Chapter 3 Cells of the Nervous System

What are the three main types of ion channels?

1. Passive 'Leak' Channels – Always open, allow ions to move down their concentration gradient.

2. Ligand-Gated Channels – Open in response to the binding of a chemical messenger (neurotransmitter).

3. Voltage-Gated Channels – Open or close in response to changes in membrane potential.

What is transcription?

The process by which DNA is copied into mRNA.

What is translation?

The process by which ribosomes use mRNA to build proteins.

What are proteins and their function?

Proteins are chains of amino acids that perform structural, enzymatic, signaling, and regulatory functions in the body.

What are enzymes?

Enzymes are proteins that catalyze (speed up) chemical reactions.

What is the plasma membrane?

A lipid bilayer that encloses the cell, controlling movement of substances in and out.

What are receptors and ligands?

Receptors are proteins on the cell surface or inside the cell that bind to ligands—signaling molecules like neurotransmitters or hormones.

What happens after a ligand binds to a receptor?

It triggers a cellular response; the ligand may be degraded, recycled, or released.

What are ions?

Charged atoms or molecules (e.g., Na⁺, K⁺, Cl⁻) that carry electrical current in cells.

What are transport proteins and ion channels?

• Transport proteins help move substances across the membrane.

• Ion channels are a type of transport protein that allows specific ions to pass through the membrane.

Approximately how many neurons are in the human nervous system?

More than 100 billion

Are most behaviors produced by single neurons or groups of neurons?

By groups of hundreds or thousands of neurons.

Do neurons maintain a fixed structure?

No, neurons can grow and shrink—they continuously change shape.

Are most CNS neurons replaced over your lifetime?

No, most CNS neurons last a lifetime and are not replaced.

Are most CNS neurons replaced over your lifetime?

No, most CNS neurons last a lifetime and are not replaced.

Does neurogenesis occur in adulthood?

Yes, but it is rare.

What are neurons specialized for?

The reception, conduction, and transmission of electrochemical signals.

What are the three basic subdivisions of a neuron?

Dendrites, Soma (cell body), and Axon.

What is the function of dendrites?

They gather information from other neurons.

What is the function of the soma (cell body)?

It contains the nucleus and integrates information.

What is the function of the axon?

It starts at the axon hillock, carries information, and ends at the axon terminals to pass signals to other cells.

What is the dendritic tree?

A collection of dendrites from a single neuron that receives input from other neurons.

How many inputs can a dendritic tree receive?

Inputs may number in the thousands.

What are dendritic spines?

Protrusions from a dendrite that increase surface area and are the typical point of contact with axons to form synapses.

Why are dendritic spines important?

They increase the neuron's surface area for synaptic input.

Are dendritic spines static or dynamic structures?

They are dynamic—spines are constantly being formed or eliminated.

What influences the formation and elimination of dendritic spines?

The type and amount of synaptic activity.