PSYU2236 W2 | The Neuron

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Questions and Answers

What defines a unipolar neuron?

Having one axon and multiple dendrites

Having a single neurite connected to the soma (correct)

Having one dendrite connected to the soma

Having multiple axons and one dendrite

Which shape describes a pyramidal neuron?

Triangular (correct)

Cuboidal

Cylindrical

Starlike

What role do dendritic spines play in neurons?

They affect the transport of neurotransmitters

They serve as the primary output signal of the neuron

They prevent neurotransmitter release

They are involved in learning and memory (correct)

How are multipolar neurons primarily distinguished?

By having multiple neurites connected to the soma Signup and view all the answers

What happens to dendritic trees over time?

They can grow or recede Signup and view all the answers

What is the main effect of the influx of Na+ ions on the membrane potential during depolarization?

It causes the membrane potential to become more positive. Signup and view all the answers

What occurs during the hyperpolarization phase after K+ ions leave the neuron?

The neuron temporarily becomes more negatively charged than resting potential. Signup and view all the answers

What happens to the voltage-gated Na+ channels during the first part of the axon when the membrane potential is positive?

They close to prevent further Na+ influx. Signup and view all the answers

Which ion primarily contributes to the depolarization of the membrane?

Na+ ions. Signup and view all the answers

Which ion movement occurs during the repolarization phase of an action potential?

K+ ions exit the neuron. Signup and view all the answers

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

It brings in 2 K+ ions and removes 3 Na+ ions. Signup and view all the answers

How does the sodium-potassium pump restore the electrical potential of the cell?

By maintaining a greater negative charge inside the cell. Signup and view all the answers

What type of channels open when the cell becomes positively charged?

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

Which ion primarily flows into the cell when K+ channels are open at rest?

K+ ions Signup and view all the answers

Which statement regarding voltage-gated Na+ ion channels is true?

They only open at depolarized potentials between -50 to +30 mV. Signup and view all the answers

What energy source does the sodium-potassium pump require for its function?

ATP Signup and view all the answers

What occurs during the communication in the brain when the cell becomes positive?

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

What factor contributes to an axon's speed of transmission?

Thickness of the axon Signup and view all the answers

When Na+/K+ pumps function effectively, what is the resultant condition of the cell?

Greater [K+] concentration inside the cell. Signup and view all the answers

During which period is a neuron unable to fire another action potential?

Absolute refractory period Signup and view all the answers

What occurs during the relative refractory period?

Neuron requires a stronger voltage change to fire Signup and view all the answers

What happens to the membrane potential when a neuron is hyperpolarized?

It becomes more negative Signup and view all the answers

Which ion channel is primarily involved in repolarization during an action potential?

Voltage-gated K+ channel Signup and view all the answers

What is the undershoot in the action potential due to?

K+ efflux before K+ channel closes Signup and view all the answers

How long does the absolute refractory period last after an action potential?

1 millisecond Signup and view all the answers

What must occur during the refractory period for a neuron to fire again?

A stronger than normal voltage change is needed Signup and view all the answers

What is one of the primary functions of glial cells in the central nervous system?

To support neurons both chemically and physically Signup and view all the answers

Which type of glial cell is responsible for myelination in the peripheral nervous system?

Schwann cells Signup and view all the answers

How do ions pass through the plasma membrane of a neuron?

They pass through channels or receptors Signup and view all the answers

What role does the sodium-potassium pump serve in maintaining the resting membrane potential?

It pumps sodium out and brings potassium into the cell Signup and view all the answers

What happens to potassium ions at rest compared to sodium ions?

Potassium can leave freely while sodium cannot enter easily Signup and view all the answers

Which of the following glial cells helps stabilize and synchronize the activity of neurons?

Astrocytes Signup and view all the answers

Why is the plasma membrane described as impermeable to ions?

The lipid bilayer does not interact with charged particles Signup and view all the answers

What characteristic of the phospholipid bilayer contributes to its selective permeability?

It has hydrophobic tails that block charged particles Signup and view all the answers

Study Notes

Neurite Classification

Neurites include axons and dendrites; one axon and one dendrite equal two neurites.
Classification based on the number of neurites connected to the soma: unipolar, bipolar, and multipolar.
Bipolar neurons are relatively common; unipolar dendrites are not found in vertebrates.

Dendritic Classification

Neurons are classified by the shape of dendrites: stellate (star-shaped) versus pyramidal (triangular).
Dendrites can be either spinous (having spines) or aspinous (lacking spines).
Dendritic spines play a crucial role in learning and memory.
Dendritic trees are dynamic and change through growth or retraction, contributing to neuroadaptation.
The number of dendrites influences the information the neuron can receive.

Glial Cells

Types of glial cells include astrocytes, oligodendrocytes, microglia, and Schwann cells.
Glial cells support neurons both chemically and physically.
In the central nervous system, glial cells connect multiple neurons, providing stability and synchronizing their activity.

Membrane Potential and Action Potential

The plasma membrane is a phospholipid bilayer that allows uncharged molecules to pass through but not ions.
Ions must pass through specific channels for membrane potential regulation.
The sodium-potassium pump moves 3 Na+ out and 2 K+ in, maintaining the chemical and electrical balance.
Potassium ions can move freely, influenced by both electrical and chemical gradients.

Ion Channels and Action Potential

Voltage-gated Na+ channels only open at specific membrane potentials (approximately -50 to +30 mV).
Voltage-gated K+ channels open when the cell’s internal environment becomes more positive.
Receptors regulate K+ flow during resting states, while Na+/K+ pumps create depolarization by allowing Na+ influx.

Refractory Periods

After an action potential, voltage-gated Na+ channels close and K+ channels open, leading to hyperpolarization.
The thickness and myelination of axons influence conduction speed due to reduced electrical resistance.
The absolute refractory period lasts approximately 1 ms after an action potential when the neuron cannot fire again.
The relative refractory period, lasting 2-4 ms post-action potential, makes it harder for the neuron to fire again due to hyperpolarization; a stronger stimulus is needed.

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Description

Explore the fundamentals of neurites in this quiz centered on Chapter 14 of your neuroscience course. Understand the definitions and classifications of axons and dendrites, as well as their significance in neural connectivity. Test your knowledge and comprehension of the material presented.