Block 3 ANS neuro SG+slides Flashcards
ANS neurotransmission
sympathetic and parasympathetic
sympathetic
preganglionic fibers-short
acethylcholine-nicotinic receptor
posganglionic fibers- NE noropinephrine-Aplha & Beta
-involves with ‘fright/flight/fight’ response to stress or arousal
parasympathetic
long-acetycholine
nicotinic
posganglionic- Ach- muscarinic rec.
Cholinergic receptors
nicotinic and muscarinic
what are adrenergic/muscarinic receptors
they are on effector tissues (cardiac,smooth muscle,glands)
ANS drugs bind to adrenergic receptors on effectors and stimulate fight/flight response are?
adrenergic agonist & sympathomimetics
ANS drugs that bind to adrenergic receptors on effectors and block fight/flight response are?
adrenergic antagonist & sympatholytics
ANS drugs that bind to muscarinic receptors on
effectors and stimulate a rest/digest response:
cholinergic/muscarinic agonists & parasympathomimetics
ANS drugs that bind to muscarinic receptors on
effectors and block a rest/digest response:
Cholinergic/Muscarinic antagonists and
parasympatholytics
what are adrenergic receptors
All adrenoreceptors are similar in structure and belong to the family
of G-protein-coupled receptors
Alpha receptors:
a1- sympathetic effector tissue:brain
a2- presynaptic neuron
Beta receptors
b1- sympathetic effector tissue-heart,adipose tissue,GI tract,renal aterioles
b2- mast cells;brain
b3- adipose tissue
Non-selective Adrenergic Agonists MOA
Bind to α and β receptors
and stimulate a sympathetic nervous system
response
Clinical Uses
Treatment for cardiac arrest, hypotension, shock
• Management of acute anaphylaxis
Non-selective Adrenergic Agonists drugs
adrenaline
noradrenaline
ephedrine
dopamine
α1-Adrenergic Agonists MOA & drugs
Bind to α1 receptors and stimulate a sympathetic nervous system response
-phenylephrine
Clinical Uses
Treat hypotension, nasal congestion, red eyes (by
promoting vasoconstriction)
• Also used as a vasoconstrictor administered in combination with local anaesthetic
a1-Agonist : Common Adverse Effects
- Hypertension
- Blurred vision
- Constipation
- Urinary retention
α1-Adrenergic Antagonists MOA & drugs
Bind to α1 receptors and block a sympathetic nervous system response
- doxazosin
Clinical Uses?
Treat mild-moderate hypertension, decreases urinary retention in benign prostatic hyperplasia
Adverse Effects
Postural hypotension, urinary frequency, erectile
disorders, nasal congestion, fatigue
β1-Adrenergic Agonists MOA & drug
Bind to β1 receptors and stimulate a sympathetic nervous system response
• dobutamine
Clinical Uses?
Treat cardiac arrest, circulatory shock, hypoperfusion (by increasing heart rate and stroke volume)
Common adverse effects:
hypertension, tachycardia, constipation
β2-Adrenergic Agonists MOA & drugs
Bind to β2 receptors and stimulate a sympathetic nervous system response
• salbutamol, terbutaline, salmeterol, formoterol
• Clinical Uses?
• COPD, asthma (by promoting bronchodilation); stop premature labour (tocolytic)
Common adverse effects:
Fine muscle tremor, tachycardia, ↑ blood glucose
β–antagonists/ Beta-blockers MOA & drugs
Bind to β receptors and block a sympathetic nervous system response
-carvedilol, labetalol
• Clinical Uses?
• Cardiac disease, hypertension, migraine prophylaxis
β–antagonists/ Beta-blockers
Examples of b1 cardio-selective blockers
metoprolol, atenolol
Clinical Uses?
Ischemic Heart Disease -
Lowering of HR and force of contraction. Lessens work of heart
Hypertension - Effective only in hypertensive patients
Drop in BP is gradual
Reflex vasoconstriction is preserved. Less postural hypotension
Adverse Effects:
- Dizziness
- Lethargy
- Insomnia
- Diarrhoea
α2-Agonists-neg feedback mechanism
Majority of α2 receptors are located on the presynaptic neuron – binding of drugs to
these receptors stops release of more
catecholamines
Clinical Uses?
clonidine
apraclonidine
Clonidine and its derivative Apraclonidine are selective α2 receptor agonists. They block sympathetic nerve transmission associated with vasomotor tone
what is Clonidine used for?
hypertension
what is apraclonidine used for?
used as an adjunct in controlling glaucoma
Adverse effects
dizziness, drowsiness, dry nose/ mouth, nausea
Nicotinic receptors:
respond to stimulation by
nicotine
Muscarinic receptors:
respond to Muscarinic
extract obtained from toadstool mushroom. 5 subtypes M1-M5
where is nicotinic receptors found?
in the brain, autonomic ganglia , neuromuscular junction (skeletal muscle), adrenal medulla