BP control Flashcards
What is BP? What is it a balance between?
- Driving force propelling blood to tissues
- Balance between organ perfusion and vascular damage (too much blood)
- Closely autoregulated
What is the equation for CO?
Cardiac output (L/min) = heart rate x stroke volume
What is the equation for mean systemic arterial pressure?
Mean systematic arterial pressure = cardiac output x total peripheral resistance
What is the equation for Total peripheral resistance?
R = resistance to blood flow L = length of vessel η = viscosity of blood flow r = radius of the blood vessel
R= 8nl/ Pi x r^4
How is the ANS regulated?
- Baroreceptors- found in aortic arch and carotid bodies/ sinus
- Local e.g. renal juxtaglomerular apparatus
Where are baroreceptors located?
Located: Carotid sinuses, Aortic Arch
How does baroreceptor increased/ decreased firing affect sympathetic and parasympathetic tone?
• ↑Baroreceptor firing – Decreases Sympathetic Tone – Increases Parasympathetic Tone • ↓Baroreceptor firing – Increases Sympathetic Tone – Decreases Parasympathetic Tone
If mean systemic arterial pressure decreased, how would that affect baroreceptor firing, sympathetic and parasympathetic tone?
If mean systemic arterial pressure decreased, baroreceptor firing would decrease, sympathetic tone would increase and parasympathetic tone would decrease.
If mean systemic arterial pressure increased, how would that affect baroreceptor firing, sympathetic and parasympathetic tone?
If mean systemic arterial pressure increases, baroreceptors fire more, sympathetic tone will decrease and parasympathetic tone will increase.
What are direct sympathetic actions?
① Positive chronotropy-SA node regulates- speeds up the HR acting on sinus node- changing the rythm
② Positive dromotropy (conduction)-AV node
③ Positive inotropy (contraction)-Ventricles and atria
④ Positive lusitropy (relaxation)-Ventricles and atria
What are systemic sympathetic actions?
① Activation of Renin-Angiotensin-Aldosterone-System (RAAS)
② Suprarenal stimulation- Catecholamines
How does the RAAS system work?
Liver to Angiotensinogen to Renin converts angiotensinogen to angiotensin I to Angiotensin converting enzyme converts AgI to AgII to Ag II leads to pituitary glands secreting aldosterone and AgII leads to vasopressin.
What is blood pressure regulated in the long term?
Natriuretic peptides
- Induce excretion of Na+ in the urine
- ANP = atrial natriuretic peptide
- BNP = brain natriuretic peptide
- Released when myocytes are mechanically stretched by increased plasma volume
What are the results of hypertension?
High BP- able to compensate for stresses in the body Ischemia Heart Disease (IHD) Cerebrovascular accident/ stroke (CVA) Cardiovascular Disease (CVD) Atrial Fibrillation (AF) Peripheral Vascular Disease (PVD)
How to classify hypertension?- Primary
Primary (Essential):
90% of cases
• Over-activation of physiological mechanisms
• Age-related decrease in baroreceptor sensitivity
• Age-related vascular calcification- causes vessels to be more stiff
• No identifiable cause
Primary- don’t know why someone has high BP- over activation of mechanisms
How to classify hypertension?- Secondary
10% of cases
• Renal – Renovascular disease, parenchymal disease
• Endocrine – Conn’s syndrome, Cushing’s syndrome, Cardiovascular – Coarctation of aorta
• Tumour – Phaeochromocytoma
• Pregnancy – Pre-eclampsia, eclampsia
Secondary- not that common- related to something else that is causing high
What is pheochromocytoma?
Pheochromocytoma is a rare tumour of adrenal gland tissue. is a rare tumour of adrenal gland tissue.
What is Conn’s syndrome?
Conn’s syndrome is a rare health problem that occurs when the adrenal glands make too much aldosterone.
What is pre-eclampsia?
Pre-eclampsia (PE) is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine.
What is white coat syndrome?
White coat syndrome- people exhibit a blood pressure level above the normal range, in a clinical setting, although they do not exhibit it in other settings
What are complications of hypertension to the heart?- LVH
Heart- LVH- left ventricular hypertrophy
High BP
No valve barrier but blood is trying to get out of an area at a higher pressure- more difficult
So muscle has to get stronger in order for this to happen.
LVH increases LV thickness, reduces LV cavity radius and therefore reduces wall stress.
What is the law of Laplace for LV cavity P?
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)
What are complications of hypertension to the heart?- Diastolic dysfunction?
Heart- Diastolic dysfunction- thickens too much- if ventricle too stiff and thick won’t relax enough for blood to move.
What are complications of hypertension to the heart?- Hypertensive heart failure
LVH to Increased stiffness to Increase LV End diastolic pressure to Increase LA pressure to Pulmonary congestion/ oedema (fluid in the lungs) to Heart failure
Diastolic dysfunction to Impaired relaxation to Increase LV End diastolic pressure to Increase LA pressure to Pulmonary congestion/ oedema (fluid in the lungs) to Heart failure
