Lecture 7 - Cardiovascular Pt 2 Flashcards
What is the Major function of the vascular system?
Maintain homeostatic bp and distribute oxygen and nutrient-rich blood flow to the tissue.
What are endothelial cells?
Innermost lining of vessels and heart
highly permeable to allow for nutrient/gas exchange
secretes paracrine factors that cause dilation/constriction
Evoke new capillary growth(angiogenesis)
Structure features of Large arteries
- large diameter
- very little smooth muscle
- elastic properties (high compliance) contribute to continuous downstream blood flow
Structure of arterioles
Smaller diameter than large arteries
a high proportion of smooth muscle, low proportion of elastic tissue
high resistance to flow
main site for flow regulation(dilation/constriction)
Structure of Venules and Veins
Highly elastic
low/no smooth muscle
Do not contribute to blood flow regulation
Represent a pooling site for blood
Structure of capillaries
Single endothelial layer to promote gas/fluid/nutrient exchange
What is arterial Blood pressure?
Force of blood on the walls of blood vessels
What is Systolic Pressure?
Maximal arterial pressure reached during peak ventricular ejection (~120mmHg)
What is Diastolic Pressure?
Minimal arterial pressure reached during peak ventricular ejection
What is Pulse Pressure?
magnitude of difference between SBP and DBP
What is Mean Arterial Pressure? What is the equation?
Average pressure throughout the cardiac cycle (diastole is longer) (~90mmHg)
MAP = DBP +1/3(SBP - DBP)
What is the major function of Large Arteries?
Low resistance tubes conducting blood from heart to systemic vasculature
- act as a pressure reservoir to maintain blood flow
How are Large Arteries a pressure reservoirs?
- Highly elastic/highly compliant
- expands to accommodate stroke volume
- during diastole, the aorta recoils to drive blood forward throughout arteries
- prevents BP from falling to 0 during diastole; ensures continuous flow to capillaries
What is vascular compliance?
Rigid large arteries will not store blood during diastole producing intermittent capillary flow
What are the 2 major factors that affect the radius of arterioles?
Local Mechanisms (active hyperemia, flow regulation)
Extrinsic Mechanisms (sympathetic nerve)
What is active hyperemia?
Vasodilation causes increase blood flow in muscle during contraction
What are the mechanisms of Active Hyperemia?
Decreased O2(consumed for ATP production)
Increased CO2 (byproduct)
Increased H+(from lactic acid)
Increased adenosine (ATP breakdown)
Increased K+ from action potential activity
Nitric Oxide release from endothelium
How do sympathetic neurons regulate arteriole radius?
Receive stimuli from sympathetic postganglionic neurons that release norepinephrine
Norepinephrine binds to alpha-adrenergic receptors to cause vasoconstriction
more sympathetic nerve activity = more vasoconstriction
What influences capillary blood flow?
Blood flow is influenced by the radius of the arterioles.
capillary blood flow is slow to maximize the time for exchanging
blood flow velocity is dependent on cross-sectional area in capillaries
What are the three main regulators of venous pressure
- Sympathetic Neural veno-constriction
- Skeletal Muscle Pump
- Respiratory Pump
What is the sympathetic neural veno-constriction regulator do for venous pressure?
Sympathetic nerves also innervate venules to cause constriction
Decreasing radius of veins increases pressure
increasing pressure gradient between peripheral and central veins drives blood back to heart
What is the skeletal muscle pump?
Skeletal muscle contraction compresses veins which increases venous pressure, forcing blood back to the heart
What is the respiratory Pump? Does inspiration or expiration drive blood back to the heart?
Contraction of the diaphragm muscle changes pressures in the chest to alter venous blood flow
Inspiration drives blood back to heart
What is the equation for mean arterial pressure
MAP = cardiac output x Total peripheral resistance
