chapter 3: neurotransmitters Flashcards
why are receptors important?
effectiveness and function of NT depends on receptor
two basic categories of neurotransmitter receptors
ionotropic receptors & metabotropic receptors
ionotropic receptors
quickly change shape and open/close ion channel when the transmitter molecule binds; fancy ion channel; direct signaling mechanism
metabotropic receptors
alter chemical reactions in the cell to open ion channels; indirect signaling mechanism
why are neurotransmitters important?
allows the brain to function and particularly important for emotion and treatments
acetylcholine (AcH)
WHERE: basal forebrain
HOW: choline + acetyl CoA -> choline acetyltransferase (ChAT) -> AcH, broken by acetylcholinesterase
RECEPTORS: muscarinic (excitatory), nicotinic (excitatory)
FUNCTION: muscle contraction, memory, arousal, attention
dopamine (DA)
WHERE: substantia nigra
HOW: tyrosine -> tyrosine hydroxylase (TH) -> L-DOPA -> DOPA decarboxylase -> dopamine, broken down by monoamine oxidase
RECEPTORS: all metabotropic, some inhibitory and some excitatory
FUNCTION: movement, reward, executive function
norepinephrine
WHERE: locus coeruleus & lateral tegmental area
HOW: dopamine -> dopamine beta hydroxylase -> norepinephrine
RECEPTORS: all metabotropic
FUNCTION: arousal, stress response, attention
serotonin
WHERE: raphe nucleus
HOW: tryptophan -> tryptophan hydroxylase -> 5 hydroxytryptophan -> 5HT, broken down by MAO
RECEPTORS: all except 5HT3 metabotropic
FUNCTION: mood, sleep, digestion
glutamate
WHERE: presynaptic neurons via glia cells
HOW: EAAT -> glutamate -> glutamine synthetase -> glutamine -> glutaminase -> glutamate
RECEPTORS: AMPA, Kainate, NMDA - ionotropic,
mGLUR - metabotropic
FUNCTION: principal excitatory NT, learning and memory
GABA
WHERE: presynaptic neurons
HOW: glutamate -> glutamic acid decarboxylase (GAD) -> GABA
RECEPTORS: GABAA (ionotropic) and GABAB (metabotropic)
FUNCTION: primary inhibitory NT, balance excitation
neuropeptides
can act as neurotransmitters, found all over the neuron. made from prepropetides, turned into peptides via golgi apparatus; opiod peptides (neuropeptide Y) & peptide hormones (oxytocin and vasopressin)
gas neurotransmitters
nitric oxide, carbon monoxide, hydrogen sulfide; on demand in neurons; modify proteins, cell metabolism, dilate blood vessels, act as protection
how do gas neurotransmitters differ?
- produced outside axon terminals in dendrites
- no receptors are involved; diffuses through cell membrane to activate second messengers
- synthesized on demand and breaks down quickly
