ANS - Adrenergic Receptor Signaling: L7

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Questions and Answers

What is the primary neurotransmitter involved in postganglionic sympathetic synapse transmission?

Noradrenaline (correct)

Acetylcholine

Dopamine

Serotonin

Which of the following processes occurs during noradrenergic transmission?

Synthesis and release (correct)

Electrochemical amplification

Atomization of neurotransmitter

Decomposition of neurotransmitter

Which type of receptors is primarily affected by drugs that interact with noradrenergic transmission?

Serotonergic receptors

Noradrenaline receptors (correct)

Dopaminergic receptors

Nicotinic receptors

What is a potential physiological consequence of interfering with cholinergic transmission in the autonomic nervous system?

Altered secretions Signup and view all the answers

Which of the following best describes the role of acetylcholine in the autonomic nervous system?

It functions at all ganglia and with muscarinic receptors in post-ganglionic transmission Signup and view all the answers

What is the rate-limiting step in the synthesis of acetylcholine?

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

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

Acetylcholinesterase Signup and view all the answers

What mechanism is blocked by vesamicol during the synthesis of acetylcholine?

Uptake of acetylcholine into presynaptic vesicles Signup and view all the answers

What are the products of the enzymatic reaction catalyzed by acetylcholinesterase?

Choline and acetic acid Signup and view all the answers

What is the role of hemicholinium in cholinergic transmission?

It blocks the reuptake of choline Signup and view all the answers

What is a primary effect of muscarinic receptor agonists on cardiovascular function?

Decrease heart rate Signup and view all the answers

Which receptor type is mainly involved in gastric acid secretion?

M1 Signup and view all the answers

What is the effect of atropine on muscarinic receptors?

Inhibit secretions Signup and view all the answers

Which of the following substances does NOT hydrolyze by acetylcholinesterase (AChE)?

Muscarine Signup and view all the answers

In the context of muscarinic actions, which of the following describes the primary effect of pilocarpine?

Stimulation of smooth muscle contraction Signup and view all the answers

Which cell signaling pathway is activated by the M2 muscarinic receptor subtype?

Increase in cAMP Signup and view all the answers

What physiological effect does muscarinic activation have on the eye?

Contraction of the ciliary muscle Signup and view all the answers

Which of the following statements is true regarding cholinergic transmission?

Muscarinic effects are paralysed by atropine Signup and view all the answers

Which muscarinic receptor subtype is primarily found in exocrine glands?

M3 Signup and view all the answers

What is a characteristic effect of muscarinic antagonists?

Dry mouth Signup and view all the answers

Study Notes

Adrenergic Receptor Signaling

Adrenergic receptors are a family of G protein-coupled receptors (GPCRs) that bind to catecholamines like norepinephrine and epinephrine.
Different types of adrenergic receptors, α1, α2, β1, β2, and β3, have different signaling pathways and effects.
α1 receptors are mostly excitatory, activating Gq proteins and increasing inositol phosphates (IP3) and diacylglycerol (DAG), leading to calcium mobilization.
α2 receptors mostly inhibitory, activating Gi proteins and decreasing cAMP levels and calcium channels.
β1,β2, and β3 receptors are mostly excitatory, activating Gs proteins and increasing cAMP levels

Adrenergic Receptor Agonists and Antagonists

Norepinephrine, epinephrine, and phenylephrine are α1-agonists.
Methyl NE and clonidine are α2-agonists
Isoproterenol, albuterol, and dobutamine are β-agonists

cAMP Pathway

Activated β-adrenergic receptors activate Gs proteins, stimulating adenylyl cyclase to convert ATP to cAMP.
cAMP activates protein kinase A (PKA), which leads to downstream effects, including smooth muscle relaxation and vasodilation.

Inositol-Phospholipid-Calcium Pathway

Activated α1-adrenergic receptors activate Gq proteins, stimulating phospholipase C (PLC) to cleave phosphatidylinositol 4,5-bisphosphate (PIP2) into diacylglycerol (DAG) and inositol trisphosphate (IP3).
IP3 causes calcium release from intracellular stores, and DAG activates protein kinase C (PKC).
Calcium and PKC activity lead to downstream effects, including smooth muscle contraction and vasoconstriction.

The Sympathetic Synapse

Summary of noradrenergic transmission (synthesis, storage, release, inactivation, and receptors).
Drugs interacting with noradrenergic transmission affecting autonomic processes, especially blood pressure regulation.

Noradrenergic Varicosity

The synthesis, storage, release, and metabolism of norepinephrine (NA).
Drugs that interfere are MAO inhibitors, reserpine, α and β-adrenergic receptor agonists and antagonists, and uptake inhibitors for NA uptake 1 and 2.

Cholinergic Transmission in the Autonomic Nervous System

Acetylcholine (ACh) is a neurotransmitter in the autonomic nervous system, acting at both ganglionic and postganglionic synapses.
Acetylcholine synthesis: substrates choline and Acetyl CoA. The rate-limiting step is choline uptake into the nerve terminal. The enzyme is Choline acetyltransferase (CAT).
Acetylcholine release: taken up by vesicles via active transport, blocked by Vesamicol. Released in response to calcium entry into the presynaptic terminal..

Cholinergic Receptors

Nicotinic receptors: located at all autonomic ganglia, and neuromuscular junctions.
Muscarinic receptors: located in the postganglionic synapses of the parasympathetic nervous system
- ACh receptor subtypes (M1, M2, M3).
  - Tissue distribution and physiological roles

Inactivation of Acetylcholine

Acetylcholinesterase (AChE) in the synaptic cleft breaks down ACh into choline and acetic acid

Muscarinic Transmission

Muscarinic agonists: Muscarine, pilocarpine, carbachol, Bethanechol, Oxotremorine
Muscarinic antagonists: Atropine and pirenzepine.
Actions: effects on the heart rate, blood vessels, the eye and other effects involving smooth muscles and CNS function.
Clinical Uses: treating glaucoma, motion sickness and other conditions

Muscarinic Receptor Subtypes

M1, M2, M3, & M4 are subtypes of muscarinic receptors, each with distinct functions.
M1 is mainly located in the CNS. M2 in the heart and presynaptic terminals. M3 in glands, smooth muscle, and vascular endothelium

Eye Effects and Glaucoma Treatments

Muscarinic agonists, like pilocarpine, can reduce intraocular pressure in glaucoma by increasing aqueous humor outflow.
Other treatments for glaucoma include carbonic anhydrase inhibitors (like acetazolamide) and topical beta-blockers (like timolol).

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Description

Test your knowledge on adrenergic receptors and their signaling pathways. This quiz covers various receptor types, their agonists and antagonists, and the cAMP pathway. Understand the roles of excitatory and inhibitory receptors in the body.