neurophysiology (Exam 2)

What is neurophysiology?

The study of how neurons function and transmit signals

What is a resting potential?

The electrical charge difference across a resting neuron

What is the typical resting membrane potential?

-65 mV

What does it mean for a neuron to be polarized?

The inside is more negative than the outside

What ions are most concentrated inside the neuron?

Potassium (K+) and negatively charged proteins

What ions are most concentrated outside the neuron?

Sodium (Na+) and chloride (Cl-)

What is an ion?

An electrically charged atom or molecule

What is a cation?

A positively charged ion

What is an anion?

A negatively charged ion

What are the four major ions involved in neural signaling?

Sodium, potassium, chloride, and calcium

What is diffusion?

Movement of ions from high concentration to low concentration

What is electrostatic pressure?

Movement of ions toward areas of opposite charge

What is selective permeability?

Allowing some ions to cross the membrane more easily than others

What ion can freely leak out of a resting neuron?

Potassium (K+)

What is an ion channel?

A protein that allows ions to cross the membrane

What is the sodium-potassium pump?

A protein that moves 3 Na+ out and 2 K+ into the neuron

What is the function of the sodium-potassium pump?

Maintains resting potential

How many sodium ions are pumped out?

3

How many potassium ions are pumped in?

2

Why does the inside of the neuron stay negative?

More positive ions leave than enter

What is equilibrium potential?

The point where diffusion and electrostatic pressure are balanced

What is depolarization?

The membrane becomes less negative

What is hyperpolarization?

The membrane becomes more negative

What is repolarization?

Return toward resting potential after depolarization

What is a graded potential?

A local change in membrane potential proportional to stimulus strength

What is a local potential?

A potential that decreases as it spreads

What is the threshold for an action potential?

About -40 mV

What happens when threshold is reached?

An action potential fires

What is an action potential?

A rapid reversal of membrane potential that travels down the axon

Where do action potentials begin?

Axon hillock

What causes depolarization during an action potential?

Sodium ions entering the cell

What channels open first during an action potential?

Voltage-gated sodium channels

What ion rushes into the cell during depolarization?

Sodium (Na+)

What is the peak of an action potential?

About +40 mV

What causes repolarization?

Potassium leaving the cell

What channels open during repolarization?

Voltage-gated potassium channels

What ion rushes out during repolarization?

Potassium (K+)

What causes hyperpolarization?

Potassium channels stay open briefly

What is the absolute refractory period?

A period when no new action potential can occur

Why can't another action potential occur during the absolute refractory period?

Sodium channels are inactivated

What is the relative refractory period?

A period when a stronger-than-normal stimulus is needed

What is propagation?

The movement of an action potential down an axon

Why does an action potential only move forward?

The refractory period prevents backward movement

What is saltatory conduction?

Action potentials jump from node to node

What is myelin?

A fatty insulating covering around axons

What is a Node of Ranvier?

A gap in the myelin sheath

Where are voltage-gated sodium channels concentrated in myelinated axons?

Nodes of Ranvier

What is the advantage of saltatory conduction?

Faster signal transmission

What does all-or-none mean?

An action potential either happens completely or not at all

Does a stronger stimulus make a larger action potential?

No