Cardiology Flashcards
Give examples of the functional responses of alpha-1 adrenoceptors.
Vasoconstriction
Increased blood pressure
Contraction of visceral smooth muscle
Relaxation of GI tract
Give examples of the functional responses of alpha-2 adrenoceptors.
Reduced transmitter and insulin release
Give examples of the functional responses of beta-1 adrenoceptors.
Increase SA node firing Lower AV refractory period Increase myocardium force Renin release from juxtaglomerular Relaxation of GI muscle
Give examples of the functional responses of beta-2 adrenoceptors.
Bronchodilation
Nitric Oxide release
Reduce histamine
Stimulate glycogenolysis
Describe the mechanism of acetylcholine.
Calcium stimulates fusion of ACh containing vesicles to the presynaptic membrane, releasing ACh into the synapse. This then binds to receptors on the post synaptic membrane
How is the cholinergic mechanism halted?
AChE cleaves the ester bond in ACh and the remaining choline is taken up into the nerve terminal to be converted back to ACh.
Describe the structure of a muscarinic acetylcholine receptor.
Slow G protein coupled receptor, monomeric with 5 subtypes, each with varying tissue distribution. Contains 1 G protein binding site and one ACh binding site
Describe the structure of a nicotinic acetylcholine receptor.
Pentameric ligand gated channel with 5 subunits (2 alpha, beta, epsilon and delta). Each has two ACh binding sites.
Define stable angina.
Chest pain occurring on exertion and alleviated by rest. Occurs due to partial occlusion of coronary arteries.
Define unstable/brittle angina.
Chest pain occurring at rest due to disruption of atherosclerotic plaque in coronary artery.
What is variant angina?
Chest pain due to reflex spasm of coronary arteries.
Describe the mechanism of stable angina.
Occurs upon release of bradykinin adenosine from muscles during exercise. Can result in maximal dilation of vessels thus release of potassium and hydrogen ions to sensory nerve terminals resulting in pain due to the inability to maintain oxygen supply.
What is the role of phosphodiesterase?
Breakdown of cGMP and cAMP
Describe the process of vascular smooth muscle contraction involving calcium.
Adrenaline binding to alpha-1 receptors activates phospholipidase C, catalysing formation of inositol triphosphate. This causes calcium ion release from the sarcoplasmic reticulum within the cell, leading to the opening of calcium sensitive chloride channels. The efflux of chloride causing depolarisation causes the opening of L-tpe calcium channels, calcium influx causes binding to calmodulin which activates myosin causing contraction.
Describe the roles of cholesterol in the body.
Essential in plasma membranes
Precursor for steroid hormones, bile acid and vitamin D3.