cholinergic receptors

What is the primary function of the autonomic nervous system (ANS)?

It regulates involuntary functions such as smooth muscle contraction, glandular secretion, and homeostasis

parasympathatic nervous system

calms the body, conserving its energy and homeostasis

sympathetic nervous system

arouses the body, mobilizing its energy in stressful situations

What is the primary neurotransmitter of the cholinergic system?

Acetylcholine (ACh)

What are the two main types of cholinergic receptors?

Nicotinic ACh receptors (nAChRs) and Muscarinic ACh receptors (mAChRs)

Where are nAChRs primarily located, and what is their mechanism of action?

Found at the neuromuscular junction (NMJ) and autonomic ganglia. They are ligand-gated ion channels that open to allow sodium influx, causing depolarization

What is the role of mAChRs, and how do they function?

Found at parasympathetic postganglionic targets; they are G-protein-coupled receptors (GPCRs) mediating slower, sustained responses

Name two types of nicotinic receptor blockers and their mechanisms

• Competitive antagonists (e.g., tubocurarine): Block ACh binding, preventing muscle contraction. Used as a muscle relaxant during surgery.

• Depolarizing blockers (e.g., suxamethonium): Maintain depolarization, causing temporary paralysis. Used as anaesthesia.
  

What are the functions and therapeutic potential of central nicotinic receptors have?

Found in the CNS and influence attention, learning, and addiction. They are being explored for treatments in Alzheimer's disease and schizophrenia.

What are the functions of the M1, M2, and M3 muscarinic receptor subtypes?

• M1: Cognitive functions in the CNS.

• M2: Reduces heart rate (cardiac tissue).

• M3: Promotes smooth muscle contraction and glandular secretion.

What are the primary effects of the parasympathetic nervous system on the heart, glands, and smooth muscle?

• Heart: Bradycardia (via M2 receptors).

• Glands: Increased secretions (saliva, sweat, tears).

• Smooth Muscle: Bronchoconstriction and increased GI motility

How does atropine work, and what are its uses?

Atropine is an mAChR antagonist that blocks parasympathetic effects. It is used to treat bradycardia, reduce secretions pre-anesthesia, muscle relaxant, and dilate pupils

What is the role of donepezil in treating Alzheimer's disease?

It is an acetylcholinesterase inhibitor that prevents ACh breakdown, enhancing cholinergic transmission to improve memory and cognition.

How does botulinum toxin (Botox) work, and what are its uses?

It blocks ACh release by cleaving SNARE proteins. Uses include reducing muscle spasms, treating migraines, reducing wrinkles, and managing hyperhidrosis

What are the primary catecholamines involved in adrenergic transmission?

Noradrenaline (NA) and adrenaline (ADR)

Catecholamine synthesis

1. Tyrosine → L-DOPA: Rate-limiting step via tyrosine hydroxylase.

2. L-DOPA → Dopamine.

3. Dopamine → Noradrenaline: Via dopamine β-hydroxylase

4. Noradrenaline → Adrenaline

Name the adrenergic receptor subtypes

alpha 1, alpha 2, beta 1, beta 2, beta 3

What are the effects of α₁-adrenoceptor activation?

Vasoconstriction, increased blood pressure, and pupil dilation.

How do α₂-adrenoceptors regulate neurotransmission?

They inhibit noradrenaline release via negative feedback

What are the primary effects of β₁-adrenoceptor activation?

Increased heart rate (positive chronotropy), increased cardiac contractility (positive inotropy), and renin release.

What are the primary effects of β₂-adrenoceptor activation?

Bronchodilation, vasodilation, uterine relaxation.

What is the primary effect of β₃-adrenoceptor activation?

Stimulates lipolysis and relaxes the bladder.

What are the dose-dependent effects of adrenaline?

• Low dose: β₂-dominant effects (vasodilation, tachycardia).

• High dose: α₁-dominant effects (vasoconstriction, increased blood pressure)

What are the effects of noradrenaline?

α₁-dominant effects (vasoconstriction, increased blood pressure)

How does salbutamol work, and what are its uses?

Treats asthma by activating β₂-receptors, causing bronchodilation provides rapid symptom relief during bronchospasm.

What is atenolol, and what is its mechanism of action?

β₁-selective antagonist reduces cardiac output and renin release, used for hypertension, angina, and heart failure.

How does pseudoephedrine relieve nasal congestion?

It stimulates noradrenaline release, causing vasoconstriction in nasal mucosa

What are indirect sympathomimetics, and how do they work?

Agents that enhance adrenergic effects by increasing noradrenaline availability