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Synaptic Transmission
Wacker 1/26/11 lecture
109
Physiology
Undergraduate 4
01/30/2011

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Term
Schwann cells
Definition
cells that wrap around axons in the PNS
Term
Schwann cells/oligodendricytes
Definition
no ions can diffuse through these cells, they serve as "electrical tape" for axons, and help prevent loss of signal
Term
Voltage gated sodium channels
Definition
what is located only on Nodes of Ranvier?
Term
100 m/s
Definition
signal speed of myelinated conduction
Term
0.25 m/s
Definition
signal speed of unmyelinated conduction
Term
Lidocaine and Tetrodotoxin
Definition
Voltage gated sodium channel blockers
Term
lidocaine
Definition
derived from cocaine, blocks action potential conduction down the axon
Term
Tetrodotoxin
Definition
puffer fish toxin
Term
Hypercalcemia
Definition
can stabilize Na current, by making the membrane potential more positive, raising the threshold so the cell is harder to depolarize
Term
HypOcalcemia
Definition
makes the membrane easier to depolarize causing increased excitability
Term
acetylcholine-(1st neurotransmitter discovered)the vagus nerve of a froggy was stimulated then they guy collected the schtuff and put it on the frogs heart and watched the hearbeat slow down
Definition
what is Vagus Schtuff and how was it discovered
Term
quanta
Definition
neurotransmitters are released in units called ____
Term
voltage gated Ca+ channels
Definition
the channel the action potential opens at the end of a neuron (terminal bouton)
Term
into the cell
Definition
when calcium channels are opened, which direction does the Ca++ flow?
Term
quanta
Definition
total neurotransmitter packaged in a vessicle
Term
it allows he synaptic vesicles to move to release sites at the presynaptic membrane.
Definition
what does the inward flux of calcium allow for at the terminal bouton
Term
Calcium
Definition
the quantity of neurotransmitter released is directly related to the amount of ____ entering the terminal
Term
not only are few released, there is only a few hundred receptors on the post-synaptic cell and it only causes a 1mV change in membrane potential
Definition
glutamate is packaged into quanta of 1000-5000 molecules, but few quanta are released, why does Glutamate not cause an EPSP normally?
Term
40-50 mV
Definition
what change in membrane potential is caused by acetyl choline on skeletal muscle
Term
the more the pre-synaptic neuron is stimulated, the more vesicles it releases, and potentially more neurotransmitters per quanta
Definition
how can more neurotransmitters be packed into each quanta (supposedly)
Term
chemical, electrical - chemical is more common
Definition
list the two types of synapses, which is more common
Term
gap junctions
Definition
in electrical synapses the neurons are connected by this, allowing the electrical current to flow directly from one cell to another
Term
no
Definition
are neurotransmitters needed for electrical synapses
Term
electrical
Definition
ions move cell to cell without stimulating voltage channels in this kind of synapse
Term
electrical synapse
Definition
this synapse can not be turned on or off because the number of ions that travel across cannot be modulated
Term
chemical synapses
Definition
release neurotransmitters from presynaptic membrane and bind to receptors on postsynaptic membrane (can be modulated)
Term
the pre-synaptic vesicle can vary the number of vesicles
the post-synaptic neuron can vary the number of receptors
Definition
how can the pre/post synaptic neurons be regulated in a chemical synapse
Term
dendrite, cell body, axon terminal
Definition
3 places neurons can synapse
Term
they can block the channels right at the end (but the potential can be blocked at several points depending on the location of the synapse)
Definition
cells that synapse at the axon terminal are special how? hint: cock blocking or missing a slam dunk
Term
axon hillock
Definition
where the summation of the incoming signals to a neuron occurs
Term
neuromuscular junction
Definition
neurons not only synapse with neurons, they synapse with other cells, such as muscles, called a ______
Term
endocrine system, like hormones in the posterior pituitary
Definition
neurons can release sunbstances into the bloodstream called ___
Term
autocrine
Definition
something that releases neurotransmitters that affect itself
Term
paracrine
Definition
when cells nearby get neurotransmitters ex: acetyl choline acting on the SA node
Term
endocrine
Definition
oxytocin and vasopresin are made in the hypothalmus neurons and released by the pituitary, this is an example of _____
Term
amino acids, amines, purine derivatives
Definition
list the 3 types of small molecule neurotransmitters
Term
axon terminals
Definition
where small molecule neurotransmitters are synthesized and packaged into synaptic vesicles
Term
soma of the neuron (made as integral components of large proteins)
Definition
where peptide neurotransmitters are synthesized
Term
glutamate
Definition
the major excitatory neurotransmitter in the CNS
Term
GABA
Definition
the major inhibitory neurotransmitter in the brain
Term
Glycine
Definition
the major inhibitory neurotransmitter in the spinal cord
Term
acetylcholine(Ach, seratonin(5-HT), Histamine
Definition
3 examples of monoamine neurotransmitters
Term
dopamine(DA), norepinephrine(NE), epinephrine(E)
Definition
3 examples of catecholamines
Term
mood, wakefullness, pleasure senses
Definition
what 5 hydroxytryptamine regulates (3 things)
Term
acetyl Coa + choline (choline acetyltransferase enzyme)
Definition
what two molecules acetyl choline comes from
Term
tryptophan
Definition
the amino acid that seratonin comes from
Term
Tyrosine
Definition
the precursor amino acid for DOPA, dopamine, norepinephrine, epinephrine
Term
only the adrenal medulla, it converts nor-epinephrine to epinephrine
Definition
where is phenylethanolamine-n methyltransferase present, and what does it do
Term
they are typically rapidly inactivated after binding to the receptor as they are broken down by enzymes in the synaptic cleft and then recycled as the pieces are re-absorbed by the terminal bouton
Definition
how long do the small molecule transmitters last
Term
less of the peptides are released than the small molecule neurotransmitters, but the peptides tend to have a prolonged duration of activity (minutes, hours, days, possibly longer)
they 1) alter ion channel function, 2) modify cell metabolism 3) modify gene expression
Definition
how long do the peptide neurotransmitters last, and how much is released
Term
histidine
Definition
neurotransmitter important in allergic reactions
Term
dopamine
Definition
important in movement, produced in teh basal ganglia
Term
dopamine
Definition
neurotransmitter (or its receptors) deficient in Parkinson's disease
Term
made in cell body in the rER (ribosome), secreted to Golgi, then shipped to the nerve terminal
Definition
the route of peptide neurotransmitters
Term
Thyrotropin-releasing hormone, luteinizing hormone releasing hormone, somatostatin
Definition
the neurotransmitters released by the hypothalamus (3)
Term
adrenocorticotropic hormone, prolactin, luteinizing hormone, thyrotropin, growth hormone, vasopressin, oxytocin
Definition
neurotransmitters released by the petuitary (7)
Term
enkephalins, opiods
Definition
list the peptide endorphins (2)
Term
Substance P, Bradykinin, Angiotensin II
Definition
Other peptide neurotransmitters (3)
Term
substance P according to the picture in the notes
Definition
which is longer, substance P or angiotensin?
Term
Nitrous oxide, Carbon monoxide
Definition
what are the gas neurotransmitters (2)
Term
nitrous oxide and carbon monoxide
Definition
strengthens/alters the pre-synaptic terminals in brain, also have to do with blood vessel diameter
Term
anandamide and arachidonyl glycerol
Definition
what are the endocannaboids (2)
Term
THC is exogenous whereas the other two (anandamide & arachidonyl glycerol) are endogenous
Definition
what is the difference between THC and the other cannabanoids?
Term
endocannabinoids
Definition
lipid based neurotransmitters (arachidonic acid) released from the post-synaptic neuron and affect the pre-synaptic terminal (they go backwards)
Term
THC Tetrahydrocannabinol
Definition
usually inhibitory to the pre-synaptic neuron, secreted in memory neurons, back inhibits the pre-synaptic neuron by decreasing excitability (something to do with pre-glutamate), in small amounts this can increase memory
Term
we know now that neurons transmit more than one type of neurotransmitter that can bind to more than one type of receptor. example: Ach + NO + peptide could all be secreted from one
Definition
neurons used to be classified by the neurotransmitter, why doesn't this work anymore
Term
norepinephrine and/or acetylcholine
Definition
what neurotransmitters would a sympathetic neuron secrete?
Term
transmitter-gated ion channels, and G-protein coupled receptors
Definition
what are the 2 types of neurotransmitter receptors?
Term
ionotropic receptors
Definition
what is another name for transmitter-gated ion channels
Term
metabotropic receptors
Definition
another name for g-protein coupled receptors
Term
Ach Nicotinic receptor
Definition
the acetyl choline receptor that is ionotropic
Term
Ach Muscarinic receptor
Definition
the acetyl choline receptor that is metabotropic
Term
sodium cotransport
Definition
what drives choline (broken down from acetyl choline) into cells?
Term
atrial muscle cell membrane (in the heart-SA node)
Definition
where the muscarinic receptor is located
Term
the g protein opens potassium channels which hyperpolarizes the membrane (especially the SA node) this slows heart rate
Definition
hows does the muscarinic receptor work?
Term
sodium channels are opened (that K+ can also use, but membrane potential at rest is close to K+ so it isn't driven by the gradient) the concentration and electric gradient drive Na+ into the cell
Definition
how does the Ach nicotinic recptor work?
Term
nicotine and muscarine(from mushrooms)
Definition
what are the agonists of acetylcholine receptors
Term
curare-(blocks)nicotinic, atropine-(blocks)muscarinic
Definition
what are the antagonists of the two acetylcholine receptors
Term
curare
Definition
the anesthetic that paralyzed people, but allowed them to still feel pain
Term
diaphragm
Definition
what is one of the last muscles to be paralyzed
Term
ionotropic
Definition
what kind of receptor is the GABA-a receptor? (metabotropic or ionotropic)
Term
a GABA agonist
Definition
what is propathol
Term
Chlorine, makes an IPSP because it brings negative charges into the cell
Definition
what channels does the GABA receptor open
Term
it controls how open the channel is when GABA is bound to it
Definition
what do drugs do to the GABA receptor
Term
benzodiazepines (valium), barbituates (phenobarbitol), steroids, alcohol (EtOH)
Definition
what things bind to the GABA-a receptor besides GABA
Term
hyperpolarizes
Definition
opening chlorine channels depolarizes the cell or hyperpolarizes the cell?
Term
G proteins
Definition
what is a key component of metabotropic receptors?
Term
1. an ion channel
2. an enzyme that produces a second messenger
Definition
activated G proteins diffuse in the membrane to act on its target, what can its target be (2 things)
Term
in the heart with potassium to slow the pacemaker cells (K+ moves out making the cell more (-) and harder to depolarize)
Definition
in what channel was the g protein opened directly
Term
advantage-the signal is amplified easily
dis-takes forever, metabotropic channels are slower
Definition
what is the advantage of adenylyl cyclase with G proteins(and metabotropic receptors in general)? disadvantage?
Term
IP3
Definition
calcium levels regulate gene expression, and can cause hypertrophy, cell death, or function in metabotropic pathways when ______ binds to the ER and releases the stored calcium
Term
kinases
Definition
phosphorylates
Term
phosphatases
Definition
de-phosphorylates
Term
protein kinases
Definition
change conformation and alter function of the protein
-can open ion channels or alter enzyme function
Term
K+ out, less Na+ in, or Cl- in
Definition
if K+ flows ___, less Na+ ___ or Cl- flows ___ there will be an IPSP
Term
Na+ in, less K+ out = EPSP (depolarization)
Definition
if more Na+ flows __ and less K+ ___, there will be an EPSP
Term
diffusion, breakdown, reuptake
Definition
what are the 3 fates of neurotransmitters once they are released?
Term
dopamine
Definition
what neurotransmitter re-uptake is blocked by cocaine?
Term
acetylcholinesterase
Definition
nerve gas blocks what enzyme?
Term
SSRI's = anti depressant/anti-anxiety medications that inhibit the re-uptake of seratonin into the pre-synaptic cell so that it stays around longer. effects take up to 2 weeks to work, and oddly receptor down regulation(usually happens) doesn't occur, so could have something to do with gene expression or a pathway.
Definition
how do SSRI's work? what are they?
Term
the idea that synapses can be strengthened by
(possibly due to NT acting back on the pre-synaptic neuron)
-increasing the release of NT(# of vessicles) from the pre-synaptic neuron
-increasing response(receptors)of the post synaptic neuron
-increasing the quanta (NT/quanta)

can also have depression(decreased signaling)
Definition
what is potentiation of synapses
Term
frequency of stimulation
Definition
potentiation is thought to change depending on _____
Term
synaptic fatigue
Definition
after many, many action potentials eventually the NT stored in vessicles is depleted called _____ ____
Term
synaptic fatigue-too many excitatory signals (and no inhibitory?)
Definition
what is thought to cause epileptic seizures
Term
10,000 times -why seizures can last a while
Definition
how many times can a neuron be fired before it is thought to fatigue?
Term
increases excitability of neurons (why seizure patients shouldn't hyperventilate)
Definition
how does alkalosis (increase in pH) affect synaptic transmission?
Term
decreases excitability of neurons (this is why diabetics don't eat and go into comas)
Definition
what does acidosis do to synaptic transmission?
Term
increases excitability
Definition
how does caffeine and theophylline affect neuron excitability?
Term
it inhibits glycine (an inhibitor) thus exciting neurons in the spinal cord, causing tonic muscle spasms that are normally controlled by glycine
Definition
how does strchnine effect synaptic transmission?
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