Parasympathetic Nervous System Quiz

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Questions and Answers

What is the primary function of the parasympathetic nervous system?

Enhance cardiovascular activity

Stimulate the fight or flight response

Regulate body functions during rest and digestion (correct)

Increase physical exertion and stress responses

Which drug classification is used primarily to treat conditions with increased parasympathetic activity?

Beta-agonists

Alpha-antagonists

Anticholinergic drugs (correct)

Cholinergic drugs

What enzyme is responsible for inactivating acetylcholine?

Acetylase

Cholinesterase

Choline acetyltransferase

Acetylcholinesterase (correct)

Which condition is NOT treated with cholinergic drugs?

Asthma Signup and view all the answers

Which receptor type is associated with smooth and cardiac muscle?

Muscarinic receptors Signup and view all the answers

Anticholinergic drugs are indicated for treating which of the following conditions?

Overactive bladder Signup and view all the answers

Which type of cholinergic receptor is located at the neuromuscular junction?

Nicotinic-muscle (Nm) receptor Signup and view all the answers

What is one of the primary effects of parasympathetic stimulation on the gastrointestinal system?

Increased motility Signup and view all the answers

What is the primary neurotransmitter released by parasympathetic nerves?

Acetylcholine Signup and view all the answers

Which type of receptor is primarily located at the neuromuscular junction?

Nicotinic receptor Signup and view all the answers

What type of drug decreases the activity of the parasympathetic nervous system?

Anticholinergic drugs Signup and view all the answers

What is the main function of acetylcholine (ACh) once it is released into the synaptic cleft?

To initiate a nerve impulse in postganglionic fibers. Signup and view all the answers

M2 receptors primarily affect which part of the body?

Cardiac muscle Signup and view all the answers

Which enzyme is primarily responsible for the degradation of acetylcholine in the synaptic cleft?

Acetylcholinesterase. Signup and view all the answers

What occurs during the synthesis of acetylcholine in the nerve terminal?

Acetyl group is sourced from acetyl-CoA. Signup and view all the answers

Which of the following actions can acetylcholine produce?

Contract smooth muscle Signup and view all the answers

What type of receptors are primarily stimulated by acetylcholine in the cardiovascular system?

Muscarinic receptors. Signup and view all the answers

Which process allows choline to be recycled back into the neuron?

Active transport via a sodium-coupled system. Signup and view all the answers

What is the role of atropine in relation to acetylcholine?

It blocks muscarinic actions. Signup and view all the answers

What effect does acetylcholine have on the gastrointestinal tract (GIT)?

Increases motility and tone. Signup and view all the answers

Which of the following statements about the parasympathetic nervous system is true?

It conserves energy and is active when the body is at rest. Signup and view all the answers

Which of the following correctly describes the two types of acetylcholine esterase enzymes?

True cholinesterase is specific and found in nerve endings; pseudocholinesterase is non-specific and found in plasma. Signup and view all the answers

What biological response results from the binding of acetylcholine to nicotinic receptors located on ganglia?

Initiation of a nerve impulse in postganglionic fibers. Signup and view all the answers

What is the role of nitric oxide (NO) in the vasodilation process initiated by acetylcholine?

It is released from the endothelium to promote vasodilation. Signup and view all the answers

Study Notes

Pharmacology 1 (PPT301) - Lecture 6

Parasympathetic Nervous System (Muscarinic Agonists): Lecture focusing on the parasympathetic nervous system and muscarinic agonists.
Learning Objectives: Students will be able to describe the neuronal release and inactivation of acetylcholine; list the three types of cholinergic receptors and their locations; compare the pharmacologic actions of direct and indirect-acting cholinergic drugs; list clinical indications for indirect-acting anticholinesterase drugs; describe pharmacologic actions, uses, and adverse effects of anticholinergic drugs; and list preferred drug treatments for common parasympathetic conditions.
Introduction: The autonomic nervous system controls internal organ function. The parasympathetic system is active during rest and is responsible for digestion and waste elimination, increasing activity in the gastrointestinal and genitourinary systems and decreasing the activity in the cardiovascular system. Drugs that increase parasympathetic activity (cholinergic) treat conditions like Alzheimer's disease, glaucoma, myasthenia gravis, and urinary/intestinal stasis. Conversely, drugs that decrease parasympathetic activity (anticholinergics) treat overactive bladder/bowel conditions, asthma, COPD, motion sickness, and aid in ophthalmic procedures.

Key Terms

Acetylcholinesterase: An enzyme that inactivates acetylcholine.
Anticholinergic: Drugs or effects that reduce parasympathetic activity.
Cholinergic: Refers to nerves, receptors, and drugs that stimulate the parasympathetic nervous system.
Muscarinic Receptor: Older term for the cholinergic receptor found in smooth and cardiac muscle.
Nicotinic-Muscle (Nm) Receptor: Cholinergic receptor at the neuromuscular junction of skeletal muscle.
Nicotinic-Neural (Nn) Receptor: Cholinergic receptor at parasympathetic and sympathetic ganglia.
Parasympatholytic: Drugs that decrease parasympathetic activity (anticholinergics)
Parasympathomimetic: Drugs that mimic parasympathetic stimulation (cholinergics).

Nervous System

The central nervous system includes the brain and spinal cord; the peripheral nervous system further divides into sensory and motor divisions. The motor division contains the somatic and autonomic systems, the latter being divided into sympathetic and parasympathetic divisions.

Cholinergic Transmission

Acetylcholine (ACh) is located at the neuromuscular junction (somatic nervous system), sympathetic ganglia, sympathetic postsynaptic fibers, all parasympathetic ganglia, and postganglionic parasympathetic nerves.

Two Major Classes of ACh Receptors

Nicotinic receptors: A ligand-gated ion channel; located in skeletal muscle.
Muscarinic receptors: G protein-coupled receptors; subtypes M₁, M₂, and M₃, with locations including the CNS, peripheral neurons, gastric parietal cells, cardiac tissue, and glandular/smooth muscle.

Action of ACh

Muscarinic actions: Can be blocked by atropine; affect smooth muscle, cardiac muscle, and glands.
Nicotinic actions: Can be blocked by hexamethonium or d-tubocurarine; affect autonomic ganglia and neuromuscular junctions.

Acetylcholine Synthesis

Acetylcholine is synthesized in nerve terminals from choline using choline acetyltransferase (CAT) and acetyl-CoA.

Recycling of Choline

Choline is reabsorbed into neurons using a sodium-coupled, high-affinity uptake system, then acetylated to form ACh, ready for subsequent release as needed.

Degradation of Acetylcholine

Acetylcholine is rapidly degraded by acetylcholinesterase (AChE) within the synaptic cleft, limiting its duration of action. Two types: a specific AChE found primarily in nerve endings, neuromuscular junctions, and red blood cells (RBCs); a non-specific AChE present in plasma, intestines, liver, and skin.

Muscarinic Actions (Cardiovascular)

Heart: Decreased force of contraction (primarily in atria), inhibition of AV conduction and decreased automaticity.
Blood Pressure: Decreased blood pressure due to vasodilation and decreased cardiac output. Vasodilation is due to NO release by endothelium.

Smooth Muscles

Gastrointestinal (GIT): Increased tone/motility and relaxation of sphincters.
Urinary Bladder: Contraction of bladder muscles and relaxation of sphincters.
Respiration: Increased bronchial secretions and contraction/spasm of bronchioles.
Exocrine Glands: Stimulation of secretions in glands innervated by the parasympathetic nervous system.

Eye

Pupil: Parasympathetic stimulation causes pupil constriction (miosis), while sympathetic stimulation causes dilation (mydriasis). Atropine paralyzes the ciliary muscle and leads to loss of accommodation (cycloplegia).

Nicotinic Actions (in Skeletal muscle, Autonomic ganglions)

Skeletal muscles: Causes muscle twitching due to depolarization of the motor end plate.
Autonomic ganglia: Increases blood pressure in the presence of atropine.
Unwanted effects of ACh: Sweating, salivation, increased tear production(lacrimation), intestinal pain, cramps, diarrhea, flushing, difficult breathing, and hypotension can occur.

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Description

Test your knowledge on the parasympathetic nervous system with this quiz. It covers primary functions, drug classifications, and neurotransmitter details related to parasympathetic activity. Perfect for students studying anatomy or pharmacology.