Pumps And Pipes Flashcards
Which GPCR stimulated signalling pathway leads to the tonic contractions typical of vascular smooth muscle? Give 2 agonists.
The Gq stimulated PLC pathway.
NA AND ACh
What product of vascular endothelial cells is responsible for smooth muscle relaxation?
NO: L-Arg converted to NO by NO- synthase NO diffuses into cell activating sGC sCG converts GTP to cGMP cGMP activates PKG PKG stimulates SR Ca uptake, activates Ca-ATPase, inhibits Ca- voltage gated ion channels
Describe a circulating hormone and signalling pathways that causes vascular smooth muscle relaxation.
Adrenaline: Activates Gs Gs activates AC AC converts ATP to cAMP cAMP activates PKC PLC inhibits MLCK
Name a local anaesthetic labour to plasma esterases.
Procaine
Name a local anaesthetic that is metabolised in the liver.
Lidocaine
What is the local anaesthetic molecular target?
A receptor site in the inner cavity of the pore of the sodium-voltage gated ion channel
How do local anaesthetics mediate their effects?
When bound to the VGIC the influx of Na is interrupted preventing action potentials
They bind more readily to the receptor site in the activates state
What is the relationship between cardiac output, total peripheral resistance and blood pressure?
Cardiac output= pressure/resistance
What is the normal blood pressure?
110/70
What is the hypertensive blood pressure?
160/100
What is a false transmitter?
A compound which closely imitated the action of a neurotransmitter
Why would a drug with alpha agonist properties lower blood pressure?
Drugs act presynaptically, inhibiting the release of the NA, reducing the heart contraction
How do K channel openers cause vasodilation?
Minoxidil:
Block the ability of ATP to bing to the channels (so the channels open)
Opening the channels causes the membranes to hyperpolarise
Hyperpolarisation causes Ca channels to close, relaxing smooth muscle
Relaxation causes the resistance to decrease, reducing hypertension
What are the consequences of vasodilatory therapy?
Reflex tachycardia due to baroreceptor activation by beta 1 stimulation
Activates the renal angiotensin system
How are vasodilatory therapy side effects prevented?
Use beta 1 antagonists as adjuncts
Why do beta 1 antagonists cause a fall in BP?
Block the juxtaglomerular kidney cells
This inhibits renin release
Relieves renin dependent hypertension
They cross the BBB (if lipophilic) to reduce the sympathetic drive
When the brain stem is targeted. The peripheral resistance reflex is switched off, decreasing hypertension
What is heart failure?
Condition where the heart is unable to sufficiently pump to maintain blood flow to meet the body’s needs
What drug treats heart failure?
Captopril:
Angiotensin converting enzyme inhibitor
What is the underlying pathophysiology of angina?
Results when there is an imbalance between the hearts oxygen demand and supply
What are the objectives of treatment of angina?
Reduce symptoms
Slow the disease progression
Reduction of future events
How do nitrates treat angina?
Nitroglycerin:
They supplement the blood concentration of NO
relaxes vascular smooth muscle
What is coronary steal?
An alteration of circulation patterns lead to a reduction in the blood directed to the coronary circulation
What effect does dipyridamole have by causing coronary steal?
It causes more ischemia
Why do beta receptor antagonists work in treating angina?
Reduce heart rate, increasing the hearts ejection fraction
Inhibit renin secretion, reducing heart oxygen demands
Name the four sites at which diuretics can act in the Kidney tubule.
Thick ascending loop of henle
Early distal tubule
Collecting tubule
Collecting duct
What is an osmotic diuretic?
Pharmacologically inert substance that inhibits the reabsorption of water and Na
They increase the osmolarity of blood and renal filtrate
Describe vasopressin.
Increasing water retention by increasing water permeability of kidneys
Causes vasoconstriction increasing peripheral vascular resistance
What drug is used in low vasopressin secretion?
Desmopressin
What is terlipressin used for?
Vasoconstrictor in some conditions
What protein kinase is activated by Calcium/calmodulin to produce vascular smooth muscle contraction?
Myosin light chain kinase
