CVS Flashcards
spread of excitation between cells is allowed for by what?
Gap junctions.
what are the steps involved in calcium induced calcium release?
- AP enters from adjacent cell
- VGCC (DHP receptor) open. allowing calcium entry.
- calcium induces calcium release though ryanodine receptor channels. (RyR)
- Local release causes calcium spark
- Sum of calcium parks create a calcium signal.
- calcium ions bind to troponin to initiate contraction
- relaxation occurs when calcium unbinds from troponin
- Calcium is pumped back into the sarcoplasmic reticulum for storage.
- Calcium is exchanged with sodium.
- sodium gradient is maintained by the sodium/potassium- ATPase.
Name some DHP blockers?
Verapamil and Diltiazem are antagonists and channel blockers
Nifedipine is a DHP and acts as an antagonist. has a greater effect on vascular
what do ryanodine receptors do?
located in the sarcoplasmic/endoplasmic reticulum membrane
responsible for the release of Ca2+ from intracellular stores during excitation-contraction coupling in both cardiac and skeletal muscle.
What is an agonist to ryanodine receptors?
Ryanodine. binds to RyR2 receptor to cause calcium induced calcium release.
What is an antagonist to Ryanodine receptors?
Dantrolene
what noradrenaline do in the innervation of the heart?
acts upon sympathetic neurones to increase influx of NA+ and Ca2+. binds to B1 receptors of the autorhythmic cells. increased rate of depolarisation and thus increased heart rate.
what does Acetylcholine do in the innervation of the heart?
Acts upon parasympathetic neurones and the muscarine receptors of the autorhythmic cells.
causes increased K+ efflux and decreased Ca2+ influx
Hyperpolarised and decreased rate of depolarisation leading to decreased heart rate.
What type of receptor are adrenergic receptors?
G protein coupled receptors.
propanolol is what?
Beta non specific antagonist
what is phenylephrine?
Alpha 1 specific agonist
Prazosin is what?
alpha specific antagonist. also an inverse agonist.
what is an intropic effect?
where there is an alteration to the force or energy of muscular contractions
what is a chronotropic effect?
effects that change the heart rate.
what is the intropic effects of noradrenaline on the heart?
Increase contraction
what can be used to increase peripheral resistance and blood pressure?
Noradrenaline
How can hypertension be reduced?
Cardioactive drugs such as beta blocker Propanolol
drugs that relax arterial smooth muscle and reduce peripheral resistance such as dihydroprydines like Nifedipine.
What is dihydropryridine?
antagonist of the V gated calcium channels on the vascular smooth muscle that can reduce peripheral resistance.
what do beta blockers do?
reduce the sympathetic effects of Noradrenaline.
what is angina?
is a transient ischemia of the heart muscle. the pain occurs when there is an inadequate cronary blood flow for the metabolic demands of the cardiac muscle.
How is angina treated with organic nitrates?
Organic nitrates produce Nitric oxide
NO activates soluble guanylate cyclase that produces cGMP
cGMP activates protein kinase G.
PKG causes smooth muscle relaxation of the coronary artery allowing better perfusion.
How does a heart attack happen?
cronary artery disease causes occlusion of the vessels. leads to reduced perfusion causing Ischemia and infarct. cells depolarise and die. can lead to dyrythsmias and heart faliure.
what are pharmocological ways of preventing coronary heart disease?
Statins that reduce cholesterol synthesis.
What are some of the acute treatments for coronary artery occlusion?
Clot busters (tissue plasminogen activator) Physical interventions such as stenting
Why are cardiac glycosides not used anymore for treating heart conditons?
very dangerous. if take wrong dose can kill very easily.
