Synaptic Transmission and Neurochemistry

Comprehensive practice flashcards covering synapse types, neurotransmitter criteria, specific chemical messengers (ACh, Glutamate, GABA, Catecholamines), and optogenetic tools as discussed in the lecture transcript.

Electrical synapses utilize __________ , which are direct physical connections allowing ions and second messengers to flow freely between neurons.

gap junctions

The pore of a gap junction is formed by subunits of __________ and is more than $1\,nm$ in diameter.

connexin

A key pro of electrical synapses is that they transmit signals more rapidly and can be __________, helping to synchronize populations of neurons.

bidirectional

A classic neurotransmitter must be released in response to presynaptic depolarization in a __________-dependent manner.

$$Ca^{2+}$$

Most small-molecule neurotransmitters are packaged in __________ vesicles that are $40$ to $60\,nm$ in diameter.

small clear-core

Neuropeptides are synthesized in the cell body and transported to the terminal via axonal transport along microtubules using __________ as the motor.

kinesin

Large dense-core vesicles, which contain neuropeptides, range from __________ to __________ nm in diameter.

$90$, $250$

Hereditary spastic paraplegias (HSPs) are linked to a missense mutation in the gene for the kinesin heavy chain _________.

Kif5a

__________ receptors combine receptor and channel functions into a single protein complex and operate on a millisecond time scale.

Ionotropic

__________ receptors usually activate G-proteins and operate on a time scale of hundreds of milliseconds to minutes.

Metabotropic

A(n) __________ is a substance that binds to a receptor and activates it, while a(n) __________ binds and inhibits its function.

agonist, antagonist

The snake venom ___________ acts as an antagonist by irreversibly binding to nAChRs and preventing ACh from opening ion channels.

$\alpha$-bungarotoxin

In the inactive state of a trimeric G-protein, the $\alpha$ subunit is bound to __________.

GDP

Protein kinases are kept inactive by a(n) __________ domain that occupies the catalytic site until a second messenger binds.

autoinhibitory

The toxin that prevents G proteins from being deactivated, leading to constitutive activation, is __________ toxin.

Cholera

__________ is the set of genetically encoded tools, like Channelrhodopsin and Halorhodopsin, used to control neuronal activity with light.

Optogenetics

Channelrhodopsin is activated by __________ light and is used to determine if a population of neurons is __________ to cause a behavior.

blue, sufficient

Halorhodopsin is activated by __________ light and allows __________ ions to enter the cell, hyperpolarizing the neuron.

yellow, $Cl^-$

The enzyme __________, which converts glutamine to glutamate, is a key part of the glutamate-glutamine cycle.

glutaminase

Glutamate is loaded into synaptic vesicles by transporters known as __________.

VGLUT

NMDA receptors are often blocked by __________ at hyperpolarized potentials, requiring depolarization to clear the pore.

$$Mg^{2+}+$$

In long-term potentiation (LTP), brief high-frequency stimulation ($100\,Hz$) leads to a large increase in $Ca^{2+}$, activating __________.

protein kinase

GABA is synthesized from glutamate by the enzyme __________, which requires pyridoxal phosphate (Vitamin B6) as a cofactor.

GAD

__________ receptors are ionotropic GABA receptors that allow chloride to flux into the cell, usually causing inhibition.

$$GABA_A$$

Dopamine, norepinephrine, and epinephrine are all synthesized starting from the precursor amino acid __________.

tyrosine

Cocaine works by inhibiting the __________, which is responsible for the reuptake of dopamine from the synaptic cleft.

DAT

Both dopamine and norepinephrine are degraded by the enzymes __________ and __________.

MAO, COMT

The synthesis of neuropeptides begins with the __________ in the rough endoplasmic reticulum (rER).

pre-propeptide

Unconventional neurotransmitters like __________ are not stored in vesicles and often participate in retrograde signaling.

nitric oxide

Endocannabinoids like 2-AG and AEA signal through __________ receptors located on the presynaptic terminal.

$$CB_1$$