Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, Pharmacology module.
PHAR 6, hypertension: treatments that are currently prescribed for hypertension, focusing on their pharmacodynamics to understand how these different drugs lower blood pressure and considering som...
Hypertension
What is hypertension ?
- condition in which blood pressure is too high
=> arterial vessels specifically: blood pushes against arterial walls
- P (pressure) = F (force) / A (area)
=> Blood Pressure = Force exerted by blood / Area of arterial wall
- blood pressure measured at brachial artery (upper arm)
=> systolic blood pressure: max pressure (heart fully contracted)
=> diastolic blood pressure: min pressure (heart fully relaxed)
=> measured in millimetres of mercury (mmHg)
- there is always force exerted on arteries (never 0)
=> elastic recoil of arteries (Windkessel effect)
=> blood continues to move around
-> recail back to
original shape
How to measure blood pressure
- sphygmomanometer/ blood pressure monitor:
- disturbs regular brachial blood flow by applying pressure to arm (inflate the cuff)
=> no blood flow
, - slowly released: sufficient pressure from heart to force blood through narrowed artery
=> turbulent blood flow: systolic pressure
=> stethoscope: rhythmic noises heard (Korotkoff sounds)
- pressure continually released until no sound
=> diastolic pressure (= no resistance)
S ⑪
Factors that influence blood pressure
- cardiac output (blood pumped by heart in a min): stroke V (blood pumped in 1 contraction)*heart rate
- total peripheral resistance/ systemic vascular resistance (SVR): diameter of vessels
- volume of circulating blood (determined by prod of RBCs and plasma)
- blood viscosity (consistency: thickness and stickiness)
- vessel walls elasticity (collagen + elastic fibres)
=> autonomic nervous system can control CO & total peripheral resistance: HR, vessel diameter...
- hypertensive: elevated systolic and/or diastolic BP
=> healthy BP depends on: - height & weight: affect metabolic demand of circulatory system
=> perfusion (blood delivery) of larger surface = increased CO & BP
=> BP increases during childhood
=> overweight + obesity = risk factor for increased BP
- age: lost of elasticity/ pathophysiological (ex: atherosclerosis)
=> BP increases as get older
arterial walls
fatty deposits
an
=> on contrary: height associated w/ low BP for old people
Blood pressure classifications
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