Quiz 1 Flashcards
what is a connexon? its composition?
gap junction channel: 6 identical subunits (connexins) > connexon. Many connexons > gap junction
How does Ca2+ affect gap junctions?
uncouples electrically coupled neurons by blocking connexons
congenital deafness is associated with:
mutations in genes encoding connexins (therefore, gap junctions)
Ionotropic receptors are associated with:
generating fast excitation and inhibition in the PNS and CNS
Metabrotropic receptors operate through what cellular mechanism?
G-protein coupled receptors > release of 2nd messengeres
GABA Type A and Glycine receptors are (inhibitory or stimulatory):
inhibitory
acetylcholine is — in skeletal muscle but — in cardiac muscle:
excitatory in skeletal muscle (nicotinic acetylcholine receptor) but inhibitory in cardiac muscle
what is the definition of inhibition:
neurotransmitter prevents Vm from reaching Vthreshold
what is the definition of excitation:
neurotransmitter promotes depolarization beyond Vthreshold
what does having a safety factor of 1:1 mean? where would you find this?
an action potential > an action potential in post-synaptic cell. “yes” or “no” signaling from brain produces immediate response without room for contradicting signals. Found in neuromuscular junction
what are muncs?
molecules that prepare SNARES for proper assembly
what is the role of synaptotagmin?
PROMOTES neurotransmitter release:
= calcium sensor that releases clamping by complexion; allows structural changes and energy release in order for membrane fusion and exocytsosis of neurotransmitter
Botox and tetanus exert their neuronal effects by:
cleaving SNARE proteins to block exocytosis of neurotransmitter
the major difference between Botox action and tetanus action:
botox acts at motoneuron junctions; tetanus is transmitted across junction and travels retrogradely to inhibit interneuron neuron
What is the cause of Lambert-Eaton Syndrome?
autoimmune disorder in which antibodies “attack” voltage dependent calcium channels needed for triggering fusion in presynaptic motor neurons and cholinergic neurons
What are they symptoms of Lambert-Eaton Syndrome?
decreased efficacy of Ca2+ channels decreases ACh release and compromises synaptic transmission»_space; muscle weakness, fatigue and autonomic dysfunction
What is the basis of myasthenia gravis?
antibodies directed at ACh receptors or MuSK enzyme that clusters AchRs.
how does desensitization occur?
prolonged exposure to acetylcholine causes a conformational change of ligand-gated ion channels to a non-conducting state.
what is the significance of m = N x P
m is Mean quantal content and it represents the average amount of neurotransmitter at a synapse. n is number of vesicles and p is probability of being released. M is high in NMJ so that a single action potential can > reaction. M is low in the CNS to allow for controlled response to input. M can change in CNS = synaptic plasticity
What is the key difference between constitutive fusion/secretion and the rapid exocystosis exhibited by synapses?
coupling of Ca2+ to synaptic vesicle fusion allows for rapid kinetics
If Vreversal is more negative than Vthreshold for an action potential, then that particular receptor’s activation will produce what kind of signal?
inhibitory
what is the importance of allosteric modulation in neurons?
modulation of neurotransmitter receptors can alter that receptor’s effect when nt binds. ex: psychoactive drugs that allosterically modify GABAa receptors.
the pre central gyrus contains neurons for:
controlling movement of face and extremities
the postcentral gyrus contains neurons for:
sensation
