Card Set Information
where the the places synapses can occur?
between axon terminals of the presynaptic neuron
across the synaptic cleft to the dendrite, cell body, or axon of the postsynaptic neuron
how does communication occur across a synapse? and how it is terminated?
volaged gated Ca+2 channels open
calcium triggers exocytosis of neurotransmitters
NT diffuses and binds to receptors
response in cell
teminated by degradation by enzymes, re-uptake by transporters and diffusion
what are the different receptors?
channel linked (ionotropic)
: ligand gated channels, fast and direct acting
G-protein linked (metabotropic) receptors
: slow, indirect, direct coupling or second messengers
what is postsynaptic potential (PSP)?
change in membrane potential in response to receptor neurotransmitter binding
what is the movment of Cl- an example of? what does it do?
Cl moves in and either inhibits (IPSP-inhibitory postsynaptic potential) or stabilizes membrane potential
difference between divergent and convergent neural integrations
divergence is a pathway that spreads information from one neuron to mutiple neurons
convergence is when several nerons synapse with a single postsynaptic neuron
what is neural integration?
the summing of input from various synapses at the axon hillock of the postsynaptic neuron to determine whether the neuron will generate action potentials
-spatial (from mutliple axon terminals)
-temporal (from one axon terminal)
what are the functional classification of neurotransmitters?
substance must be in pre-synaptic nerve terminal and packaged into synaptic vesicles
substance must be released from the nerve terminal upon arrival of action potential or depolarization
specific receptors in post synaptic membrance for substance
effects may be excitory or inhibitory, direct or indirect (determined by receptor type)
found in PNS and CNS
synthsized in cytosol of axon terminal
choline acetyl transferase (CAT) is the enzyme for synthesis
degradation occurs in synaptic cleft
typical choliinergic synapse
action potential depolarize axon terminal
calcium enter cytoplasm of axon terminal
ACh release occurs through exocytosis, diffuses across synaptic cleft and binds to receptors on postsynaptic membrane
sodium channels on postsynaptic surface are activated producing graded depolarization
Ache release stops b/c calcium are removed
depolarization ends as Ache is broken down to acetate and choline by AchE
axon terminal reabsorbs choline from synaptic cleft and uses it resynthesize Ach
what are two types of cholinergic receptors that Ach activates?
describe biogenic amines (monoamines) aka catecholamines
all biogenic amine neurotransmitters are derived from amino acids
: derived from tyrosine (dopamine, norepinephrine-noradrenaline, epinephrine-adrenaline)
all involved in reward pleasure and learning brain centers
dopamine is the principle NT involved in addiction pathway
synthesis and release of catecholamines
synthesis in the cytosol axon terminal, packaged in synaptic vesicles, released by neurons in CNS (dopamine and norepinephrine) and PNS (norepinephrine)
epinephrine relased by some neurons in CNS but more commonly in adrenal medulla
for epinephrine and norepinephrine NT
alpha (1,2) Beta (1,2,3)
G protein coupled and linked to second messengers)
serotonin, biogenic amines
a CNS NT, broadly distributed in the brain
derived from tryptophan
involved in sleep, dreaming, hunger, arousal, emotional behaviors and biological clock
depletion leads to depression
inhibitory in pain pathways
histamine (biogenic amines)
CNS NT, found in hypothalamus
derived from histidine
release from non-neuronal cells during allergic reactions
amino acid NT
most abundant NTs in CNS
Aspartate and Glutamate (most common) excitatory
Glycine and GABA (most common) inhibitory
short chains of amino acids synthesized in cell body like proteins
most are co-localized in axon terminals with other neurotransmitters and modulate response caused by other NT
depress physical functions like breathing and may produce physical dependence
most known for actions as hormones
acetylcholine role in body
NT used by spinal cord neurons to control muscles and by neurons in brain to regulate memory. mostly excitatory
NT produces feelings of pleasure when relased by brain reward system, dopamine has multiple functions depending on where in the brain it acts. usually inhibitory
major inhibitory NT in brain
NT and hormone. In PNS, it is part of fight or flight response. in brain it acts as NT regulating normal brain processes. usually excitatory
how can drug interfere with neurotransmission?
increase number of nerve impulses
release NT from vesicles with or without impulses
block reuptake or block receptors
produces more or less NT
prevent vesicles from releasing NT
how does methamphetamine alter dopmine transmission?
enters dopamine vesicles in axon terminal causing release of NT
blocks dopamine transporters from pumping dopamine back into NT neuron
causes neurons to fire more often--euphoric feeling
after drug wears off, dopmine levels drop, and user crashes
-causes dopamine axons to wither and die
How does Nicotine work?
binds to presynaptic receptors exciting neurons to fire more action potential causing an increase in dopamine release
increase number of synaptic vesicles relased
affects cognition, mood, and memroy by altering the serotonin neural pathway in several brain centers
short term effects (changes in brain chemistry and behavior)
alters neuron membranes, ion channels, enzymes and receptors
binds directly to receptors for NT and hormones like GABA
-when GABA attaches to receptor on postsynaptic membrane, it allows Cl- ions to pass into the neuron (hyperpolarizing)
-alcohol binds to GABA receptors and amplifies the hyperpolization effect of GABA
this accounts fro some of the sedative effects of alc
how to increase or descrease or no change in neurotransmitter release?
release NT from vesciesl with or without impulses
release more NT in response to an impulse
prevent vesicles from releasing NT
block receptor wth another molecules (no change)
how to increase or decrease NT in synaptic cleft?
produce less NT