Chapter 4

Question 1

electrographic seizures

Answer 1

Abnormal rhythmic neuronal discharges; may be recorded by an electroencephalogram.

Question 2

electrical stimulation

Answer 2

Passage of an electrical current from the uninsulated tip of an electrode through tissue, resulting in changes in the electrical activity of the tissue.

Question 3

voltmeter

Answer 3

Device that measures the flow and the strength of electrical voltage by recording the difference in electrical potential between two bodies.

Question 4

electroencephalogram (EEG)

Answer 4

Graph that records electrical activity from the brain and mainly indicates graded potentials of many neurons.

Question 5

oscilloscope

Answer 5

Device that serves as a sensitive voltmeter by registering changes in voltage over time.

Question 6

microelectrode

Answer 6

A microscopic insulated wire or a saltwater-filled glass tube whose uninsulated tip is used to stimulate or record from neurons.

Question 7

diffusion

Answer 7

Movement of ions from an area of higher concentration to an area of lower concentration through random motion.

Question 8

concentration gradient

Answer 8

Difference in the relative abundance of a substance among regions of a container; allows the substance to diffuse from an area of higher concentration to an area of lower concentration.

Question 9

voltage gradient

Answer 9

Difference in charge between two regions that allows a flow of current if the two regions are connected.

Question 10

resting potential

Answer 10

Electrical charge across the insulating cell membrane in the absence of stimulation; a store of potential energy produced by a greater negative charge on the intracellular side relative to the extracellular side.

Question 11

graded potential

Answer 11

Small voltage fluctuation across the cell membrane.

Question 12

hyperpolarization

Answer 12

Increase in electrical charge across a membrane, usually due to the inward flow of chloride or sodium ions or the outward flow of potassium ions.

Question 13

depolarization

Answer 13

Decrease in electrical charge across a membrane, usually due to the inward flow of sodium ions.

Question 14

action potential

Answer 14

Large, brief reversal in the polarity of an axon membrane

Question 15

threshold potential

Answer 15

Voltage on a neural membrane at which an action potential is triggered by the opening of sodium and potassium voltage-sensitive channels; about –50 mV relative to extracellular surround. Also called threshold limit.

Question 16

voltage-sensitive channel

Answer 16

Gated protein channel that opens or closes only at specific membrane voltages.

Question 17

absolutely refractory

Answer 17

The state of an axon in the repolarizing period, during which a new action potential cannot be elicited (with some exceptions), because gate 2 of sodium channels, which are not voltage sensitive, are closed.

Question 18

relatively refractory

Answer 18

The state of an axon in the later phase of an action potential during which increased electrical current is required to produce another action potential; a phase during which potassium channels are still open.

Question 19

nerve impulse

Answer 19

Propagation of an action potential on the membrane of an axon.

Question 20

node of Ranvier

Answer 20

The part of an axon that is not covered by myelin.

Question 21

saltatory conduction

Answer 21

Fast propagation of an action potential at successive nodes of Ranvier; saltatory means leaping.

Question 22

multiple sclerosis (Ms)

Answer 22

Nervous system disorder resulting from the loss of myelin around axons in the CNS.

Question 23

autoimmune disease

Answer 23

Illness resulting from an abnormal immune response by the body against substances and tissues normally present in the body.

Question 24

excitatory postsynaptic potential (EPsP)

Answer 24

Brief depolarization of a neuron membrane in response to stimulation, making the neuron more likely to produce an action potential.

Question 25

inhibitory postsynaptic potential (IPsP)

Answer 25

Brief hyperpolarization of a neuron membrane in response to stimulation, making the neuron less likely to produce an action potential.

Question 26

initial segment

Answer 26

Area near or overlapping the axon hillock where the action potential begins.

Question 27

temporal summation

Answer 27

Addition of one graded potential to another that occur close in time.

Question 28

spatial summation

Answer 28

Addition of one graded potential to another that occur close in space.

Question 29

back propagation

Answer 29

Reverse movement of an action potential into the soma and dendritic field of a neuron; postulated to play a role in plastic changes that underlie learning.

Question 30

optogenetics

Answer 30

Transgenic technique that combines genetics and light to excite or inhibit targeted cells in living tissue.

Question 31

stretch-sensitive channel

Answer 31

Ion channel on a tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse.

Question 32

end plate

Answer 32

On a muscle, the receptor–ion complex that is activated by the release of the neurotransmitter acetylcholine from the terminal of a motor neuron.

Question 33

transmitter-sensitive channel

Answer 33

Receptor complex that has both a receptor site for a chemical and a pore through which ions can flow.