Pharmacology I · Exam 1 · Lecture 3

Autonomic Receptor Chart

Alpha-1, alpha-2, beta-1, beta-2, muscarinic and nicotinic — where each one sits, what it does, and every drug in the lecture that turns it on or off.

Six receptors, each read the way he said to think: where it sits → what it does → which drugs turn it on and off, with every drug filed under the class the lecture puts it in. Slides cited on every card.

The deck has no table like this. It teaches the receptors on slides 22 to 24 and 76 to 78, the organ actions as a figure on slide 11, and then the drugs one at a time across nearly a hundred slides. Everything here is from those slides; putting it in one place is what the page is for.

Two memory hooks are NOT from the lecture and are labeled where they appear: one heart, two lungs for beta-1 against beta-2. They are standard mnemonics, included because the point of this page is to be memorable, and flagged so they are not mistaken for something the deck said.

Six lines Alpha-1 Alpha-2 Beta-1 Beta-2 Muscarinic Nicotinic Organ by organ

The whole thing in six lines memorize this

Alpha-1

Squeeze

constricts vessels · raises pressure

Alpha-2

Brake

presynaptic — turns the system DOWN

Beta-1

Heart

rate & force up · renin up

Beta-2

Lungs

opens airways · dilates muscle beds

Muscarinic

Rest and digest

secretions, contractions, slowing

Nicotinic

Ganglia and muscle

ganglia, adrenal medulla, muscle

The two that catch people. Alpha-1 and alpha-2 pull in opposite directions, and it is not the number that decides — it is where the receptor sits. Alpha-1 is on the target organ, so stimulating it squeezes. Alpha-2 is on the nerve ending before the target, so stimulating it turns the whole outflow down. That is why phenylephrine raises blood pressure and clonidine lowers it, though both are alpha agonists.

And beta-2 is why “non-selective” matters. Propranolol, timolol and nadolol block beta-2 as well as beta-1 — which closes airways.

Alpha-1 Squeeze

Where

On the postsynaptic membrane of the effector organ — the receiving end.

What it does

Vasoconstriction, so blood pressure rises — systolic and diastolic
Pupil dilates by contracting the iris radial muscle
Contracts the bladder trigone and sphincter
Decreases renin secretion — the opposite of beta-1

Hook

Alpha-1 squeezes. Vessels, sphincters and the pupil all tighten.

Turned ON by

Direct-acting — catecholaminesnorepinephrine · epinephrine (higher doses) · dopamine (very high doses)

Direct-acting — syntheticphenylephrine · oxymetazoline

Indirect-actingamphetamine · cocaine

Mixed-actionephedrine · pseudoephedrine

Turned OFF by

Selective alpha-1 blockers — the “-osins”prazosin · terazosin · doxazosin · tamsulosin · alfuzosin

Non-selective alpha blockersphentolamine (competitive) · phenoxybenzamine (irreversible)

Combined alpha and beta blockerslabetalol · carvedilol

Slides 76, 82, 96, 99, 103, 107, 111

Alpha-2 Brake

Where

On presynaptic nerve endings — the sending end, not the target organ.

What it does

Reduces sympathetic outflow from the central vasomotor centers
Vasodilation and a fall in blood pressure follow
This is why an alpha-2 agonist lowers pressure while an alpha-1 agonist raises it — the location, not the letter, decides

Hook

Alpha-2 is the brake on the system itself. Because it sits presynaptically, stimulating it turns the sympathetic outflow DOWN.

Turned ON by

Direct-acting — syntheticclonidine · oxymetazoline

Turned OFF by

Non-selective alpha blockersphentolamine · phenoxybenzamine

Slides 76, 82, 97, 107, 108

Beta-1 Heart

Where

Mainly the heart, and the kidney.

What it does

Increases heart rate — positive chronotrope
Increases contractility — positive inotrope
Increases renin secretion from the kidney

Hook

You have ONE heart — beta-1. Memory hook, not from the slides.

Turned ON by

Direct-acting — catecholaminesisoproterenol · epinephrine · norepinephrine · dopamine

Direct-acting — syntheticdobutamine (beta-1 selective)

Indirect-actingamphetamine

Turned OFF by

Selective beta-1 antagonistsmetoprolol · atenolol · bisoprolol · betaxolol · acebutolol

Non-selective beta antagonistspropranolol · timolol · nadolol

With partial agonist activityacebutolol · pindolol

Combined alpha and beta blockerslabetalol · carvedilol

Slides 11, 79, 82, 94, 113, 114, 120, 121, 122

Beta-2 Lungs

Where

Bronchial smooth muscle, and the vessels of skeletal muscle.

What it does

Bronchodilation
Vasodilation in skeletal muscle beds
Relaxes the uterus
Contributes to hyperglycemia with epinephrine

Hook

You have TWO lungs — beta-2. Memory hook, not from the slides. It is also why a NON-selective beta blocker is a problem in asthma: blocking beta-2 closes the airway.

Turned ON by

Direct-acting — catecholaminesisoproterenol · epinephrine

Direct-acting — syntheticalbuterol (beta-2 selective)

Mixed-actionephedrine · pseudoephedrine

Turned OFF by

Non-selective beta antagonistspropranolol · timolol · nadolol — this is the asthma problem

Combined alpha and beta blockerslabetalol · carvedilol

Slides 79, 84, 98, 103, 113, 119, 122

Muscarinic Rest and digest

Where

M1 neurons and gastric parietal cells · M2 neurons, cardiac cells and smooth muscle · M3 neurons, bladder, exocrine glands and smooth muscle. Only these three are functionally characterized.

What it does

Defecation · Urination · Miosis
Bradycardia · Bronchorrhea · Bronchospasm
Emesis · Lacrimation · Salivation
The lens also accommodates for near vision

Hook

DUMBBELS — and every one of them is a secretion, a contraction or a slowing. Blocking them gives you the exact opposite, which is the anticholinergic toxidrome.

Turned ON by

Direct-acting — choline estersacetylcholine · carbachol · bethanechol

Direct-acting — natural alkaloidspilocarpine

Indirect — reversible cholinesterase inhibitorsedrophonium · physostigmine · neostigmine · pyridostigmine · donepezil, rivastigmine, galantamine

Indirect — irreversiblethe organophosphates

Turned OFF by

Antimuscarinics — naturalatropine · scopolamine

Antimuscarinics — syntheticipratropium · tiotropium · glycopyrrolate

Antimuscarinics — bladder agentsoxybutynin · tolterodine · solifenacin · darifenacin · fesoterodine · trospium

Slides 11, 23, 26, 28, 30, 34, 40, 42, 46, 47, 55, 56

Nicotinic Ganglia and muscle

Where

Autonomic ganglia, the adrenal medulla, the neuromuscular junction and the central nervous system.

What it does

Mydriasis · Tachycardia
Weakness, meaning paralysis
Hypertension · Fasciculations
Structurally a ligand-gated ion channel: two acetylcholine molecules bind and sodium flows in

Hook

M-T-W-H-F, the days of the week — and note it is the mirror image of the muscarinic list on the pupil and the heart.

Turned ON by

Direct-acting — choline esterscarbachol (muscarinic and nicotinic) · acetylcholine

Depolarizing neuromuscular blockersuccinylcholine — agonist first, paralysis second

Ganglionic stimulantnicotine — stimulates low, blocks high

Turned OFF by

Non-depolarizing neuromuscular blockersrocuronium · vecuronium · pancuronium · cisatracurium · tubocurarine

Ganglionic blockersall non-depolarizing competitive antagonists except nicotine

Slides 24, 29, 58, 59, 61, 62, 66

The same thing organ by organ slide 11

Sympathetic actions in red, parasympathetic in blue. Read it against the cards above: everything red is alpha or beta, everything blue is muscarinic.

Actions of the sympathetic and parasympathetic nervous systems on each effector organ, sympathetic in red and parasympathetic in blue — Actions of the sympathetic and parasympathetic nervous systems on effector organs — lecture slide 11.