Neuroscience: Nerve Impulses and Action Potentials

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Questions and Answers

What happens to Na+ channel activity at the peak of an action potential?

Na+ channels close at the peak of an action potential.

Explain why the efflux of K+ is rapid during repolarization.

The efflux of K+ is rapid due to both a large K+ concentration gradient and a strong electrical gradient.

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

The Na+/K+ pump restores the resting membrane potential (RMP) after an action potential.

How does the myelin sheath influence action potential propagation?

The myelin sheath increases the speed of action potential propagation by facilitating saltatory conduction. Signup and view all the answers

Describe the significance of the electrical gradient in the context of neuronal action potentials.

The electrical gradient is significant as it drives the movement of Na+ and K+ across the membrane during action potentials. Signup and view all the answers

What is the resting membrane potential of a typical neuron?

-70 mV Signup and view all the answers

How fast does a nerve impulse travel in meters per second?

100 m/s Signup and view all the answers

What is the speed of nerve impulses compared to copper wire?

4 x 10^10 times faster Signup and view all the answers

How much slower is diffusion than nerve impulse transmission?

3 x 10^6 times slower Signup and view all the answers

What is the speed of diffusion in kilometers per hour?

0.000000008 Km/h Signup and view all the answers

What is the equivalent distance traveled by a nerve impulse in an hour?

360,000 m Signup and view all the answers

What ion's movement is primarily responsible for initiating a nerve impulse?

Na+ (sodium ions) Signup and view all the answers

What is the maximum potential reached during a nerve impulse depolarization?

+30 mV Signup and view all the answers

How does the speed of nerve impulses compare to that of a typical physical object?

Much faster than normal objects, like sound or light in a vacuum. Signup and view all the answers

In terms of physiological importance, why is the speed of nerve impulses significant?

Essential for rapid communication and response in the nervous system. Signup and view all the answers

How does the brain differentiate between similar action potentials from different stimuli?

The brain differentiates between stimuli by determining the origin of action potentials based on the specific nerve pathways they travel through. Signup and view all the answers

What role do neurotransmitters play in sensory cell signaling?

Neurotransmitters facilitate communication between sensory cells and nerve cells by being released from the pre-synaptic cell and binding to receptors on the post-synaptic cell. Signup and view all the answers

Explain how graded potentials can affect the generation of action potentials.

Graded potentials influence the likelihood of generating action potentials by changing the membrane potential at the axon hillock; if the threshold of -55 mV is reached, action potentials are initiated. Signup and view all the answers

Why is the directional propagation of action potentials crucial in neural communication?

Directional propagation of action potentials ensures that signals move efficiently from the axon to nerve terminals without reversing, maintaining a clear flow of information. Signup and view all the answers

What is the effect of not reaching the threshold of -55 mV in a sensory neuron?

If the threshold of -55 mV is not reached, the neuron will not generate any action potentials, resulting in no communicated signal. Signup and view all the answers

Describe the process that occurs when an action potential arrives at the nerve terminal.

When an action potential arrives at the nerve terminal, it triggers the release of neurotransmitters into the synaptic cleft, allowing for communication with adjacent neurons. Signup and view all the answers

Discuss the significance of sensory cells in the nervous system.

Sensory cells are pivotal for detecting environmental stimuli and converting them into electrical signals through graded potentials. Signup and view all the answers

What happens during the activation of gated Na+ channels in sensory cells?

The activation of gated Na+ channels during stimulation causes a rapid influx of Na+ ions, leading to a change in the membrane potential. Signup and view all the answers

What phenomenon occurs when a sensory cell is at its resting membrane potential?

Nothing happens; the cell remains at -70mV. Signup and view all the answers

What does low frequency of action potentials indicate about neurotransmitter release?

It indicates that there is not enough stimulation to create a significant response. Signup and view all the answers

What is the significance of the 'medium' frequency of action potentials?

It indicates an optimal level of stimulation, leading to adequate responses. Signup and view all the answers

How does a high frequency of action potentials affect neurotransmitter activity?

It indicates excessive stimulation, potentially leading to neurotransmitter overload. Signup and view all the answers

What are action potentials fundamentally characterized by?

They are small identical electrical changes in specific neuron parts. Signup and view all the answers

Explain the role of neuroglia in the propagation of action potentials.

Neuroglia support neurons and contribute to the environment necessary for proper action potential propagation. Signup and view all the answers

What determines whether a graded potential can lead to an action potential?

The strength and duration of the graded potential are critical for triggering an action potential. Signup and view all the answers

How does synaptic transmission occur by diffusion?

Neurotransmitters released into the synaptic cleft diffuse across to bind to receptors. Signup and view all the answers

What is the time it would take for ion diffusion to achieve equilibrium over 1µm in a nerve?

It would take approximately 0.0000005 seconds. Signup and view all the answers

Describe the role of sensory cells in the nervous system.

Sensory cells detect stimuli and initiate graded potentials that influence action potentials. Signup and view all the answers

What is the significance of reaching -55 mV in the context of graded potentials?

Reaching -55 mV is the threshold potential that triggers the opening of voltage-gated Na+ channels, leading to an action potential. Signup and view all the answers

How do graded potentials affect the membrane potential before triggering an action potential?

Graded potentials can cause a change in membrane potential, increasing it towards the threshold required for an action potential. Signup and view all the answers

What role do voltage-gated Na+ and K+ channels play in action potentials?

Voltage-gated Na+ channels allow Na+ ions to flow into the cell, causing depolarization, while voltage-gated K+ channels close after depolarization to help repolarize the membrane. Signup and view all the answers

Explain why the resting membrane potential is typically around -70 mV.

The resting membrane potential of -70 mV is maintained by the unequal distribution of ions, primarily Na+ and K+, and the selective permeability of the neuron's membrane. Signup and view all the answers

What happens to the membrane potential when Na+ channels open at -55 mV?

When Na+ channels open at -55 mV, sodium ions rush into the neuron, causing rapid depolarization of the membrane potential towards +30 mV. Signup and view all the answers

Describe how graded potentials can lead to action potentials.

Graded potentials summate and, if they reach the threshold of -55 mV, trigger voltage-gated Na+ channels to open, initiating an action potential. Signup and view all the answers

Why is immediate repolarization important after an action potential?

Immediate repolarization is important to restore the resting membrane potential and ensure that the neuron is ready for the next stimulus. Signup and view all the answers

What determines the amplitude and duration of a graded potential?

The amplitude and duration of a graded potential are determined by the strength and duration of the stimulus that generated them. Signup and view all the answers

How does the influx of Na+ ions influence the overall behavior of a neuron?

The influx of Na+ ions during an action potential creates a positive feedback loop that rapidly depolarizes the neuron, leading to signal propagation. Signup and view all the answers

What would happen if the threshold potential of -55 mV were not reached?

If the threshold potential of -55 mV is not reached, voltage-gated Na+ channels will not open, preventing the generation of an action potential. Signup and view all the answers

Study Notes

Nerve Impulses

The brain differentiates between stimuli due to nerve endings terminating in different brain regions.
Sensory cells generate graded potentials upon stimulation, leading to graded release of neurotransmitters.
Neurotransmitters (NTs) released from the pre-synaptic cell diffuse a short distance to the post-synaptic cell.
NT receptors on the nerve cell body generate graded potentials at the axon hillock.
If the threshold of -55 mV is not reached, nothing happens.
If the threshold of -55 mV is reached, a low frequency of action potentials is generated and propagated along the axon.
Maintaining the threshold of -55 mV results in a high frequency of action potentials being generated and propagated along the axon.
The arrival of action potentials triggers NT release and binding to other nerve cells.

Nerve Impulse Generation

The activation of gated Na+ channels on the surface of sensory cells causes rapid Na+ influx.

Action potentials

Action potentials are rapid changes in membrane potential.
Action potentials rely on the opening and closing of voltage-gated Na+ and K+ channels in the axon.

Nerve impulse timing

A nerve impulse can travel 1 meter in 1/100 of a second.
The speed of nerve impulses is 360 km/h.
Copper wire is 3 x 10^6 times faster than a nerve impulse, while diffusion is 4 x 10^10 times slower.

Graded Potentials

Graded potentials can work by diffusion because they travel short distances within a cell.

Action Potential Mechanism

The resting membrane potential is -70 mV.
The influx of Na+ due to the opening of Na+ channels rapidly increases membrane potential to +30 mV.
Na+ channels close when the peak of the action potential is reached.
The opening of K+ channels at +30 mV results in a rapid efflux of K+ and decreases membrane potential to –90 mV.
The Na+/K+ pump helps reset the membrane potential to -70 mV.

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Description

This quiz covers the fundamentals of nerve impulses, including how the brain processes stimuli through nerve endings and the role of neurotransmitters in signal transmission. Learn about graded potentials and the conditions required for generating action potentials. Test your understanding of these essential concepts in neuroscience.