muscarinic antagonists or anti-muscarinic medications are a class of medications that prevent muscarinic receptors of the parasympathetic nervous system from getting stimulated by acetylcholine okay first things first the nervous system is divided into the central nervous system so the brain and the spinal cord and the peripheral nervous system the peripheral nervous system can be divided into the somatic nervous system which controls voluntary movement of our skeletal muscle and the autonomic nervous system which is further divided into the sympathetic and parasympathetic nervous systems and controls the involuntary movement of the smooth muscles and the glands of our organs now the autonomic nervous system is made up of a relay that includes two neurons we'll focus on just the parasympathetic nervous system signals for the parasympathetic nervous system start with the hypothalamus these hypothalamic neurons synapse with nuclei in the brain stem or spinal cord which sends out sign to preganglionic neurons that travel to the rest of the body their targets are the parasympathetic ganglions which consist of many postganglionic neuron cell bodies and are located nearby or directly in the Target organs the postganglionic neurons extend the rest of the way to the Target cell where they release the neurotransmitter acetyl coine which is why they are also called colonic neurons acetylcholine binds to a type of receptor known as muscarinic receptors on the cells of the target organs which all allow the parasympathetic nervous system to trigger a rest and digest response meaning that it keeps the body energy use as low as possible to stimulate activities like digestion it acts in the heart slowing the heart rate and reducing the cardiac output in the gastrointestinal tract it increases motility to stimulate digestion and defecation in the bladder it causes constriction of the bladder muscle called the detrusor muscle which stimulates urination in salivary sweat and lacrimal glands it increases their secretions in the liver it triggers glucose storage to reduce blood glucose levels in the lungs it causes Bronco constriction since in a relaxed State our cells do not consume as much oxygen in the eyes it triggers meiosis or constriction of the pupils to improve close vision and stimulates the contraction of the ciliary muscles increasing the outflow of aquous humor which is the fluid in the anterior chamber of the eye and this decreases the intraocular pressure finally its effects on the brain are extremely complicated but generally they cause overall stimulation and they participate in many wanted and unwanted functions such as movement control and vomiting respectively all right so medications that block the effects of acetylcholine on muscarinic receptors are called muscarinic antagonists or antimuscarinic medications now the most famous muscarinic antagonist is atropine atropine blocks the rest and digest effect from the parasympathetic system so clinically it can be used to to treat bradicardia or slowed heart rate it decreases bladder smooth muscle contraction so it's useful for preventing nocturnal enuresis or bed weding in children opthalmologists can also use atropine to dilate the pupils finally it's an antidote for poisoning by acetylon esterases like Organo phosphates found in pesticides these agents prolong the effect of acetylcholine by inhibiting their breakdown so atropine can help simply by blocking The muscarinic receptors now for side effects at can produce tachicardia or increased heart rate constipation and urinary retention dry mouth skin and eyes and blurry vision the more severe side effects include hypothermia dizziness confusion and delirium it's also contraindicated in individuals suffering from narrow angle glaucoma since it can worsen the obstruction of aquous humor drainage now other muscarinic antagonists are more effective at targeting certain organs oxybutinin works on muscarinic receptors in the bladder where they decrease D truser muscle spasms and prevent urge incontinence or involuntary urination due to an overactive bladder now otrum and tiotropium are well-known muscarinic antagonists that work as Bronco dilators they're usually given via inhalers where they enter the lungs and bind to muscarinic receptors on the tracheal and bronchial smooth muscles causing smooth muscle relaxation and dilation of the bronchi this makes them effective in relieving chronic obstructive pulmonary Ary disease COPD for short and Asthma what sets them apart mainly is their duration of action hopium is short acting while tiotropium is long acting finally there are muscarinic antagonists which act primarily in the brain like Scopolamine bends tropine and trixy fenadol Scopolamine prevents the action of acetylcholine on muscarinic receptors in the vomiting center of the brain stem this makes it effective in preventing motion sickness during travel or nausea and vomiting after surgery on the other hand Ben's tropine and triex fenil are mainly active in the striatum which is part of the basil ganglia in the brain since there's usually a balance of signaling between dopamine and acetylcholine in the striatum a loss of dopamine like in Parkinson's disease increases the relative amount of acetylcholine signaling there therefore they can be given to restore the balance of coleric and dopaminergic signaling and improve the Tremors seen in Parkinson's disease however due to their central nervous system effects all three of these drugs can produce sedation and mental confusion now we want to make a simple and fun nemonic that'll help you efficiently memorize and retain all these Farm facts so let's have an island with a large tropical palm tree for Atropine so under the tree we have a kid who's taking a nap he peed on the blankets for nocturnal enuresis and now he's staring at the stain with big dilated pupils he put a frozen heart which represents Bray cardia over the stain to try to cover it up for side effects the boy's mother got heat stroke which represents hypothermia in the CNS side effects like dizziness and confusion there's an empty water bottle next to her to help you remember dryness in the skin eyes and mouth the dad is out of ideas so he desperately went to a portapotty to see if he can move her to a cooler spot the portapotty has a clo sign on it to help you remember urinary retention and constipation the father's eyes are popping out as he saw the sign to represent the contraindication for people with glaucoma okay let's go over the medications that Target specific organs first there's oxybutinin which is represented by an oxygen tank with a large button on it to release oxygen it's connected to a hose that's inflating a bladder like a balloon to help you remember it's used for urge Inc continence next let's have a short palm tree with a rat on top for the short acting ipratropium and next to it is a tall palm tree with ties on it for tiotropium a cop with asthma is sitting between the trees and is using his inhaler to help you remember these drugs treat COPD and Asthma finally we have the medications that mainly affect the brain so by the trees we have the parking space the cop was checking which represents Parkinson's disease there's a Mercedes-Benz parked there for Ben's tropine and there's three witches inside trying to cast hex's on the cop for triex fenil getting out of the car is the witch's pet a giant walking scallop for Scopolamine it's vomiting since the witch is poor driving ding skills gave it motion sickness all right there's a quick recap muscarinic antagonists inhibit the effects of acetylcholine on muscarinic receptors this includes the prototypical medication atropine which can be used to induce pupil dilation treat Brady cardia nocturnal enuresis and reverse Organo phosphate poisoning oxybutinin is given an urge incontinence and iopi and tiotropium are used for COPD and asthma scopal is given for motion sickness and Ben tropine and trixy fodil are used to treat Tremors in Parkinson's disease antimuscarinic side effects are tachicardia constipation urinary retention dry mouth skin and eyes blurry vision hypothermia and confusion the main contraindication for these medications is narrow angle glaucoma but wait there's more here's a mind map with all the pneumonics from the video go ahead and pause the video so you can test yourself and see what you remember stay tuned for the answers at the end helping current and future clinicians Focus learn retain and thrive learn more