Flashcards in Cardiovascular Lecture 5 Deck (29):
What is the main functional difference between the heart and vasculature?
Heart provides driving force for blood movement, while vasuclature plays active role in regulating blood pressure and distribution
What does vasuclature branching and specialization try to match?
Blood flow and demand (size affects velocity)
Are vessels specific for structure and function
What are some different parts of the vasuclature?
Arteries: elastic, absorb blood that comes out
Arterioles: variable radius, which is important
Capillaries: material exchange over a thin wall.
Veins: expandable, but not elastic. Also absorb blood.
What is the endothelium?
A smooth, single-celled layer that envelopes the entire circulatory system (from heart to capillaries)
What are the functions that endothelial cells provide?
1. Serve as a physical lining that blood cells will not adhere to
2. Serve as permeability barier for exchange of nutriebts, metabolic end products, fluid, etc; regulate transport of macromolecules and other substances
3. Secrete paracrine agents that act on adjacent vascular smooth muscle cells (vasodilators and vasoconstrictors)
4. Mediate angiogenesis (new capillary growth)
5. Central role in vascular remodellig by detecting signals and releasing paracrine agents
6. Contribute to formation and maintenance of extracellular matrix
7. Produce growth factors in response to damage
8. Secrete substances that regulate platelet clumping, clotting and anticlotting
9. Other non-cardiac effects
Describe the systemic arteries
Have thick walls with large amounts of elastic tissue and three layers: intima, media, adventitia
Describe the intima
Inner layer, single layer of endothelial cells, metabolically active barrier between blood and vessel wall
Describe the media
Vascular smooth muscle, elastin, and collagen fibres
Strength, contraction, and elastic properties
Describe the adventitia
Contains nerves, lymphatics and blood supply to vessel wall
Describe the two primary functions of the arterial system based upon their structure
1. Large radius: low-resistance tubes conducting blood to various organs; blood moves quickly through them.
2. Elasticity: Pressure resevoir for maintaining blood flow during diastole (compliance)
The inverse of stiffness. Compliance = change in volume / change in pressure.
Describe elasticity in relation to age.
Decreases, creating additional work for the heart via increased afterload.
What are the physiological determinants (can be controlled) of arterial blood pressure?
Cardiac output (how much blood came out)
Heart rate x stroke volume
Peripheral resistance (if arterial radium decreases, resistance increases)
What are the physical determinants (can't be controlled) of arterial blood pressure?
Arterial blood volume (more volume, more pressure)
What three measurements are taken in account for blood pressire?
Systolic (Ps, maximum)
Diastolic (Pd, minimum)
What is pulse pressure (PP)?
What is Pa?
What does the dicrotic notch in the blood pressure curve represent?
Aortic valve closure
What does arterial volume depend on?
The rate of inflow from the heart (Qh) and rate of outflow through the resistance vessels (Qr)
What increases mean pressure?
Increased cardiac output or peripheral resistance
What increases pulse pressure?
Increased peripheral resistance, arterial volume, or decreased compliance
How does a catheter measure bp?
In peripheral arteries using strain gauges
How does a sphygmomanometer measure bp?
Palpating radial artery - while cuff pressure exceeds systolic pressure no pulse percieved, a slight pulse percieved when they are equal
The asculatory method is more sensitive and permits measurement of diastolic pressure (Korotkoff's sounds)
Describe artioles in respect to blood flow
Regulate the rate and distribution of flow
Describe the composition of arterioles
Smooth muscles arranged in rings around the vessel, allowing changes in vessel diameter (vasoconstriction and vasodilation)
Describe the dual control of arterioles
Intrinsic (local conditions surrounding blood vessels) and extrinsic (nervous system input)
What are the three sources of intrinsic control of arterioles?
1. autoregulation/myogenic regulation
-blood flow adjusted to metabolic activity of tissue
-when metabolism steady, increased arterial blood pressure regults in changes in vascular resistance to maintain stable flow
-vessels contrict when blood pressure elevated and dilated when reduced
-due to changes in pressure across vessel wall (transmural pressure)
-related to stretch-induced Ca2+ release
-inactive under normal conditions, as baroreceptor reflex maintains constant blood pressure
2. Endothelium-mediated regulation
-endothelium lining produces substances that relax (ie nitric oxide) or contract (ie angiotensin II and endothelin) vascular smooth muscle
3. metabolic regulation
-Inadequate Inadequate O2 supply to tissue (increased metabolic rate or decreased O2
delivery) results in release of vasodilator metabolites that act locally to dilate
• Candidate Vasodilator Substances:
- Lactic acid, CO2, H+, PO2, K+, inorganic phosphates, interstitial osmolarity, Adenosine, Prostaglandins
• Basal tone: (i) myogenic response to stretch;
(ii) high PO2 of arterial blood; (iii) presence of Ca2+
• Responsible for reactive hyperemia