Nerve Impulse and Action Potentials
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Questions and Answers

What is the primary function of the sodium-potassium pump in maintaining the resting potential of a neuron?

  • To create a higher concentration of sodium ions outside the neuron and potassium ions inside the neuron. (correct)
  • To create a higher concentration of sodium ions inside the neuron and potassium ions outside the neuron.
  • To facilitate the passive diffusion of sodium and potassium ions across the cell membrane.
  • To equalize the concentrations of sodium and potassium ions across the cell membrane.

Why is the inside of a neuron negatively charged relative to the outside at resting potential?

  • Due to the presence of large, negatively charged molecules in the cytoplasm. (correct)
  • Due to the higher concentration of sodium ions inside the cell.
  • Due to the active transport of potassium ions outside the cell.
  • Due to the equal distribution of all ions across the cell membrane.

What is the relationship between a nerve impulse and an action potential?

  • A nerve impulse is the process of returning to resting potential, and an action potential is the initial stimulus.
  • A nerve impulse and action potential are the same term, referring to the electrical signal used for neuronal communication. (correct)
  • A nerve impulse is the resting state of the neuron, and an action potential is the state during communication.
  • A nerve impulse is a long chain of action potentials in a single neuron axon.

What is the approximate threshold for a neuron to transition from its resting potential to an action potential?

<p>-70mV to +40mV (A)</p> Signup and view all the answers

Which of the following accurately describes the distribution of ions in a neuron at resting potential?

<p>High concentration of sodium (Na+) ions outside and potassium (K+) ions inside the cell. (C)</p> Signup and view all the answers

Hodgkin and Huxley's experiments on the giant squid axon were significant because:

<p>They were able to discover the mechanism of the action potential. (A)</p> Signup and view all the answers

What would be the immediate effect on the resting potential if the sodium-potassium pump stopped functioning?

<p>The neuron's resting potential would slowly break down, as the concentration gradient would diffuse. (A)</p> Signup and view all the answers

In addition to sodium and potassium ions, what other ions are mentioned as contributing to the overall charge across the neuronal membrane?

<p>Calcium and chloride (A)</p> Signup and view all the answers

What happens immediately after a stimulus reaches threshold?

<p>Sodium channels open (D)</p> Signup and view all the answers

What is the electrical state of a neuron during its resting potential?

<p>Negative on the inside and positive on the outside (D)</p> Signup and view all the answers

What is the role of the Na+/K+ pump in the context of an action potential?

<p>To maintain the resting membrane potential by actively transporting ions. (C)</p> Signup and view all the answers

During which phase of the action potential do voltage-gated potassium channels primarily open?

<p>During repolarization. (A)</p> Signup and view all the answers

What is the significance of the refractory period after an action potential?

<p>It prevents the action potential from traveling backwards along the axon. (B)</p> Signup and view all the answers

Which of the following events is a direct consequence of the opening of voltage-gated sodium channels during an action potential?

<p>The membrane potential becomes more positive. (B)</p> Signup and view all the answers

How does saltatory conduction increase the speed of action potential propagation?

<p>By making the action potential jump between Nodes of Ranvier. (A)</p> Signup and view all the answers

What would happen if the neuron's membrane potential does not reach the threshold potential?

<p>An action potential will not be generated. (A)</p> Signup and view all the answers

What is the primary effect of the treatments for Multiple Sclerosis discussed in the text?

<p>To reduce inflammation by suppressing the immune system. (B)</p> Signup and view all the answers

What causes the hyperpolarization phase of an action potential?

<p>Slow closing of potassium channels, causing excess potassium outflow. (B)</p> Signup and view all the answers

What aspect of action potentials is best described as 'all or none'?

<p>The amplitude of the action potential once it reaches threshold. (D)</p> Signup and view all the answers

How does membrane depolarization immediately lead to another action potential in unmyelinated axons?

<p>By opening adjacent voltage-gated sodium channels. (A)</p> Signup and view all the answers

Flashcards

Resting Potential

The difference in electrical charge between the inside and outside of a neuron when it is not transmitting a signal.

Action Potential

A rapid change in the electrical potential across the membrane of a neuron, transmitting a signal.

Neuron

A specialized cell that transmits electrical signals throughout the body.

Membrane Potential

The difference in electrical charge between the inside and outside of a neuron when it is transmitting a signal.

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Na-K Pump

A protein pump that actively transports 3 sodium ions (Na+) out of the cell and 2 potassium ions (K+) into the cell.

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Threshold Stimulus

A stimulus strong enough to trigger an action potential.

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Refractory Period

The state where a neuron cannot generate another action potential immediately after one has occurred.

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Nerve Impulse Propagation

The movement of an action potential along the axon of a neuron.

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Synapse

The point where the axon of one neuron communicates with another neuron or target cell.

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Neurotransmitters

Chemical messengers that transmit signals across synapses.

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Threshold Potential

The minimum level of depolarization required to trigger an action potential. If the stimulus does not reach this threshold, no action potential will be fired.

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Depolarization

The rapid increase in membrane potential caused by the influx of sodium ions through voltage-gated sodium channels.

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Repolarization

The return of the membrane potential to its resting state, caused by the efflux of potassium ions through voltage-gated potassium channels.

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Absolute Refractory Period

A time period during the refractory period when no action potential can be generated, no matter how strong the stimulus.

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Relative Refractory Period

A time period during the refractory period when a stronger than usual stimulus is needed to generate an action potential.

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Propagation of Action Potential

The rapid movement of an action potential down an axon.

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Saltatory Conduction

A type of action potential propagation that occurs in myelinated axons. Action potentials jump between the gaps in the myelin sheath, called nodes of Ranvier. This makes conduction faster.

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Multiple Sclerosis (MS)

A disease that damages the myelin sheath, disrupting the propagation of action potentials. This can lead to a variety of neurological problems.

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Study Notes

Nerve Impulse/Action Potential

  • Neurons communicate with other neurons, muscles, and glands using electrical signals.
  • These electrical signals are called nerve impulses or action potentials.
  • Hodgkin and Huxley discovered action potentials in the 1940s using an axon from a giant squid.

The Nerve Impulse as an Electrochemical Event

  • The nerve impulse is an electrochemical event.
  • Cells have a specific charge difference across their membranes.
  • The distribution of ions (anions and cations) inside and outside the cell determines this charge.
  • Inside the neuron is negatively charged relative to the outside.

Resting Potential

  • A neuron that's not transmitting a signal is at its resting potential (typically -70mV).
  • The inside of the neuron is negatively charged relative to the outside due to large, negatively charged molecules in the cytoplasm.
  • The sodium-potassium pump maintains concentration gradients for sodium and potassium ions. It pumps 3 sodium ions out and 2 potassium ions in, against their concentration gradients.

Action Potential

  • When nerves are stimulated, they are excited from their resting potential (-70mV) to their action potential (+40mV).
  • A sufficiently large stimulus reaching the membrane triggers an action potential.
  • Action potentials are 'all-or-none' responses; a stimulus must reach a specific threshold potential for the neuron to fire.

Action Potential Phases

  • Depolarization: Sodium channels open, and sodium ions flow into the neuron, causing the membrane potential to become more positive.
  • Repolarization: Sodium channels close, and potassium channels open, allowing potassium ions to flow out of the neuron, restoring the negative membrane potential.
  • Hyperpolarization: Potassium channels remain open for a short time, leading to a temporary undershoot of the resting potential, before returning to the resting potential.

Propagation of Action Potentials

  • In myelinated axons, action potentials "jump" between Nodes of Ranvier, a process known as saltatory conduction, which is faster than continuous conduction in unmyelinated axons.
  • In unmyelinated axons, action potentials travel continuously along the axon.

Multiple Sclerosis (MS)

  • MS is a disease where the immune system attacks the myelin sheath around the neurons, disrupting nerve impulses.
  • Treatments for MS often focus on suppressing the immune system to prevent further damage to neurons.

Graded Potentials

  • When a small region of a cell is depolarized, a graded potential is generated.
  • These signals are transmitted over a short distance, and weaken as they travel.
  • All cells can produce graded potentials. However, neurons, muscle cells, and some endocrine/immune cells can also produce action potentials.

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Description

Explore the fascinating mechanics of nerve impulses and action potentials in this quiz. Learn about how neurons communicate through electrochemical events and the significance of resting potential. This quiz covers essential concepts and discoveries related to neural activity.

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