the threshold voltage (D)</p> Signup and view all the answers

Maintaining precise levels of ion distribution across the neuron membrane is essential for what?

<p>Priming the neuron to fire an action potential when sufficiently stimulated. (A)</p> Signup and view all the answers

Where does the action potential typically initiate in a neuron?

<p>At the axon hillock, due to high concentration of voltage-gated channels. (D)</p> Signup and view all the answers

During which state are voltage-gated sodium channels unresponsive to further changes in membrane potential?

<p>Inactivated state (A)</p> Signup and view all the answers

A certain neurotoxin prevents voltage-gated sodium channels from transitioning from the inactivated state to the closed state. What is the most likely consequence?

<p>The neuron will be unable to generate new action potentials for a period after initial activation. (B)</p> Signup and view all the answers

Which of the following scenarios would most likely prevent a neuron from reaching the threshold voltage required to fire an action potential?

<p>A continuous influx of chloride ions into the neuron (C)</p> Signup and view all the answers

Flashcards

Impulse

A rapid change in voltage across a neuron's membrane that signals communication.

Resting Potential

The electrical charge difference across a neuron's membrane when it is not activated, typically around -70 millivolts.

Action Potential

A sudden increase in voltage across a neuron’s membrane triggered by a stimulus exceeding a threshold.

Depolarization

The process during action potential where sodium channels open, and sodium ions enter the neuron, making it more positive inside.

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Sodium Channels

Protein channels in the neuron membrane that allow sodium ions to enter, critical for depolarization.

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Threshold

The level of stimulus intensity needed to trigger an action potential in a neuron.

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Stimulus

A signal or event that causes a neuron to initiate an action potential, like sensory input or chemical signals.

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Neurons

Specialized cells that transmit electrical impulses throughout the nervous system.

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Threshold Level

The minimum depolarization required to trigger an action potential.

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All or Nothing Principle

An action potential either occurs fully or not at all, with no partial responses.

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Propagation

The process by which an action potential moves along the axon of a neuron.

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Saltatory Conduction

The skipping of action potentials from node to node in myelinated neurons, speeding up transmission.

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Potassium Channels

Membrane channels that open during repolarisation, allowing potassium ions to leave the neuron.

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Hyperpolarisation

A state where the membrane potential becomes more negative than the resting potential.

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Sodium-Potassium Pump

A membrane protein that pumps sodium out and potassium into the neuron to restore resting potential.

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Synaptic Transmission

The process through which neurotransmitters are released from one neuron and bind to another neuron’s receptors.

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Dendrites

Branch-like extensions of a neuron that receive signals from other neurons.

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Axon

A long, thin part of the neuron that transmits electrical impulses away from the cell body.

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Axon Terminals

The end part of an axon that releases neurotransmitters into the synaptic cleft.

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Ions in neurons

Sodium, potassium, and chloride are ions involved in neuronal functions.

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Sodium concentration

Higher sodium ion concentration is found outside the cell compared to inside.

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Potassium concentration

Higher potassium ion concentration is located inside the cell than outside.

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Resting neuron

A neuron at rest has separations of ions across its membrane, influencing its activity.

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Ionic separation

Ionic separation occurs at the cell membrane, creating gradients.

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Chemical gradient

The difference in ion concentration across the cell membrane.

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Electrical gradient

The difference in charge across the cell membrane due to ion distribution.

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Electrochemical gradient

Combined effect of chemical and electrical gradients on ion movement.

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Stimulation Strength

The level of energy in an incoming signal that influences whether it's passed on.

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Ion Movement

The action of charged particles (ions) moving to transmit neural signals.

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Potassium and Sodium Ions

Key ions involved in creating action potentials in neurons.

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Neuronal Signal Transmission

The process by which signals are passed along neurons using electrical impulses.

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Resting Membrane Potential

The stable voltage across a neuron's membrane at rest, typically around -70mV.

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Action Potential Triggering

The process where a neuron fires an action potential when stimulated above -55mV.

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Neuron Stimulation

Outside signals large enough to raise the membrane potential to threshold levels.

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Axon Hillock

The area where the action potential is initiated after reaching the threshold.

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Voltage-Gated Sodium Channels

Channels that open during an action potential, allowing sodium ions to enter the neuron.

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Sodium Channel States

The three possible conditions of sodium channels: closed, open, and inactivated.

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Depolarization Phase

The phase in action potential where the inside of the neuron becomes more positive due to sodium inflow.

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Overshoot Phase

The stage during an action potential where membrane potential exceeds 0mV due to rapid sodium influx.

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Study Notes

Impulse Transmission

  • Neurons have a resting potential, an electrical charge difference across their membrane when not transmitting an impulse. Typically around -70 millivolts (mV).
  • A stimulus, strong enough to exceed a threshold, triggers an action potential. This can be due to sensory input or chemical signals from other neurons.
  • Depolarization begins the action potential. Sodium (Na+) channels open, allowing Na+ ions to rush into the neuron, making the inside more positive.
  • An action potential is generated if depolarization reaches a threshold. This is an all-or-nothing response; once the threshold is reached, the potential will occur fully.
  • The action potential travels down the axon through saltatory conduction in myelinated neurons, where the impulse jumps between Nodes of Ranvier.
  • Repolarization occurs after the peak of the action potential. Potassium (K+) channels open, allowing K+ ions to flow out of the neuron, restoring the negative charge inside.
  • Hyperpolarization sometimes follows, where the membrane potential becomes more negative than the resting potential due to prolonged potassium channel opening.
  • The neuron returns to its resting potential through the action of the sodium-potassium pump which actively transports sodium out and potassium back in.
  • Synaptic Transmission: At the axon terminals, neurotransmitters are released into the synaptic cleft. They bind to receptors on the next neuron, continuing the impulse transmission.
  • Dendrites receive information; the cell body processes and integrates this information. The axon carries information along long distances from one part of the neuron to another. The axon terminal transmits the information to the next cell in the chain..
  • Nerves can be very long & dendrites receive incoming signals. Based on the strength, the neuron decides whether or not to pass this signal along
  • The difference in total charge inside and outside the cell is the membrane potential. At rest, the membrane potential is approximately -70mV.
  • Channels like sodium and potassium channels are important. Ions pass through channels by passive diffusion along their concentration gradients.
  • Voltage-gated ion channels open when the membrane potential reaches a particular value.
  • Ligand-gated ion channels are triggered to open when a specific molecule binds to them.

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Impulse Transmission PDF

Description

Explore neuron impulse transmission: resting potential, action potential triggers, and depolarization via sodium channels. Understand how action potentials travel down axons through saltatory conduction in myelinated neurons, and the role of potassium channels in repolarization.

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