LQB185 Chapter Notes - Chapter 21: Vascular Resistance, Mean Arterial Pressure, Blood Vessel
21.3 Hemodynamics: Factors Affecting Blood Flow
➢ Blood flow is the volume of blood that flows through any tissue
➢ Cardia Output (CO) depends on 2 factors:
1. Pressure differences
2. resistance
➢ Blood Pressure
- Contraction of ventricles generates blood pressure
- Mean arterial pressure (MAP) is the average blood pressure in
arteries.
➢ Vascular Resistance
- Opposition to blood flow die to friction between blood and walls
of vessel
- Resistance depends on:
1. Size of the lumen: smaller the lumen=greater the resistance
2. Blood viscosity: higher the blood viscosity= higher the
resistance, thickness of the blood, ration of red blood cells:
plasma volume.
3. Total blood vessel length: longer the vessel= greater resistance,
resistance is directly proportional to length of blood vessel
- Systemic Vascular Resistance (SVR): refers to all vascular
resistances offered by systemic blood vessels.
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➢ Venous Return
- Volume of blood flowing back to heart.
- Besides the heart, 2 other mechanism help pump blood from the
lower body back to the heart.
1. Skeletal muscle pump: milking that causes contraction that
drive venous blood toward heart
2. The respiratory pump: compression and decompression of
veins
➢ Velocity of Blood Flow
- The speed of blood flow, blood moves slower
and slower s blood moves further away from
the heart. Slowest in capillaries.
- Circulation time: time required for blood to
pass R) atrium to L) atrium and all the way
back to the R) atrium again.
21.4 Control of Blood Pressure and Blood Flow
➢ Several interconnected negative feedback systems control BP b adjusting
heart rate, stroke volume, systemic vascular resistance and blood
volume.
➢ Role of Cardiovascular Centre (CV)
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Document Summary
Blood flow is the volume of blood that flows through any tissue. Cardia output (co) depends on 2 factors: pressure differences, resistance. Mean arterial pressure (map) is the average blood pressure in arteries. Opposition to blood flow die to friction between blood and walls of vessel. Systemic vascular resistance (svr): refers to all vascular resistances offered by systemic blood vessels. Volume of blood flowing back to heart. The speed of blood flow, blood moves slower and slower s blood moves further away from the heart. Circulation time: time required for blood to pass r) atrium to l) atrium and all the way back to the r) atrium again. 21. 4 control of blood pressure and blood flow. Several interconnected negative feedback systems control bp b adjusting heart rate, stroke volume, systemic vascular resistance and blood volume. Role of cardiovascular centre (cv) (cv) in the medulla oblongata helps regulate heart rate and stroke volume.