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Questions and Answers
Which adrenergic antagonist is commonly used in cases of hypertension?
Which adrenergic antagonist is commonly used in cases of hypertension?
What effect do beta blockers have on heart rate and contractility?
What effect do beta blockers have on heart rate and contractility?
What type of adrenergic blocker binds and blocks either beta1 or beta2 receptors but not both?
What type of adrenergic blocker binds and blocks either beta1 or beta2 receptors but not both?
Which of the following medications can prevent necrosis when norepinephrine has leaked into tissues?
Which of the following medications can prevent necrosis when norepinephrine has leaked into tissues?
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What does the term 'sympathomimetic' refer to in pharmacology?
What does the term 'sympathomimetic' refer to in pharmacology?
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What is the primary use of atropine in medical treatments?
What is the primary use of atropine in medical treatments?
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Which of the following drugs act as a CNS stimulant?
Which of the following drugs act as a CNS stimulant?
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Which drug is commonly used as an antidote for benzodiazepine overdose?
Which drug is commonly used as an antidote for benzodiazepine overdose?
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What is a common side effect of using paracetamol?
What is a common side effect of using paracetamol?
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Which of the following is a characteristic feature of barbiturates?
Which of the following is a characteristic feature of barbiturates?
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What is the primary neurotransmitter at the autonomic ganglia?
What is the primary neurotransmitter at the autonomic ganglia?
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Which neurotransmitter is primarily associated with the sympathetic postganglionic neuron-effector cell synapses?
Which neurotransmitter is primarily associated with the sympathetic postganglionic neuron-effector cell synapses?
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Which type of receptor does acetylcholine primarily bind to?
Which type of receptor does acetylcholine primarily bind to?
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In which tissues are the exceptions where acetylcholine is released instead of norepinephrine?
In which tissues are the exceptions where acetylcholine is released instead of norepinephrine?
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What are the effects of norepinephrine in renal blood vessels?
What are the effects of norepinephrine in renal blood vessels?
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Which neurotransmitter is released by sympathetic fibers to the thermoregulatory sweat glands?
Which neurotransmitter is released by sympathetic fibers to the thermoregulatory sweat glands?
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What is the main neurotransmitter involved in cholinergic transmission at the neuromuscular junction?
What is the main neurotransmitter involved in cholinergic transmission at the neuromuscular junction?
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Which of the following substances is identified as a chemical signal involved in therapeutic drugs?
Which of the following substances is identified as a chemical signal involved in therapeutic drugs?
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What type of receptors respond to acetylcholine in the parasympathetic system?
What type of receptors respond to acetylcholine in the parasympathetic system?
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Which type of drug is designed to stimulate adrenergic receptors?
Which type of drug is designed to stimulate adrenergic receptors?
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What is the main function of cholinergic antagonists?
What is the main function of cholinergic antagonists?
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Which receptors are primarily found in the adrenal gland?
Which receptors are primarily found in the adrenal gland?
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What is the effect of adrenergic antagonists on the adrenergic response?
What is the effect of adrenergic antagonists on the adrenergic response?
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What type of receptors can be activated by catecholamines?
What type of receptors can be activated by catecholamines?
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What neurotransmitter is released by the sympathetic nervous system at the adrenal gland?
What neurotransmitter is released by the sympathetic nervous system at the adrenal gland?
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What results from the activation of muscarinic receptors in smooth muscles?
What results from the activation of muscarinic receptors in smooth muscles?
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What is the primary effect of cholinergic drugs?
What is the primary effect of cholinergic drugs?
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Which type of antagonist is atropine classified as?
Which type of antagonist is atropine classified as?
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Why should nonselective adrenergic antagonists be avoided in patients with asthma?
Why should nonselective adrenergic antagonists be avoided in patients with asthma?
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What medication is often used for bradycardia treatment in prehospital settings?
What medication is often used for bradycardia treatment in prehospital settings?
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What effect does atropine have at high dosages on the pulmonary system?
What effect does atropine have at high dosages on the pulmonary system?
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Which of the following is a characteristic of cholinergic agonists?
Which of the following is a characteristic of cholinergic agonists?
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Which drug is classified as a cholinergic agonist used for managing poisoning?
Which drug is classified as a cholinergic agonist used for managing poisoning?
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What is the primary action of beta-selective blockers?
What is the primary action of beta-selective blockers?
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Study Notes
Drugs Affecting the Nervous System
- Drugs affecting the nervous system are categorized into modules, with this material being Module 6.
- The nervous system is broken down into peripheral and central nervous systems.
- The peripheral nervous system is further divided into efferent and afferent divisions.
- The efferent division is also split into autonomic and somatic systems.
- The autonomic system affects internal organs, which include intestines and smooth/visceral muscles.
- The somatic system is involved in skeletal muscle movement.
- Autonomic pharmacology discusses drugs that affect the autonomic nervous system.
- The autonomic nervous system has two divisions: parasympathetic (PNS) and sympathetic (SNS).
- The parasympathetic nervous system's main function is "rest and digest."
- The sympathetic nervous system's function is "fight or flight."
- The sympathetic and parasympathetic nervous systems often have opposing actions on organs to maintain homeostasis.
- Key autonomic effector organs and their sympathetic and parasympathetic responses are detailed.
- The central nervous system involves the brain and spinal cord, affecting both.
- Many chemical signals are crucial to nervous system function, including norepinephrine, epinephrine, acetylcholine, dopamine, serotonin, histamine, glutamate, and γ-aminobutyric acid.
- Each chemical signal binds to a specific family of receptors.
Autonomic Pharmacology
- Two main types of neurotransmitters: cholinergic and adrenergic.
- Cholinergic transmission is mediated by acetylcholine (ACh).
- ACh is the primary neurotransmitter in all autonomic ganglia and also at the synapses between parasympathetic postganglionic neurons and effector cells.
- ACh is also the primary neurotransmitter in the somatic (voluntary) skeletal muscle neuromuscular junction.
- Adrenergic transmission uses norepinephrine (NE).
- NE is the primary transmitter at sympathetic postganglionic neuron-effector cell synapses.
- Exceptions exist, like fibers to sweat glands needing ACh
- Dopamine may be a vasodilator transmitter in the renal blood vessels, but NE is a vasoconstrictor in other vessels.
- NE is the primary transmitter at sympathetic postganglionic neuron-effector cell synapses.
Actions of sympathetic and parasympathetic nervous systems on effector organs
- Various effector organs (e.g., eye, heart, kidneys, bladder, GI system) are presented with their corresponding sympathetic and parasympathetic responses.
- Sympathetic responses are often characterized by an increase in activity, such as increased heart rate.
- Parasympathetic responses usually involve decreased activity; for example, decreased heart rate.
Fight or Flight Response vs. Rest and Digest
- Each response has a different system functioning.
- The sympathetic nervous system is responsible for a "fight or flight" response.
- The parasympathetic nervous system is the primary system for the "rest and digest" response.
- These systems have different overall functions and ways of responding to stimuli.
Sympathetic vs. Parasympathetic Nervous Systems
- These two systems maintain homeostasis through balanced activity.
- Sympathetic activity generally dominates during "fight or flight" responses.
- Parasympathetic activity is usually dominant during "rest and digest" states.
Neuron
- Neurons are the basic structural and functional units of the nervous system.
- Axons are the long, slender projections that transmit signals away from the neuron.
- Dendrites are short, branched projections that receive signals from other neurons and transmit them to the cell body where the signals are processed.
- The myelin sheath is an insulating layer that surrounds the axons and helps to speed up the transmission of signals.
- Neurotransmitters are chemical messengers that transmit signals between neurons.
- Neuron-transmitter mechanisms happen via synaptic signaling.
Types of Neurotransmitters
- There are many neurotransmitters in the nervous system impacting and related to drugs.
- Norepinephrine, epinephrine, acetylcholine, dopamine, serotonin, histamine, glutamate, and γ-aminobutyric acid are among the most involved in drug therapies.
- Each of these has receptors, the chemical signals bind to these receptors.
Cholinergic Transmission
- Acetylcholine (ACh) is the primary neurotransmitter for many functions in the nervous system.
- ACh, at all autonomic ganglia, plays a role in the synapses between parasympathetic postganglionic neurons and their effector cells.
- ACh acts at postganglionic sympathetic neurons to control thermoregulatory sweat glands.
Adrenergic Transmission
- Norepinephrine is the primary neurotransmitter in sympathetic systems.
- NE plays a role at sympathetic postganglionic neurons in many pathways.
- NE has important roles including in sweat glands and vasodilation of skeletal muscles.
Motor Fiber
- ACh is released from preganglionic fibers;
- In sympathetic neurons, NE(or EPI) is released.
Receptor Organs
- The autonomic nervous system and neurotransmitters control various organs.
- Adrenergic and cholinergic responses differ considerably by organ.
Drugs Affecting the ANS
- Four main types of drugs are:
- Adrenergic agonists (sympathomimetics)
- Adrenergic antagonists (sympatholytics)
- Cholinergic agonists (parasympathomimetics)
- Cholinergic antagonists (parasympatholytics)
- Drugs affecting the ANS function in several therapeutic ways and areas.
Adrenergic Agonists (Sympathomimetic Drugs)
- Several sympathomimetics are widely used.
- Norepinephrine (Levophed) is an alpha agonist causing vasoconstriction in blood vessels.
- Epinephrine (Adrenaline) impacts both alpha and beta receptors, and is used in cardiac arrest, anaphylaxis, and asthma.
- Albuterol (Ventolin) is a beta2 agonist used for dilation of bronchi and asthma.
- Dopamine affects blood pressure and is used in emergency medicine and critical care.
Adrenergic Antagonists (Sympatholytic Drugs)
- Phentolamine (Regitine) is an alpha blocker, preventing vasoconstriction.
- This can be used in hypertensive crises and necrosis prevention due to extravasation of NE/EPI or dopamine.
- Several medications are categorized as adrenergic antagonists, and useful in several conditions.
- Beta blockers, non-selective or selective, block beta receptors, useful in cardiac disease.
Cholinergic Agonists (Parasympathomimetic Drugs)
- These drugs increase parasympathetic activity.
- Physostigmine (Antilirium) is a treatment for poisoning from atropine-type drugs.
Cholinergic Antagonists (Parasympatholytic Drugs)
- Atropine is a common cholinergic antagonist.
- It's used to treat bradycardia and has other effects on the pulmonary system, leading to bronchodilation and suppressing secretions.
- Atropine is the drug of choice for nerve agent and organophosphate poisoning.
Drugs Affecting CNS
- Several diverse drug types affect the central nervous system (CNS).
- Analgesics, anesthetics, anxiolytics, and sedative-hypnotics, CNS stimulants, antipsychotic drugs, antidepressants, and neurodegenerative drugs, all have important roles in CNS function.
Analgesics
- Analgesics decrease pain sensation.
- Opioid analgesics (e.g., morphine, codeine, fentanyl, hydrocodone), Act on mu and kappa receptors.
- Non-opioid analgesics include salicylates (e.g., aspirin) and nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., ibuprofen, naproxen).
- Acetaminophen is an analgesic but doesn't affect peripheral prostaglandin synthesis.
Opioids
- Opioids are derived from opium, mimicking the actions of endorphins.
- A prototype opioid, morphine, acts primarily on mu receptors.
- The effects of opioids vary by receptor type.
Actions at Opioid Receptors
- Opioids can trigger different actions at opioid receptors, depending on the drug type and the specific receptors it interacts with.
- Some agents are pure agonists or antagonists, or are mixed agonist-antagonists.
Morphine Sulfate
- Morphine Sulfate is an opioid used for pain relief in many areas, including moderate to severe pain.
- Appropriate use of morphine involves evaluating patients and closely monitoring their responses.
- Adverse reactions are presented.
Fentanyl Citrate (Sublimaze)
- Fentanyl is a powerful opioid analgesic.
- It is used in various medical situations requiring strong pain relief.
- It's used for acute pain, as well as sedation, and in some surgical procedures.
- Risks and benefits need to be carefully considered regarding its use.
Ondansetron (Zofran)
- Ondansetron is an antiemetic used to prevent/treat nausea and vomiting.
- It acts by blocking serotonin receptors in the brain.
- Important considerations are presented, as well as relevant adverse effects.
Non-opioid Analgesics
- Salicylates (like aspirin)
- NSAIDs (like ibuprofen, naproxen, and diclofenac) have different mechanisms and therapeutic uses.
NSAID Properties
- Specific NSAIDS have different properties.
- The properties are antipyretic, anti-inflammatory, and analgesic.
CNS Stimulants
- Amphetamines are used for their effects on neurotransmitter release and have several side effects.
- Methylphenidate (Ritalin) is used for attention deficit disorder to increase focus and concentration.
- Methylxanthines (like caffeine and theophylline) act by blocking adenosine receptors.
Anesthetics
- General anesthetics include nitrous oxide and others which act to impact consciousness and loss of sensation.
- Local anesthetics like lidocaine affect areas around injections.
Anti-anxiety & Hypnotic Medications
- These drugs are used for sedation, hypnotism, anxiety reduction, and insomnia relief.
- Two primary classes are barbiturates and benzodiazepines (e.g., diazepam, lorazepam, midazolam, alprazolam).
Mechanism of Action of Anti-Anxiety/Sedative-Hypnotics
- Both barbiturates and benzodiazepines influence/enhance the actions of GABA receptors in the CNS, but do so in different ways.
- GABA is a crucial inhibitory neurotransmitter in the brain.
Benzodiazepines vs. Barbiturates
- Considerations like safety, degree of CNS effect, and abuse potential distinguish these drug types.
Anti-seizure Medications
- Multiple chemical classes lower the frequency of action potentials associated with seizures, useful and essential for a variety of seizure types and conditions.
Psychotherapeutic Medications
- Psychotherapeutic medications treat dysfunction related to neurotransmitter imbalances, typically involving monoamines like norepinephrine, dopamine, and serotonin.
- These medications aim to restore neurotransmitter balance impacting various pathways, symptoms, and conditions.
Antipsychotic Drugs (Neuroleptics)
- Antipsychotic medications are used to address conditions like schizophrenia and other conditions where dopamine release is thought to be too high.
- These medications often lower dopamine activity. Classes include phenothiazines and butyrophenones (e.g., chlorpromazine, haloperidol).
Antipsychotic MOA (Mechanism of Action)
- Antipsychotics often work through receptor antagonism, particularly affecting dopamine receptors in the brain.
- They also, depending on the type of antagonist, may affect muscarinic cholinergic receptors, histaminergic receptors, and adrenergic receptors.
Antipsychotic Side Effects
- Side effects related to antipsychotic use tend to be immediate.
- Extrapyramidal symptoms (EPS)
- Anticholinergic effects (dry mouth, blurred vision, constipation, etc.)
- Orthostatic hypotension (a sudden drop in blood pressure)
- Sedation
- Reduced seizure threshold
Antidepressants
- Antidepressants address imbalances in monoamines (norepinephrine, dopamine, serotonin). Treatments often involve increasing neurotransmitter synthesis within presynaptic nerve endings, boosting neurotransmitter release from these endings, and/or inhibiting reuptake of neurotransmitters by presynaptic endings.
Tricyclic Antidepressants (TCAs)
- TCAs block the reuptake of norepinephrine (NE) and serotonin (5-HT).
- They have similar side effects to phenothiazines, including orthostatic hypotension, sedation, and anticholinergic effects; they can also present cardiac toxicity.
TCA Side Effects
- Orthostatic hypotension, sedation, and anticholinergic effects are among the key side effects of TCAs.
- Cardiac effects, including ventricular arrhythmias, can be serious.
Selective Serotonin Reuptake Inhibitors (SSRIs)
- SSRIs block only serotonin reuptake, unlike TCAs which impact norepinephrine as well.
- They tend to have fewer side effects than TCAs, including no orthostatic hypotension, anticholinergic effects, and cardiac toxicity.
Monoamine Oxidase Inhibitors (MAOIs)
- MAOIs inhibit the enzyme monoamine oxidase, which inactivates monoamines.
- This action can elevate neurotransmitters within the brain.
- Importantly, MAOIs interact with tyramine. This interaction can cause significant side effects, a critical aspect of treatment or patient education.
MAOI Side Effects
- CNS stimulation (anxiety, agitation); orthostatic hypotension; hypertensive crisis (from tyramine consumption).
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Test your knowledge on adrenergic antagonists and CNS stimulants with this quiz. Explore concepts such as beta blockers, sympathomimetics, and neurotransmitters. This quiz provides a comprehensive review of pharmacological agents and their mechanisms of action.
