L7 Neurobiology ✅

Multipolar

Bipolar

Unipolar or pseudounipolar

Sensory neuron

Interneuron

Motor neuron

What cells depend on ion movement across membranes?

What creates the membrane potential?

Many processes from cell body multiple dendrites & one axon

Two main processes

One main process from cell body

Transmit information about sensory stimuli from receptors to the central nervous system

Connect neurons to one another, often short, unmyelinated axons and complex dendrite

Carry impulses from central nervous system to effector organ and Initiate contractions or secretions

Neurons/muscles

Facilitated diffusion of ions across cell membranes

Membrane potential

What charge does cytoplasm have?

Plasma membrane

Define electrochemical gradient

Voltage difference across cell membrane measured in V or mV with inside of cell negative relative to outside of cell that arises from unequal distribution of ions across membrane

Net neutral charge

Functions as capacitor that stores electrical energy by accumulating charges on two closely spaced surfaces insulated from each other

Gradient independent from membrane potential that is based on concentration that moves ions according to the net effect of concentration and charge

Equilibrium potential (reversal potential of an ion)

What can be used to calculate equilibrium potential?

Resting membrane potential

What helps maintain RMP?

How do resting neurons maintain concentration gradients?

What are leaky channels?

The membrane voltage at which an ion is at equilibrium where no net movement occurs, and if the membrane potential changes from this value, the driving force (net electrochemical gradient) causes the ion to flow into or out of the cell, depending on which gradient (electrical or concentration) is stronger.

Nernst equation:

In neurons, -70 mV where its actively maintained using dynamic equilibrium

• More + ions outside, with more - inside the plasma membrane

• Na/K pump: maintains ionic gradients by active transport

• Leaky channels: predominant determinant of RMP

Active transport

Constitutively active channels that allow facilitated diffusion and leak based on gradients

What causes electrical signals?

What changes membrane potential?

Driving force

Depolarization

Hyperpolarization

Repolarization

Changes in membrane permeability

Opening and closing ion channels

Governs predominant ion flow as the difference between membrane potential and ion equilibrium potential with larger difference meaning larger driving force

Membrane potential becomes less negative with +ions entering and -ions exiting

Membrane potential becomes more negative with +ions exiting and -ions entering

Membrane potential returns toward RMP