11-Drugs affecting the ANS Flashcards
What are the receptors of the somatic nervous system? Which neurotransmitter is associated with these receptors?
Nicotinic Cholinergic Receptors. Acetylcholine.
Which drugs are used to block the somatic nervous? What is the effect of these drugs?
Neuromuscular Blocking Agents. Induce paralysis of skeletal muscle.
When are NMBAs (Neuromuscular blocking agents) used? What is an example of an NMBA?
Specifically used in the context of surgery, endotracheal intubation or mechanical ventilation (to keep muscles from contracting so we can cut open).
Vecuronium (Norcuron) is an NMBA.
What is the antagonist to Vecuronium (an NMBA)? What is its mechanism of action?
Acetylcholinesterase inhibitors (neostigmine). Inhibits the activity of acetylcholinesterase which metabolizes acetylcholine. Ach levels will rise and compete actively against Vecuronium.
True or False. Neuromuscular blocking agents have an affect on the autonomic nervous system.
False. They bind to nicotinic-cholinergic receptors of the somatic nervous system, a different subtype than the ones found in the ANS.
Which receptors are associated with the sympathetic division of the ANS? What neurotransmitter is associated?
Adrenergic receptors (alpha and beta). Norepinephrine.
Which receptors are associated with the parasympathetic division of the ANS? What neurotransmitter is associated?
Muscarinic cholinergic receptors . Acetylcholine.
True or False: Nicotinic Cholinergic receptors are only found in the parasympathetic division?
False. Nicotinic Cholinergic receptors are found in sympathetic and parasympathetic postganglionic neurons.
Which organs and glands do not receive input from both branches of the ANS? Which input do they receive?
The arterioles. They only receive sympathetic input.
True or False: sympathetic and parasympathetic input to organs is of equal strength.
False. One system will always predominate (typically the parasympathetic with bursts of sympathetic tone).
Nicotininc cholinergic receptor antagonists (Autonomic Nervous System):
- mechanism of action
- outcome
- inhibits both the smaller sympathetic input and the predominant parasympathetic input
- results in a net sympathetic effect
What would the effect of a nicotinic cholinergic receptor antagonist be on the heart?
The heart receives both sympathetic and parasympathetic input. The parasympathetic input predominates and slows the intrinsic rhythm. If a nicotinic cholinergic receptor antagonist is used, then the predominant parasympathetic input will be blocked, resulting in a net sympathetic effect. Therefore tachycardia will result.
Why do we not longer use drugs that target nicotinic cholinergic receptors?
They result in a messy dose response curve because we are all a little different in which system predominates. The target is not as specific.
Which receptors are found in the target tissues of the sympathetic division vs. the parasympathetic division.
Sympathetic - Adrenergic receptor
Parasympathetic - Muscarinic cholinergic receptor
What are two other names for cholinergic drugs class?
Muscarinic agonists and parasympathomimetics.
What effects do cholinergic drugs have?
stimulate smooth muscle (lungs, GI), stimulate gland secretions, decrease heart rate and force of contraction, constrict the pupil
What are two other names for anticholinergic drug class?
Muscarinic antagonists and parasympatholytics.
What effects do anticholinergic drugs have?
Opposite of cholinergics - Suppression of smooth muscle (lungs and GI), suppression of oral secretions, increased heart rate and force of contractions, pupil dilation.
Direct acting cholinergic drugs vs. Indirect acting cholinergic drugs.
Direct acting cholinergic drugs bind to muscarinic cholinergic receptors whereas indirect acting inhibit acetylcholinesterase which causes an increase in acetylcholine. Ach levels rise systemically which means that it binds to receptors in the SNS as well as ANS.
Clinical use of direct acting cholinergic drugs (Bethanechol).
- Bethanechol stimulates smooth muscle contraction via M3 receptors couple to Gq proteins.
- It is used to treat postoperative ileus and bladder atony
- drugs used in surgery can have negative effects on the gut and bladder and sometimes people require a kickstart with bethanechol
Clinical use of indirect acting cholinergic drugs.
Myasthenia graivs and Alzheimer’s disease (Ach is important to memory at the level of the hippocampus) - Because these drugs affect autonomic gnaglia, muscarinic receptors, skeletal muscle and cholinergic receptors in the CNS, we only use them when we don’t have anything else.
Which drug class are insecticides? What are the two types of insecticides and how do they differ?
Indirect acting cholinergic drugs.
Carbamate insecticides reversibly bind and the effects are often reverse 2-8 hours post exposure.
Organophosphate insecticides irreversibly bind and recovery requires synthesis of new enzymes (1-2 weeks).
What can insecticides induce?
Cholinergic crisis.
Explain a cholinergic crisis.
Nicotinic effects: muscle fasiculations and fatigue
Muscarinic effects (pro-parasympathetic): salivation, lacrimation, urination, diarrhea, dyspnea, bradycardia, sweating, pin-prick pupils
This pro-parasympathetic state happens early on and very quickly.
