week 2 vocab (ch 3 & 4)

microelectrode

small electrode used to record electircal potentials in living cells

sodium-potassium pump

pump 3 Na+ out and 2 K+ in, creates net buildup of negative charge in cell

equilibrium potential

electrical charge that balances the concentration gradient

axon hillock

cone-shaped region where axon emerges from cell body

action potential happens in the segment of the axon after the axon hillock

action potential

brief but large changes in neuronal polarization

info sent by neuron is encoded in a pattern of action potentials

hyperpolarization

increase in membrane potential (neuron more negative)

depolarization

decrease in membrane potential (neuron closed to 0)

graded response

neurons change in potential proportional to incoming stimulus

local potentials

potential initiated by stimulation at specific site which is a graded response that spread passively across cell membrane → decrease in strength with time and distance

threshold

stimulus intensity adequate to trigger action potential in an axon

all-or-none property

action potential either fires at full potential or doesn’t

afterpotentials

positive or negative change in membrane potential that may follow an action potential

voltage-gated Na+ channel

central Na+ selective pores are gated

if simulated or affected by synapses → axon may be depolarized

if depolarized enough → channel shape changes, opens “gate” to let Na+ in

absolute refractory phase

brief period following action potential

not responsive to more stimulus b/c Na+ channels can’t respond

relative refractory phase

only strong stimulation can reach threshold to produce another action potential

conduction velocity

speed of action potentials, larger axons (diameter) → faster

myelin sheath

glial cells around axon, can speed up conduction

nodes of Ranvier

small gaps between myelin sheath

saltatory conduction

form of conduction in myelinated axons, action potential jumps from one node of Ranvier to the next

multiple schlerosis

disorder characterized by widespread degeneration of myelin

neurotransmitter

chemical released by axon when action potential reaches the end of it

presynaptic cell

“transmitting” side of synapse

postsynaptic cell

region of synapse that receives and responds to neurotransmitters

excitatory postsynaptic potential (EPSP)

depolarizing potential in a neuron normally caused by synaptic excitation

increase probability that the postsynaptic neuron will fire

inhibitory postsynaptic potential (IPSP)

when inhibitory presynaptic neuron activated → postsynaptic membrane becomes more negative (hyperpolarized)

spatial summation

summation of postsynaptic potentials that reach the axon hillock from different locations across the cell body

temporal summation

summation of postsynaptic potentials based on how close they are in time

synaptic delay

time needed for Ca2+ to enter the terminal, for transmitter to diffuse across synaptic cleft, and for transmitter molecules to interact with their receptors before postsynaptic cell responds

ligand

molecule of correct shape that can fit into a receptor protein and activate/block it

neurotransmitter receptor

specialized protein, embedded in cell membrane, that selectively sense and reacts to molecules of corresponding neurotransmitter

acetylcholine (ACh)

neurotransmitter produced and released by various parasympathetic neurons

if ACh receptors blocked → paralysis

agonist

substance that mimics/boosts action of signaling molecule

antagonist

substance that interferes/prevents actions of signaling molecule

transporters

special receptors on presynaptic axon, bring transmitter back

axo-dendritic synapses

synapse at which presynaptic axon terminal synapses onto a dendrite of the postsynaptic neuron

axo-somatic synapse

synapse at which presynaptic axon terminal synapses onto a cell body (soma) of the postsynaptic neuron

axo-axonic synapse

synapse at which presynaptic axon terminal synapses onto an axon terminal of another neuron

denduo-dendric synapse

synapse at which synaptic connection forms between the dendrites of 2 neurons

electroencephalogram (EEG)

recording of gross electrical activity of the brain via large electrodes placed on the scalp

ionotropic receptors

ion channels that change shape when bound by neurotransmitter

metabotropic receptors

don’t contain ion channels, link across cell membrane

when activated → alter inner workings of postsynaptic cell

second messengers: cause changes in excitability or slow/large scale responses

receptor subtypes

any type of receptor with functional characteristics that distinguish it from other types of receptors for the same neurotransmitter

amino acid neurotransmitter

based on single amino acid molecule

peptide neurotransmitter (neuropeptide)

based on short chains of amino acids (peptides)

amine neurotransmitters

based on modifications of a single amino acid

ex. acetylcholine, serotonin, dopamine

gas neurotransmitters

soluble gases that diffuse between neurons

glutamate

amino acid transmitter, most common excitatory transmitter

gamma-aminobutyric acid (GABA)

amino, most prominent inhibitory neurotransmitter

co-localization

synthesis & release of > 1 type of transmitter

cholingergic

ACh-containing neurons found in nuclei w/ basal forebrain

basal forebrain

region vertical to basal ganglia, major source of cholingergic projections

dopamine (DA)

found in substantria nigra and ventral tegmental area

norepinephrine

originates from locus coeruleus

serotonin

originates from raphe nuclei

acetlycholine

originates from nucleus basalis and medial septal area

serotonergic

cells that use serotonin as synaptic transmitter

noradrenergic

cells using norepinephrine as transmitter in brainstem and midbrain

retrograde transmitters

ability to diffuse from postsynaptic back to presynaptic neuron

pscychoactive drugs

compounds that alter function of the brain and thereby affect conscious experiences

ligand

any substance that binds to a receptor

partial agonists

drug that when bound to a receptor has less effect than the endegenous ligand would

efficacy

extent to which drug activates receptors

agonists have high efficacy

dose-response curve

graphed relationship between drug doses and observed effect

bioavaliable

free to act on target tissue, not used elsewhere or in the process of being eliminated

metabolic tolerance

body becomes more effective at eliminating the drug from the bloodstream

functional tolerance

when target tissue changes its sensitivity to the drug

change in number of receptors on surface

down-regulate

decrease number of receptors that drug can bind to

up-regulate

increase number of drug receptors

cross-tolerance

drug tolerance generalized to drugs of same chemical class

autoreceptors

receptor for synaptic transmitter located in the presynaptic membrane and tells axon terminal how much transmitter released