Sympathetic Nervous System Overview

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Questions and Answers

What is the primary action of the presynaptic α2 receptor concerning Ca2+ influx?

Stimulates the synthesis of norepinephrine

Modifies the action of neurotransmitters in the synapse

Inhibits Ca2+ influx through voltage-dependent channels (correct)

Enhances Ca2+ influx through voltage-dependent channels

Which of the following is not a direct action of norepinephrine (NE) in the sympathetic nervous system?

Reuptake into pre-synaptic neurons

Release into the synapse

Synthesis from tyrosine (correct)

Activation of postsynaptic receptors

What is the function of metyrosine in the synthesis of norepinephrine?

Increases the production of dopamine

Inhibits the conversion of tyrosine to dopa (correct)

Stimulates the activity of presynaptic adrenoceptors

Enhances vesicular storage of norepinephrine

Which drug is known to block the vesicular storage of dopamine and norepinephrine?

Reserpine Signup and view all the answers

What effect does cocaine have on norepinephrine following its release?

Inhibits the neuronal reuptake of norepinephrine Signup and view all the answers

Which process is involved in increasing the transport of norepinephrine into the synapse?

Amphetamine action Signup and view all the answers

How does the presynaptic α2 receptor affect sympathetic neurotransmission?

Inhibits calcium influx, reducing norepinephrine release Signup and view all the answers

Which component is NOT a part of the norepinephrine synthesis pathway?

Acetylcholine Signup and view all the answers

What is the primary action of reserpine in relation to noradrenaline?

It blocks the vesicular monoamine transporter (VMAT), preventing noradrenaline storage. Signup and view all the answers

What adverse effect is NOT typically associated with reserpine use?

Increased serotonin levels Signup and view all the answers

How do indirect-acting sympathomimetic drugs primarily enhance noradrenaline action?

By reducing noradrenaline reuptake and facilitating its release. Signup and view all the answers

What pathway allows drug molecules to displace noradrenaline within the neuron?

Via the norepinephrine transporter (NET) into the presynaptic neuron. Signup and view all the answers

Which neurotransmitter is NOT mentioned as being depleted by reserpine?

Glutamate Signup and view all the answers

What happens to noradrenaline (NA) when reserpine blocks the VMAT?

NA accumulates in the cytoplasm and is degraded. Signup and view all the answers

What additional effect does reserpine have beyond noradrenaline depletion?

It depletes serotonin and dopamine from neurons in the brain. Signup and view all the answers

Which mechanism describes how amphetamine indirectly acts as a sympathomimetic drug?

It enters the neuron, exchanging with noradrenaline stored in vesicles. Signup and view all the answers

What is the primary focus of the video on adrenergic antagonists?

Illustrating noradrenergic neuro transmission Signup and view all the answers

Which drugs are covered in the video regarding psychomotor stimulants?

Amphetamines, methylphenidate, and cocaine Signup and view all the answers

What additional information does the video on monoamine oxidase inhibitors provide?

Further details about MAO inhibitors Signup and view all the answers

Which chapters from Rang and Dale’s Pharmacology focus on neurodegenerative diseases?

Chapter 40 and Chapter 48 Signup and view all the answers

What is a potential negative consequence discussed in the video on psychomotor stimulants?

Drug abuse factors related to stimulants Signup and view all the answers

What is the primary role of COMT inhibitors in the treatment of Parkinson's disease?

To prevent the metabolism of dopamine in the brain and periphery Signup and view all the answers

Which COMT inhibitor acts in the brain?

Tolcapone Signup and view all the answers

What is the effect of MAO-B inhibitors in the context of Parkinson's disease?

They prevent inactivation of dopamine in the brain Signup and view all the answers

Which of the following drugs acts directly on striatal dopamine receptors in Parkinson's treatment?

Dopamine agonists Signup and view all the answers

What is a common indication for using methyldopa?

Hypertension treatment Signup and view all the answers

In the context of adrenergic drug action, what does MAO stand for?

Monoamine oxidase Signup and view all the answers

What is the effect of drugs that inhibit norepinephrine reuptake?

Enhance the effect of norepinephrine at receptor sites Signup and view all the answers

Which of these drugs primarily displaces norepinephrine from the presynaptic neuron?

Amphetamines Signup and view all the answers

What is the primary effect of sympathomimetic drugs on the sympathetic nervous system?

They enhance the sympathetic response. Signup and view all the answers

Which of the following drug classes inhibits the reuptake of noradrenaline?

Antidepressants Signup and view all the answers

What term is used for drugs that block the sympathetic nervous system's response?

Sympatholytic Signup and view all the answers

Which mechanism do drugs like reserpine utilize to affect noradrenaline?

They displace NA from presynaptic storage sites. Signup and view all the answers

Amphetamines primarily function by which of the following actions?

Displacing NA from storage Signup and view all the answers

Which of these substances is known to inhibit the metabolism of noradrenaline?

Cocaine Signup and view all the answers

What is a significant characteristic of direct-acting sympathetic drugs?

They mimic the action of neurotransmitters. Signup and view all the answers

Which of the following outcomes is expected when sympatholytic drugs are administered?

Decreased blood pressure Signup and view all the answers

What is the role of drugs that inhibit norepinephrine reuptake in the nervous system?

They enhance the synaptic effect of norepinephrine. Signup and view all the answers

Which of the following accurately describes the effect of sympathomimetic and sympatholytic drugs?

Sympathomimetics mimic noradrenaline while sympatholytics block its effects. Signup and view all the answers

Methyldopa is known to primarily act on which aspect of noradrenergic neurotransmission?

Inhibiting the synthesis of norepinephrine Signup and view all the answers

What type of effects would you expect from a drug that enhances norepinephrine activity?

Increased alertness Signup and view all the answers

Sympathomimetics may have various clinical uses due to their action on which systems?

The adrenergic nervous system Signup and view all the answers

Which factor is critical to understanding the role of sympatholytic drugs?

They decrease sympathetic activity. Signup and view all the answers

What effect will a drug that blocks the sympathetic division have on the parasympathetic response?

It will increase the parasympathetic response. Signup and view all the answers

Which receptors are involved in the inhibitory feedback mechanism that affects the release of norepinephrine?

α2 receptors Signup and view all the answers

Which component is inhibited by the activation of presynaptic α2 receptors?

Release of norepinephrine Signup and view all the answers

What type of drug, such as pseudoephedrine, has both direct and indirect actions?

Mixed-acting agonists Signup and view all the answers

Activation of which protein diminishes the action of adenylyl cyclase when α2 receptors are activated?

Gi protein Signup and view all the answers

What is a consequence of reserpine's action on noradrenaline storage within neurons?

Decrease in tissue noradrenaline content Signup and view all the answers

Which mechanism does amphetamine use to enhance noradrenaline action?

Displacement of noradrenaline into the cytoplasm Signup and view all the answers

What is a significant adverse effect of reserpine?

Depression Signup and view all the answers

How does reserpine affect serotonin levels in the brain?

Depletes serotonin levels Signup and view all the answers

Which of the following statements about the action of indirect-acting sympathomimetics is correct?

They reduce norepinephrine reuptake via NET. Signup and view all the answers

What role does the vesicular monoamine transporter (VMAT) play regarding noradrenaline?

Transports noradrenaline into storage vesicles Signup and view all the answers

What happens to noradrenaline once it accumulates in the cytoplasm due to reserpine action?

It is degraded by monoamine oxidase (MAO). Signup and view all the answers

What is the primary effect of blocking vesicular monoamine transporter (VMAT) with reserpine?

Decreased release of noradrenaline Signup and view all the answers

What is the role of βγ subunits of the G protein associated with presynaptic α2 receptors?

They inhibit Ca2+ influx. Signup and view all the answers

Which of the following pathways correctly describes the conversion of tyrosine to norepinephrine?

Tyrosine → Dopa → Dopamine → Norepinephrine Signup and view all the answers

What effect does the drug bretylium have on norepinephrine release?

It inhibits norepinephrine release. Signup and view all the answers

Which drug increases the transport of norepinephrine into the synapse by indirect action?

Amphetamine Signup and view all the answers

Which mechanism describes how neuronal reuptake of norepinephrine is affected?

Inhibited by cocaine Signup and view all the answers

What is the effect of reserpine on neurotransmitters?

It depletes dopamine and norepinephrine. Signup and view all the answers

Which dietary source is rich in tyrosine, crucial for norepinephrine synthesis?

High-protein food products Signup and view all the answers

What would be the expected effect of sympathomimetic drugs?

Enhancement of sympathetic nervous system activity Signup and view all the answers

What is a central action of amphetamine as an indirect sympathomimetic drug?

Appetite suppression Signup and view all the answers

Which of the following effects is NOT caused by indirect-acting sympathomimetic drugs like amphetamine?

Peripheral vasodilation Signup and view all the answers

How does amphetamine primarily enhance the action of norepinephrine?

By displacing NA from vesicles Signup and view all the answers

What is a primary therapeutic use for methylphenidate, another indirect sympathomimetic drug?

Treating ADHD Signup and view all the answers

Which receptor types are activated by the norepinephrine displaced by amphetamine?

Both alpha and beta receptors Signup and view all the answers

What potential negative effect is associated with the use of amphetamine?

Significant potential for abuse Signup and view all the answers

What happens to norepinephrine during the action of amphetamine in the nerve terminal?

NA is displaced into the synaptic cleft Signup and view all the answers

What overall effect do indirect-acting sympathomimetic drugs have on the cardiovascular system?

They can raise arterial pressure and heart rate. Signup and view all the answers

What is the primary action of sympathomimetic drugs?

They mimic the action of norepinephrine. Signup and view all the answers

Which class of drugs is specifically known to inhibit the reuptake of norepinephrine?

Antidepressants Signup and view all the answers

Which effect is associated with the use of sympatholytic drugs?

Decreased blood pressure Signup and view all the answers

What is the main mechanism through which amphetamines enhance the action of norepinephrine?

By displacing norepinephrine from presynaptic neurons Signup and view all the answers

Which drug is known for its ability to block the vesicular storage of norepinephrine?

Reserpine Signup and view all the answers

In the context of noradrenergic neurotransmission, what do the terms sympathomimetic and sympatholytic signify?

Drugs that respectively enhance and inhibit sympathetic responses. Signup and view all the answers

What adverse effect is commonly associated with drugs that inhibit norepinephrine reuptake?

Insomnia Signup and view all the answers

Methyldopa is primarily used to treat which condition?

Hypertension Signup and view all the answers

Which process does reserpine influence regarding norepinephrine?

Storage Signup and view all the answers

What effect does cocaine have on norepinephrine levels?

Inhibits its reuptake Signup and view all the answers

Which of the following characteristics identifies direct-acting sympathomimetic drugs?

They directly stimulate adrenergic receptors. Signup and view all the answers

How do drugs that inhibit the metabolism of norepinephrine affect its levels?

Increase norepinephrine levels Signup and view all the answers

What is a key effect of sympathomimetics on the parasympathetic response?

Decreases parasympathetic activity Signup and view all the answers

Study Notes

Sympathetic Nervous System and Noradrenergic Transmission

Sympathomimetic drugs increase the sympathetic response, while sympatholytic drugs block the sympathetic response. This means that sympathomimetic drugs inhibit the parasympathetic response and vice versa.
Direct-acting sympathetic drugs mimic the action of norepinephrine (NA), while indirect-acting sympathetic drugs influence the release or termination of NA.
The sympathetic nervous system is responsible for the "fight or flight" response, preparing the body for stressful situations.
The presynaptic α2 receptor in the sympathetic nervous system inhibits Ca2+ influx, leading to a decrease in norepinephrine release.

Noradrenaline (NA) Synthesis, Storage, Release, and Termination

NA synthesis: Tyrosine is converted to dopamine, which is then converted to NA.
NA storage: NA is stored in synaptic vesicles.
NA release: NA is released into the synapse in response to nerve stimulation.
NA termination: NA is terminated through reuptake into the presynaptic neuron and metabolism by enzymes like Monoamine Oxidase (MAO) and Catechol-O-methyl transferase (COMT).

Indirect-Acting Sympathetic Drugs: Displacers of NA

Reserpine blocks the vesicular monoamine transporter (VMAT), which prevents the transport of NA into storage vesicles. This leads to a decrease in available NA, blocking sympathetic transmission, and potentially causing depression and parkinsonism.
Amphetamines enter the presynaptic neuron and displace NA from storage vesicles, increasing NA release. They also inhibit NA reuptake.

Catechol-O-Methyl Transferase (COMT) Inhibitors

COMT inhibitors prevent the metabolism of dopamine, primarily used in the treatment of Parkinson's disease due to dopamine deficiency in the basal ganglia.
Tolcapone and entacapone are examples of COMT inhibitors.
Some COMT inhibitors act in the periphery (tolcapone, entacapone), while others act in the brain (tolcapone).

Sites of Action of Drugs Affecting Noradrenergic Neurotransmission

Presynaptic neuron: Drugs can act on the synthesis, storage, release, and reuptake of NA.
Postsynaptic receptor: Drugs can either activate or block the NA receptors.

Resources for Learning

Osmosis videos: Consider utilizing "Adrenergic antagonists: presynaptic antagonists," "Monoamine oxidase inhibitors," and "Psychomotor stimulants" videos to supplement your understanding.

Noradrenergic Transmission and Indirect-Acting Sympathetic Drugs

Indirect-acting sympathetic drugs affect the sympathetic nervous system by acting inside the post-ganglionic neuron.
These drugs enhance or inhibit the sympathetic nervous system by affecting the synthesis, storage, release, re-uptake or binding of NA to its target receptors.

Drug Classes Affecting Noradrenergic Neurotransmission

Drugs that affect NA storage: These drugs displace NA from the presynaptic neuron, including methyldopa, reserpine, amphetamines.
Drugs that affect NA reuptake: These drugs inhibit NA reuptake into the presynaptic neuron, including cocaine and antidepressants.
Drugs that affect NA metabolism: These drugs inhibit the metabolism of NA.

Presynaptic Feedback Control of the Sympathetic Nervous System

The inhibitory feedback mechanism is mediated through the α2 receptors.
Activation of presynaptic α2 receptors activates Gi protein, which inhibits adenylyl cyclase.
This inhibition prevents the opening of calcium channels, decreasing exocytosis and inhibiting the release of NA.

Reserpine

Reserpine blocks the vesicular monoamine transporter (VMAT), preventing the transport of noradrenaline and other amines into storage vesicles.
This leads to an accumulation of NA in the cytoplasm, where it is degraded by monoamine oxidase (MAO).
Reserpine depletes NA, serotonin (5-HT), and dopamine from neurons in the brain.
Adverse effects: depression, parkinsonism, gynaecomastia.

Indirect-Acting Sympathomimetic Drugs

Displacers of NA: These drugs are structurally similar to NA and are taken up into the presynaptic neuron by the NA transporter (NET).
Once inside, they displace NA from storage vesicles, leading to an increase in NA concentration in the synapse.
They also reduce NA reuptake via NET, enhancing the action of the released NA.
Examples include amphetamine, methylphenidate, and atomoxetine.

Clinical Uses of Displacers of NA

Amphetamine: Narcolepsy, ADHD.
Methylphenidate: ADD, ADHD.
Atomoxetine: ADHD.

Widespread Effects of Indirect-Acting Sympathomimetic Drugs

They increase NA levels in the synapse, activating all adrenergic receptors (α and β).
This results in various effects throughout the body:
- Bronchodilation
- Raised arterial pressure
- Peripheral vasoconstriction
- Increased heart rate and force of myocardial contraction
- Inhibition of gut motility.

Central Effects of Displacers of NA

They have significant central effects:
- Appetite suppression
- CNS stimulant effects
- Potential for abuse.

Therapeutic Uses of Indirect-Acting Sympathomimetic Drugs

They have limited therapeutic uses due to their widespread and significant effects.

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Description

This quiz covers the fundamental concepts of the sympathetic nervous system and noradrenergic transmission. You will learn about the roles of sympathomimetic and sympatholytic drugs, the mechanisms of norepinephrine synthesis, and its impacts on the body's fight or flight response.