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Intro to Cholinergics
Terms in this set (20)
What is the autonomic nervous system? (subconscious control)
system of motor neurons that innervates smooth and cardiac muscle and glands
- ensures support of body activities
Functions of ANS?
1. Shunts blood to needy areas
2. Slows HR, adjusts BP, temperature, gastric secretions
3. maintains homeostasis of body
Role of PSNS?
"rest and digest"
promotes maintenance activities and conserves body energy
What are the neurotransmitters of the ANS?
1. Cholinergic fibers
2. Adrenergic fibers
SNS physiology and drugs that stimulate it ?
- arises from thoracic and lumbar and has short preganglionic and long postganglionic fibers
- ADRENERGICS (receptor for NE)
PNS physiology and drugs that stimulate it ?
- arises from cranial and sacral regions with long preganglionic and short post ganglionic fibers
- CHOLINERGICS (receptor for ACh)
Cholinergic meaning, and purpose of its drugs?
- increases levels of ACh or choline in the brain
- drugs produce same effects of ACh
How do cholinergic drugs function?
1. Direct Acting Cholinergics (mimics ACh effects)
2. Indirect Acting Cholinergics (blocks acetylcholinesterase enzyme effects)
Indirect acting cholinergic drugs examples ?
Reverisble: physostigmine, neostigmine, edrophonium
Ireversible: Parathion, isofluorate, oranophosphates
What 2 types of receptor binds to ACh?
1. Muscarinic ( activated by mushroom poisoning muscarine)
- excitatory or inhibitory( dependent on receptor type)
- M1 - M5 subtypes
2. Nicotinic (responds to nicotine)
- allows movement of positiviely charged ions from synaptic cleft into cytoplasm.
- activated by binding of 2 acetylcholine molecules, and by the binding of nicotine
What are some uses of indirect acting cholinergics?
1. Causes skeletal muscle contractions
2. used for diagnosis and treatment of myastenia gravis
3. Used to reverse neuromuscualr blocking agents
4. Used to reverse anticholinergic poisoning (antidote)
Locations of Nicotinic Receptors?
1. Sarcolemma of skeletal muscle cells at NMJ
2. All postganglionic neurons (PSNS & SNS)
3. Hormone-producing cells of adrenal medulla
How are nicontinic receptors able to cause an excitatory effect?
- opens ion channels, depolarizing postsynaptic cell
What are the main cholinergic actions?
1.Contraction of circular muscle (sphincter pupillae) of iris (miosis)
2. Contraction of ciliary muscles for near vision
bradycardia ( heart rate)
Contraction of muscles
Relaxation of sphincter
Increase of sweat, saliva, lacrimal, bronchial, intestinal secretions
relaxation of sphincter (diarrhea)
increased bronchoconstriction, bronchial secretion
Effects of anticholinergic drugs ?
1.relaxation of circular (sphincter pupillae) muscles (Mydriasis) (pupil dilation)
2. relaxation of ciliary muscles (Cycloplegia) loss of accommodation, paralysis of ciliary muscle
Tachycardia ( heart rate)
Relaxation of muscles
contraction of sphincter
Decrease all secretions
contraction of sphincter (constipation)
decreased bronchodilation, bronchial secretions
What are some other names for cholinergic drugs ?
cholinergic agonists, parasympathomimetics
What is Myastenis Gravis ?
*chronic autoimmune neuromuscular disease that causes weakness in skeletal muscle
- caused by error in transmission of nerve impulses to muscles
- antibodies block, alter, or destroy receptors for Ach (preventing muscle contraction)
What are some conditions that call for direct acting cholinergics? What drugs are they usually prescribed ?
1. Glaucoma: reduces introcular pressure by increasing drainage (Carbachol, Pilocarpine)
2. Atony and Neurogenic Bladder: used to increase postsurgical atony of bladder and GI tract allowing them to empty (Bethanechol)
What are some conditions that call for indirect acting cholinergic drugs? What are they usually prescribed?
1. Myasthenia Gravis: helps skeletal muscle contractions and inhibits the breakdown of Ach (Physostigmine or pyridostigmine)
2. Alzheimer's Disease: delays cognitive deterioration and increases concentrations of ACh in brain (Donepezil aka Aricept)
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