chapter 4

Question 1

membrane potential

Answer 1

the difference in electrical charge between the inside and the outside of a cell

Question 2

resting potential

Answer 2

the steady membrane potential of about -70 mV is called the neuron’s resting potential

Question 3

ions

Answer 3

the salts in neural tissue separate into positively and negatively charged particles called ions

Question 4

ion channels

Answer 4

These unequal distributions of Na + and K+ ions are maintained even though there are specialized pores

Question 5

natrium

Answer 5

sodium jions

Question 6

kalium

Answer 6

potassium ions

Question 7

electrostatic pressure

Answer 7

from the resting membrane potential
because opposite charges attract, the -70 mV charge attracts the positively charged Na+ ions into resting neurons

Question 8

concentration gradient

Answer 8

they are more likely to move from areas of high concentration to areas of low concentration than vice versa

Question 9

sodium-potassium pump

Answer 9

ion transport is performed by mechanisms in the cell membrane that continually exchange three Na+ ions inside the neuron for two K+ ions outside

Question 10

transporters

Answer 10

mechanisms in membrane of a cell that actively transport ions or molecules across the membrane

Question 11

neurotransmitters

Answer 11

chemicals that diffuse across the synaptic clefts and interact with specialized receptor molecules on the receptive membranes of the next neurons in the circuit

Question 12

depolarize

Answer 12

decrease the resting membrane potential, from -70 to -67 mV, for example

Question 13

hyperpolarize

Answer 13

increase the resting membrane potential from -70 to -72 mV

Question 14

EPSP’s

Answer 14

excitatory postsynaptic potentials
increase the likelihood that the neuron will fire

Question 15

IPSPs

Answer 15

inhibitory postsynaptic potentials
decrease the likelihood that the neuron will fire

Question 16

axon hillock

Answer 16

the conical structure at the junction between the cell body and the axon

Question 17

threshold of excitation

Answer 17

-65 mV
when an action potential is generated

Question 18

action potential

Answer 18

massive but momentary - lasting for 1 millisecond - reversal of the membrane potential from about -70 to about +50

Question 19

all or none response

Answer 19

the action potential either occurs to their full extent or do not occur at all

Question 20

integration

Answer 20

adding or combining a number of individual signals into one overall signal

done through spatial summation and temporal summation

Question 21

voltage-activated ion channels

Answer 21

ion channels that open or close in response to changes in the level of the membrane potential

Question 22

absolute refractory period

Answer 22

a brief period of about 1 to 2 milliseconds after the initiation of an action potential during which it is impossible to elicit a second one

Question 23

relative refractory period

Answer 23

the period in which it is possible to fire the neuron again but only by applying higher-than normal levels of stimulation

the end of the relative refractory period is the point at which the amount of stimulation necessary to fire a neuron returns to baseline

Question 24

myelin

Answer 24

insulated from the extracellular fluid by segments of fatty tissue

Question 25

nodes of ranvier

Answer 25

the gaps between adjacent myelin segments

Question 26

saltatory conduction

Answer 26

the transmission of action potentials in myelinated axons

Question 27

dendritic spines

Answer 27

nodules of various shapes that are located on the surfaces of many dendrites

Question 28

synaptic vesicles

Answer 28

packages small- molecule neurotransmitters and are typically synthesized in the cytoplasm of the terminal button

Question 29

microtubules

Answer 29

transport the vesicles to the terminal buttons at a rate of about 40 centimeters per day

Question 30

exocytosis

Answer 30

the process of neurotransmitter release

Question 31

Ca2+

Answer 31

when stimulated by action potentials these channels open and Ca2+ enter the button the entry causes synaptic vesicles to fuse with the presynaptic membrane and empty their contents into the synaptic cleft

Question 32

receptors

Answer 32

a protein that contains binding sites for only particular neurotransmitters neurotransmitter can influence only those cells that have receptors for it

Question 33

ligand

Answer 33

any molecule that binds to another

Question 34

ionotropic receptors

Answer 34

associated with ligand-activated ion channels

Question 35

metabotropic receptors

Answer 35

G proteins - Guanosine-triphosphate-sensitive proteins receptor activates G protein Does not directly open ion channels Requires metabolism Effects are slower,longer-lasting, more diffuse and more varied than ionictropic receptors

Question 36

autoreceptors

Answer 36

metabotropic receptors that have two unconventional characteristics they bind to their neurons own neurotransmitter molecules they are located on the presynaptic, rather than the postsynaptic, membrane

Question 37

reuptake

Answer 37

the majority of neurotransmitters, once released, are almost immediately drawn back into the presynaptic buttons by transporter mechanisms

Question 38

enzymatic degradation

Answer 38

neurotransmitters are degraded in the synapse by the action of enzymes

Question 39

amino acid neurotransmitters: glutamate, GABA, glycine

Answer 39

common in the proteins we consume, whereas GABA is synthesized by a simple modification of the structure of glutamate Glutamate is the most prevalent excitatory neurotransmitter in the mammalian central nervous system GABA is the most prevalent inhibitory neurotransmitter

Question 40

Monoamines: dopamine,serotonin, epi/norepipephrine

Answer 40

catecholamines each is synthesized from the amino acid tyrosine Tyrosine is converted to L-dopa which in turn is converted to dopamine

Question 41

Catecholamines

Question 42

Catecholamines

Answer 42

synthesized from the amino acid tyrosine

Question 43

indoamines

Answer 43

different structure than catecholamines

Question 44

adrenergic

Answer 44

release epinephrine

Question 45

noradrenergic

Answer 45

release norepinephrine

Question 46

acetylcholine

Answer 46

small molecule neurotransmitter broken down in the synapse by the enzyme acetylcholinesterase

Question 47

cholinergic

Answer 47

neurons that release acetylcholine

Question 48

unconventional neurotransmitters

Answer 48

act in ways that are different from those that neuroscientists have come to think of as typical for such substances

Question 49

nitric oxide

Answer 49

soluble-gas neurotransmitters produced in the natural cytoplasm and immediately diffuse through the cell membrane into extra-cellular fluid and then into nearby cells

Question 50

endocannabinoids

Answer 50

are neurotransmitters that are similar to delta-9-tetrahydrocannabinol the main psychoactive constituent of marijuana synthesized from fatty compounds in the cell membrane; they tend to be released from the dendrites and cell body tend to have most of their effects on presynaptic neurons inhibiting subsequent synaptic transmission

Question 51

THC

Answer 51

main psychoactive constituent of marijuana

Question 52

anandamide

Answer 52

produced immediately before they are released like soluble gases

Question 53

agonists

Answer 53

drugs that facilitate the effects of a particular neurotransmitter

Question 54

antagonists

Answer 54

drugs that inhibit the effects of a particular neurotransmitter

Question 55

atropine

Answer 55

receptor blocker that exerts its antagonist effect by binding to muscarinic receptors, thereby blocking the effects of acetylcholine on them

Question 56

curare

Answer 56

an extract of a certain class of woody vines South American natives have long used curare on the tips of darts they used to kill their game receptor blocker at cholinergic synapses, but it acts at nicotinic receptors by binding to nicotinic receptors, blocks transmission at neuromuscular junctions thus paralyzing them

Question 57

botox

Answer 57

neurotoxin released by a bacterium often found in spoiled food blocks the release of acetylcholine at neuromuscular junctions and is thus a deadly poison

Question 58

endogenous opioids

Answer 58

occurring naturally within the body all endogenous opioid neurotransmitters are neuropeptides and their receptors are metabotropic

Question 59

morphine

Answer 59

addictive effective analgesic (painkiller)

Question 60

Periaqueductal gray (PAG)

Answer 60

area of the brain stem around the cerebral aqueduct, which connects the third and fourth ventricles; this part of the brain stem is PAG