Chemical Basis of Behavior (Lecture 4) Flashcards Preview

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Flashcards in Chemical Basis of Behavior (Lecture 4) Deck (50):
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synaptic transition

the flow of information between neurons through a synapse

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synapse

fluid-filled gap between terminal button of one neuron and receptive area of another neuron

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the most common synapse is:

chemical synapse

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gap junction

when adjacent cells have an interconnected channel that allows for the transfer of ionic currents, it is very fast and has bidirectional communication

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directed synapses

site of release is near the site of receptive

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3 types of directed synapses

axodendritic, axosomatic, axoaxonic

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axodendritic synapses

contribute most to A.P., high proportion of voltage gated channels in this membrane

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axoaxonic synapses

presynaptic facilitation and good for inhibiting axon potentials at the axon

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non-directed synapses

site of release is distant from the site of reception

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2 types of non-directed synapses

varicosities and diffuse modulatory systems

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varicosities

full of neurotransmitters that diffuse over a wide range of area and bind to far away receptor sites

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diffuse modulatory systems

serotonin, norepinephrine, dopamine are most common for this

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4 main categories of neurotransmitters

amino acids, amines, acetylcholine, peptides

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amino acids

small, GABA, glutamate

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amines

small, DA, NE, 5-HT

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acetylcholine

its own category because of the way it is synthesized

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peptides

large, dynorphin, enkephalin

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large peptide neurotransmitter synthesis

made in the soma, packaged into vesicles in the Golgi, and travel down the axon microtubules to reach the terminal button

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small neurotransmitter synthesis

made in the terminal button of the cell, from precursor enzymes and packaged into vesicles at the terminal

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activation of receptors

neurotransmitter is released into the synapse and may bind to postsynaptic receptors

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ligand

molecule that binds to another

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2 main receptor types:

ionotropic and metabotropic

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ionotropic receptor

when NT binds to receptor site on the ion channel, the channel opens or closes, altering the flow of ions in or out of the cell, direct and fast

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metabotropic receptor

when NT binds to receptor it signals a membrane signal protein that is linked to a G protein, and the G proteins can either directly open ion channels or activate secondary messengers, indirect and slow

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secondary messengers

can open/close ion channels or activate enzymes that modulate ion pumps, ion channels, receptors, or gene transcription

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pre-synaptc receptors

autoreceptors that are located on cell membrane

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autoreceptors

located on cell membrane (terminal button), regulates internal processes (the synthesis and release of neurotransmitter, does not change membrane potential

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post-synaptic potentials

can either be depolarizing (EPSP) or hyperpolarizing (IPSP), determined by the receptor that is stimulated, not the NT itself

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2 possibilities for the termination of PSPs

re-uptake and enzymatic degradation

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termination of PSPs via re-uptake

NT is returned to terminal button through transporters in the presynaptic membrane

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termination of PSPs via enzymatic degradation

acetylcholine + acetylcholinesterase= choline and acetate

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glutamate

glutamic acid, major excitatory NT in brain, 3 ionotropic (EPSPs), 8 metabotropic

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GABA

(gama-amino butyric acid), synthesized from glutamate, major inhibitory NT in brain (1 ionotropic, 2 G-protein coupled receptors)

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agonist neurotransmitter

chemical that binds to a receptor of a cell and triggers a response by that cell

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antagonist neurotransmitter

ligand or drug that does not provoke a biological response itself upon binding to a receptor, but clocks or dampens agonist-mediated responses

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dopamine (DA)

2 diffuse modulatory systems (nigrostriatal regulate motor and mesocorticolimbic regulate motivation), all receptors are metabotropic

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norepinephrine (NE)

diffuse modulatory system (locus coeruleus regulates attention, learning, sleep/wake, arousal, anxiety), all receptors are metabotropic

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serotonin (5-HT)

diffuse modulatory system (raphe nuclei regulate arousal, mood, sleep/wake), some receptors are ionotropic, most are metabotropic

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acetylcholine (Ach)

diffuse modulatory system (basal forebrain regulate learning, memory, regulation of sensory system), 2 receptors: nicotinic ionotropic and muscarinic metabotropic

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nicotinic ionotropic receptors in Ach

permeable to potassium, calcium, and sodium, non-specific, 1 subtype, generally excitatory, curare

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muscarinic metabotropic

all bound to G-proteins, lead to a wide range of effects, 5 subtypes, atropine

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peptide neurotransmitters

made as polypeptides, synthesized on the rER, packaged by Golgi apparatus, transported on microtubules, all receptors are G-protein coupled

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endorphins

released during exercise, excitement, pain, consumption of spicy food, orgasm, bind with u-opioid receptor, analgesia, euphoria

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dynorphins

modulate pain, homeostasis, and response to stress, bind to k-opioid receptor, dysphoria

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soluble gas

nitric oxide (NO) and carbon monoxide (CO), can be synthesized in cell body or axon terminal, diffusible, can pass through lipid membrane into extracellular space, activates 2nd messenger

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endocannabinoids

"post" to "pre" synaptic neurons, enzymes synthesize endocannabinoid, release is automatic, membrane permeable, not stored in vesicles, they bind to CB1 receptors

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EPSP

excitatory post-synaptic potential, temporary depolarization caused by the flow of positively charged ions into the postsynaptic cell

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IPSP

inhibitory post-synaptic potential, either by the flow of negatively charged ions into the cell or positively charged ions out of the cell

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a postsynaptic potential is defined as excitatory when:

it makes the neuron more likely to fire an action potential

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larger EPSPs result in:

greater membrane depolarization, increasing the likelihood the postsynaptic cell reaches the threshold for firing an action potential