Neurophysiology

What is a membrane potential?

stored energy

What is resting membrane potential?

stored energy when the cell is undisturbed

What is an ion?

charged particle

What are the 4 main ions we talked about?

sodium, chloride, potassium, calcium

What is force?

the capacity to work or cause change

What are concentration gradients?

molecules move from areas of high concentration to low concentration

What are electrical gradients?

opposites attract and likes repel

What is equilibrium potential?

the transmembrane potential which equalizes fluxes for a particular ion (means that ions don’t need to move because they have reached a balanced state)

What is polarization?

separation of electrical charge

What is depolarization?

remove/loss of separation of electrical charge

What is repolarization?

reestablish the separation of charge

How is membrane potential measured?

measure the charge of the extracellular fluid and the inside of the cell

What are electrical signals?

created by temporary charges in ion movement into and out of the neuron

What is the membrane potential created by?

a separation of charge between the inside and outside of the cell

What determines if a particular ion will move into or out of the cell?

the two forces (electrical gradient and concentration gradient)

What are the two reasons that both diffusion and electrostatic pressure are pulling NA+ in the cell, yet it remains in highest concentration outside the cell?

membrane permeability and NA/K pump

What is membrane permeability?

ions cannot permeate the membrane well without a channel

What is the NA/K pump?

designed to remove 3 molecules of NA+ from inside the cell and replace it with 2 molecules of K+. It constantly works to maintain RMP

What are the energy requirements of the NA/K pump?

40% of the metabolic resources of the brain go to operating this pump

What is threshold?

opening of voltage gated sodium channels when the membrane is at a certain voltage

How long does a membrane potential usually last?

around 1-2 milliseconds

What are some characteristics of an action potential?

all-or-none, all this is necessary is reaching threshold, propagation is active, the signal is always depolarization, and APs are very stereotyped (the stimulus doesn’t matter, action potentials all look the same)

What determines the intensity or speed of movement of a signal?

how frequently the action potentials occur (intervals between the action potentials) and number of action potentials or nerve fibers being activated

What determines the meaning of the stimulus?

neural pathways that are activated

What are the two types of conduction?

passive conductance or local potential and active conductance

What is passive conductance?

small subthreshold depolarizations that need to summate at the axon hillock to try to reach threshold

What is active conductance?

conduction of nerve impulses on the axon by regenerating action potentials down the entire length of the axon

What is saltatory conduction?

if it is a myelinated axon (“leap” between the nodes)

What are two advantages of saltatory conduction?

speed and economical (reduces the number of sodium potassium pumps in the myelinated axons because you only need them in the nodes)

What is reuptake?

proteins bond the neurotransmitters and brings them back up into the presynaptic terminal

What are the two ways to stop synaptic transmission?

reuptake and enzymatic deactivation

What is enzymatic deactivation?

ACh esterase will break down the enzyme

What are auto receptors

neurons can get feedback on what they are doing

What are the 4 types of synaptic connections?

axodendritic, axosomatic, axo-axonic, and dendro-dendritic