Chemical Basis of Behavior (Lecture 4) Flashcards
synaptic transition
the flow of information between neurons through a synapse
synapse
fluid-filled gap between terminal button of one neuron and receptive area of another neuron
the most common synapse is:
chemical synapse
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
directed synapses
site of release is near the site of receptive
3 types of directed synapses
axodendritic, axosomatic, axoaxonic
axodendritic synapses
contribute most to A.P., high proportion of voltage gated channels in this membrane
axoaxonic synapses
presynaptic facilitation and good for inhibiting axon potentials at the axon
non-directed synapses
site of release is distant from the site of reception
2 types of non-directed synapses
varicosities and diffuse modulatory systems
varicosities
full of neurotransmitters that diffuse over a wide range of area and bind to far away receptor sites
diffuse modulatory systems
serotonin, norepinephrine, dopamine are most common for this
4 main categories of neurotransmitters
amino acids, amines, acetylcholine, peptides
amino acids
small, GABA, glutamate
amines
small, DA, NE, 5-HT
acetylcholine
its own category because of the way it is synthesized
peptides
large, dynorphin, enkephalin
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
small neurotransmitter synthesis
made in the terminal button of the cell, from precursor enzymes and packaged into vesicles at the terminal
activation of receptors
neurotransmitter is released into the synapse and may bind to postsynaptic receptors
ligand
molecule that binds to another
2 main receptor types:
ionotropic and metabotropic
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
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
secondary messengers
can open/close ion channels or activate enzymes that modulate ion pumps, ion channels, receptors, or gene transcription
pre-synaptc receptors
autoreceptors that are located on cell membrane
autoreceptors
located on cell membrane (terminal button), regulates internal processes (the synthesis and release of neurotransmitter, does not change membrane potential
post-synaptic potentials
can either be depolarizing (EPSP) or hyperpolarizing (IPSP), determined by the receptor that is stimulated, not the NT itself
2 possibilities for the termination of PSPs
re-uptake and enzymatic degradation
termination of PSPs via re-uptake
NT is returned to terminal button through transporters in the presynaptic membrane
termination of PSPs via enzymatic degradation
acetylcholine + acetylcholinesterase= choline and acetate
glutamate
glutamic acid, major excitatory NT in brain, 3 ionotropic (EPSPs), 8 metabotropic
GABA
(gama-amino butyric acid), synthesized from glutamate, major inhibitory NT in brain (1 ionotropic, 2 G-protein coupled receptors)
agonist neurotransmitter
chemical that binds to a receptor of a cell and triggers a response by that cell
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
dopamine (DA)
2 diffuse modulatory systems (nigrostriatal regulate motor and mesocorticolimbic regulate motivation), all receptors are metabotropic
norepinephrine (NE)
diffuse modulatory system (locus coeruleus regulates attention, learning, sleep/wake, arousal, anxiety), all receptors are metabotropic
serotonin (5-HT)
diffuse modulatory system (raphe nuclei regulate arousal, mood, sleep/wake), some receptors are ionotropic, most are metabotropic
acetylcholine (Ach)
diffuse modulatory system (basal forebrain regulate learning, memory, regulation of sensory system), 2 receptors: nicotinic ionotropic and muscarinic metabotropic
nicotinic ionotropic receptors in Ach
permeable to potassium, calcium, and sodium, non-specific, 1 subtype, generally excitatory, curare
muscarinic metabotropic
all bound to G-proteins, lead to a wide range of effects, 5 subtypes, atropine
peptide neurotransmitters
made as polypeptides, synthesized on the rER, packaged by Golgi apparatus, transported on microtubules, all receptors are G-protein coupled
endorphins
released during exercise, excitement, pain, consumption of spicy food, orgasm, bind with u-opioid receptor, analgesia, euphoria
dynorphins
modulate pain, homeostasis, and response to stress, bind to k-opioid receptor, dysphoria
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
endocannabinoids
“post” to “pre” synaptic neurons, enzymes synthesize endocannabinoid, release is automatic, membrane permeable, not stored in vesicles, they bind to CB1 receptors
EPSP
excitatory post-synaptic potential, temporary depolarization caused by the flow of positively charged ions into the postsynaptic cell
IPSP
inhibitory post-synaptic potential, either by the flow of negatively charged ions into the cell or positively charged ions out of the cell
a postsynaptic potential is defined as excitatory when:
it makes the neuron more likely to fire an action potential
larger EPSPs result in:
greater membrane depolarization, increasing the likelihood the postsynaptic cell reaches the threshold for firing an action potential
