Biopsych Ch 4

Front 1

neurons integrate many thousands of inputs before generating an action potential by engaging in what:

Back 1

temporal summation of inputs arriving close in time

Front 2

which ionic event is primarily reponsible for the depolorization phase of an action potential?

Back 2

-influx of Na+

Front 3

membrane potential

Back 3

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

Front 4

Microelectrodes

Back 4

intracellular electrodes whose tips are less than one-thousandth of a millimeter in diameter. (too small to be seen by the naked eye)

Front 5

resting potential

Back 5

a steady membrane potential of about -70 mV. K+ and Protein- on inside. Na+ and Cl- on outside

Front 6

ions

Back 6

positively and negatively charged particles

Front 7

sodium-potassium pumps

Back 7

Transporters in cell membrane that continually exchange three Na+ ions inside the neuron for two K+ ions outside

Front 8

transporter

Back 8

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

Front 9

depolarization

Back 9

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

Front 10

hyperpolarize

Back 10

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

Front 11

EPSPs (excitatory postsynaptic potentials)

Back 11

postsynaptic depolarizations.
Increase the likelihood that the neuron will fire.

Front 12

IPSPs (inhibitory postsynaptic potentials)

Back 12

postsynaptic hyperpolarizations.
Decrease the likelihood that the neuron will fire

Front 13

Graded responses

Back 13

Amplitudes are proportional to the intensity of the signals that elicit them. Weak signals elicit small postsynaptic potentials and vice versa.

Front 14

Transmission of postsynaptic potentials (EPSPs and IPSPs)

Back 14

Passive
1)Rapid -- so rapid it can be assumed instantaneous
2)Decremental -- EPSPs and IPSPs decrease in amplitude as they travel through the neuron

Front 15

axon hillock

Back 15

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

Front 16

Threshold excitation

Back 16

the sum of the depolarizations and hyperpolarizations reaching the section of the axon adjacent to the axon hillock at any time is sufficient to depolarize the membrane-- this generates an action potential

Front 17

action potential

Back 17

a massive but momentary reversal of the membrane potential from about -70 mV to about +50 mV. Not graded responses (magnitude doesnt relate to intensity)
Differs from EPSPs and IPSPs in two important ways
1)action potentials along an axon is nondecremental; action potentials do not grow weaker as they travel along the axonal membrane
2) action potentials are conducted more slowly than postsynaptic potentials

Front 18

all-or-none responses

Back 18

they either occur to their full extent or do not occur at all. (shooting a gun)

Front 19

integration

Back 19

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

Front 20

Spatial summation

Back 20

when local EPSPs are produced simultaneously on different parts of the receptive membrane sum to form greater EPSP. Same for IPSP. EPSP and IPSP can sum to cancel each other out

Front 21

Temporal summation

Back 21

postsynaptic potentials produced in rapid succession at the SAME SYNAPSE sum to form a greater signal

Front 22

voltage-activated ion channels

Back 22

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

Front 23

absolute refractory period

Back 23

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

Front 24

relative refractory period

Back 24

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

Front 25

antidromic conduction

Back 25

axonal conduction opposite to the normal direction; conduction from axon terminals back towards the cell body

Front 26

orthodromic conduction

Back 26

axonal conduction in the natural direction; from cell body to terminal buttons

Front 27

nodes of ranvier

Back 27

gaps between adjacent myelin segments

Front 28

saltatory conduction

Back 28

the transmission of action potentials in myelinated axons.
Signal jumps along the axon from node to node

Front 29

dendritic spines

Back 29

tiny nodules of various shapes that are located on the surfaces of many dendrites and are the sites of most excitatory synapses in the mature mammalian brain

Front 30

directed synapses

Back 30

synapses at which the site of neurotransmitter release and the site of neurotransmitter reception are in close proximity

Front 31

nondirected synapses

Back 31

synapses at which the site of release is at some distance from the site of reception

Front 32

Neuropeptides

Back 32

short amino acid chains comprising between 3 and 36 amino acids; in effect, they are short proteins

Front 33

synaptic vesicles

Back 33

release neurotransmitters

Front 34

coexistence

Back 34

neurons containing two neurotransmitters

Front 35

exocytosis

Back 35

the process of neurotransmitter release

Front 36

receptor

Back 36

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

Front 37

ligand

Back 37

any molecule that binds to another
A neurotransmitter is said to be the ligand of its receptor

Front 38

Ionotropic Receptors

Back 38

receptors associated with ligand-activated ion channels.
Ex. When a neurotransmitter binds to an ionotropic receptor, the associated ion channel usually opens or closes immediately, thereby inducing immediate postsynaptic potential.

Front 39

Metabotropic Receptors

Back 39

receptors associated with signal proteins and G-proteins.
More prevalent and slower than ionotropic

Front 40

second messenger

Back 40

in metabtropic reception when a subunit of an associated G protein breaks off and triggers the second messenger. various long lasting effects

Front 41

autoreceptors

Back 41

metabotropic receptors with 2 unusual characteristics
1)they bind to the neurons own neurotransmitter. On presynaptic membrane instead of the postsynaptic membrane.
2)function is to moniter the number of neurotransmitter molecules in the synapse

Front 42

gap junctions

Back 42

narrow spaces between adjacent neurons that are bridges by fine tubular channels, called connexins, that contain cytoplasm. Also called electrical synapses

Front 43

Amino acid neurotransmitters

Back 43

Glutamate, asparate, glycine, and GABA.
Glutamate is most prevalent excitatory NT and GABA is the most prevalent inhibitory NT in the CNS

Front 44

Monoamine neurotransmitters

Back 44

slightly larger than amino acid NTs and their effects are more diffuse. Divided into two groups
1)Catecholamines
2)Indolamines

Front 45

Catecholamines

Back 45

Tryosine --> L-dopa --> dopamine --> norepinephrine --> epinephrine

Front 46

Indolamines

Back 46

tryptophan --> serotonin

Front 47

Acetylcholine (Ach)

Back 47

small-molecule NT at neuromuscular junctions, at many of the synapses in the autonomic nervous system, and at synapses in several parts of the CNS

Front 48

Unconventional Neurotransmitters

Back 48

Soluble gas NTs: nitric oxide, carbon monoxide
Endocannabinoids

Front 49

Agonists

Back 49

Drugs that facilitate the effects of a particular neurotransmitter

Front 50

Antagonists

Back 50

drugs that inhibit the effects of a particular neurotransmitter

Front 51

receptor blockers

Back 51

bind to postsynaptic receptors without activating them and, in so doing, block the access of the usual NT. (example of antagonistic drug)

Front 52

atropine

Back 52

active ingredient in belladonna (makes your pupils big)
Receptor blacker that is an antagonist

Front 53

botox

Back 53

another nicotonic agonist
blocks the release of Ach

Front 54

endogenous

Back 54

occuring naturally within the body