Neuron Structure

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Questions and Answers

What triggers the action potential in a neuron?

A significant influx of Na+ ions after reaching the threshold (correct)

A decrease in Na+ ion concentration outside the cell

A small increase in potassium concentration inside the cell

A closing of the Na+ channels limiting ion flow

What is the primary function of the sodium-potassium pump?

To transport Na+ and K+ ions to establish membrane potential (correct)

To maintain a high concentration of potassium inside the cell

To allow voltage-gated channels to remain open

To depolarize the neuron's membrane

During repolarization, which ions primarily flow out of the neuron?

Chloride ions (Cl-)

Calcium ions (Ca+)

Potassium ions (K+) (correct)

Sodium ions (Na+)

What is the significance of the Hodgkin-Huxley cycle?

It amplifies the depolarization during the action potential Signup and view all the answers

What is the voltage inside a neuron approximately during depolarization?

+50 mV Signup and view all the answers

Which channels are responsible for initiating the action potential when a stimulus is received?

Voltage-gated Na+ channels Signup and view all the answers

What happens to sodium channels after they are activated during an action potential?

They quickly inactivate Signup and view all the answers

What causes the membrane potential to return to its negative resting state?

Increased K+ permeability allowing K+ to leave Signup and view all the answers

What role do dendrites play in a neuron?

They collect electrical signals from other neurons. Signup and view all the answers

Which component of a neuron is responsible for initiating an action potential?

Axon hillock Signup and view all the answers

What is myelin's primary function in neuron structure?

To insulate the axon and speed up signal transmission Signup and view all the answers

What occurs at the synapse in neuron communication?

Neurotransmitters are released into the synaptic cleft Signup and view all the answers

What is the resting membrane potential of a typical neuron?

-70 mV Signup and view all the answers

What happens during saltatory conduction?

The action potential jumps from node to node. Signup and view all the answers

Which part of the neuron is primarily involved in integrating incoming signals?

Cell body Signup and view all the answers

What key components contribute to the negative resting potential of a neuron?

High concentrations of potassium (K+) and negatively charged proteins (A-) Signup and view all the answers

Study Notes

Neuron Structure

Cell Body (Soma): Contains the nucleus and organelles that maintain the cell's health and function. Integrates incoming signals from other neurons, and if the cumulative input is strong enough, generates an action potential.
Dendrites: Short, branching processes extending from the cell body. Primary site of input, receiving synaptic contacts from other neurons. Collect electrical signals and send them towards the cell body.
Axon: Long, narrow projection extending from the cell body. Main output pathway for transmitting signals to other cells. Carries action potentials away from the cell body.
Axon Hillock: Cone-shaped region where the axon joins the cell body. Action potential initiation occurs here if the signals received by the cell body reach a threshold.
Myelin: Fatty substance covering many axons, acting as insulation. Increases the speed of electrical signal transmission.
Nodes of Ranvier: Gaps between segments of the myelin sheath along the axon. Enable the action potential to "jump" from node to node (saltatory conduction), further increasing signal transmission speed.
Axon Terminals (Buttons): Button-like structures at the end of the axon that release neurotransmitters into the synapse.
Synapse: Gap between two neurons. When the action potential reaches the axon terminal of a neuron, neurotransmitters are released into the synaptic cleft and bind to receptors on the next neuron, propagating the signal.

Membrane Potentials

Resting Potential: Inside of a neuron is negatively charged (~-70mV) compared to the outside. This is due to ion concentration differences maintained by ion pumps in the cell membrane.
Ion Distribution: High concentrations of potassium (K+) and negatively charged proteins (A-) inside the neuron. High concentrations of sodium (Na+) and chloride (Cl-) ions outside.
Sodium-Potassium Pump: Actively transports Na+ and K+ ions, maintaining the negative charge inside the neuron.
Forces on Ions:
- Concentration Gradient: Ions move from areas of high to low concentration.
- Electrical Gradient: Positively charged ions (like Na+) are attracted to the negatively charged inside of the cell.

Changes in Membrane Potential

Depolarization: Na+ channels open, sodium ions flow into the neuron, making the inside more positive. This is called an Excitatory Postsynaptic Potential (EPSP). If sufficient depolarization occurs, and the membrane potential reaches ~-55mV, an action potential is triggered.
Action Potential: All-or-none event. Once the threshold is reached, sodium channels rapidly open, allowing a massive influx of Na+ which spikes the membrane potential up to ~+50mV. This depolarization travels down the axon in a wave-like manner.
Repolarization: After depolarization, potassium channels open, allowing potassium to flow out, restoring the membrane potential to its negative resting state.

Hodgkin-Huxley Cycle

Positive Feedback Loop: Amplifies the depolarization of the neuron's membrane during action potential generation.
Initiation: Small depolarizing event (EPSP) causes the membrane potential to reach a threshold level (~-55mV).
Sodium Channel Opening: Depolarization causes voltage-gated sodium (Na+) channels to open, allowing Na+ ions to rush into the cell.
Amplified Depolarization: More Na+ ions entering the cell further depolarizes the membrane, opening more voltage-gated Na+ channels.
Action Potential Spike: This positive feedback loop continues until the sodium channels inactivate, causing a rapid spike in the membrane potential (~+50mV).
Repolarization: Voltage-gated potassium (K+) channels open, allowing K+ ions to exit the cell, restoring the membrane potential to its resting state.

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Description

Explore the intricate structure of neurons, including the cell body, dendrites, axon, and more. This quiz covers the functions and characteristics of each component essential for neuronal communication. Test your understanding of how these parts work together to transmit signals in the nervous system.