Neuron 2025

Question 1

What are the four key regions of a neuron and their main roles?

Answer 1

• Dendrites: Receive input.
• Soma (Cell Body): Integrates input.
• Axon: Conducts action potentials.
• Axon Terminals: Transmit output to other neurons.

Question 2

What are dendritic spines?

Answer 2

Small protrusions from dendrites that increase surface area and receive synaptic input.

Question 3

What is the resting membrane potential of a typical neuron?

Answer 3

Approximately -70 mV

Question 4

Which ions are involved in maintaining the resting membrane potential?

Answer 4

Na⁺, K⁺, Cl⁻, and A⁻ (proteins).

Question 5

What is the role of the Na⁺/K⁺ ATPase pump?

Answer 5

Maintains ion gradients by pumping 3 Na⁺ out and 2 K⁺ in, consuming ATP.

Question 6

What causes the rapid depolarization in an action potential?

Answer 6

Opening of voltage-gated Na⁺ channels, allowing Na⁺ influx.

Question 7

What leads to repolarization?

Answer 7

Opening of voltage-gated K⁺ channels, allowing K⁺ efflux

Question 8

What is the refractory period?

Answer 8

A period following an action potential during which a neuron cannot fire another AP (absolute) or requires a stronger stimulus (relative).

Question 9

What does a patch clamp technique measure?

Answer 9

The ionic currents through individual ion channels or whole cells.

Question 10

What is a “voltage clamp”?

Answer 10

A technique to hold membrane potential constant to study ionic currents.

Question 11

What is a “current clamp”?

Answer 11

A technique to inject current and measure changes in membrane potential

Question 12

What triggers neurotransmitter release at the synaptic terminal?

Answer 12

: Influx of Ca²⁺ through voltage-gated calcium channels.

Question 13

What is an Excitatory Post-Synaptic Potential?

Answer 13

Excitatory Post-Synaptic Potential—a depolarization caused by Na⁺ influx

Question 14

: What is an Inhibitory Post-Synaptic Potential?

Answer 14

Inhibitory Post-Synaptic Potential—a hyperpolarization caused by Cl⁻ influx or K⁺ efflux.

Question 15

What is the primary excitatory neurotransmitter in the CNS?

Answer 15

Glutamate

Question 16

What is the primary inhibitory neurotransmitter?

Answer 16

GABA

Question 17

What’s the difference between ionotropic and metabotropic receptors?

Answer 17

• Ionotropic: Ligand-gated ion channels (fast).
• Metabotropic: G-protein-coupled receptors (slow, modulatory).

Question 18

What is spatial summation?

Answer 18

Combined effect of simultaneous inputs at different locations on the neuron

Question 19

: What is temporal summation

Answer 19

Repeated input from the same synapse over time adding together

Question 20

What determines whether a neuron will fire an action potential?

Answer 20

: If the sum of EPSPs and IPSPs at the axon hillock depolarizes the membrane above threshold (usually ~–55 mV).

Question 21

What is the axon hillock?

Answer 21

region where action potentials are initiated; it has a high density of voltage-gated Na⁺ channels

Question 22

Why don’t action potentials go backwards?

Answer 22

Due to the refractory period, where Na⁺ channels are inactivated and cannot reopen immediately.

Question 23

How is action potential conduction velocity increased?

Answer 23

By myelination (insulation by oligodendrocytes/Schwann cells) and larger axon diameter.

Question 24

What is saltatory conduction?

Answer 24

The jumping of action potentials from one node of Ranvier to the next in myelinated axons.

Question 25

What is “whole-cell” patch clamp?

Answer 25

Access to the interior of the cell by rupturing the membrane patch under the pipette tip.

Question 26

What are the two main forces that drive ion movement across membranes?

Answer 26

The chemical (concentration) gradient and the electrical (voltage) gradient—together forming the electrochemical gradient.

Question 27

What equation calculates the equilibrium potential of a single ion?

Answer 27

The Nernst equation.

Question 28

: What does the Goldman-Hodgkin-Katz (GHK) equation calculate?

Answer 28

A: The membrane potential when multiple ions are permeable.

Question 29

Outline the steps of chemical synaptic transmission.

Answer 29

1. Action potential arrives at axon terminal 2. Ca²⁺ channels open, Ca²⁺ enters 3. Vesicles fuse with membrane via SNARE complex 4. Neurotransmitter is released into synaptic cleft 5. Binds to receptors on postsynaptic membrane 6. Ion channels open → EPSP/IPSP 7. Neurotransmitter removed (reuptake, degradation, diffusion)

Question 30

What is synaptic plasticity?

Answer 30

ability of synapses to change strength with use (e.g., LTP or LTD), crucial for learning and memory.

Question 31

What is long-term potentiation (LTP)?

Answer 31

A long-lasting increase in synaptic strength following high-frequency stimulation—commonly studied in the hippocampus

Question 32

What receptor is crucial for LTP initiation?

Answer 32

NMDA receptor (a glutamate receptor that requires both ligand binding and depolarization to remove Mg²⁺ block).

Question 33

How are neurotransmitters removed from the synaptic cleft?

Answer 33

* Reuptake (into presynaptic terminal or glial cells) * Enzymatic degradation (e.g., acetylcholinesterase) * Diffusion away from synaptic cleft

Question 34

Why is neurotransmitter removal important

Answer 34

To terminate the signal and prevent continuous stimulation.