Cholinergic Agonist/Antagonist Flashcards
What is the autonomic nervous system responsible for?
It controls visceral functions such as cardiac output, blood flow distribution, and digestion without conscious control
What are the two main divisions of the autonomic nervous system?
Sympathetic and Parasympathetic divisions
Where do sympathetic preganglionic fibers originate?
Thoracic, lumbar, and sacral spinal nerves
Where do parasympathetic preganglionic fibers originate?
Cranial nerves III, VII, IX,
and X
What fibers release acetylcholine (ACh)?
Cholinergic fibers, including:
All preganglionic autonomic fibers.
Somatic motor fibers to skeletal muscle.
Most parasympathetic postganglionic fibers.
Some sympathetic postganglionic fibers
What are the two main neurotransmitters of the ANS?
Acetylcholine (ACh) and Norepinephrine (NE)
What fibers release norepinephrine (NE)?
Adrenergic (noradrenergic) fibers, mostly postganglionic sympathetic fibers.
What is the enteric nervous system?
A third division of the ANS that controls the GI tract independently
What are additional neurotransmitters of the ANS?
Dopamine and Epinephrine
What are adrenoceptors?
Receptors that respond to catecholamines like norepinephrine
What are the two types of cholinoceptors (acetylcholine receptors)?
Muscarinic and Nicotinic receptors
What are the subclasses of adrenergic receptors?
α-Adrenoceptors: α1 and α2
β-Adrenoceptors: β1, β2, β3.
Dopamine receptors
What are cholinomimetics?
Drugs that mimic acetylcholine by stimulating ACh receptors or inhibiting cholinesterase
How are cholinomimetics classified?
By receptor type: Muscarinic vs. Nicotinic.
By mechanism of action: Direct-acting vs. Indirect-acting.
What is the mechanism of direct-acting cholinomimetics?
They bind to and activate cholinoceptors (muscarinic or nicotinic)
What is the mechanism of indirect-acting cholinomimetics?
They inhibit acetylcholinesterase, increasing ACh levels
What are the effects of muscarinic agonists on the eye?
Miosis (pupil constriction) and accommodation
What are the cardiovascular effects of muscarinic agonists?
Increased potassium current (SA/AV nodes, Purkinje fibers).
Decreased slow inward calcium current.
Slower pacemaker rate
What are the respiratory effects of muscarinic agonists?
Bronchoconstriction.
Increased mucus secretion
What are the GI effects of muscarinic agonists?
Increased gut motility and secretions.
Increased salivation and gastric gland activity
What are the genitourinary (GU) effects of muscarinic agonists?
Detrusor muscle stimulation.
Relaxation of trigone and sphincter muscles (promotes urination)
What is acetylcholine used for clinically?
No significant therapeutic use due to its broad systemic effects
What is bethanechol used for?
Atonic bladder (postpartum or post-op urinary retention)
What is pilocarpine used for?
Glaucoma (lowers intraocular pressure).
Xerostomia (dry mouth) in Sjögren’s syndrome or radiation therapy
