L6

Question 1

Q: What are the two main chemicals involved in the autonomic nervous system (ANS)?

Answer 1

A: Acetylcholine and noradrenaline.

Question 2

Q: How does the sympathetic nervous system differ from the parasympathetic nervous system in terms of neurotransmitter release?

Answer 2

A: The sympathetic system primarily releases noradrenaline, while the parasympathetic system releases acetylcholine.

Question 3

Q: What are the three divisions of the autonomic nervous system?

Answer 3

A: Sympathetic, parasympathetic, and enteric nervous systems.

Question 4

Q: What type of receptors does acetylcholine bind to in the parasympathetic nervous system?

Answer 4

A: Muscarinic acetylcholine receptors (mAChRs).

Question 5

Q: What is the function of α1-adrenoceptors and which organ systems do they affect?

Answer 5

A: α1-adrenoceptors activate phospholipase C, increase IP3, and cause smooth muscle contraction, leading to vasoconstriction.

Question 6

Q: Name a drug that is an agonist of β2-adrenoceptors and its clinical use.

Answer 6

A: Salbutamol, used as a bronchodilator to treat asthma.

Question 7

Q: What is the role of β1-adrenoceptors in the heart?

Answer 7

A: They increase heart rate and the force of contraction by activating adenylate cyclase and increasing cAMP.

Question 8

Q: What is the primary effect of β2-adrenoceptor activation in smooth muscle?

Answer 8

A: It causes relaxation of smooth muscle by increasing cAMP levels.

Question 8

Q: How do M2 muscarinic acetylcholine receptors affect heart function?

Answer 8

A: M2 receptors inhibit the heart by activating potassium channels, causing hyperpolarization, and reducing Ca2+ channel activity, which decreases heart rate and force of contraction.

Question 9

Q: What enzyme converts noradrenaline to adrenaline in the adrenaline biosynthesis pathway?

Answer 9

A: Phenylethanolamine N-methyltransferase (PNMT).

Question 10

Q: Which drug inhibits noradrenaline uptake in presynaptic neurons, and what is its use?

Answer 10

A: Cocaine; it inhibits noradrenaline uptake, leading to increased stimulation of adrenergic receptors.

Question 11

Q: What is the clinical application of Metoprolol, a β1-adrenoceptor antagonist?

Answer 11

A: It is used to treat conditions such as angina, hypertension, and dysrhythmias.

Question 12

Q: Which enzyme breaks down acetylcholine in the synaptic cleft?

Answer 12

A: Acetylcholinesterase (AChE).

Question 13

Q: What is the function of DOPA decarboxylase in catecholamine biosynthesis?

Answer 13

A: It converts DOPA to dopamine

Question 14

Q: What are the effects of α2-adrenoceptor agonists, such as clonidine, on blood pressure?

Answer 14

A: They lower blood pressure by inhibiting noradrenaline release from presynaptic neurons

Question 15

Q: Explain noradrenergic transmission and how drugs can influence this pathway.

Answer 15

A: Noradrenaline is synthesized from tyrosine and stored in vesicles. It’s released during nerve activation and acts on α and β-adrenoceptors. Drugs like reserpine block its storage, cocaine blocks its reuptake, and MAO inhibitors prevent its breakdown, affecting conditions like hypertension and depression.

Question 16

Q: Compare the roles of α1- and β2-adrenoceptors in smooth muscle regulation, and give examples of drugs that act on these receptors.

Answer 16

A: α1-adrenoceptors cause smooth muscle contraction and vasoconstriction (e.g., phenylephrine for congestion). β2-adrenoceptors cause smooth muscle relaxation (e.g., salbutamol for asthma). α1 is stimulatory, while β2 is inhibitory in smooth muscle.

Question 17

Q: Describe how M2 and M3 muscarinic acetylcholine receptors (mAChRs) function in different organs.

Answer 17

A: M2 receptors inhibit heart rate by opening K+ channels and reducing Ca2+ influx. M3 receptors stimulate smooth muscle contraction and gland secretion via IP3 and Ca2+ release. M3 agonists like pilocarpine treat glaucoma, while M2 agonists are still being researched.

Question 18

Q: Discuss the clinical applications of β1-adrenoceptor antagonists and agonists on heart function.

Answer 18

A: β1-adrenoceptor agonists like dobutamine increase heart rate and contraction, used for cardiogenic shock. Antagonists like metoprolol reduce heart rate and are used for hypertension, angina, and arrhythmias.

Question 19

Q: How do drugs affecting nicotinic acetylcholine receptors (nAChRs) at autonomic ganglia function?

Answer 19

A: nAChR agonists like nicotine stimulate both sympathetic and parasympathetic systems, causing tachycardia and secretions, but have little clinical use due to widespread effects. Antagonists like hexamethonium block autonomic ganglia, causing hypotension, but are now rarely used.