The nerve impulse

Question 1

Membrane potential

Answer 1

A form of potential energy resulting from the separation of charges between the inside and outside of a cell membrane; voltage across a cell membrane

Question 2

Polarization

Answer 2

The process of generating a resting membrane potential, averaging about -70mV

Question 3

Sodium-potassium exchange pump

Answer 3

A system located within the cell membrane that actively transports 3Na+ ions out and 2K+ ions into the cell using carrier proteins. The result is a positive charge outside the cell. Overall, the active transport of sodium and potassium ions and their subsequent diffusion back across the membrane results in the constant membrane potential of -70mV.

Question 4

Voltage

Answer 4

Electrical potential difference across a membrane as measured by a voltmeter

Question 5

Polarized membrane

Answer 5

The state of the cell membrane in an unstimulated neuron in which the inside of the neuron is negatively charged in comparison with the outside of the neuron; the resting state of a membrane averaging approximately -70mV

Question 6

Resting membrane potential

Answer 6

The voltage that exists across a cell membrane during the resting state of an excitable cell, such as a neuron; averages around -70mV, but may range from -50 to -200 mV depending on the cell.

Question 7

Action Potential

Answer 7

The change in change that occurs when the gates of the potassium ion channels close and the gates of the sodium ion channels open; a large depolarization even that is conducted along the membrane of a nerve cell or a muscle cell

Question 8

Threshold stimulus

Answer 8

The weakest possible stimulus that is needed to conduct a nerve impulse

Question 9

Depolarization

Answer 9

The loss or reduction of the negative resting membrane potential

Question 10

Repolarization

Answer 10

Restoring the resting membrane potential from the depolarized state

Question 11

Refractory period

Answer 11

The short time immediately after an action potential in which the neuron cannot respond to another stimulus; period of time it takes to reestablish the net positive charge on the outside of the neuron and net negative on the inside, where there are more sodium ions on the outside, and more potassium ions on the inside of the neuron.

Question 12

All-or-none response

Answer 12

Action that occurs either completely or not at all, such as the generation of an action potential by a neuron.

Question 13

Threshold potential

Answer 13

The smallest change in the membrane potential of a cell membrane that is needed to initiate an action potential; about -55mV

Question 14

Myelinated Neuron

Answer 14

A neuron whose axon is wrapped by Schwann cells, which produces a myelin sheath. Myelinated neurons make up the white matter in the brain and spinal cord and send nerve impulses very quickly.

Question 15

Unmyelinated Neuron

Answer 15

A neuron that does not have Schwann cells and therefore lacks a myelin sheath. Unmyelinated neurons make up the grey matter in the brain and spinal cord and transmit nerve impulses more slowly than myelinates neurons.

Question 16

Saltatory conduction

Answer 16

Rapid transmission of a nerve impulse along an axon resulting from a nerve impulse jumping from one node of Ranvier to another, skipping the myelinated regions of the membrane.

Question 17

Synapse

Answer 17

The connection between two neurons or a neuron and an effector

Question 18

Neuromuscular Junction

Answer 18

Synapse between a motor neuron and a muscle cell.

Question 19

Neurotransmitters

Answer 19

Chemical messengers that carry a neural signal from one neuron to another neuron or to an effector such as a gland or muscle fibre.