Autonomic Nervous System Agents Overview
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Questions and Answers

Which of the following medications is primarily used as a tocolytic agent?

  • Ritodrine (correct)
  • Salmeterol
  • Methylphenidate
  • Mirabegron

What is the main therapeutic use of Mirabegron?

  • Uterine relaxation during pregnancy
  • Treatment of bronchial asthma
  • Attention deficit hyperactivity disorder
  • Overactive bladder management (correct)

Which of the following drugs is commonly associated with tachyphylaxis upon repeated dosing?

  • Amphetamines (correct)
  • Atomoxetine
  • Modafinil
  • Levalbuterol

Which drug would be most appropriate for treating a patient with ADHD who requires a non-stimulant option?

<p>Atomoxetine (A)</p> Signup and view all the answers

Based on its effects on the cardiovascular system, which medication is the vasopressor of choice during pregnancy?

<p>Ephedrine (A)</p> Signup and view all the answers

Which of the following statements about amphetamines is incorrect?

<p>They are non-addictive substances. (C)</p> Signup and view all the answers

Which of the following is a risk associated with Pemoline?

<p>Life-threatening hepatotoxicity (D)</p> Signup and view all the answers

Which of the following actions best describes the mechanism of indirectly acting sympathomimetics?

<p>Increase release of norepinephrine in the synaptic cleft (D)</p> Signup and view all the answers

What type of drug would increase heart rate by mimicking the sympathetic nervous system?

<p>Adrenergic drug (B)</p> Signup and view all the answers

Which of the following receptor types is NOT primarily associated with the sympathetic nervous system?

<p>Muscarinic (C)</p> Signup and view all the answers

What is the main effect of stimulating alpha1 adrenergic receptors?

<p>Constriction of arterioles (A)</p> Signup and view all the answers

Which type of drug action produces opposing responses in the same organ?

<p>Sympathomimetic and Cholinergic drugs (A)</p> Signup and view all the answers

Which receptor subtype would primarily mediate the response to a drug that stimulates the sympathetic system causing decreased activity in the gastrointestinal tract?

<p>Beta2 (C)</p> Signup and view all the answers

What happens when acetylcholine is inactivated by acetylcholinesterase before reaching receptor cells?

<p>Decreased parasympathetic effects (D)</p> Signup and view all the answers

Which drug type would block signals from the parasympathetic nervous system?

<p>Parasympatholytic (C)</p> Signup and view all the answers

Which adrenergic receptor type is widely distributed in blood vessels and is primarily responsible for vasoconstriction?

<p>Alpha1 (B)</p> Signup and view all the answers

What is the primary action of dopamine at a dose of 1-2 µg/kg/min?

<p>Renal vasodilation (B)</p> Signup and view all the answers

Which agent is primarily used to increase blood pressure in hypotensive states?

<p>Phenylephrine (D)</p> Signup and view all the answers

Which of the following medications is a selective β₁ agonist?

<p>Prenaltrenol (B)</p> Signup and view all the answers

What is a common side effect associated with prolonged use of nasal decongestants like naphazoline?

<p>Atrophic rhinitis (B)</p> Signup and view all the answers

Which agent is known for its use in the treatment of glaucoma?

<p>Apraclonidine (C)</p> Signup and view all the answers

What is one of the uses of clonidine beyond hypertension treatment?

<p>Diarrhea control in diabetics (B)</p> Signup and view all the answers

What condition is Midodrine, a prodrug, used to treat?

<p>Hypotension (B)</p> Signup and view all the answers

Which medication is contraindicated due to the risk of hemorrhagic stroke?

<p>Phenylpropanolamine (B)</p> Signup and view all the answers

What primary function does the autonomic nervous system (ANS) perform?

<p>Control and regulation of smooth muscles and glands (C)</p> Signup and view all the answers

Which neurotransmitter is primarily associated with the sympathetic nervous system?

<p>Norepinephrine (A)</p> Signup and view all the answers

What distinguishes the efferent pathways of the autonomic nervous system?

<p>They can be classified into sympathetic and parasympathetic branches. (C)</p> Signup and view all the answers

In contrast to the autonomic nervous system, what type of control does the somatic nervous system provide?

<p>Voluntary control over skeletal muscles (A)</p> Signup and view all the answers

Identify the receptors associated with the adrenergic system.

<p>Beta1, beta2, alpha1, and alpha2 receptors (D)</p> Signup and view all the answers

What is the role of afferent neurons in the autonomic nervous system?

<p>They send sensory information to the CNS for processing. (C)</p> Signup and view all the answers

Which system is responsible for promoting 'rest and digest' functions in the body?

<p>Parasympathetic nervous system (D)</p> Signup and view all the answers

Which of the following accurately describes the autonomic nervous system?

<p>It functions independently from conscious control. (B)</p> Signup and view all the answers

What is the primary action of selective alpha1 blockers?

<p>Decrease blood pressure (B)</p> Signup and view all the answers

Which of the following is a characteristic of phenoxybenzamine?

<p>It is an irreversible antagonist. (D)</p> Signup and view all the answers

Which condition is primarily treated using selective alpha1 blockers?

<p>Benign hyperplasia of prostate (B)</p> Signup and view all the answers

What adverse effect is commonly associated with the first few doses of selective alpha1 blockers?

<p>Postural hypotension (D)</p> Signup and view all the answers

Which drug is specifically used to prevent hypertensive episodes in pheochromocytoma?

<p>Phenoxybenzamine (B)</p> Signup and view all the answers

What is a notable difference between nonselective and selective alpha-blockers regarding tachycardia?

<p>Nonselective alpha blockers lead to marked tachycardia. (B)</p> Signup and view all the answers

Which selective alpha1 blocker has a unique action on prostatic receptors?

<p>Silodosin (A)</p> Signup and view all the answers

What is a potential effect of long-term use of selective alpha1 blockers?

<p>Tolerance to postural hypotension (C)</p> Signup and view all the answers

What effect does stimulation of beta1 receptors have on the body?

<p>Increases myocardial contractility (C)</p> Signup and view all the answers

Which receptor is primarily responsible for bronchodilation?

<p>Beta2 receptor (C)</p> Signup and view all the answers

What is one of the main roles of dopaminergic receptors in the body?

<p>Dilates vessels to increase blood flow (D)</p> Signup and view all the answers

How are neurotransmitters primarily inactivated after their function?

<p>Via reuptake into the neuron (A)</p> Signup and view all the answers

Which enzymes are responsible for the degradation of norepinephrine in the body?

<p>MAO and COMT (B)</p> Signup and view all the answers

Which functional effects are associated with the stimulation of beta2 receptors?

<p>Relaxation of uterine muscles (B)</p> Signup and view all the answers

What role does reuptake play in the inactivation of norepinephrine?

<p>It is more important than enzymatic inactivation. (A)</p> Signup and view all the answers

What mnemonic aids in remembering the functions of beta1 and beta2 receptors?

<p>One heart, two lungs (B)</p> Signup and view all the answers

Flashcards

What is the CNS?

The central nervous system (CNS) is made up of the brain and spinal cord.

What is the PNS?

The peripheral nervous system (PNS) is located outside the brain and spinal cord and has two branches: the autonomic and somatic.

What does the ANS control?

The autonomic nervous system (ANS), also called the visceral system, acts on smooth muscles and glands. Its main function is to control and regulate organs like the heart, lungs, stomach, and bladder.

What does the somatic nervous system control?

The somatic nervous system is a voluntary system that controls skeletal muscles. You can consciously move your body.

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What's the sympathetic nervous system's role?

The sympathetic nervous system, also called the adrenergic system, uses norepinephrine as its neurotransmitter. It is responsible for "fight or flight" responses.

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What's the parasympathetic nervous system's role?

The parasympathetic nervous system, also called the cholinergic system, uses acetylcholine as its neurotransmitter. It is responsible for "rest and digest" responses.

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How do the sympathetic and parasympathetic systems interact?

The sympathetic and parasympathetic nervous systems work together to maintain homeostasis, which is a state of balance in the body.

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How do drugs affect the autonomic nervous system?

Drugs can either stimulate or depress the sympathetic and parasympathetic nervous system.

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What are Beta1 receptors and where are they located?

Beta1 receptors are found primarily in the heart, increasing myocardial contractility and heart rate.

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What are Beta2 receptors and their role in the lungs?

Located mainly in the lungs, beta2 receptors cause bronchodilation by relaxing smooth muscles, leading to easier breathing.

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How do Beta2 receptors affect the gastrointestinal tract?

Beta2 receptors also cause relaxation of the smooth muscles in the gastrointestinal tract, reducing its tone and motility.

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What is norepinephrine and what does it do to blood vessels?

Norepinephrine is a neurotransmitter that causes vasoconstriction, which increases blood pressure.

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What is the effect of stimulating alpha receptors on blood pressure?

When stimulated, alpha receptors inhibit the release of norepinephrine, leading to vasodilation and a decrease in blood pressure.

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Where are dopaminergic receptors located and what is their role in blood flow?

Dopaminergic receptors are found in various arteries and dilate vessels upon stimulation, increasing blood flow.

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What is the main way norepinephrine is inactivated?

Reuptake of the neurotransmitter back into the neuron is the primary mechanism for inactivating norepinephrine.

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What enzymes break down norepinephrine?

Two enzymes, MAO and COMT, degrade norepinephrine after it is reuptaken into the neuron.

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Cholinergic Receptors

The cholinergic receptors at organ cells are either nicotinic or muscarinic, meaning that they are stimulated by the alkaloids nicotine and muscarine, respectively.

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Acetylcholine and Acetylcholinesterase

Acetylcholine stimulates the receptor cells to produce a response, but the enzyme acetylcholinesterase may inactivate acetylcholine before it reaches the receptor cell.

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Opposite Effects of Sympathetic and Parasympathetic Mimics

Drugs that mimic the neurotransmitters norepinephrine and acetylcholine produce responses opposite to each other in the same organ.

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Effects on Heart Rate

For example, an adrenergic drug (sympathomimetic) increases the heart rate, whereas a cholinergic drug (parasympathomimetic) decreases the heart rate.

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Similar Effects from Mimicry and Blocking

However, a drug that mimics the sympathetic nervous system and a drug that blocks the parasympathetic nervous system can cause similar responses in the organ.

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Sympathomimetics

Drugs that stimulate the sympathetic nervous system are called adrenergics, adrenergic agonists, or sympathomimetics, because they mimic the sympathetic neurotransmitters nor- epinephrine and epinephrine.

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Adrenergic Receptor Locations

They act on one or more adrenergic receptor sites located in the effector cells of muscles, such as the heart, bronchiole walls, gastrointestinal (GI) tract, urinary bladder, and ciliary muscle of the eye.

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Alpha1-Adrenergic Receptor Effects

The alpha-adrenergic receptors are located in blood vessels, eye, bladder, and prostate. When the alpha1 receptors in vascular tissues (vessels) of muscles are stimulated, the arterioles and venules constrict, increasing peripheral resistance and blood return to the heart. Circulation is improved, and blood pressure is increased.

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Beta-2 agonists

Drugs that stimulate beta-2 receptors in the lungs, relaxing bronchial muscles and improving airflow. Used to treat asthma.

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Indirectly acting sympathomimetics

Drugs that increase the release of norepinephrine (NE) in the synaptic cleft or inhibit its reuptake. They enter nerve cells, displace NE from storage vesicles, and cause its release.

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Mixed action sympathomimetics

Drugs that enhance norepinephrine (NE) release and directly activate both alpha and beta receptors. Commonly used in cold remedies for nasal decongestion and bronchodilation.

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Tachyphylaxis

A common side effect of indirectly acting sympathomimetics occurring with repeated dosing at short intervals. This means the drug's effectiveness decreases rapidly.

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Mirabegron

A drug that acts as a selective beta-3 receptor agonist in the bladder, improving bladder function and reducing urinary frequency. Used to treat overactive bladder.

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Methylphenidate

A drug used for the treatment of attention deficit hyperactivity disorder (ADHD). Prefers because it has a lower risk of abuse compared to amphetamines.

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Modafinil

A drug used for the treatment of narcolepsy and to relieve fatigue in multiple sclerosis. May also be used as an adjunct in obstructive sleep apnea.

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Ephedrine

A drug that is a vasopressor of choice in pregnancy due to its beta-2 mediated vasodilatory action, which helps maintain placental circulation.

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Sympatholytic Drugs

Drugs that block alpha and/or beta-adrenergic receptors, affecting the sympathetic nervous system.

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Nonselective Alpha-Blockers

These drugs block both alpha1 and alpha2 receptors, causing vasodilation and a drop in blood pressure.

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Phenoxybenzamine

A type of nonselective alpha-blocker that causes long-lasting blockage due to forming permanent bonds with receptors.

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Selective Alpha1-Blockers

Drugs that specifically block alpha1 receptors, leading to vasodilation and a reduction in blood pressure.

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Lesser Tachycardia

This effect occurs when alpha1-blockers cause a decrease in blood pressure, but not a significant increase in heart rate.

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Favorable Lipid Profile

Selective alpha1-blockers can improve lipid profiles by raising HDL (good) and lowering LDL (bad) cholesterol.

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Improved Urinary Flow

Selective alpha1-blockers relax smooth muscle in the bladder and prostate, improving urinary flow.

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Postural Hypotension

Selective alpha1-blockers can cause postural hypotension, especially with the first dose or dose increases.

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What is dopamine's role in cardiogenic shock with oliguric renal failure?

Dopamine is the preferred drug for cardiogenic shock linked to oliguric renal failure. It works on D1 (at 1-2 µg/kg/min), β1 (at 2-10 µg/kg/min), and α1 (at over 10 µg/kg/min) receptors. D1 receptor activation causes renal vasodilation, enhancing renal perfusion and GFR.

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Compare dopamine and norepinephrine’s impact on renal function in cardiogenic shock?

Norepinephrine (NA) causes vasoconstriction in the kidneys, worsening renal failure. This contrasts with dopamine’s beneficial effects on renal perfusion.

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What is dobutamine’s primary effect and its unique characteristic?

Dobutamine is a selective β1 agonist that doesn't impact DA receptors. It elevates cardiac output with minimal change in heart rate.

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Describe the combined effects of dopexamine and how it works.

Dopexamine combines β1 and D1 agonist effects with NA reuptake inhibition. It increases cardiac output and improves kidney functions.

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What is fenoldopam's application and its specific mechanism of action?

Fenoldopam is a D1 agonist useful in hypertensive emergencies. It reduces blood pressure by selectively dilating renal blood vessels.

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What are the applications and risks of using α1 agonists as nasal decongestants?

Alpha 1 (α1) agonists like naphazoline, oxymetazoline, and xylometazoline are nasal decongestants. They can cause rebound congestion and atrophic rhinitis (Rhinitis medicamentosa) with prolonged use.

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What are the therapeutic applications of α2 agonists, particularly clonidine?

Clonidine and methyldopa (a prodrug) are α2 agonists used in hypertension management. Clonidine has other benefits: controlling diabetic diarrhea, migraine prophylaxis, withdrawal symptom management, pain relief, and ADHD treatment.

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How are selective α2 agonists, like apraclonidine and dexmedetomidine, therapeutically applied?

Apraclonidine and brimonidine are selective α2 agonists applied topically for glaucoma treatment. Dexmedetomidine, a central α2 agonist, is used for pre-anesthetic medication and sedation.

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Study Notes

Autonomic Nervous System Agents

  • The central nervous system (CNS) is the body's primary nervous system, including the brain and spinal cord.
  • The peripheral nervous system (PNS) is outside the CNS and has two divisions: autonomic and somatic.
  • The autonomic nervous system (ANS) controls involuntary functions like heart rate and digestion, affecting smooth muscles and glands.
  • The somatic nervous system controls voluntary actions, impacting skeletal muscles.
  • The ANS has afferent (sensory) and efferent (motor) neurons.
  • Efferent pathways are divided into sympathetic and parasympathetic branches.
  • The sympathetic and parasympathetic systems act on the same organs but create opposing responses for homeostasis.

Sympathetic Nervous System

  • Also known as the adrenergic system, once believed to use adrenaline as the neurotransmitter.
  • The primary neurotransmitter is norepinephrine.
  • Adrenergic receptors include alpha1, alpha2, beta1, and beta2.
  • Norepinephrine is released from nerve endings, stimulating cell receptors.

Parasympathetic Nervous System

  • Also called the cholinergic system, primarily uses acetylcholine as the neurotransmitter between neurons and the target organ.
  • Cholinergic receptors are either nicotinic or muscarinic, activating by nicotine and muscarine, respectively.
  • Acetylcholinesterase breaks down acetylcholine to prevent prolonged action.
  • Drugs mimicking these neurotransmitters produce opposite effects in organs.

Sympathetic and Parasympathetic Responses to Drugs

  • Sympathomimetics (mimic sympathetic) and parasympathomimetics (mimic parasympathetic) cause opposite responses.
  • Sympatholytics (block sympathetic) and parasympatholytics (block parasympathetic) can cause similar results in certain organs.
  • Sympathetic and parasympathetic responses have opposite effects on various body parts (e.g., pupils dilate/constrict, bronchi dilate/constrict etc).

Adrenergic Agonists

  • Drugs stimulating the sympathetic system, mimicking norepinephrine and epinephrine.
  • Act on adrenergic receptor sites (alpha1, alpha2, beta1, and beta2) in various organs.
  • Alpha receptors found in blood vessels, eye, bladder, prostate, constricting arterioles, increasing blood pressure/improved circulation
  • Alpha2 receptors located in postganglionic endings, inhibiting norepinephrine release, leading to less vasoconstriction and reduced blood pressure.
  • Beta1 receptors predominantly in the heart, increasing myocardial contractility and heart rate. Receptors also located in the kidney impacting blood pressure.
  • Beta2 receptors located in lungs, liver and uterine muscle. Relax smooth muscle, causing bronchodilation, decreasing GI tone/motility, increasing blood glucose, and relaxing uterine muscle.

Inactivation of Neurotransmitters

  • Neurotransmitter action is terminated by reuptake, enzymatic degradation (e.g., MAO, COMT), or diffusion.
  • Drugs can prolong neurotransmitter action by inhibiting reuptake or degradation.

Directly Acting Sympathomimetics

  • Catecholamines (e.g., adrenaline) and non-catecholamines (e.g., isoprenaline) directly stimulate alpha and beta receptors.
  • Adrenaline is a crucial drug for anaphylactic shock, given intramuscularly.

Indirectly Acting Sympathomimetics

  • These drugs increase norepinephrine in the synapse by blocking reuptake or releasing it from storage vesicles.
  • Tyramine and methylphenidate are examples. Methylphenidate is used for ADHD.

Mixed Action Sympathomimetics

  • Drugs with both direct and indirect effects on sympathetic activity.
  • Ephedrine and pseudoephedrine are examples, found in cold remedies.

Sympatholytic Drugs - Alpha Blockers

  • These drugs, in particular phenoxybenzamine (irreversible), phentolamine, and tolazoline (reversible), block alpha receptors.
  • Non-selective alpha blockers result in vasodilation and postural hypotension.
  • Selective alpha1-blockers such as prazosin and terazosin are useful for benign prostatic hyperplasia (BPH) due to relaxation of the prostate and urethra, impacting blood pressure to a lesser degree than non-selective blockers.

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Autonomic Nervous System Agents PDF

Description

This quiz explores the key components of the autonomic nervous system (ANS), detailing its structure and function. It covers the differences between the sympathetic and parasympathetic systems and their roles in regulating involuntary bodily functions. Test your knowledge on neurotransmitters and receptor types involved in these processes.

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