EXAM I Intro to the Nervous System Flashcards
describe the general principles of direct actions of neurotransmitters
- NT binds to and opens ion channels
- promotes rapid responses by altering membrane potential
describe the general principles of indirect actions of neurotransmitters
- NT acts through intracellular second messengers, usually G protein pathways
- broader, longer-lasting effects
___ is an excitatory neurotransmitter
glutamate
___ and ___ are inhibitory neurotransmitters
dopamine and GABA
___, ___, and ___ are both excitatory and inhibitory neurotransmitters
acetylcholine, norepinephrine, and serotonin
is GABA a direct or indirect acting neurotransmitter?
direct
___ membrane channels open and close in response to voltage changes across the membrane; what are some examples?
- voltage-gated
- examples: voltage-gated Na+ channels and lidocaine
___ membrane channels involve a hormone, drug, or transmitter than bind to the protein and the channel opens up; what are some examples?
- ligand-gated (ionotropic)
- examples: glutamate (AMPA), nicotine ACh receptors, and GABA
what is the action length of ligand-gated (ionotropic) receptors?
action is immediate and brief
are ligand-gated (ionotropic) receptors excitatory or inhibitory?
- some are excitatory and open channels for small cations
- some are inhibitory and allow Cl- influx or K+ efflux to cause hyperpolarization
T or F:
metabotropic receptors are not directly linked to ion channels
true
how do metabotropic receptors work?
- initiates a biochemical process that mediates more long-term effects and modifies the responsiveness of the neuron
- NT acts as the first messenger which activates a second messenger that in turn changes the excitability of a neuron
what are the two types of metabotropic receptors?
- membrane-delimited - occur entirely in plane of membrane
- when G-proteins interact with calcium channels, they inhibit channel function (presynaptic inhibition)
- when G-proteins interact with K+ channels, they open (activate) channels causing postsynaptic inhibition
- diffusible second messengers
what are examples of diffusible second messengers (metabotropic)?
beta-adrenergic receptors and cAMP
___ are receptors on an axon terminal through which the neuron’s own NT can influence the function of the terminal (usually inhibitory) - for example, D2 receptors
autoreceptors
___ are receptors on an axon terminal through which NTs from other neuronal types can influence the function of the terminal
heteroreceptor
what are the 3 catecholamines?
dopamine, norepinephrine, and epinephrine
___ can act like dopamine due to its similar structure
amphetamine
which enzyme catalyzes the conversion of NE to epi?
phenylethanolamine-N-methyltransferase (PNMT)
epinephrine is typically made by ___, but can also be made by some ___
- adrenal medullary cells
- CNS neurons
what is a monoamine?
one amino group connected to an aromatic group by a 2-carbon chain
what are 3 exmamples of monoamines?
catecholamines, serotonin, histamine
is serotonin a catecholamine?
no, it is an indoleamine
which amino acid is inhibitory?
GABA
which amino acid is excitatory?
glutamate
H3 (histamine) receptor is thought to function as an ___
inhibitory heteroreceptor
thus, activtaion of brain H3 receptors decreases the release of acetylcholine, dopamine, norepinephrine, serotonin, and certain peptides
what is neurotensin? where is it found?
- a neuropeptide that acts as an endogenous neuroleptic and regulates dopamine systems (inhibitory feedback)
- it is found in the GI tract (inhibits GI motility) and circulation (causes vasodilation)
describe nitric oxide
- gaseous signaling molecule
- CNS role is controversial
- relaxes vascular smooth muscle
how do endorphins make you happy?
endorphins bind to µ receptors, causing a decrease in GABA release, which causes an increase in dopamine release (= happy feeling)
