Week 3: Synaptic Activity Flashcards
_____________ synapse in which there is direct contact between cells through gap junctions (connexons/pores).
Electrical Synapse
_____________ synapse which involve intermediary messengers which pass information, from one cell to another, in the form of a chemical.
Chemical Synapse
The chemical messengers used in the system are called ______________.
Neurotransmitters
Neurotransmitters can be classified as excitatory or inhibitory, depending on the \_\_\_\_\_\_\_\_\_ they interact with. A) proteins B) mitochondria C) receptors D) free ribosomes
C) receptors
True or False?
The advantage of chemical synapses is that they have far more variable postsynaptic cell outcomes when compared to electrical synapses.
True.
At a chemical synapse, arriving action potentials may or may not release enough neurotransmitters to bring the post synaptic cell to \_\_\_\_\_\_\_\_\_. A) equilibrium B) threshold C) inhibition D) synapse
B) threshold
Which synapses are more abundant? Electrical or Chemical?
Chemical Synapse
Arrange the events of a Cholinergic Synapse.
______ Extracellular Ca++ enters the cytosol of the synaptic terminal triggering exocytosis
______ An action potential arrives and depolarizes the axon terminal
______ ACh is removed by AChE
______ ACh binds to postsynaptic receptor and depolarizes the membrane
Step 2
Step 1
Step 4
Step 3
Step 1 of a Cholinergic Synapse:
A combination of _________ gated Na+ and K+ membrane have __________ an impulse.
From the axon ________, to the _________ and finally to the synaptic end bulb (axon terminal).
voltage, propagated
hillock, telodendria
Step 2 of a Cholinergic Synapse:
The synaptic terminal replaces voltage gated Na+ and K+ membrane channels with voltage gated ____ channels.
The arrival of an action potential at the synaptic terminal causes influx of Ca++ into the ________.
Influx of Ca++ at the synaptic terminal causes exocytosis and release of ACh into the ______ ________.
Ca++
cytosol
synaptic cleft
True or False?
Ca++ is quickly removed from the synaptic cleft by passive transport.
False.
Ca++ is quickly removed from the synaptic cleft by ACTIVE transport.
Step 3 of a Cholinergic Synapse:
When ACh is released through ___________, it crosses the synaptic cleft.
It binds to ____________ gated Na+ channels on the postsynaptic membrane.
___________ Na+ rushes in bringing about a ________ potential in the postsynaptic membrane.
Opening of Na+ channels brings about rapid __________.
This effect lasts for ________.
exocytosis
chemically
Extracellular, graded
depolarization
20 msecs.
Step 4 of a Cholinergic Synapse:
As the ACh are attempting to cross the synaptic cleft, _____ breakdown 1/2 the ACh released before making it to the __________.
AChE detach the rest of the ACh within ____ msec.
AChE, receptor
20
A _______ _______ of 0.2 msec - 0.5 msec occurs between the arrival of an action potential at the synaptic knob until affecting the postsynaptic membrane.
Synaptic Delay
Most of the synaptic delay involves an influx and release of what?
Ca++ influx and AChE release
The \_\_\_\_\_\_ synapses involved, the \_\_\_\_\_\_ synaptic delay. A) more, shorter B) fewer, longer C) more, longer D) fewer, shorter
D) fewer, shorter
Neurotransmitters can be excitatory or inhibitory depending on their interaction with postsynaptic _________.
receptors
A neurotransmitter that is typically excitatory; fight or flight.
Norepinephrine
A neurotransmitter that is typically inhibitory; if absent or diminished, Parkinson’s disease results.
Dopamine
A decrease in this neurotransmitter can affect emotional states and attention.
Serotonin
A neurotransmitter that is generally inhibitory ; may reduce anxiety.
GABA
This neurotransmitter includes Nitric Oxide (which innervate smooth muscle in blood vessel walls) and Carbon Monoxide (functions as neurotransmitter).
Gases
Synaptic terminals release a variety of active compounds along with neurotransmitters called _______________.
Neuromodulators
Neuromodulators either alter the rate of neurotransmitter _________ by presynaptic cells or change the _____________ ____________ ________.
release, postsynaptic cells response
Neuromodulators called _____________ have similar effects to opium and morphine.
Opioids
Opioids inhibit the release of a neurotransmitter, which is responsible for slow pain or chronic pain, called ______________.
Substance P
Neurotransmitters that have a direct effect open or close ____________ gated ion channels in the _____ -synaptic membrane directly.
Because neurotransmitters alter ion movement across the cell membrane, they are said to have an _______________ effect.
chemically, postsynaptic
ionotropic
Neurotransmitters that have an indirect effect (metabotropic) work through intermediaries called _____________ messengers.
In this case, the neurotransmitter delivers a message to receptors in the postsynaptic cell membrane acting as the _____________ messenger.
Ions or molecules produced or released inside the cell when the first messenger binds are called the __________ messenger.
The link between 1st and 2nd messenger typically involves activating a _____________.
second
first
second
G-protein
The G-protein, for example, could activate adenylate cyclase which converts \_\_\_\_\_\_\_ in the cytosol to \_\_\_\_\_\_. A) cAMP, ATP B) ATP, ADP C) ATP, cAMP D) ADP, ATP
C) ATP, cAMP
cAMP (cyclic AMP) is the second messenger in this case, which can open membrane channels and or activate intracellular enzymes.
True or False?
Nitric Oxide and Carbon Monoxide are lipid-soluble gases, so they cannot diffuse through the plasma membrane.
False.
They CAN EASILY diffuse through the plasma membrane.
Once nitric oxide and carbon monoxide are in the cell, they bind to _______ on the inner ________ of the plasma membrane
enzymes, surface
These enzymes then promote the appearance of second messengers that can affect cellular activity.
True or False?
Postsynaptic potentials are graded potentials in the postsynaptic membrane in response to neurotransmitters.
True.
____________ postsynaptic potentials are depolarizing postsynaptic graded potentials.
Excitatory (EPSP)
____________ postsynaptic potentials are hyperpolarizing postsynaptic graded potentials.
Inhibitory (IPSP)
Before action potentials can happen, a ____ mV depolarization must occur.
10 mV
-70 mV (RMP) to -60 mV (threshold)
Individual EPSP’s combine through the process of __________ which integrates all the effects of graded potentials.
summation
____________ summation is the addition of stimuli occurring in rapid succession at a single synapse.
Temporal
Each graded depolarization lasts 20 msec and each individual EPSP is 0.5 mV.
In temporal summation, it would take 20 consecutive stimulations (1 msec) apart at one spot to bring about ________ potential.
action
Note: (voltage) 0.5 x (stimulations) 20 = 10 mV
____________ summation occurs when simultaneous stimuli applied at different locations.
Spatial
Spatial summation results in a cumulative effect on \_\_\_\_\_\_\_\_\_ potential. A) transmembrane B) action C) graded D) resting membrane
A) transmembrane
True or False?
Spatial summation involves multiple synapses active simultaneously which can include both excitatory and inhibitory stimuli.
True.
An action potential will result if the net result of both excitatory and inhibitory stimuli is 10 mV of depolarization.
If summation is underway yet the initial segment has not depolarized to threshold, the postsynaptic neuron is said to be: Facilitated or Inhibited?
Facilitated.
If postsynaptic summation is moving the membrane further away from threshold, the postsynaptic neuron is said to be: Facilitated or Inhibited?
Inhibited.
EPSP’s typically result from the opening of chemically gated ___ channels. Na+ or K+?
Na+
IPSP’s typically result from the opening of chemically gated ___ channels. Na+ or K+?
K+
True or False?
The role of the axon hillock is to calculate the sum of all graded excitatory and inhibitory potentials.
True.
If the effect on TMP is greater than 10 mV within 20 msec, threshold is achieved and an action potential occurs.
Inhibitory and excitatory neurotransmitter antagonism at the ________ _________ results in dynamic and responsive information processing.
Synaptic Cleft
At the axon terminal of a presynaptic neuron, another axon can synapse onto that presynaptic terminal affecting the amount of \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ released. A) GABA B) Na+ C) neurotransmitter D) K+
C) neurotransmitter
If the axoaxonal synapse is inhibitory, the presynaptic neuron is inhibited and therefore releases _______ neurotransmitters. More or Less?
Less.
This is called Presynaptic Inhibition.
If the axoaxonal synapse is excitatory, the presynaptic neuron is facilitated and therefore releases ________ neurotransmitters. More or Less?
More.
This is called Presynaptic Facilitation.
What are typical neurotransmitters involved in presynaptic facilitation and inhibition affecting Ca+ channels?
GABA and Serotonin.
Synaptic __________ occurs when a neuron is under intense stimulation.
fatigue
Synaptic fatigue results from a neuron reaching its limits of ______________ ACh at the axon ___________ and _______________ new ACh from the cell body.
resynthesizing, terminal, transporting
