perfusion Flashcards
Perfusion
the flow of blood through arteries, capillaries, veins delivering nutrients to the tissues, at adequate pressure, and removing metabolic waste.
Central perfusion:
flow of blood from the heart towards tissues and back to the heart
Tissue perfusion:
flow of blood through the capillaries and tissues
What kinds of variation in perfusion impairment are there?
duration: acute vs chronic
Type: central vs tissue
Degree of impairment: ischemia vs infarction
What is the function of the arterial system?
distributing blood to the tissues, pressure reservoire
What is the function of the venous system?
returns blood to the heart, volume reservoir
What factors influence normal central perfusion?
- CO
- contractility
- BP
- BV
- vascular resistance
What factors influence normal tissue perfusion?
-adequate pressure to meet demands
- external pressure must not exceed capillary pressure
- patency of blood vessels
- occlusions
metabolic demand
- central perfusion
How is BP regulated in the body neurally?
neural: baroreceptors in carotid artery and signal to the brain, the medulla triggers homeostatic mechanisms that lower the blood pressure (vasodilation and bradycardia)
How is BP regulated in the body hormonally?
RAAS (hormonal): drop in BP, sensed by the kidneys, produce renin, renin acts on angiotensinogen to become angiotensin I, lung and vascular endothelium converts angiotensin I into angiotensin II, systemic arteries constrict and increase BP, angiotensin II also causes production of aldosterone with increases Na+ and H2O reabsorption in the kidneys, increases the BP by increasing BV
Epinephrine/norepinephrine (hormonal):
Constrict most blood vessels (GI tract for example)
Dilate blood vessels that go to the heart and skeletal muscles
What are the three factors that cause variation in BP
- Age: bp increases with age due to vessels stiffening and narrowing
- Stress: BP increases transiently during physiological or emotional stress
- Circadian variations: BP is highest shortly after waking, lowest between 2-5am
exercise
Auscultatory gap:
no sound somewhere between the systolic and diastolic number, probably caused by stiffening of vessels
What are the three ways that the body can regulate BP?
- local
- neural
- hormonal
Arterial system function:
distributes blood to tissues, pressure reservoir
Venous system function:
returns blood to the heart, volume reservoir
What is the scope of perfusion?
optimal: tissue demands for oxygen and nutrients are met
impaired: ischemia, tissue damage
no perfusion: cell death, infarction
What factors influence normal tissue perfusion?
Adequate pressure to meet demands
External pressure must not exceed capillary pressure
Patency of blood vessels (how strong they are)
Occlusions
Metabolic demand
Central perfusion
Consequences of impaired perfusion (central and tissue)
Central: CO decreases, increased HR, ventricular hypertrophy, cardiogenic shock
Tissues: tissue death, peripheral shock, organ failure
What two things influence blood pressure?
CO and SVR
Explain how blood pressure is controlled hormonally
drop in BP, sensed by the kidneys, produce renin, renin acts on angiotensinogen to become angiotensin I, lung and vascular endothelium converts angiotensin I into angiotensin II, systemic arteries constrict and increase BP, angiotensin II also causes production of aldosterone with increases Na+ and H2O reabsorption in the kidneys, increases the BP by increasing BV
Explain how blood pressure is controlled neurally
baroreceptors in the carotid artery signal to the medulla that blood pressure is high, triggers homeostatic mechanisms that cause vasodilation and bradycardia
