Controlling Blood Pressure Flashcards
Equation for total peripheral resistance?
R = resistance to blood flow
L = length of vessel
n = viscosity of blood flow
r = radius of blood vessel
Changing what aspect would have greatest effect on total peripheral resistance?
Change in radius
Why does BP need to be autoregulated?
Balance between organ perfusion and vascular damage –> driving force propelling blood to tissues
How is the ANS regulated?
- Baroreceptors
- Local (e.g. renal juxtaglomerular apparatus)
- Higher senses e.g fear
What are chronotropic effects?
Effects that change the heart rate
What is ionotropy?
An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular contraction.
What is dromotropy?
A dromotropic agent is one which affects the conduction speed in the AV node, and subsequently the rate of electrical impulses in the heart.
What is lusitropy?
Lusitropy is the rate of myocardial relaxation.
What is a natriuretic peptide?
A natriuretic peptide is a peptide which induces natriuresis - the excretion of sodium by the kidneys. Known natriuretic peptides include:
- Atrial natriuretic peptide (ANP)
- Brain natriuretic peptide (BNP)
What is effect of increased natriuretic peptides?
Induce excretion of Na+ in urine –> pee out more water, reduces pressure
When are natriuretic peptides released?
When myocytes are mechanically stretched by increased plasma volume (e.g. during heart failure)
What is hypertension defined as?
SBP ≥ 140mmHg
DBP ≥ 90mmHg
What are the 2 classifications of hypertension? How common is each?
- Primary (90% of cases)
- Secondary (10% of cases)
What is 1ary hypertension caused by?
- Over-activation of physiological mechanisms
- Age-related decrease in baroreceptor sensitivity
- Age-related vascular calcification (reduces compliance)
- No identifiable cause