Neurobiology Exam 2

How does information transfer occur at chemical synapses?

Electrical depolarization of the nerve terminal causes the release of chemicals that open postsynaptic ligand-gated ion channels which pass current, depolarizing the postsynaptic cell

Dendritic spines are commonly a site for

excitatory synaptic transmission

How does acetycholinesterase function at synapses that release acetylcholine?

It is a synaptic cleft enzyme that breaks down the transmitter acetylcholine

How do transmitters act on the postsynaptic cell at direct chemical synapses?

They bind to ligand-gated ion channels to induce postsynaptic current flux

Synaptic vesicles are concentrated in large numbers within nerve terminals. What is their function?

They store and release chemical transmitter molecules

Why does the plant alkaloid nicotine cause skeletal muscle contraction?

Nicotine is an agonist at postsynaptic nicotinic acetylcholine receptors

How does the technique called ionophoresis work?

Molecules inside a glass pipet can be expelled by electrical charge

How are acetylcholine receptors distributed along the muscle membrane?

They are highly concentrated directly under the presynaptic terminal at the NMJ

What is the reversal potential for a channel?

The membrane potential at which the net current flux through a channel is zero, and on either side of which the net current flux moves in opposite directions

What is the principal excitatory transmitter in the CNS?

Glutamate

How does information transfer occur at chemical synapses?

Electrical depolarization of the nerve terminal causes the release of chemicals that open postsynaptic ligand-gated ion channels which pass current, depolarizing the postsynaptic cell

When comparing direct and indirect synaptic transmission, indirect synaptic transmission is mediated by?

metabotropic receptors that activate intracellular second-messenger pathways

The G proteins that are coupled to metabotropic receptors are

heterotrimeric GTP binding proteins made up of α-, β-, and γ-subunits.

For G protein-coupled metabotropic receptors, GTP binds to the

α-subunit of the heterotrimer

How is G protein-mediated signaling terminated?

Hydrolysis of GTP to GDP by the endogenous GTPase activity of the α-subunit leads to reassociation of the αβγ-complex, terminating the response

The particular neurotransmitter present at a synapse

does not indicate the subtype of G protein or second messenger that will be coupled to the receptor

What would happen to metabotropic signaling in a cell if you added GTP-γ-s to the cell cytoplasm?

This would irreversibly activate all G protein-coupled metabotropic signaling

What happens when PIP2 is cleaved by PLC?

his cleavage generates inositol-1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) that act as second messengers

How many transmembrane domains do all G protein-coupled metabotropic receptors have?

All G protein-coupled metabotropic receptors has 7 transmembrane domains

Which of the following neurotransmitters is not stored in synaptic vesicles?

Endocannibinoids

The particular neurotransmitter present at a synapse

does not indicate the subtype of G protein or second messenger that will be coupled to the receptor

What explains why there is a threshold depolarization of about 45 mV above resting membrane potential before any transmitter release occurs?

This is the magnitude of depolarization required to activate presynaptic voltage-gated calcium channels

Which is both necessary and sufficient to trigger chemical transmitter release from a presynaptic nerve terminal?

An increase in presynaptic calcium concentration

If one would like to use the voltage clamp technique to record presynaptic calcium currents from a nerve terminal, why are tetrodotoxin (TTX) and tetraethylammonium  (TEA) used? 

TTX blocks sodium channels and TEA blocks potassium channels

What is thought to significantly restrict the spread of calcium ions after they enter the nerve terminal through presynaptic calcium channels?

Calcium buffers and binding proteins (chelators)

What is the definition of a quantum of transmitter?

A multimolecular packet containing about 7000 transmitter molecules

What is the calcium sensor for synaptic vesicle exocytosis?

Synaptotagmin

What is kiss-and-run exocytosis?

Vesicle pore formation with the plasma membrane that is not followed by full vesicle fusion, but rather by closure of the pore

What is the synaptic delay at a synapse that uses chemical transmitters at room temperature?

0.5 milliseconds

What is a nanodomain of presynaptic calcium ions?

The collected intracellular calcium ions that form around the mouth of a single open calcium channel