Module 11 Flashcards
What is the autonomic nervous system (ANS)?
Responsible for regulating involuntary physiological processes such as HR, digestion, RR and BP. It has 3 divisions:
1. Sympathetic Nervous System (SNS)
2. Parasympathetic Nervous System (PNS)
3. Enteric Nervous System (ENS)
What is the sympathetic nervous system responsible for?
Flight or fight
* Increased HR and force of contraction
* Dilated airways for improved O2 intake
* Increased blood flow to muscles, heart and lungs
* Dilation of pupils (Mydriasis)
* Inhibition of digestive processes (slowed peristalsis, reduced secretions)
* Release of glucose from the liver for energy
* Increased blood pressure by constricting blood vessels
What are the neurotransmitters and receptors involved in the SNS?
NE & E
Adrenergic receptors:
- alpha-1: Smooth muscle cells (blood vessels = vasoconstrict causing elevated BP
- alpha-2: Presynaptic neurons, inhibiting further release of NE, leading to reduction in sympathetic activity
- beta-1: Heart, increased HR and contractility
- beta-2: smooth muscle of lungs and blood vessels = bronchodilation and vasodilation
What are the drug classes that impact the SNS?
Adrenergic agonists:
- beta-agonists like albuterol (reduction of bronchospasm in asthma)
- alpha-agonists like phenylephrine, vasoconstriction and increase BP
Adrenergic Antagonists:
- Beta-blockers like metoprolol to reduce HR and BP
- Alpha-blockers like prazosin to reduce BP by causing vasodilation
What is the Parasympathetic System responsible for?
Rest & Digest
- decrease HR and force of contraction
- bronchoconstriction
- increased digestion
- constriction of pupils (miosis)
- Stimulated salivation and other secretions in digestive tract
- relaxation of bladder and increased urination
What are the neurotransmitters and receptors involved in the PNS?
ACh (Acetylchoine)
Cholinergic Receptors:
1. Muscarinic Receptors:
- M1: CNS and gastric glands
- M2: Heart
- M3: Smooth muscle
2. Nicotinic receptors: postganglionic neurons in SNS and PNS
What are the drug classes that impact the PNS?
Muscarinic Agonists like Pilocarpine for glaucoma
Muscarinic Antagonists like Atropine or ipratropium
What is the Enteric Nervous System?
Neurons embedded within the lining of the GI tract
- Regulates GI function independent of CNS
- Controls peristalsis, enzyme secretion, and blood flow to digestive organs
- involved in local reflexes, such as the stretch reflexes of the intestines
- coordinates with the SNS and PNS to modulate digestion and absorption
What are the neurotransmitters and receptors involved in the ENS?
Neurotransmitters:
- ACh (acetylcholine) = GI motility and secretion
- NE = modulates digestion by inhibiting motility in certain regions - - Serotonin (5-HT) = Regulates motility, secretion, and blood flow in intestines.
Receptors:
- Cholinergic: muscarinic and nicotinic. Muscarinic = peristalsis and secretion
- Adrenergic receptors: Alpha-1 with vasoconstriction and beta-2 modulate motility
- Serotonin: peristalsis, secretion and blood flow
What are the drug classes that impact the ENS?
Prokinetic agents that increase GI motility. e.g. Metoclopramide
Antispasmodics (anticholinergics): decreased GI motility by inhibiting muscarinic receptors
Serotonergic Drugs: e.g. Ondansetron (5-HT3 receptor antagonist) for N/V by blocking serotonin receptors.
What are muscarinic receptors?
Subtype of acetylcholine receptors found in heart, eye, GI tract and smooth muscle.
Part of parasympathetic system.
What are the effects of Muscarinic agonism on the eye?
Miosis (constriction)
Increases accommodation (near vision)
Increased aqueous humor outflow, reducing intraocular pressure.
What are the effects of muscarinic agonism on the heart?
Bradycardia
Decreased contractility
Decreased conduction velocity (slower HR)
What are the effects of muscarinic antagonism on the eye?
Mydiasis (dilation)
Cycloplegia (loss of accommodation)
Decreased outflow, potentially increasing ocular pressure
What are the effects of muscarinic antagonism on the heart?
Tachycardia
Increased contractility
Increased conduction velocity
What are the S&S of anticholinergic/antimuscarinic toxicity?
Blind as a bat, mad as a hatter, red a as a beet, hot as a hare, dry as a bone, the bowel and bladder lose their tone and the heart goes pitter patter.
What are the risks associated with long term anticholinergic use?
Elderly d/t age related physiologic changes in the brain = increase r/o cognitive impairment, dementia (ACh plays a role in memory and learning), and falls (drowsiness and vision effects of anticholinergics)
Peripheral side effects like dry mouth, blurred vision, constipation, urinary retention, flushing, rapid pulse
What are some strategies to minimize risks associated with anticholinergic use?
- Assess if alternatives can be used
- minimize dose and taper if possible
- consider comorbidities and age
- pt education on OTC anticholinergics (sleep aids or gravol)
- monitor systems for S&S of anticholinergic toxicity
