Controlling Blood Pressure Flashcards
(37 cards)
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
What is 2ary hypertension caused by?
Related to something else causing high BP
- Renal –> renovascular disease, parenchymal disease
- Endocrine –> Conn’s syndrome, Cushing’s syndrome
- Cardiovascular –> coarction of aorta
- Tumour
- Pregnancy
What is effect of hypertension on left ventricle?
- Left ventricular hypertrophy –> muscular wall builds up
- Increased stiffness
- Increased LV end diastolic pressure
- Increased LA pressure
- Pulmonary congestion
- Heart failure with preserved EF
What is effects of left ventricular hypertrophy?
Ventricle cannot fill up properly because it is too small and contracts too often/strongly
What is Laplace’s Law?
For any given LV cavity pressure (P), the wall stress will be directly proportional to the LV cavity size or radius (R) and inversely proportional to the LV thickness (T)
LVH increases LV thickness, reduces LV cavity radius and therefore reduces wall stress
What is effect of hypertension on diastolic dysfunction?
- Impaired relaxation
- Increased LV end diastolic pressure
- Increase LA pressure
- Pulmonary congestion
- Heart failure with preserved EF
What effect does prolonged hypertension have on vasculature?
Vascular remodelling. More prone to atherosclerosis and large vessel structural damage
What is eutrophic remodelling and when does it occur? How does this affect blood pressure?
Small arteries undergo remodelling due to hypertension which results in an increase in wall thickness and reduction in lumen diameter.
Increased SA:Volume ratio leading to increased diastolic BP
What is hypertrophic remodelling? How does this affect blood pressure?
Large arteries –> increased wall stiffness but lumen diameter is preserved, leading to increased systolic BP
What are complications of hypertension on kidneys?
- Renal arteriole thickening leads to luminal narrowing
- Resulting ischaemia –> tubular atrophy (waste away) and interstitial fibrosis
- Damage to glomeruli –> haematoproteinuria (blood + excess protein in urine)
