Alpha Blockers/Beta Blockers/ Calcium Channel Blockers Flashcards
(25 cards)
Atropine
An anatagonist at all muscarinic receptors - causes heart rate to increase
Alpha 1 receptors
Vascular smooth muscle - VASOCONSTRICTION
GPCR- Gq = activates PLC
Higher affinitey to NE>E
Beta 1 receptors
Increase heart rate + force
GPCR - Gs = stimulate adenyl cyclase
Higher affinity to epinephrine
Mechanism of alpha 1 receptors
1) agonists lead to formation of IP3
2) IP3 formed by PLC activates IP3R = releases calcium from the sarcoplasmic reticulum
3) free Ca in the cytosol activates RYR - releases more Ca in the CDCR = Ca spark
Smooth muscle contraction mechanism
1)Ca spark = binding of 4 Ca ions to calmodulin
2)Ca - CaM complex activates myosin light chain kinase - phosphorylates regulatory light chain = associated with each neck of the dimeric myosin 2 heavy chain
3) Phosphorylation causes a conformational change in myosin head = increases angle in head/neck domain of myosin - increases ATPase activity - interact efficiently with action = molecular motor
CROSS BRIDGE CYCLING AND SMOOTH MUSCLE CONTRACTION
Mechanism of B1 receptor
1) cAMP formed by AC = PKA - phosphorylates a number or receptors (more likely to open)
2)IP3R and RYR2 are phosphorylated = more Ca released from sarcoplasmic reticulum into the cytosol
3) free Ca in the cytosol activates RYR2 = more Ca in CDCR
INCREASED FORCE OF CONTRACTION
Increased chrontropy
High [Ca2+] at SAN&AVN = increases depolarisation rate
Increased inotropy
High [Ca2+] in cardiac myocytes = increases force of contraction
M2 receptor mechanism to decrease heart rate
1) PNS send AP from medulla oblongata via vagus nerve to the heart = control heart rate
2) Vagus nerve releases ACh - acts on M2 receptors of SAN/AVN - reduce pacemaker activity
3) M2 receptors - inhibitory Gi - agonist = decrease in cAMP/PKA = decrease heart rate
4) Reduction in pace maker = reduction in heart rate = decrease in cardiac output
Atropine is an antagonist at muscarinic receptors. At M2 will it increase heart rate or decrease heart rate?
INCREASE HEART RATE
M2 = Gi - inhibitory
Antagonist - increase cAMP and PKA = increase heart rate
The a1 agonist phenylephrine is added to cold medications will it cause vasoconstriction or vasodilation?
VASOCONSTRICTION
a1 - Gq - increase in IP3 and Ca2+
Phenylephrine
reduce nasal congestion
a1 agonist
Clonidine
resistant hypertension - causes vasodilation
a2 agonist
Dobutamine
Cardiogenic shock
B1 agonist
increased heart rate + force of contraction
Salbutamol
Bronchodilation
B2 agonist
Epinephrine
anaphylaxis and MI
agonist of a1/a2/B1/B2
increased heart rate + force of contration and central shunting of blood
Norepinephrine
Agonist of a1/a2/B1
Doxazosin
resitant hypertension - vasodilation
a1 antagonist
Prazosin
resistant hypertension and benign prostatic hyperplasia
a1 antagonist
Atenolol/Bisoprolol/Metaprolol
primarily hypertension + heart failure after MI
cardio selective - B1 antagonist ONLY
Phenoxybenzamnine
phaeochromocytoma
non selective a1/a2 antagonist - causes irreversible blockade of all a adrenoreceptors
Propranolol
hypertension/angina
non selective B1/B2 antagonist (same as timolol)
A 45 year old Caucasian man presents clammy + crushing pain. Has a blue inhaler. Which beta adrenergic agonist should be administered?
Epinephrine
- heart attack
A man with asthma had MI now has heart failure. Which beta adrenergic antagonist should not be administered?
Propranolol
- non selective beta blocker = cause bronchoconstriction - asthma
NEED CARDIO SELECTIVE
