Bio 168 Chapter 11 Part 2

Neuron Excitability

Neurons respond to stimuli by generating action potentials

Action Potential

Nerve impulse generated by neurons in response to stimuli

Membrane Ion Channels

Proteins facilitating ion flow across membranes

Leakage Channels

ion channels that are always open allowing passive ion flow

Gated Channels

Ion channels opening/closing in response to stimuli

Graded Potentials

Short-distance, variable strength membrane signals

Action Potential (AP)

Brief membrane potential reversal for long-distance signaling

Depolarization

membrane potential becomes less negative making the neuron more likely to fire (excitation)

Hyperpolarization

Inside of membrane becomes more negative than resting membrane potential

Probability of producing impulse decreases

Threshold

Membrane potential level to trigger an action potential

Absolute Refractory Period

Time after AP when new AP cannot be generated

Relative Refractory Period

Follows absolute refractory period, harder to trigger AP

Conduction Velocity

Speed of nerve impulse propagation along axons

Myelination

Insulation of axons for faster impulse conduction

Multiple Sclerosis (MS)

Autoimmune disease affecting myelin sheaths in CNS

Nerve Fiber Classification

Categorization based on diameter, myelination, and conduction speed

ligand-gated ion channel

A protein pore in the plasma membrane that opens or closes in response to a chemical signal, allowing or blocking the flow of specific ions.

voltage-gated ion channels

A specialized ion channel that opens or closes in response to changes in membrane potential

mechanically gated ion channels

Respond to membrane distortion

Found in sensory receptors that respond to touch, pressure, or vibration

Resting Membrane Potential (RMP)

Electrical potential energy produced by separation of oppositely charged particles across plasma membrane in all cells

How do Na+ and K+ concentrations differ in extracellular fluid and intracellular fluid?

Extracellular fluid has more Na+ than K+

Intracellular fluid has more K+ than Na+

How does the CNS differentiate between a weak stimulus and a strong stimulus?

Strong stimuli generate more frequent action potentials than weak stimuli

continuous conduction

slow conduction that occurs in nonmyelinated axons

saltatory conduction

the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

Which ion is moving during the rising phase of an action potential?

Na+ moving into the cell

Which ion is moving during the falling phase of an action potential?

K+ moving out of the cell