Autonomic Nervous System High-Yield Study Guide

Flashcards covering key concepts from the Autonomic Nervous System lecture notes, including sympathetic and parasympathetic pathways, receptor pharmacology, and clinical toxidromes.

What is the primary location of sympathetic preganglionic neurons?

The intermediolateral cell column (T1–L2) of the spinal cord

Which type of rami communicantes is myelinated and found only at T1-L2?

White rami communicantes

What is the neurotransmitter released by sympathetic preganglionic neurons and which receptor does it bind to?

Acetylcholine (ACh) to the nicotinic Nn receptor

What is the primary neurotransmitter released by sympathetic postganglionic neurons?

Norepinephrine (NE)

What is the classic triad of Horner Syndrome?

Ptosis, Anhidrosis, and Miosis (PAM)

What is a common classic association causing Horner Syndrome?

Pancoast tumor compressing the sympathetic chain

Which cranial nerve initiates the parasympathetic pathway to the lacrimal gland?

Cranial Nerve VII (Facial nerve)

Which receptor type mediates glandular secretion in the lacrimal gland via the parasympathetic pathway?

Muscarinic M3 receptor

What effect do antimuscarinic drugs like atropine or scopolamine have on the lacrimal glands?

They cause dry eyes by blocking muscarinic M3 receptors

What mnemonic describes the classic signs of antimuscarinic toxidrome?

'Hot as a hare, Dry as a bone, Red as a beet, Mad as a hatter, Blind as a bat'

What mnemonic helps remember the symptoms of muscarinic (cholinergic excess) toxidrome?

DUMBBELSS (Diarrhea, Urination, Miosis, Bronchospasm, Bradycardia, Emesis, Lacrimation, Sweating, Salivation)

What is the effect of organophosphates on the nervous system?

They are irreversible acetylcholinesterase (AChE) inhibitors, leading to cholinergic crisis

What is the treatment for organophosphate poisoning?

Atropine + Pralidoxime (2-PAM)

What is the physiological mechanism behind vasovagal syncope?

Increased vagal tone (parasympathetic) and decreased sympathetic activity leading to bradycardia and hypotension

What second messenger pathway is activated by M3 receptor stimulation?

Gq protein-coupled receptor pathway, leading to IP3/DAG and increased intracellular Ca²■

List key effects of M3 receptor activation.

Increased gland secretion, increased gut motility, miosis, bronchoconstriction, and bladder contraction

How does acetylcholine affect blood vessels with an intact endothelium?

ACh acts on M3 receptors in the endothelium, causing nitric oxide (NO) release and vasodilation

What is the effect of an alpha-1 receptor agonist like phenylephrine?

It causes vasoconstriction, leading to an increase in Blood Pressure (BP)

How do presynaptic alpha-2 receptor agonists like clonidine or methyldopa reduce blood pressure?

They decrease norepinephrine (NE) release from presynaptic terminals

What are the main effects of beta-2 receptor agonists?

Bronchodilation in the lungs and vasodilation in skeletal muscle

Describe Dale’s Vasomotor Reversal phenomenon after irreversible alpha-blockade.

Epinephrine, after irreversible alpha-blockade (e.g., phenoxybenzamine), causes a decrease in blood pressure due to unopposed beta-2 receptor activity

What are the effects of low-dose epinephrine on blood pressure and heart rate?

Increased systolic blood pressure, decreased diastolic blood pressure, widened pulse pressure, and increased heart rate

What are the characteristic effects of norepinephrine infusion on blood pressure and heart rate?

Increased systolic blood pressure and increased diastolic blood pressure, along with reflex bradycardia, without widening of the pulse pressure

What drug is used to treat a hypertensive crisis caused by tyramine and MAOIs, and by what mechanism?

Phentolamine, an IV alpha-blocker, reverses vasoconstriction and lowers blood pressure

Why is Labetalol considered safe for hypertensive emergencies in pregnancy?

It is a combined alpha-1 and beta-1/beta-2 blocker that can be used intravenously and is safe in pregnancy-induced hypertension such as preeclampsia/eclampsia

What are the two main types of nicotinic receptors and their primary locations?

Nm receptors are found on skeletal muscle (blocked by curare), and Nn receptors are found in autonomic ganglia and the adrenal medulla (blocked by hexamethonium)

List some common muscarinic antagonists and their uses.

Atropine (prototype, causes mydriasis, tachycardia, dry secretions), Scopolamine (motion sickness), Ipratropium/Tiotropium (COPD/asthma)

Name some reversible and irreversible anticholinesterase inhibitors.

Reversible: edrophonium, neostigmine, physostigmine. Irreversible: organophosphates.

What are the common adrenergic receptor mnemonics for their primary effects?

α1 = constriction, α2 = decrease NE, β1 = increase HR (1 heart), β2 = bronchodilation (2 lungs), β3 = bladder relaxation, lipolysis

List alternative antihypertensives considered safe in pregnancy besides Labetalol.

Hydralazine, Methyldopa, and Nifedipine