Neuropsych 315 Chapter 5 Part 1

What chemical inhibits a frog's heart rate?

Acetylcholine

What chemical increases a frog's heart rate?

Epinephrine (adrenaline)

What is the main excitatory compound affecting the heart in humans?

Norepinephrine (noradrenaline)

What structural difference exists between epinephrine and norepinephrine?

Epinephrine has an additional methyl group (CH3).

What are neurohormones?

Substances that act as neurotransmitters when released by neurons and as hormones when released by adrenal glands.

What type of neurons secrete acetylcholine?

Cholinergic neurons

What type of neurons secrete epinephrine?

Adrenergic neurons

What type of neurons secrete norepinephrine?

Noradrenergic neurons

How many neurotransmitters have been identified in the brain and body?

Around 100 neurotransmitters.

What determines whether a neurotransmitter has excitatory or inhibitory effects?

The type of receptor it interacts with.

What are muscarinic receptors associated with?

Inhibitory action of acetylcholine in the parasympathetic nervous system.

What are nicotinic receptors associated with?

Excitatory action of acetylcholine in skeletal muscles.

What is the primary excitatory neurotransmitter?

Glutamate

What is the primary inhibitory neurotransmitter?

GABA

What type of receptors are ionotropic receptors?

Receptors that act as ion channels for rapid and short-duration graded potentials.

What type of receptors are metabotropic receptors?

Receptors that activate slower signaling cascades inside the neuron.

What are the main components of a chemical synapse?

Axon terminal, postsynaptic membrane, and synaptic cleft.

What are synaptic vesicles?

Structures within the axon terminal filled with neurotransmitters.

What is a gap junction?

An electrical synapse where pre and post junction cell membranes fuse, allowing small ions to pass freely.

What is the first step in neurotransmitter transmission across a synapse?

The synthesis stage, where neurotransmitters are produced, transported to the axon terminal and stored in vesicles.

What occurs during the vesicle transport stage?

Vesicles are transported to the presynaptic membrane to release their contents into the synaptic cleft

What is the role of alpha receptors in the nervous system?

Facilitate vasoconstriction and afford inhibitory action.

What is the role of beta receptors in the nervous system?

Found on heart muscles and afford excitatory action.

What is the post-synaptic density?

It consists mostly of proteins that serve as channels or pumps for ions, or as receptor sites for neurotransmitters.

What is the function of storage granules in axon terminals?

To hold several synaptic vesicles.

How do gap junctions impact information flow?

They eliminate the delay in information flow that occurs during chemical transmission.

What happens to vesicles in response to an action potential?

Vesicles are transported to the presynaptic membrane to release their contents.

What do neurotransmitters (NTs) do after being released?

They traverse the synaptic cleft to interact with receptors on the postsynaptic membrane.

Where do neurotransmitters interact after crossing the synaptic cleft?

They interact with receptors on the postsynaptic membrane.

What triggers the release of neurotransmitters from vesicles?

An action potential.

What is the role of vesicles in neurotransmitter release?

They transport neurotransmitters to the presynaptic membrane for release.

What happens to neurotransmitters (NTs) after they are released into the synaptic cleft?

They are either reabsorbed by the presynaptic axon (reuptake), broken down by enzymes, or diffuse away to be taken up by other cells.

How are neurotransmitters synthesized?

They are synthesized inside the cell body according to DNA instructions and packaged into membranes on the Golgi bodies, or synthesized in the axon terminal from precursor chemicals.

What is an example of a precursor chemical for serotonin?

Tryptophan, which can be converted into 5-hydroxytryptophan (5-HTP) and then into serotonin (5-hydroxytryptamine or 5-HT).

What role do mitochondria play in neurotransmitter synthesis?

They provide energy for synthesizing neurotransmitters from precursor chemicals that enter the cell.

How are neurotransmitters stored in the axon terminal?

They are drawn inside synaptic vesicles, which can exist in groups as storage granules, attach to microfilaments, or attach to the presynaptic membrane for quick release.

What is exocytosis in the context of neurotransmitter release?

It is the process where the contents of a membrane-bound vesicle are released after the vesicle membrane fuses with the cell membrane.

What are co-transmitters?

Neurotransmitters that can be released together from the same neuron, often stored in separate synaptic vesicles.

What distinguishes small-molecule neurotransmitters from neuropeptides?

Small-molecule neurotransmitters have one amino group (monoamines) and are physically smaller than neuropeptides, which have multiple amino groups.

How does the frequency of nerve impulses affect neurotransmitter release?

Low frequency increases Ca2+ concentration slightly, affecting only small-molecule transmitters, while high frequency increases Ca2+ enough to release larger neuropeptides.

What is the role of autoreceptors in neurotransmitter release?

They inhibit further exocytosis when a presynaptic neuron senses sufficient neurotransmitter levels in the synapse.

What therapeutic potential do direct agonists for serotonin receptors hold?

They could be beneficial for treating depression, but no such medications currently exist.

What is the function of transporter proteins in neurotransmitter synthesis?

They allow precursor chemicals to enter the neuron and can also pump in ready-made neurotransmitters from the blood or extracellular fluid.

What happens to neurotransmitters that remain bound to receptors on the postsynaptic membrane?

They continue to activate or inhibit the receiving neuron.

What is the significance of calcium ions (Ca2+) in neurotransmitter release?

They participate in chemical reactions that trigger the release of neurotransmitters from vesicles during exocytosis.

What is the role of synaptogmin in neurotransmitter release?

It interacts with calcium ions to create a complex that opens vesicles near the presynaptic membrane for neurotransmitter release.

What occurs when a neuron releases a large amount of neurotransmitter at once?

Autoreceptors may activate to inhibit further release of neurotransmitters.

How do neurotransmitters diffuse across the synaptic cleft?

They move from the presynaptic membrane to bind to receptors on the postsynaptic membrane.

What is the effect of a high concentration of calcium ions in the presynaptic terminal?

It can induce the release of larger neuropeptides from vesicles that are not docked at the membrane.

What is the function of voltage-sensitive calcium channels?

They open in response to an action potential, allowing calcium (Na+) ions to enter the presynaptic terminal.

What happens to empty vesicles after neurotransmitter release?

Other vesicles move to take their place on the presynaptic membrane to release their contents.

What can happen to neurotransmitters that are not reabsorbed or broken down?

They may float away and be taken up by other cells.

What is the role of ATP in neurotransmitter packaging?

ATP is used by transporter proteins to pump neurotransmitters into the vesicles' lumen.

What is the importance of the extracellular fluid around an axon terminal?

It is rich in calcium ions, which are essential for neurotransmitter release.

What is the process of neurotransmitter binding to postsynaptic receptors?

Neurotransmitters diffuse across the synaptic cleft and bind to specialized protein molecules in the postsynaptic membrane.

What do NaSSAs do in relation to autoreceptors?

NaSSAs block autoreceptors, preventing the shutdown of neurotransmitter output, leading to increased signaling.

What are the four main processes of neurotransmitter deactivation?

Diffusion, degradation, reuptake, and glial storage.

How does diffusion affect neurotransmitter availability?

Some neurotransmitters simply diffuse away from the synaptic cleft, making them unavailable for further action.

What is the function of enzymes in neurotransmitter degradation?

Enzymes in the synaptic cleft break down neurotransmitters, reducing their availability.

What is reuptake in the context of neurotransmitters?

Reuptake is the process where neurotransmitters are recycled back into the presynaptic cell via specific transporter proteins.

What role do glial cells play in neurotransmitter storage?

Glial cells, such as astrocytes, can store neurotransmitters for future use or export them back to neurons.

What is the primary action of SSRIs?

SSRIs block the reuptake of serotonin, increasing its availability in the synaptic cleft.

How do TCADs differ from SSRIs and NARIs?

TCADs block the reuptake of both serotonin and noradrenaline, with different side effects and overdose profiles.

What do MAOIs do in the synapse?

MAOIs inhibit enzymes that break down monoamines, allowing neurotransmitters to remain longer in the synapse.

What happens to neurotransmitter production when an axon terminal is highly active?

The amount of neurotransmitter produced and stored increases in response to high activity.

What is an axodendritic synapse?

An axodendritic synapse is where the axon terminal of one neuron connects with the dendrite of another neuron.

What is the function of axoaxonic synapses?

Axoaxonic synapses allow for faster regulation of action potentials by bypassing the summation action of the soma.

What is the difference between excitatory and inhibitory synapses?

Excitatory synapses increase the likelihood of an action potential, while inhibitory synapses decrease it.

Where are excitatory synapses typically located?

Excitatory synapses are usually found on the shafts and spines of dendrites.

What characterizes the vesicles in excitatory versus inhibitory synapses?

Excitatory synapses have round vesicles, while inhibitory synapses have flat vesicles.

Why are inhibitory neurons positioned close to the cell body?

This positioning is efficient for survival, as it helps prevent overstimulation of the neuron.

What is an axosecretory synapse?

An axosecretory synapse is where an axon terminal synapses with a blood vessel to secrete neurotransmitters into the bloodstream.

What is the significance of gap junctions in electrical synapses?

Gap junctions allow for synchronization of signals between neurons and enable nutrient exchange between glial cells.

What is the role of dendrodendritic synapses?

Dendrodendritic synapses allow communication between dendrites of neurons that lack axons.

What is the purpose of axoextracellular synapses?

Axoextracellular synapses release neurotransmitters into the extracellular fluid, which may be taken up by nearby cells.

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