Autonomic Flashcards
What are the two main divisions of the ANS?
Sympathetic Nervous System (SNS) (“fight-or-flight”)
Parasympathetic Nervous System (PNS) (“rest-and-digest”)
What is the function of the autonomic nervous system?
Controls involuntary bodily functions such as blood pressure, digestion, respiration, sweating, and body temperature.
What is the role of the enteric nervous system?
A semi-independent division of the ANS that regulates the gastrointestinal tract.
How does the baroreceptor reflex maintain blood pressure?
Baroreceptors (mechanoreceptors) detect changes in blood pressure and trigger compensatory autonomic responses.
Where do sympathetic nerves originate?
Thoracolumbar (T1-L2) spinal segments.
What is the neurotransmitter released by sympathetic postganglionic neurons?
Norepinephrine (NE), except in sweat glands (which release acetylcholine).
What is the function of the adrenal medulla in the SNS?
Releases 80% epinephrine and 20% norepinephrine into the bloodstream upon stimulation.
What is the rate-limiting enzyme in catecholamine synthesis?
Tyrosine hydroxylase converts tyrosine into L-DOPA.
What is the IB4D acronym for sympathetic effects?
Increased Heart Rate
Bronchodilation
Dilation of Pupils
Decreased GI Motility & Secretions
Decreased Urination & Lacrimation
How is norepinephrine action terminated?
Reuptake by Norepinephrine Transporter (NET)
Metabolism by COMT & MAO
What are the key adrenergic receptors and their functions?
α1: Vasoconstriction (Gq)
α2: Decreases NE release (Gi)
β1: Increases heart rate and contractility (Gs)
β2: Bronchodilation, vasodilation (Gs)
Where do parasympathetic nerves originate?
Craniosacral (CN III, VII, IX, X, and S2-S4)
What is the primary neurotransmitter of the PNS?
Acetylcholine (ACh)
How is acetylcholine synthesized and broken down?
Synthesized by choline acetyltransferase (ChAT)
Broken down by acetylcholinesterase (AChE)
What is the SLUDD acronym for parasympathetic effects?
Salivation
Lacrimation
Urination
Digestion
Defecation
What are the types of cholinergic receptors?
Nicotinic (N1 & N2): Ionotropic, found in neuromuscular junctions and ganglia.
Muscarinic (M1-M5): Metabotropic, affecting organs.
What are direct-acting sympathomimetic drugs?
Phenylephrine (α1-agonist), Albuterol (β2-agonist), Dobutamine (β1-agonist)
What is the mechanism of indirect sympathomimetics like amphetamines?
Displace NE from vesicles, leading to increased NE in synapse.
What is the function of MAO and COMT inhibitors?
Inhibit catecholamine breakdown, prolonging adrenergic effects.
What are the key adrenergic antagonists (sympatholytics)?
Nonselective Beta-Blockers: Propranolol (β1 & β2)
Selective Beta-Blockers: Metoprolol (β1)
Alpha-Blockers: Prazosin (α1), Phentolamine (α1 & α2)
Which drug blocks both alpha and beta receptors?
Labetalol & Carvedilol
What are muscarinic agonists used for?
Pilocarpine & Cevimeline: Treat xerostomia
Bethanechol: Treats urinary retention
Carbachol: Treats glaucoma
What are muscarinic antagonists (anticholinergics)?
Atropine: Increases HR, reduces secretions.
Scopolamine: Motion sickness.
Ipratropium: COPD treatment.
What are acetylcholinesterase inhibitors used for?
Donepezil: Alzheimer’s
Neostigmine: Myasthenia gravis
Edrophonium: Myasthenia gravis diagnosis
What is Horner’s syndrome?
Sympathetic denervation of the face
Symptoms: Ptosis, Miosis, Anhidrosis
What is POTS (Postural Orthostatic Tachycardia Syndrome)?
Dysautonomia disorder characterized by excessive HR increase upon standing.
What is Shy-Drager syndrome?
Multiple system atrophy (MSA) leading to autonomic failure.
What is vasovagal syncope?
Excessive vagal stimulation causing fainting.
What is Hirschsprung’s disease?
Lack of parasympathetic ganglia in colon, leading to severe constipation.
Why is epinephrine used in anaphylaxis?
β2: Bronchodilation
α1: Vasoconstriction to counteract hypotension
Why should beta-blockers be avoided in asthmatics?
They block β2 receptors, causing bronchoconstriction.
What are the dangers of abrupt beta-blocker withdrawal?
Rebound hypertension & angina due to receptor upregulation.
What drug is used to reverse neuromuscular blockade?
Neostigmine (AChE inhibitor)
What type of autonomic drugs should be avoided together?
Beta-blockers + Verapamil (excess bradycardia)
MAOIs + Sympathomimetics (hypertensive crisis)
What drug is best for orthostatic hypotension?
Midodrine (α1 agonist) to increase BP.
