Synaptic Physiology I Flashcards
The summation of excitatory and inhibitory potentials in neurons is called _____.
synaptic integration
What is facilitation?
residual Ca++ builds up inside the nerve terminal from previous APs to allow increased strength of new APs
This is the spontaneous exocytosis of a single synaptic vesicle.
MEPP (Miniature End Plate Potentials)
What is the strength of the NMJ synapse?
strong
Drugs like amphetamine, cocaine, and Prozac exert their actions by _____ of monamine transmitters like dopamine and serotonin.
blocking reuptake
What is synaptic depression?
depletion of releasable synaptic vesicles, reducing the strength of new APs
What would happen without the sodium channels at the NMJ?
total paralysis bc the depolarization wouldn’t spread
What is synaptic integration?
the summation of excitatory and inhibitory potentials in neurons
What is exocytosis?
the process of vesicle and surface membrane lipid fusion to create a pore by which the NT can diffuse out of the cell
What does MEPP stand for and what does it mean?
Miniature End Plate Potentials; the spontaneous exocytosis of a single synaptic vesicle
Name 2 kinds of diseases that weaken the NMJ synapse.
- those that reduce the amount of NT secreted
- those that block ACh receptor
Drugs like ____, ____, and ____ exert their actions by blocking reuptake of monamine transmitters like dopamine and serotonin.
amphetamine, cocaine, and Prozac
What is the speed of the NMJ synapse?
fast
Drugs like amphetamine, cocaine, and Prozac exert their actions by blocking reuptake of monamine transmitters like ____ and _____.
dopamine and serotonin
In the CNS the major excitatory NT is ____.
glutamate
What is the “intelligence” of the CNS?
smart
What is the effect of the NMJ synapse?
excitatory
Slow synaptic transmission is called _____.
neuromodulation
Name 2 types of Ca++ pumps in the plasma membrane.
- primary active transporter
- Na+/Ca++ exchanger (antiporter)
How long does synaptic vesicle recycling take?
a few seconds in a well-rested synapse; a few minutes in a hard working one
This is the process of vesicle and surface membrane lipid fusing to create a pore by which the NT can diffuse out of the cell.
exocytosis
Motor neurons in the spinal cord send myelinated axons through _____ and _____ to connect with skeletal muscle fibers.
ventral roots; peripheral nerves
Virtually every psych drug in use today work specifically at _____.
synapses
_____ selectively blocks inhibitory synaptic transmission to produce a powerful, persistent, involuntary skeletal muscle contraction.
Tetanus toxin
The main channel opened by glutamate is _____.
an NSC channel
What is the “intelligence” of the NMJ?
stupid
This is the product of the stimulation of the excitatory input that causes depolarization.
excitatory post-synaptic potential (EPSP)
A decrease in K+ ion permeability of the post-synaptic membrane = ______.
depolarization
What is the resting membrane potential of a muscle fiber?
-80mV
What is the threshold for an AP in a muscle cell?
-50mV
What is the motor end plate?
the end of the motor axon where it loses its myelin sheath and splays onto the muscle fiber
What is myasthenia gravis?
- an autoimmune disease
- Abs to ACh receptors
- results in profound weakness upon exertion
What is the NT for the CNS synapse?
- ACh
- glutamate
- GABA
- 5-HC
- dopamine
- aspartate
- glycine
- ATP
- histamine
- NE
Ca++ ions that flowed into the motor nerve terminal will be _____.
pumped out of the cell
These are small protuberances from dendrites that make synaptic contact with incoming axon terminals.
dendritic spines
What is the NT for the NMJ synapse?
ACh
Where does AChE come from?
the synaptic cleft
A single motor axon innervates ____ muscle fibers.
many
This is an enzyme that cleaves ACh, producing acetate and choline.
AChE
What does GABA do?
it increases chloride permeability in the postsynaptic membrane
Name 3 mechanisms for clearing NTs from the synaptic cleft.
- diffusion
- recycling (pumped out)
- destruction
When does depolarization at the NMJ begin?
when ACh-gated channels are activated
What is AChE?
acetylecholine esterase; an enzyme that cleaves ACh, producing acetate and choline
The ACh receptor is a _____ channel.
ligand-gated ion
What happens if the safety factor of the synaptic transmission is reduced?
neuromuscular transmission can fail during repetitive activity–> muscle weakness
Where is the trigger zone? What does it do?
btw the cell body and the axon; it’s where APs arise
What is the effect of the CNS synapse?
excitatory OR inhibitory
An AP in the inhibitory terminal releases ____, which opens Cl- channels in its target presynaptic terminal.
GABA
Where do APs always arise from?
the trigger zone
Name 2 receptors that ACh acts upon in the CNS.
- nicotinic
- muscarinic
A skeletal muscle receives synaptic input from ____ motor neuron.
one
What is the transmitter termination for the NMJ?
- diffusion
- degradation by esterase
The major inhibitory NT in the CNS is _____.
GABA
What are dendritic spines?
small protuberances from dendrites that make synaptic contact with incoming axon terminals
What is the speed of the CNS synapse?
fast OR slow
This is when residual Ca++ builds up inside the nerve terminal from previous APs to allow increased strength of new APs.
facilitation
Post-exocytic vesicles are retrieved by the formation of ______.
clathrin coated pits
This is the end of the motor axon where it loses its myelin sheath and splays onto the muscle fiber.
the motor end plate
What is the difference btw Myasthenia gravis and myasthenic syndrome?
- Myasthenia gravis = post-synaptic block
- myasthenic syndrome = pre-synaptic block
Why do APs arise at the trigger zone?
the threshold is lower here bc of the high density of voltage-gated Na+ channels
An AP in the inhibitory terminal releases GABA, which ______ in its target presynaptic terminal.
opens Cl- channels
What happens to ACh?
- it diffuses out it’s destroyed by ACh0
- it is re-taken up
Why is the ACh-gated ion channel called a Non-Selective Cation (NSC) channel?
it is permeable to ALL cations
Binding of ACh (the ligand) opens the gate and Na+ ions flow into the muscle fiber to _____ it.
depolarize
CNS neurons receive synaptic input from _____ neurons.
many
What is the strength of the CNS synapse?
weak
In skeletal muscle only, the postsynaptic membrane is _____ to increase surface area.
folded
Dx?
- an autoimmune disease
- Abs to ACh receptors
- results in profound weakness upon exertion
Myasthenia gravis
How does the AP propogate all the way to the tendon?
voltage-gated Na+ channels open in both directions away from each other
The binding of Ca++ triggers the fusion of ____ of the vesicle and surface membranes, opening a _____.
lipids; fusion pore
A single AP in the motor axon causes every muscle fiber to twitch ____.
once
This is the depletion of releasable synaptic vesicles, reducing the strength of new APs.
synaptic depression
What is the transmitter termination for the CNS?
- reuptake
- diffusion
What is an EPSP?
an excitatory post-synaptic potential; product of the stimulation of the excitatory input that causes depolarization
A postsynaptic response can be either ____ or ____.
excitatory; inhibitory
Binding of ACh (the ligand) opens the gate and ____ ions flow into the muscle fiber to depolarize it.
Na+
During repetitive nerve stimulation, what 2 important and opposing changes occur in the presynaptic terminal?
- the Ca++ ion concentration builds up
- the pool of releasable vesicles is depleted
