Vascular Physiology & Pharmacology: Neuronal Control of Blood Pressure

Vocabulary flashcards covering the neuronal and pharmacological control of blood pressure, including baroreceptor mechanisms, adrenergic drugs, and calcium channel antagonists.

Poiseuille’s law

A law stating that the radius of a blood vessel presents the largest contribution to resistance of blood flow, where resistance is inversely proportional to the radius to the fourth power ($1/r^4$).

Baroreceptors

Sensory receptors located in the aortic arch and carotid sinus that detect changes in blood pressure and send input to the vasomotor centre.

Vasomotor centre

An area in the brain that receives input from baroreceptors and produces reciprocal changes in sympathetic activity to regulate blood pressure.

Reserpine

An alkaloid extract of the roots of a climbing shrub that affects the storage of noradrenaline (NA) by binding to storage vesicles and stopping them from concentrating NA.

Guanethidine

An anti-hypertensive used in the 1970s that is taken up by uptake 1 and competes with noradrenaline for storage vesicles; it also interferes with depolarisation secretion coupling.

Uptake 1

A pump mechanism that takes up noradrenaline into the sympathetic nerve terminal; it is also the route by which reserpine and guanethidine enter the nerve.

$\alpha_1$-adrenoceptors

Adrenoceptors found on arterial smooth muscle that, when activated by noradrenaline, lead to arterial contraction via the PLCeta, $IP_3$, and $Ca^{2+}$ pathway.

$\alpha_2$-adrenoceptors

Adrenoceptors found on nerve terminals (pre-junctional) that act to inhibit transmitter release when activated.

Shock

A clinical syndrome characterised by inadequate perfusion of tissues, usually associated with hypotension and failure of organ systems, caused by factors like hypovolemia or cardiac failure.

Methoxamine and Phenylephrine

$\alpha_1$-adrenoceptor agonists used to increase blood pressure in the treatment of hypotension and shock.

Prazosin

An $\alpha_1$-adrenoceptor antagonist used in the treatment of hypertension to block noradrenaline-induced artery constriction.

Clonidine and Methyldopa

$\alpha_2$-adrenoceptor agonists that activate pre-junctional receptors to block transmitter release from sympathetic nerves.

Yohimbine

An $\alpha_2$-adrenoceptor antagonist that blocks pre-junctional receptors and potentiates transmitter release from sympathetic nerves.

N-type calcium channels

Voltage-dependent calcium channels located on neurons involved with transmitter release.

L-type calcium channels

Long-lasting voltage-dependent calcium channels found on smooth muscle that are targeted by anti-hypertensive blockers.

Dihydropyridines (DHPs)

A class of L-type calcium channel blockers, such as nifedipine, that primarily affect smooth muscle to treat hypertension.

Verapamil

A phenethylalkamine L-type calcium channel blocker that primarily affects the heart.

Diltiazem

A benzothiazepine L-type calcium channel blocker that affects both the heart and smooth muscle.

Mode 0

A state of the L-type calcium channel where it cannot open on depolarisation; stabilized by dihydropyridine calcium channel blockers like nifedipine.

BAY K 8644

A dihydropyridine L-type calcium channel opener that increases calcium currents by stabilizing Mode 2 (high probability of opening).