Dr. Chirwa Flashcards
Presynaptic Mechanisms
Two types of presynaptic Mechanisms?
electrical and chemical
Electrical synapse
the movement of electrical current jumping from gap junction to gap junction.
Chemical synapse
The movement of neurotransmitters from one neuron to another
Post synaptic neurons
Have a slight delay
contains electrical vesicles in the presynaptic neuron
chemical synapse
Why does chemical synapse take much longer than electrical synapse?
because NT on chemical synapse to to line up with receptors of the post synaptic neuron, then release the presynaptic NT from the synaptic vesicle.
Synaptic vesicle
stores NT in vesicles in the presynaptic neuron in chemical synapse.
2 millisecond delay
is seen with chemical delay occurs slowly due to neurons aligning releasing and binding of NT
1 millisecond delay
seen with electrical delay which occurs quickly through gap junctions
Synapsin
anchors group of NT vesicles together
Docking
NT being free and going close to the plasmalemma
What must occur before NT vesicles release NTs docked on the plasmalemma?
Calcium must enter the neuron through calcium channels.
Clathrin
A protein that reclaims back old NT cleaving inward.
Dyanamine protein
takes the neck of the Clathrin vesicle so it can be released
At rest the presynaptic terminal is negative or positive.
it is negative until an AP occurs the presynaptic terminal becomes more positive (depolarize)
When does depolarization occur?
When calcium enter the neuron through calcium channels
What type of cells pick up calcium ions in the synaptic cleft?
glial cells
What holds syntaxin and synaptobrevin together?
SNAP-25 protein
What is the name of the “calcium sensor”?
Synaptotagmin
What can happen if BoTx or TeTx is injected in the veins?
it prevents the binding of syntaxin and synaptobrevin and acetocholine can not bind for a long time which can paralyze the diaphragm because it also needs acetylcholine. Patient will need a ventilator
Lambert-Eaton Myasthenic syndrome
Botulin toxin
Tetanus Toxin
Which statement regarding metabotropic and ionotropic receptors is true?
Ionotropic receptors have immediate efects; metabotropic receptors
produce long-term efects.
Which event is the first in the series of events that take place
during chemical synaptic transmission?
Voltage gated Ca2+ channels open
In the sequence of events in neurotransmission, which event occurs just after the action potential arrives at the presynaptic terminal?
Influx of Ca2+ into the presynaptic terminal
How would application of a Ca2+ channel blocker affect the function of a synapse?
It would eliminate the postsynaptic potential and the presynaptic Ca2+ current.
Which protein plays a key role in endocytosis?
Clathrin
A scientist wishes to develop a new drug that prevents
synaptic communication via neuropeptides but not small
molecule neurotransmitters. Which mechanism would be a
good target for his drug?
Disruption of fast anterograde axonal transport
Which treatment would prevent the release of neurotransmitter
from the presynaptic terminal?
A toxin that cleaves synaptobrevin
Clostridial Toxin
Cleaves syntaxin, synaptobrevin, SNAP-25
The most important factor determining whether a receptor-operated ion channel is inhibitory or excitatory is
whether the permeant ion’s reversal potential is positive or negative to threshold.
Which statement about a nicotinic acetylcholine receptor at the
neuromuscular junction is accurate?
It has two binding sites, and binding of two molecules ofacetylcholine, one to each site, is required to activate the receptor.
Which molecule binds NMDA receptors and prevents the
flow of ions at resting and hyper polarized membrane
potentals?
Mg2+
Which change could be responsible for increasing the amplitude of an
excitatory postsynaptic potential (EPSP)?
An increase in the amount of glutamate released into the synapse
Cell X fires an action potential and releases GABA onto Cell Y.
Assuming only GABAA receptors are present on the postsynaptic
membrane, which is at rest at –55mV, which ion is responsible for
the changes that would be observed?
Chloride
Which statement describes a possible outcome for a neurotransmitter after release into the synaptic clef?
Activation of G-protein-coupled receptor on postsynaptic cell
Which has more lasting affect Inotropic or Metabotropic receptors?
Metabotropic receptors
Nicotinic Acetylcholinergic Receptor
requires two Ach to bind to its alpha subunit
AMPA Receptors
activated by glutamate
NMDA Receptor
activated by glutamate and glycine
Mg2+ is its gate keeper
Depolarization of the membrane kicks Mg2+ out
Which receptors produces fast excitatory postsynaptic current
AMPA and NMDA
Where does the trigeminal nerve enter the brain?
mid pons
