Week 5- the cardiovascular system Flashcards
What is the purpose of the cardiovascular system?
-transport of oxygen and nutrients to the tissues
-removal of CO2 wastes from tissues
-regulation of body temperature
What are the two major adjustments of blood flow during exercise?
-increased cardiac output
-redistribution of blood flow from inactive to active muscles
What is the role of arteries and arterioles?
To carry blood away from the heart
What is the role of capillaries?
exchange of O2, CO2 and nutrients with tissues
What is the role of veins and venules?
carry blood towards the heart
What is the pulmonary circuit?
-right side of the heart
-pumps deoxygenated blood to the lungs via pulmonary arteries
-return oxygenated blood to the left of the heart via pulmonary veins
What is the systemic circuit?
-left side of the heart
-pumps oxygenated blood to the right side of the heart via veins
-left ventricle–> aortic arch- receives blood at a high pressure from the left ventricle
-aorta is elastic so can stretch and expand to cope with the high pressure of blood
What are the wall components of blood vessels?
-smooth muscle
-collagen
-elastin
-endothelium
What vessel contains valves to prevent backflow of blood?
Veins
What produces the main resistance to flow?
arteries and arterioles
What happens at the precapillary sphincters?
resistance is created by vasoconstriction to redirect blood flow
What is resistance?
measure of hinderance or opposition to blood flow through a vessel, caused by friction between the blood and the vessel wall
What is total peripheral resistance?
sum of resistances to flow in all individual organs
What is blood flow directly proportional to?
the pressure difference between the two ends of the system
what is pressure proportional to?
the difference between MAP and right arterial pressure
What is resistance dependent upon?
-length of the vessel
-viscosity of the blood
-radius of the vessel (greatest influence on resistance)
What is local vascular resistance?
the resistance to blood flow in an organ or tissue calculated from pressure and local organ/tissue flow
What are the sources of vascular resistance?
-MAP decreases throughout the systematic circulation
-larges BP decrease occurs across the arterioles- they are called ‘resistance vessels’
What is arteriovenous difference?
The amount of oxygen taken up from 100ml of blood at each heart beat
What is the Fick equation a relationship between?
cardiac output and a-vO2 difference and VO2
What send afferent feedback to higher brain centres for the initial drive of the cardiovascular system?
-heart mechanoreceptors
-muscle chemoreceptors (muscle spindles and GTO)
-pressure sensitive receptors (baroreceptors)
What are baroreceptors sensitive to?
changes in arterial blood pressure
What are muscle mechanoreceptors sensitive to?
force and speed of muscular movement
What are muscle chemoreceptors sensitive to?
changes in the chemical environment
(H ions, CO2, pH changes)
Where is a hypotensive stimulus detected?
in the aorta by baroreceptors
What does a hypotensive stimulus cause?
-increase in the total peripheral resistance
-increased HR
-increased cardiac output which increase blood flow
What plays an important role in resetting the arterial baroreflex during exercise?
-Central command
-exercise pressor reflex
