regulation of cvs pt 2

perfusion

the flow of blood per unit volume of tissue

perfusion pressure

• controlled variable in the circulation is not flow but pefusion pressure

• failure to achieve adequae perfusion pressure results in circulatory shock resulting in hypoxia, impaired metabolism- necrosis

• excessive perfusion pressure results in capillary damage, endothelial injury and fluid exudation

systolic arterial pressure

peak pressure in the artieries when the left ventricle is ejecting blood during systole

diastolic arterial pressure

residual pressure in the artieries when the left ventricles is filling during diastole

calculating mean arterial pressure

MAP= DAP+ (SAP-DAP)/3

mean arterial pressure from co and tpr

map= co x tpr

baroreceptor

• short term regulation

• non encapsulated nerve endings in adventitial layer or arteries (aortic arch and carotid sinus)

• central axons terminate in medulla oblongata

• serve as mechanoreceptor- increase firing in response to distension

• increase heart rate- increase firing and vice versa

baroreceptor reflex

• increase in baroreceptor discharge (acute rise in bp)➟brainstem➟increased vagal output➟⤵ heart rate➟⤵ bp

• brainstem➟decreased sympathetic output➟⤵ contractility, heart rate, arteriolar tone➟⤵ blood pressure

Renin angiotensin aldosterone system

low blood pressure↪decrease renal perfusion↪renin↪angiotensinogen to angiotensin I ↪angiotensin ii through ACE⤸⤸⤸

• posterior pituitary↪vasopressin/ADH↪sodium and water retention↪increase plasma volume↪increase CO↪increase BP

• arterioles and venules↪vasoconstriction

• peptidases↪inactive peptides

• adrenal cortex↪aldosterone↪sodium and water retention↪increase plasma volume↪increase CO↪increase BP

how is total arterial resistance controlled

• arterioles are main source of resistance

• arteriolar diameter determines resistance to blood flow

• arteriolar radius controls TPR (total peripheral resistance)

long term control

• involves control of fluid volume

• ADH, vasopressin

• renin angitensin aldosterone system

what is angiotensin ii

hormone and peptide which narrows blood vessels and triggers release of other hormones to increase bp

flow from driving force and resistance

driving force/ resistance

how is total peripheral resistance controlled

• arterioles are main source of resistance as greatest fall in pressure occurs across arterioles

• arteriolar diameter determines resistance and therefore controls blood flow

• arteriolar radius controls TPR