Term
| What are the 2 types of synapses? |
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Definition
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Term
Electrical or chemical:
allow current to directly pass from one cell to another. Not very efficient but very fast |
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Definition
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Term
| In an electrical synapse, where does most of the current go? Why? |
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Definition
| When current flows out of the cell, there is a very low resistance pathway that goes into the extracellular space. Most of the current will go that way and only a little bit will be transmitted to the next cell. |
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Term
| In electrical synapses, if 2 cells have a high _________ you might get 0.5 of the transferred to the next cell, if it's low than maybe only 0.1. |
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Definition
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Term
What mediates electrical synapses?
What are the units that make this up?
What does this structure allow to flow through? |
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Definition
Gap Junction
2 connexon (hemi-channels) made up of 6 connexins
electrical current and small molecules |
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Term
Electrical or Chemical synapse:
uni OR bidirectional
sign conserving (+ signal causes + signaling in next cell)
synaptic delay
inhibitory OR excitatory OR both
amplification
some modulation of the gap junction channels
plasticity (long term changes in the strength of synapses)
Key for learning and memory |
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Definition
electrical (chemical is unidirectional)
electrical
chemical (electrical is very fast)
chemical
chemical (electrical is dissipative)
chemical
chemical |
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Term
| Are there electrical, chemical synapses, or both at the neuromuscular junction? |
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Definition
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Term
What is an infolding of the postsynaptic membrane in the muscle cell?
What receptors are located here (across from synaptic cleft/active zone)? |
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Definition
junctional fold
acetylcholine receptors |
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Term
| Synaptic transmission at the NMJ is mediated by what receptors? |
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Definition
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Term
| What happens when you poison the neuromuscular junction with curare? |
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Definition
| blocks the nicotinic ACh receptor, so endplate potential is not large enough to reach threshold and there's no action potential |
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Term
If you were to stimulate a muscle and got an EPP, would it be active or passive?
Why is this? |
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Definition
passive (response falls off very rapidly)
muscles have a short length and time constant (want to generate action potential instead to propagate all up and down that muscle fiber) |
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Term
| What type of channel is the acetylcholine receptor channel? |
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Definition
| non-selective cation channel (transports K and Na at the same time - equilibrium potential for the ACh receptors comes to be 0mV) |
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Term
| “It has been suggested that the end-plate potential (epp) at a single nerve-muscle junction is built up statistically of small all-or-none units [______ or discrete packets of transmitter] which are identical in size with the spontaneous ‘miniature epp’s’” |
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Definition
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Term
In the mEPPs quantal hypothesis, the smallest evoked EPP = ___________
normal EPP = ______ quanta or vesicles (quantal content) |
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Definition
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Term
What is the phase when vesicles are ready to release their neurotransmitter?
What attaches them to the membrane and what are they in close proximity to? |
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Definition
priming
synaptic vesicle protein
calcium channel (Ca enter the cell and helps release) |
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Term
| What are the requirement for neurotransmitter release? |
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Definition
| depolarization AND calcium required |
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Term
What is the calcium sensor on the vesicle?
Does it have a high or low affinity for calcium? |
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Definition
synaptotagmin
low affinity (vesicles must be close to Ca2+ channels) |
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Term
| What is the enzyme that clears the neurotransmitter acetylcholine? |
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Definition
| acetylcholinesterase (breaks ACh down into choline making it unable to activate the receptor. This shortens up the duration of the EPP) |
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Term
What is the disease of the NMJ (loss in number of functioning postsynaptic ACh receptors)?
The tension test using what to test for this? |
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Definition
Myasthenia gravis
acetylcholinesterase inhibitor (makes ACh hang around longer) |
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Term
Are central synapses (smaller or larger than NMJ?
Do they have more or less active zones? |
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Definition
smaller
fewer
(release few vesicles, failures, don’t reach AP threshold) |
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Term
What is a synapse between an axon and the soma and give an example.
axon and dendrite?
cell sends process over that makes a synapse onto the other axon (decreases amount of neurotransmitter produced)
2 dendrites come close enough to make contact and release neurotransmitter form one to the other. |
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Definition
axosomatic (inhibition)
axodendritic (excitation spines)
axoaxonic (presynaptic inhibition-rare)
dendrodendritic (reciprocal excitation) |
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Term
| how do the multiple inputs combine to determine the output firing pattern of the neuron? |
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Definition
Algebraic summation - can add excitatory and inhibitory response and go with the stronger one
Spatial summation-many signals from different presynaptic neurons
Temporal summation- many signals from one presynaptic neuron that adds up |
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Term
What are the inhibitory neurotransmitters in the CNS?
What channels are they coupled to?
Will this cause hyperpolarization or depolarization |
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Definition
GABA and glycine
chlorine
hyperpolarization |
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Term
What are the excitation neurotransmitters in the CNS?
What channels do they activate?
Will this cause hyper polarization or depolarization? |
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Definition
glutamate
ACh serotonin
nonspecific cation channels
depolarization (think NMJ) |
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Term
What is it when inhibitory transmitters (e.g. GABA) open Cl- permeable channels.
E(cl) is always more (positive or negative) than AP threshold. opening up a large amount of inhibitory channels will limit an excitatory depolarization by “clamping” the membrane potential near to ECl and (increasing or decreasing) the membrane conductance ((increasing or decreasing) the resistance). Ohm’s Law. |
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Definition
shunting inhibition
ECl is always more negative than AP threshold. opening up a large amount of inhibitory channels will limit an excitatory depolarization by “clamping” the membrane potential near to ECl and increasing the membrane conductance (decreasing the resistance). Ohm’s Law. |
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Term
| Will there be a postsynaptic action potential if the action potentials are separated in time or closely space in time? |
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Definition
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Term
| What is the most important mechanism for termination of neurotransmitter action in glutamate and GABA mediated transmission? |
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Definition
| uptake of neurotransmitters via neurotransmitter transporters |
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Term
You are a neurotransmitter if you….
are produced within a _________, and are present in the ___________
are released during _________ (action potential-dependent)
act on __________ to cause a biological effect
have a mechanism of __________ |
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Definition
are produced within a neuron, and are present in the presynaptic terminal
are released during depolarization (action potential-dependent)
act on receptors to cause a biological effect
have a mechanism of termination |
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Term
True or False:
To be a neurotransmitter, a particular substance, when applied to the post-synaptic cell in quantities equal to that released by the pre-synaptic cell, produces the same post-synaptic response as does a pre-synaptic action potential |
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Definition
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Term
What is NOT a major neurotransmitter?
Acetylcholine (ACh)
Glutamate
GABA
glycine
tyrosine
Dopamine
Norepinephrine (Epinephrine)
Serotonin (5-HT)
Histamine
Nucleotides
ATP
Adenosine
Neuropeptides |
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Definition
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Term
Small molecule transmitters or neuropeptides:
are packaged mostly in the nerve terminal?
peptide precursors made in cell body and modified in nerve terminal? |
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Definition
small molecule transmitters
neuropeptides |
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Term
| Do neuropeptides or small molecule transmitters require higher Ca levels to be released? |
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Definition
| neuropeptides (needs a train of APs to release while a single AP will release glutamate and GABA) |
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Term
*Where are the following transmitters?
Acetylcholine
Dopamine
Serotonin (5HT)
Norepinephrine |
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Definition
Acetylcholine-nucleus basalis of Meynert (origin of ACh fibers that go up to the cortex)
Dopamine (innervate hippocampus, basal ganglia, cortex)-substantia nigra and ventral tegmental areas
Serotonin (5HT)- raphe nuclei
Norepinephrine-locus coeruleus |
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Term
Glutamate, GABA, or Glycine:
everywhere in CNS, major excitatory transmitter in CNS, most projection neurons in cortex use |
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Definition
| glutamate (synthesized from glutamine) |
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Term
Glutamate, GABA, or Glycine:
everywhere in CNS, major inhibitory transmitter in cortex, found (not always) in local circuit neurons (interneurons), synthesized off the Krebs cycle |
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Definition
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Term
Glutamate, GABA, or Glycine:
major inhibitory transmitter in brainstem and spinal cord |
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Definition
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Term
What type of receptors ionotropic receptors?
What type of receptors are metabotropic receptors? |
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Definition
ligand-gated ion channels (fast, direct)
G-protein coupled receptors (slow, indirect) |
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Term
ionotropic receptor or metabotropic receptor:
Ligand binding activates GTP-binding proteins (indirect)
Are closed (impermeable to ions) in absence of transmitter
Neurotransmitter binding opens receptor (direct) |
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Definition
metabotropic receptors
ionotropic receptors
ionotropic receptors |
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Term
Are the following ionotropic, metabotropic, or both?
Dopamine
Glutamate
GABA
Glycine
Norepinephrine
ACh
Serotonin |
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Definition
Dopamine-metabotropic
Glutamate-both
GABA-both
Glycine- ionotropic
Norepinephrine-metabotropic
ACh-both
Serotonin-both |
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