Neurophysiology-membrane Dynamics

Question 1

Resting potential

Answer 1

The electrical potential of a neuron or other excitable cell relative to its surroundings when not stimulated or involved in passage of an impulse.

Question 2

Graded potential

Answer 2

Are charges in membrane potential that vary in size. As opposed to being all-or-none. They arise from the summation of the individuals actions of ligand-gated ion channel proteins, and decrease over time and space.

Question 3

Action potential

Answer 3

The change in electrical potential associated with the passage of an impulse along the membrane of a muscle or nerve cell.

Question 4

Electrochemical gradient

Answer 4

A gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical grade t, or difference in solute concentration across a membrane and the electrical gradient, or difference in change across a membrane.

Question 5

Electrochemical equilibrium

Answer 5

When the chemical and electrical gradients are equal in magnitude, the ion is said to be in electrochemical equilibrium, and the membrane potential that is established at equilibrium is said to be the equilibrium potential for that ion under the existing concentration gradient.

Question 6

Equilibrium potential

Answer 6

For each ion, the equilibrium (or reverse) potential is the membrane potential where the net flow through any open channels is 0. In other words the chemical and electrical forces are in balance.

Question 7

Chemically gated channels

Answer 7

Are a group of transmembrane ion channel proteins which open to allow ions such as Na, K, Ca and/or Cl to pass through the membrane in rep once to the binding of a chemical messenger, such as a neurotransmitter.

Question 8

Voltage gated ion channels

Answer 8

Are transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential near the channel. The membrane potential alters the conformation of the channel proteins, regulating their opening and closing.

Question 9

Mechanically gated channels

Answer 9

Are membrane proteins capable of responding to mechanical streets over a wide dynamic range of external mechanical stimuli.

Question 10

Local current

Answer 10

Depolarize the membrane immediately adjacent to the action potential. When depolarization caused by local caused by local currents reaches threshold. A new action potential is produced adjacent to the original one.

Question 11

Depolarization

Answer 11

Resting state-> stimulus-> open Na channels-> charge increases to threshold -55. -> then to fire +40. -> local current-> spread of Na ions.

Question 12

Depolarization

Answer 12

Restoration of resting state ion distribution-> ion channel control-> Na/K pump activity, works more effectively when there is more Na inside the cell. -> Na leaves the cell -> charge decreases below the resting point -70.

Question 13

Hyperpolarization

Answer 13

K gates open

The charge drops below -70mV

Question 14

Nervous system stimulants

Answer 14

Bring cell closer to threshold.

EX: caffeine

Question 15

Nervous system depressant

Answer 15

Brings cell farther from threshold.

EX: alcohol

Question 16

Action potential

Answer 16

The change in electrical potential associated with the passage of an impulse along the membrane of a muscle or nerve cell.

Question 17

Threshold potential

Answer 17

Is the critical level to which a membrane potential must be depolarized to intimate an action potential. -55mV

Question 18

Refractory period

Answer 18

The recently depolarized area of the membrane is in absolute refractory period and cannot generate an action potential. Keep the action potential traveling in one direction.

Question 19

all-or-nothing principle

Answer 19

If the stimulus exceeds the threshold potential, the nerve or muscle fiber will give a complete response; otherwise, there is no response.

Question 20

Continuous propagation

Answer 20

When an action potential in an axon spreads to a neighboring region of its membrane by a series of small steps.

Question 21

Saltatory propagation

Answer 21

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