Autonomic Nervous System Quiz

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Questions and Answers

What is the role of the vesicle-associated transporter (VAT) in neurotransmitter transport?

It releases neurotransmitters into the synapse.

It transports acetylcholine into vesicles. (correct)

It transports Ca²⁺ into the presynaptic terminal.

It converts dopamine to noradrenaline.

What triggers the exocytosis of neurotransmitter vesicles at the nerve terminal?

Influx of K⁺ through ion channels.

Influx of Ca²⁺ through voltage-gated channels. (correct)

Propagation of an action potential.

Influx of Na⁺ through voltage-gated channels.

Which enzyme is responsible for converting tyrosine to Dopa in adrenergic transmission?

Vesicular monoamine transporter.

Dopamine-β-hydroxylase.

Dopa decarboxylase.

Tyrosine hydroxylase. (correct)

Which statement about dopamine in adrenergic transmission is true?

Dopamine is converted to noradrenaline inside the vesicle. Signup and view all the answers

What role does the vesicular monoamine transporter (VMAT) play in adrenergic transmission?

It transports dopamine into vesicles. Signup and view all the answers

What is the main precursor for the synthesis of acetylcholine (ACh)?

Choline Signup and view all the answers

Which enzyme is responsible for synthesizing acetylcholine from acetyl-CoA and choline?

Choline acetyltransferase Signup and view all the answers

How is the action of neurotransmitters typically terminated in the synapse?

Both metabolism and neuronal reuptake Signup and view all the answers

Where are most neurotransmitters synthesized in the autonomic nervous system?

Axon terminal Signup and view all the answers

What type of neurotransmitter is ATP considered in the context of the autonomic nervous system?

NANC Signup and view all the answers

Which neurotransmitter is NOT included when discussing the main autonomic transmitters?

Serotonin Signup and view all the answers

In the context of neurotransmission, what do drugs specifically target?

Various steps in neurotransmission Signup and view all the answers

What kind of transport mechanism is used for choline to enter the nerve terminal?

Active transport Signup and view all the answers

Which neurotransmitter is classified as a NANC mediator in the sympathetic nervous system?

Neuropeptide Y Signup and view all the answers

What is the role of hemicholinium in cholinergic neurotransmission?

Blocks the synthesis of acetylcholine Signup and view all the answers

Which of the following is NOT considered a NANC neurotransmitter?

Noradrenaline Signup and view all the answers

What does vesamicol block in cholinergic neurotransmission?

Vesicle-associated transporter Signup and view all the answers

Which step of neurotransmission is primarily affected when drugs interfere with the release of neurotransmitters?

Release into the synapse Signup and view all the answers

Which of the following is a common effect of drugs on neurotransmission?

Inhibiting neurotransmitter interactions with post-synaptic receptors Signup and view all the answers

Which neurotransmitter is not classified under the category of NANC mediators of the ANS?

Acetylcholine Signup and view all the answers

What is the primary function of nitric oxide as a NANC neurotransmitter?

Facilitate vasodilation Signup and view all the answers

Which drug can inhibit the breakdown of norepinephrine?

Entacapone Signup and view all the answers

What is the effect of tricyclic antidepressants on norepinephrine?

They prevent the re-uptake of norepinephrine Signup and view all the answers

What is the role of MAO inhibitors like selegiline in neurotransmission?

To inhibit the breakdown of neurotransmitters Signup and view all the answers

Which neurotransmitter is also known as noradrenaline?

Norepinephrine Signup and view all the answers

Which of the following is a non-adrenergic, non-cholinergic neurotransmitter?

Substance P Signup and view all the answers

What is the role of metyrosine in the synthesis of neurotransmitters?

It inhibits the conversion of tyrosine to dopa. Signup and view all the answers

How does reserpine affect neurotransmitter storage?

It blocks the vesicular monoamine transporter (VMAT). Signup and view all the answers

Which drug inhibits the release of norepinephrine into the synapse?

Bretylium Signup and view all the answers

What class of drug is salbutamol and what is its primary action?

An agonist that stimulates β₂ adrenergic receptors. Signup and view all the answers

What effect does guanethidine have in the context of adrenergic neurotransmission?

It inhibits the release of norepinephrine into the synapse. Signup and view all the answers

Which statement correctly describes the function of acetylcholinesterase?

It degrades acetylcholine in the synaptic cleft. Signup and view all the answers

Which of the following is NOT a site of drug action in adrenergic neurotransmission?

Degradation of neurotransmitters in the synapse Signup and view all the answers

The role of presynaptic receptors at muscarinic cholinergic junctions is to:

Inhibit the release of acetylcholine. Signup and view all the answers

What effect do tricyclic antidepressants have on norepinephrine levels in the synapse?

They inhibit the re-uptake of norepinephrine. Signup and view all the answers

Which drug class is capable of inhibiting the breakdown of norepinephrine in the body?

COMT-inhibitors Signup and view all the answers

What is the primary role of MAO inhibitors like selegiline in neurotransmission?

To inhibit the breakdown of norepinephrine. Signup and view all the answers

What neurotransmitter is also known as norepinephrine?

Noradrenaline Signup and view all the answers

Which of the following statements about COMT-inhibitors is true?

They enhance the activity of norepinephrine by inhibiting its breakdown. Signup and view all the answers

What is the significance of the influx of Ca²⁺ at the nerve terminal during neurotransmission?

It triggers exocytosis of vesicles containing neurotransmitters. Signup and view all the answers

Which enzyme is responsible for converting Dopamine to Noradrenaline (NA) within the vesicle?

Dopamine-β-hydroxylase Signup and view all the answers

How is Tyrosine transported into the presynaptic nerve terminal during adrenergic transmission?

Through an Na⁺ dependent carrier Signup and view all the answers

What role does the vesicular monoamine transporter (VMAT) perform in adrenergic neurotransmission?

It transports Noradrenaline from the cytoplasm into vesicles. Signup and view all the answers

What initiates the process of neurotransmitter release at the nerve terminal?

Depolarization of the presynaptic neuron membrane Signup and view all the answers

Which enzyme is responsible for the conversion of Dopa to Dopamine in the synthesis of catecholamines?

Dopa decarboxylase Signup and view all the answers

What is the primary urinary metabolite produced from noradrenaline metabolism?

Vanillylmandelic acid (VMA) Signup and view all the answers

Which enzyme primarily catalyzes the main oxidative pathway in the metabolism of noradrenaline?

Aldehyde dehydrogenase (ADH) Signup and view all the answers

Which compound inhibits the rate-limiting step in catecholamine synthesis?

Metyrosine (α-methyltyrosine) Signup and view all the answers

Which of the following is a less abundant metabolite produced in noradrenaline metabolism?

3-methoxy-4-hydroxyphenylglycol (MHPG) Signup and view all the answers

What is the initial step in the synthesis of acetylcholine (ACh) in the cholinergic transmission process?

Transport of choline into the nerve terminal Signup and view all the answers

How does the conjugation of MHPG before excretion relate to noradrenaline release?

It reflects noradrenaline release in the brain. Signup and view all the answers

What is noradrenaline also known as?

Norepinephrine Signup and view all the answers

Which of the following best describes how neurotransmitter action is terminated?

By metabolic breakdown or neuronal reuptake Signup and view all the answers

Which of the following enzymes is involved in the metabolism of catecholamines but is not a rate-limiting step?

Monoamine oxidase (MAO) Signup and view all the answers

What characterizes neurotransmitters synthesized in the nerve terminals of the autonomic nervous system?

They are synthesized, stored, and released in response to nerve stimulation Signup and view all the answers

What role do drugs typically play in neurochemical transmission?

They target specific steps in neurotransmission Signup and view all the answers

Which of the following is a non-adrenergic, non-cholinergic (NANC) neurotransmitter involved in the autonomic nervous system?

Substance P Signup and view all the answers

What is the primary function of the enzyme choline acetyltransferase (ChAT)?

Synthesizing acetylcholine from acetyl-CoA and choline Signup and view all the answers

What is the effect of ATP as a NANC neurotransmitter in the autonomic nervous system?

It acts as a signaling molecule for various physiological responses Signup and view all the answers

Which component is fundamental to the process of storing neurotransmitters in the autonomic nervous system?

Membrane-bound vesicles Signup and view all the answers

What effect does botulinum toxin have on acetylcholine release at the nerve terminal?

It blocks exocytosis of vesicles, inhibiting release. Signup and view all the answers

How do acetylcholinesterase inhibitors like pyridostigmine affect acetylcholine levels?

They inhibit the breakdown of acetylcholine by AChE. Signup and view all the answers

What is the role of presynaptic nicotinic receptors at the cholinergic synapse?

To facilitate the release of acetylcholine during continuous activity. Signup and view all the answers

What is the primary effect of using agonist drugs at postsynaptic nicotinic receptors?

They enhance acetylcholine's effects at the postsynaptic site. Signup and view all the answers

What occurs to acetylcholine levels when acetylcholinesterase is inhibited?

Acetylcholine levels increase due to decreased breakdown. Signup and view all the answers

What type of receptors are present at muscarinic cholinergic junctions?

Muscarinic receptors. Signup and view all the answers

Which of the following statements about acetylcholine leakage is true under normal conditions?

Acetylcholine leakage is insignificant and does not affect baseline communication. Signup and view all the answers

What is the primary mechanism of action for atropine in the cholinergic system?

It serves as an antagonist at muscarinic receptors. Signup and view all the answers

What is the role of the vesicular monoamine transporter (VMAT) in the process of adrenergic transmission?

Transports Dopamine into the vesicle. Signup and view all the answers

Which of the following correctly describes the influx of Ca²⁺ at the nerve terminal?

It causes the release of neurotransmitters through exocytosis. Signup and view all the answers

Which enzyme is specifically responsible for converting Dopamine into Noradrenaline (NA) within the vesicle?

Dopamine-β-hydroxylase. Signup and view all the answers

What role does tyrosine hydroxylase play in adrenergic transmission?

It converts Tyrosine into Dopa. Signup and view all the answers

Which transport mechanism is utilized for the uptake of Tyrosine into the presynaptic nerve terminal?

Na⁺ dependent carrier transport. Signup and view all the answers

What effect do tricyclic antidepressants have on norepinephrine levels in the synapse?

They inhibit the re-uptake of norepinephrine. Signup and view all the answers

Which drug class can inhibit the breakdown of norepinephrine?

MAO inhibitors Signup and view all the answers

Which of the following neurotransmitters is predominantly associated with the parasympathetic nervous system as a NANC mediator?

Nitric oxide Signup and view all the answers

Which neurotransmitter is also known as noradrenaline?

Norepinephrine Signup and view all the answers

Which step of neurotransmission involves the blockage of the choline transporter by hemicholinium?

Synthesis of neurotransmitter Signup and view all the answers

What is the role of COMT inhibitors in neurotransmission?

They inhibit the enzymatic breakdown of norepinephrine. Signup and view all the answers

Which compound acts as a neurotransmitter that is non-adrenergic and non-cholinergic (NANC)?

ATP Signup and view all the answers

Vesamicol primarily inhibits neurotransmission by acting on which aspect?

Neurotransmitter storage in vesicles Signup and view all the answers

Which of the following is NOT recognized as a major NANC mediator in the sympathetic nervous system?

Nitric oxide Signup and view all the answers

Which neurotransmitter is associated with inhibitory effects and is classified among the NANC neurotransmitters?

GABA Signup and view all the answers

What is the main mechanism through which drugs can disrupt neurotransmission?

Inhibit neurotransmitter synthesis Signup and view all the answers

Which neurotransmitter plays a significant role in both NANC mediation and as a neurotransmitter in the central nervous system?

Dopamine Signup and view all the answers

What is one of the critical actions of ATP as a neurotransmitter in the sympathetic nervous system?

Modulating neurotransmitter release Signup and view all the answers

What is the main urinary metabolite produced from the oxidative metabolism of noradrenaline?

Vanillylmandelic acid Signup and view all the answers

Which enzyme is primarily responsible for converting noradrenaline into its metabolites in the brain?

Catechol-O-methyltransferase (COMT) Signup and view all the answers

What is inhibited by the drug metyrosine during catecholamine synthesis?

Tyrosine hydroxylase Signup and view all the answers

Which of the following statements accurately reflects the role of aldehyde reductase (AR) in noradrenaline metabolism?

It reduces aldehyde forms to 3-methoxy-4-hydroxyphenylglycol (MHPG). Signup and view all the answers

Which neurotransmitter is chemically modified to form noradrenaline during its synthesis?

Dopamine Signup and view all the answers

In the context of noradrenaline metabolism, what does MHPG sulfate excretion indicate?

Release of noradrenaline in the brain Signup and view all the answers

What role does catechol-O-methyltransferase (COMT) play in the metabolism of catecholamines?

It is involved in the methylation process of neurotransmitters. Signup and view all the answers

Which enzyme indicates the primary pathway leading to the formation of the main urinary metabolite from noradrenaline?

Aldehyde dehydrogenase Signup and view all the answers

What is the primary mechanism of action for the drug bretylium in adrenergic neurotransmission?

It blocks the exocytosis of norepinephrine. Signup and view all the answers

Which of the following drugs acts as an antagonist at specific adrenergic receptor subtypes?

Guanethidine Signup and view all the answers

What is the impact of resperine on neurotransmitter storage?

It prevents the transport of dopamine into vesicles. Signup and view all the answers

How do agonists like salbutamol function at the adrenergic synapse?

They activate specific adrenergic receptor subtypes. Signup and view all the answers

Which process is primarily inhibited by guanethidine in the context of adrenergic neurotransmission?

Release of norepinephrine into the synapse. Signup and view all the answers

What is the biological consequence of using metyrosine in adrenergic neurotransmission?

It inhibits the conversion of tyrosine to dopa. Signup and view all the answers

What role do postsynaptic muscarinic receptors play in adrenergic neurotransmission?

They interact with neurotransmitters at cholinergic junctions. Signup and view all the answers

What is the primary site of action for drugs designed to inhibit vesicular storage of neurotransmitters?

Vesicular monoamine transporter Signup and view all the answers

Study Notes

Autonomic Nervous System Transmission

Autonomic neurotransmission involves the synthesis, storage, release, and termination of neurotransmitters in response to nerve stimulation.
Most neurotransmitters are synthesized in nerve terminals, stored in membrane-bound vesicles, and released into the synapse upon nerve stimulation.
Neurotransmitter action is terminated by metabolism or reuptake from the synapse.
Drugs often exert effects on specific steps in the neurotransmission process.

Cholinergic Transmission

The precursor for acetylcholine (ACh) is choline, transported into nerve terminals by the choline transporter (CHT).
ACh is synthesized in the cytoplasm using acetyl-CoA and choline, catalyzed by the enzyme choline acetyltransferase (ChAT).
ACh is transported from the cytoplasm into vesicles by a vesicle-associated transporter (VAT).
Nerve stimulation triggers an influx of calcium ions (Ca²⁺) through voltage-gated Ca²⁺ channels, leading to vesicle exocytosis and ACh release into the synapse.

Adrenergic Transmission

Tyrosine is transported into the presynaptic nerve terminal by a sodium-dependent carrier.
Tyrosine is converted to Dopa by the enzyme tyrosine hydroxylase.
Dopa is converted to Dopamine by the enzyme dopa decarboxylase.
Dopamine is transported into vesicles by the vesicular monoamine transporter (VMAT).
Inside the vesicle, Dopamine is converted to Noradrenaline (NA) by the enzyme dopamine-β-hydroxylase.

Non-Adrenergic Non-Cholinergic (NANC) Mediators

NANC neurotransmitters are those other than NA and ACh.
Major NANC mediators in the autonomic nervous system include:
- Nitric oxide and vasoactive intestinal peptide (VIP) in the parasympathetic nervous system.
- ATP and neuropeptide Y in the sympathetic nervous system.
Other NANC mediators include 5-hydroxytryptamine (serotonin), GABA, and dopamine.

Drug Effects on Neurotransmission

Drugs can interfere with neurotransmission at various stages:
- Synthesis of neurotransmitters
- Storage of neurotransmitters in vesicles
- Release of neurotransmitters into the synapse
- Interaction of neurotransmitters with post-synaptic receptors
- Termination of neurotransmitter action

Drug Effects on Cholinergic Neurotransmission

Hemicholinium blocks the choline transporter, preventing the transport of choline into the nerve terminal, thereby inhibiting ACh synthesis.
Vesamicol blocks the vesicle-associated transporter (VAT), preventing ACh from being transported from the cytoplasm into the vesicle.

Drug Effects on Adrenergic Neurotransmission

Metyrosine inhibits the conversion of tyrosine to Dopa, disrupting the NA synthesis pathway.
Reserpine blocks the vesicular monoamine transporter (VMAT), preventing dopamine from being transported from the cytoplasm into the vesicle.
Bretylium and guanethidine inhibit the release of NA via exocytosis into the synapse.
Salbutamol acts as an agonist at specific beta-2 receptors, simulating their activity.
Propranolol acts as an antagonist at specific beta receptors, blocking their activity.
COMT-inhibitors (e.g. entacapone) and MAO inhibitors (e.g. selegeline) inhibit the breakdown of NA.
Tricyclic antidepressants and cocaine inhibit the re-uptake of NA back into the presynaptic neuron.

Neurotransmission

Neurotransmission involves the synthesis, storage, release, and termination of action of neurotransmitters
Most neurotransmitters are synthesized in nerve terminals, stored in membrane-bound vesicles, and released into the synapse in response to nerve stimulation
Neurotransmitter action is terminated either by metabolism or neuronal reuptake from the synapse
Drugs act on specific steps in neurotransmission

Cholinergic Transmission

Choline is transported into the nerve terminal by the choline transporter (CHT)
Acetylcholine (ACh) is synthesized from acetyl-CoA and choline by the enzyme choline acetyltransferase (ChAT)
ACh is transported into vesicles by a vesicle-associated transporter (VAT)
In response to nerve stimulation, calcium influx through voltage-gated calcium channels causes exocytosis of vesicles, releasing ACh into the synapse

Adrenergic Transmission

Tyrosine is transported into the presynaptic nerve terminal by a sodium-dependent carrier.
Tyrosine is converted to Dopa by tyrosine hydroxylase
Dopa is converted to Dopamine by dopa decarboxylase
Dopamine is transported into the vesicle by the vesicular monoamine transporter (VMAT)
Dopamine is converted to Noradrenaline (NA) by dopamine-β-hydroxylase

Catecholamine Synthesis

Tyrosine is converted to Dopa by tyrosine hydroxylase.
Dopa is converted to Dopamine by dopa decarboxylase.
Dopamine is converted to Noradrenaline (NA) by dopamine-β-hydroxylase
Noradrenaline is converted to Adrenaline by phenylethanolamine-N-methyltransferase

Catecholamine Metabolism

Catecholamines are metabolized by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO)

Drug Effects on Cholinergic Neurotransmission

Botulinum toxin blocks exocytosis of synaptic vesicles, inhibiting ACh release
Pilocarpine acts as an agonist at post-synaptic receptors
Atropine acts as an antagonist at post-synaptic receptors
Acetylcholinesterase inhibitors like pyridostigmine inhibit ACh breakdown by AChE

Drug Effects on Adrenergic Neurotransmission

Breakdown of NA can be inhibited by COMT-inhibitors like entacapone, or MAO inhibitors like selegiline
Re-uptake of NA into the presynaptic neuron can be inhibited by tricyclic antidepressants and cocaine

Non-Adrenergic, Non-Cholinergic (NANC) Neurotransmitters

Include ATP, Substance P, nitric oxide, and dopamine

Acetylcholine Neurotransmission

Acetylcholine (ACh) is transported from the cytoplasm into vesicles by a vesicle-associated transporter (VAT).
When an action potential reaches the nerve terminal, it causes an influx of calcium ions (Ca²⁺) through voltage-gated Ca²⁺ channels.
This calcium influx triggers exocytosis of the vesicles, releasing ACh into the synapse.

Adrenergic Transmission

Tyrosine is transported into the presynaptic nerve terminal by a sodium-dependent carrier.
Tyrosine is converted to Dopa by the enzyme tyrosine hydroxylase.
Dopa is converted to Dopamine by the enzyme dopa decarboxylase.
Dopamine is transported into the vesicle by the vesicular monoamine transporter (VMAT).
Inside the vesicle, Dopamine is converted to Noradrenaline (NA) by the enzyme dopamine-β-hydroxylase.

Catecholamine Synthesis

The rate-limiting step in catecholamine synthesis is the conversion of tyrosine to dopa, which can be inhibited by metyrosine (α-methyltyrosine).

Catecholamine Metabolism

Catecholamines are primarily metabolized by two enzymes: catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO).

Non-Adrenergic Non-Cholinergic (NANC) Mediators

Non-adrenergic non-cholinergic (NANC) neurotransmitters describe neurotransmitters other than noradrenaline (NA) and acetylcholine (ACh).
Major NANC mediators in the autonomic nervous system (ANS) include:
- Nitric oxide and vasoactive intestinal peptide (VIP) in the parasympathetic NS.
- ATP and neuropeptide Y in the sympathetic NS.
Other NANC mediators include 5-hydroxytryptamine (serotonin), GABA, and dopamine.

Drug Effects on Neurotransmission

Drugs can interfere with neurotransmission at the following steps:
- Synthesis of neurotransmitters (NT).
- Storage of NT in vesicles.
- Release of NT into the synapse.
- Interaction of the NT with post-synaptic receptors.
- Termination of NT action.

Drug Effects on Cholinergic Neurotransmission

Hemicholinium blocks the choline transporter from transporting choline into the nerve terminal, thus preventing ACh synthesis.
Vesamicol blocks the vesicle-associated transporter (VAT) from transporting ACh from the cytoplasm into the vesicle.

Drug Effects on Adrenergic Neurotransmission

Synthesis of NT:
- Metyrosine inhibits the conversion of tyrosine to dopa.
Storage of NT in vesicles:
- Reserpine blocks the vesicular monoamine transporter (VMAT), preventing dopamine from entering the vesicle.
Release of NT into the synapse:
- Release of NA via exocytosis is inhibited by bretylium and guanethidine.
Interaction of the NT with post-synaptic receptors:
- Drugs can act as agonists or antagonists at specific receptor subtypes.
Termination of NT action:
Breakdown of NA can be inhibited by COMT-inhibitors (e.g., entacapone) or MAO inhibitors (e.g., selegeline).
Tricyclic antidepressants and cocaine inhibit the re-uptake of NA back into the presynaptic neuron.

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Description

Test your knowledge on autonomic neurotransmission and cholinergic transmission. This quiz covers the synthesis, storage, release, and termination of neurotransmitters, and their mechanisms within the autonomic nervous system. Explore the roles of key neurotransmitters and their drug interactions.