Nerve Impulse Quiz: Action Potential and More

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Questions and Answers

What is the voltage during the Depolarisation Stage?

0 mV

-90 mV

-70 mV

+40 mV (correct)

What happens to the Sodium channels when the threshold is reached?

They close (correct)

They open further

They remain unchanged

They become permeable to potassium ions

What is the result of the K+ release during the Repolarisation Stage?

The membrane potential remains unchanged

The membrane potential becomes more positive

The membrane potential becomes more negative (correct)

The membrane potential becomes zero

What is the significance of the Depolarisation Stage?

It helps to generate an action potential Signup and view all the answers

What is the direction of Na+ movement during the Depolarisation Stage?

Na+ moves into the cell Signup and view all the answers

What is the speed of the impulse that occurs from the axon hillock?

0.1 to 10 meters per second Signup and view all the answers

What is the main reason for the transmission of the impulse or action potential in a nerve cell?

Movement of ions across the nerve cell membrane Signup and view all the answers

What is the electric charge of the inside of the nerve cell membrane in the resting state?

Negative Signup and view all the answers

What is the main intracellular cation involved in the resting membrane potential?

K+ Signup and view all the answers

What is the approximate resting potential of a neuron in millivolts?

-70 mV Signup and view all the answers

What is the characteristic of an action potential in terms of ionic movement?

Influx of positively charged sodium ions Signup and view all the answers

What is the result of the influx of positively charged sodium ions during an action potential?

The propagation of the impulse along the neuron Signup and view all the answers

What is the term for the release of too much potassium from the cell, resulting in a -90 mV impulse?

Hyperpolarization Signup and view all the answers

What occurs during the Refractory Stage of the action potential?

3 Na+ ions are received through the membrane and 2 K+ ions are released Signup and view all the answers

What is the primary function of the myelinated sheath?

To increase the conduction speed of impulses Signup and view all the answers

What is the direction of the movement of the action potential signal?

From the dendrites to the axon terminals Signup and view all the answers

What is the result of the Hyperpolarization Phase of the action potential?

The membrane potential becomes more negative Signup and view all the answers

Which type of nerve fiber has a slower conduction time?

Non-myelinated nerve fibers Signup and view all the answers

What is the result of the Depolarisation Stage in the action potential?

The cell membrane becomes positively charged Signup and view all the answers

Which neurotransmitter is responsible for signaling voluntary muscle movement?

Acetylcholine Signup and view all the answers

What is the result of the Repolarisation Stage in the action potential?

The cell membrane becomes negatively charged Signup and view all the answers

Which type of receptors do Catecholamines bind to?

Alpha and beta receptors Signup and view all the answers

What is the result of the Hyperpolarisation Phase in the action potential?

The membrane potential falls below -70 mV Signup and view all the answers

What is the role of the Parasympathetic Neuron in the body?

To decrease heart rate and constrict pupils Signup and view all the answers

What is the primary function of reuptake pumps in a synapse?

To remove excess neurotransmitters from the synapse Signup and view all the answers

What is the effect of blocking reuptake pumps on the concentration of serotonin in the synapse?

Serotonin levels increase Signup and view all the answers

Which of the following is NOT a way to remove excess neurotransmitters from the synapse?

Action potential generation Signup and view all the answers

Which neurotransmitter is NOT listed as a catecholamine?

Serotonin Signup and view all the answers

What is the name of the neurotransmitter that is also known as Gamma-Aminobutyric Acid?

GABA Signup and view all the answers

Study Notes

Action Potential

Action potential is a momentary change in the voltage difference across the cell membrane of a neuron, characterized by an influx of positively charged sodium ions (Na+)
This results in the propagation of the impulse along the neuron
Resting potential of the neuron is approximately -70 millivolts (mV)

Resting Membrane Potential

The principal ions involved are:
- Na+ (main extracellular cation)
- K+ (main intracellular cation)
Nerves and muscles are excitable tissue, both use this potential by undergoing transient fluctuations in membrane potential
Two kinds of potential:
- Action potential
- Graded potential

Generation of Action Potential

High concentration of Na+ outside the cell
A stimulus occurs (e.g. pressure at the finger)
Na+ rushes through the cell membrane, changing the inner surface to +40 mV
This causes the inner cell membrane to be positively charged
This is known as the Depolarisation Stage

Depolarisation Stage

When the threshold is reached, the sodium channels open
At this stage, the sodium channels are active, allowing sodium ions to rush into the cell
The polarity of the inside of the cell becomes positive

Repolarisation Stage

Membrane becomes more permeable to potassium ions (K+)
K+ gated ion channels open, allowing K+ to rush out of the cell
Higher concentration of K+ outside of the cell compared to the intracellular
This causes the cell membrane to become negatively charged
K+ release causes the membrane potential to fall below -70 mV (approx. -90 mV)
This is known as the Repolarisation Stage

Hyperpolarisation Phase

Too much K+ is released from the cell
This causes a -90 mV impulse
This is known as the Hyperpolarisation Phase

Refractory Stage

The refractory stage of the action potential occurs with the assistance of the Na+/K+ pump
3 Na+ ions are received through the membrane and 2 K+ ions are released
This returns the resting membrane to -70 mV

Propagation of Action Potential

Action potential occurs at a very small area of the membrane
Positive charge exists on the outside of the membrane
Negative charge exists inside of the membrane
Stimulus occurs, leading to the phases of the action potential
This causes a "domino" type effect through the cells/neuron until it reaches the end terminal

Myelinated vs. Non-Myelinated Axons

Myelinated sheath around a nerve
- Impulses move more quickly
- Increases information processing speed
- Found in the central and peripheral nervous system
- Utilizes a significant amount of metabolic energy to produce the many layers of the sheath
Non-Myelinated axons
- Comprise the smaller axons of the CNS
- Slower conduction time
- Found in the peripheral nervous system
- Found in the visceral nervous system (internal organs)

Neurotransmitters

Acetylcholine
- Can be found in the neuromuscular junction
- Signals voluntary muscle movement
Catecholamines:
- Dopamine, Norepinephrine, Epinephrine
- Family of neurotransmitters that 'speed up' heart rate, dilate airways, dilate pupils
- Signal a sympathetic response
- Receptor type is alpha and beta
Serotonin
- If we block the reuptake pumps, we end up with more Serotonin
Histamine
GABA (Gamma-Aminobutyric Acid)
Glutamate

Synapse

The neurotransmitter is released into a space called the synapse
Chemicals released from neurons communicate with other neurons
Neurotransmitter = The 'Key'
Receptor = The 'Lock'
Ways to remove excess neurotransmitters:
- Diffusion
- Enzymes
- Reuptake pumps
- Astrocyte endfeet

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Description

Test your understanding of the transmission of nerve impulses, including the resting state of the nerve cell membrane, polarization, and the changes that occur during the action potential. Learn about the movement of ions and the electric charge differences that enable nerve impulses.

Nerve Impulse and Action Potential

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