Autonomic Nervous System Mechanisms

Questions and Answers

What is the effect of α1 adrenergic receptor activation on intracellular calcium?

Variable effect on intracellular calcium

Increase in intracellular calcium (correct)

Decrease in intracellular calcium

No effect on intracellular calcium

Which of the following is an agonist of muscarinic receptors?

Noradrenaline

Carbachol (correct)

Atropine

Propranolol

What is the effect of M2 receptor activation on heart rate?

Variable effect on heart rate

Increase in heart rate

No effect on heart rate

Decrease in heart rate (correct)

Which of the following is an antagonist of nicotinic receptors?

Hexamethonium Signup and view all the answers

What is the effect of β1 adrenergic receptor activation on adenyl cyclase?

Activation of adenyl cyclase Signup and view all the answers

Which of the following receptors is coupled to Gi protein?

M2 Signup and view all the answers

What is the effect of M3 receptor activation on smooth muscle cells?

Contraction of smooth muscle cells Signup and view all the answers

Which of the following is a characteristic of nicotinic receptors?

Increase in cation permeability Signup and view all the answers

What is the primary function of Neostigmine in clinical use?

To inhibit Acetylcholine esterase Signup and view all the answers

What type of receptor is involved in the modulation of sympathetic signal transduction?

α2 receptor Signup and view all the answers

What is the primary function of Bethanechol in clinical use?

To treat dry mouth and urinary retention Signup and view all the answers

What is the role of VMAT in the modulation of sympathetic signal transduction?

To store Noradrenaline Signup and view all the answers

What is the role of Tyrosine hydroxylase in the modulation of sympathetic signal transduction?

To synthesize Dopamine Signup and view all the answers

What is the role of MAO in the modulation of sympathetic signal transduction?

To break down Dopamine Signup and view all the answers

What is the primary function of Hyoscine butylbromide in clinical use?

To alleviate abdominal cramp and oesophageal spasms Signup and view all the answers

What is the final step in the synthesis of Noradrenaline from Tyrosine?

Dopamine β-hydroxylase converts Dopamine to Noradrenaline Signup and view all the answers

What is the role of calcium ions in cholinergic signal transduction?

Facilitating the synthesis of acetylcholine Signup and view all the answers

What is the effect of tetrodotoxin on cholinergic signal transduction?

Inhibiting the release of acetylcholine Signup and view all the answers

What is the role of hemicholinium in cholinergic signal transduction?

Inhibiting the synthesis of acetylcholine Signup and view all the answers

What is the effect of botulinum toxin on cholinergic signal transduction?

Inhibiting the release of acetylcholine Signup and view all the answers

What is the role of vesamicol in cholinergic signal transduction?

Inhibiting the storage of acetylcholine Signup and view all the answers

What is the effect of atropine on cholinergic signal transduction?

Inhibiting the receptor binding site Signup and view all the answers

What is the role of edrophonium in cholinergic signal transduction?

Inhibiting the degradation of acetylcholine Signup and view all the answers

What is the effect of tubocurarine on cholinergic signal transduction?

Inhibiting the receptor binding site Signup and view all the answers

Which of the following is NOT a stimulus for the baroreflex in blood pressure control?

Changes in heart rate Signup and view all the answers

What is the primary function of afferent nerve endings in the baroreflex mechanism?

To transmit signals to the NTS Signup and view all the answers

Which of the following medications is used to treat overactive bladder?

Mirabegron Signup and view all the answers

What is the mechanism of action of clonidine?

Alpha 2 receptor agonist Signup and view all the answers

Which of the following medications is used to treat anaphylaxis?

Adrenaline Signup and view all the answers

What is the primary function of the NTS in the baroreflex mechanism?

To compare blood pressure to a set point Signup and view all the answers

Which of the following medications is used to treat asthma?

Salbutamol Signup and view all the answers

What is the effect of increasing blood pressure on the arterial wall?

It stimulates afferent nerve endings Signup and view all the answers

What is the primary function of dopamine β-hydroxylase in sympathetic signal transduction?

To convert dopamine into norepinephrine Signup and view all the answers

What is the effect of reserpine on sympathetic signal transduction?

It decreases the release of norepinephrine from the synaptic cleft Signup and view all the answers

Which of the following is an indirect sympathomimetic?

Cocaine Signup and view all the answers

What is the enzyme responsible for converting tyrosine into DOPA?

Tyrosine hydroxylase Signup and view all the answers

Which of the following is a direct sympathomimetic?

Phenylephrine Signup and view all the answers

What is the effect of carbidopa on the synthesis of dopamine?

It increases the synthesis of dopamine Signup and view all the answers

What is the primary function of MAO in sympathetic signal transduction?

To break down norepinephrine Signup and view all the answers

What is the effect of α2 receptor activation on sympathetic signal transduction?

It decreases the release of norepinephrine Signup and view all the answers

Study Notes

Cholinergic Signaling

M2 receptors coupled with Gi protein decrease cAMP and intracellular calcium, found in autonomic ganglia, NMJ, and CNS.
M3 receptors coupled with Gq protein increase intracellular calcium and activate PKC, found in target tissues (heart, glands, smooth muscles).
Agonists: Acetylcholine, carbachol, nicotine, muscarine.
Antagonists: Tubocurarine, hexamethonium, mecamylamine, atropine, dicycloverine, oxybutynin.

Adrenergic Signaling

Adrenergic receptors (α1, α2, β1, β2, β3) are G-protein coupled receptors with 7 transmembrane domains.
Found in target tissues (heart, lungs, glands, smooth muscles).
α1 receptors coupled with Gq protein increase intracellular calcium and activate PKC.
α2 receptors coupled with Gi protein decrease intracellular calcium and inhibit PKA.
β1, β2, β3 receptors coupled with Gs protein increase intracellular calcium and activate PKA.
Agonists: Noradrenaline, adrenaline, Isoprenaline, phenylephrine.
Antagonists: Propranolol, atenolol, prazosin.

Parasympathetic Signaling

Acetylcholine in the heart activates M2 receptor, decreasing heart rate.
Acetylcholine in smooth muscle cells activates M3 receptor, causing contraction.

Modulation of Cholinergic Signal Transduction

Modulation of acetylcholine synthesis, storage, release, receptor binding, re-uptake, and degradation.
Inhibitors: Tetrodotoxin, vesamicol, botulinum toxin, hemicholinium.
Agonists: Edrophonium, neostigmine.

Clinical Use

Hyoscine butylbromide: treats abdominal cramp, oesophageal and bladder spasms.
Bethanechol: treats dry mouth and urinary retention.
Neostigmine: acetylcholine esterase inhibitor.

Sympathetic Neuroeffector Junction

Modulation of tyrosine hydroxylase, dopamine, and noradrenaline synthesis, storage, release, receptor binding, re-uptake, and degradation.
Inhibitors: α-methyl-p-tyrosine, carbidopa, reserpine, MAO inhibitors, COMT.
Agonists: Imipramine, cocaine, guanethidine.

Sympathomimetics

Direct sympathomimetics: activate adrenoceptors directly (e.g., phenylephrine).
Indirect sympathomimetics: increase noradrenaline concentration in the synaptic cleft (e.g., amphetamine, tyramine, ephedrine).

Clinical Use of Sympathomimetics

Clonidine: alpha2 agonist, treats hypertension.
Adrenaline: adrenergic receptor agonist, treats heart restart and anaphylaxis.
Prazosin: alpha1 antagonist, treats hypertension.
Salbutamol: beta2 agonist, treats asthma.
Mirabegron: beta3 receptor agonist, treats overactive bladder.

The SNS and PNS work together to mediate baroreflex in BP control.
↑ BP distends arterial wall, stimulating afferent nerve endings, which send a signal to the NTS, comparing the BP signal to a set point.

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Description

This quiz covers the mechanisms of the autonomic nervous system, focusing on the M2 and M5 muscarinic receptors, their functions, and the impact of various agonists and antagonists. Test your understanding of excitatory and inhibitory signaling pathways, as well as the role of cAMP and intracellular calcium. Ideal for students studying physiology or pharmacology.