Cleft binds to ach ligand regulated ion gates postsyn

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Unformatted text preview: erywhere in body neurotransmitter Synaptic transmission- can be excitatory or inhibitory; can excitatory can open ligand-regulated ions or act w/ a 2nd messenger open • Examples of 3 different kinds of synapses Examples • Excitatory cholinergic, inhibitory GABA-ergic, & excitatory Excitatory adrenergic synapse adrenergic Excitatory Cholinergic Synapse Excitatory ACh excites (skeletal muscle) & inhibits (cardiac, some ACh smooth & glandular) postsynaptic neurons smooth 5 steps of transmission @ synapse• Presynaptic neuron- nerve signal arrives @ synapse, opens Presynaptic voltage-regulated Ca2+ gates voltage-regulated • Ca2+ enters s.knob, triggers exocytosis of synaptic vesicles • Empty vesicles refill w/ Ach while ‘reserve pool’ move Empty forward forward • ACh diffuses across s.cleft, binds to ACh ligand-regulated ion gates (Postsyn-), Na+ in/K+ out Na • Na spreads along p.membrane & Na depolarizes it (postsynaptic potential) depolarizes • If reaches axon hillock, then AP generated If Inhibitory GABA-ergic Synapse Inhibitory GABA= γ-aminobutyric acid; most common inhibitory γ-aminobutyric most neurotransmitter in body neurotransmitter • GABA receptors on postsynaptic neuron • Cl-channels that open & Cl- enter cell to make ‘more –’ than RMP (hyperpolarized) RMP Excitatory adrenergic synapse= norepinephrine (NE), & others, norepinephrine others, use 2nd-messenger system (cAMP common) use • NE binds to protein receptor, G-protein activated • G-protein then activates adenylate G-protein cyclase to convert ATP to cAMP which then can have multiple effects which Cessation & Neural Integration Cessation Cessation of signal can occur 3 ways- diffusion of neurotransmitter away from synapse…astrocytes absorb; reuptake by s.knob; reuptake degradation in s.cleft by AChE, etc. degradation Neuromodulators- hormones, neuropeptides, etc. modify by hormones, stimulating postsyn- to inc/dec # of receptors stimulating • Adjusts sensitivity to neurotransmitter, or can alter rate of Adjusts neurotrans synthesis, release, reuptake, breakdown, etc. neurotrans Neural integration- ability to process info, store & recall it, & make ability decisions • Chemical synapses are the decision-making devices of NS… Chemical more synapses, greater info-processing capabilities more • Based on postsynaptic potentials (EPSP or IPSP) • EPSP= depolarizing from –70 to ~-55 mV, makes it more likely depolarizing to fire to • Caused usaully by Na+ into cell Postsynaptic Potentials/Memory Postsynaptic Neural integration (cont.)• IPSP= hyperpolarized by neurotran’s, so cell less likely to fire • Cl-channels open & cell becomes ‘more –’ then RMP • Or K-gates open & K flows out Neurons fire @ a ‘background’ rate (due to passive diffusion of Neurons ions) even when not stimulated…but EPSP & IPSP change rate of firing by either inc/dec # of AP’s rate Memory- physical basis of a memory is a pathway through physical brain (memory trace) brain • Synapses are formed, removed, modified in response to Synapses experiences to make transmission easier/harder (=synaptic experiences synaptic plasticity) plasticity • ‘Training’ of synapses= synaptic potentiation Training’ synaptic 3 kinds of memory- immediate, short-term, long-term memory Memory Memory Immediate- ability to hold something in mind for a few seconds • Gives us the sense of the present moment Gives sense Short-term (STM)- ~few sec to few hrs; limited to bits of info ~few like phone #’s like • Can be lost if stop mentally reciting it, distracted, or move to Can new things to remember new • ‘Working memory’ allows us to hold idea long enough to act • Ca-level elevated in s.knob of recently used cells & so only Ca-level need to ‘jog’ memory to recall events several hrs ago (= posttetanic potential) (= Long-term (LTM)- retain up to lifetime; 2 forms: declarative retain forms: declarative (events, facts) & procedural (motor skills) (events, • Long-term potentiation causes molecular changes in synapses by remodeling or inc # of receptors by...
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