KN 252 Lecture 4: Circulatory Physiology – blood flow from the heart to the heart

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Department
Kinesiology
Course
KN 252
Professor
Marone Jane, Michael Jones
Semester
Spring

Description
Circulatory Physiology – blood flow from the heart to the heart Fluid Dynamics Three factors which effect the movement of blood from the heart through the blood vessels and back to the heart: • Pressure (BP) – the force per unit area exerted on the wall of the blood vessel by the blood contained within. This is driven by a drop in pressure from beginning to end of the circulatory pathway o Compliance affects BP – “stretchability” of the artery; more compliance, less pressure build up o Cardiac Cycle affects BP § Systole – pressure generated during contraction § Diastole – pressure maintained during relaxation o Location (in vascular system) affects BP § Arteries = highest pressure (average BP of large artery ~ 93.3 mmHg) § Capillaries = enter bed at ~ 40 mmHg (leave at ~ 20mmHg) § Veins = enter at ~ 20 mmHg (leave at ~ 0 mmHg at vena cava) • Flow (volume of flow) – same as Cardiac Output (hr x sv) Calculating Average Pressure o Venous Return (influences cardiac output) Mean Arterial Pressure = diastolic § Muscle pump (influences venous return) – pressure + pulse pressure/3 positive pressure § Respiratory pump (influences venous return) – Pulse Pressure = systolic – diastolic sucking in blood to thorax pressure • Resistance – retarding factor; affected by the following: o Viscosity – thickness of blood (hematocrit); thicker blood, greater resistance § Heart has to pump harder o Length of blood vessel – longer vessel, greater resistance o Diameter of blood vessel – smaller diameter, greater resistance § Due to laminar flow – fluid close to the sides of the tube is slowed by friction § The body regulates the diameter of the blood vessel/ uses this as a degree of resistance of blood flow ∗ Change in blood vessel diameter is neurologically controlled. This allowed manipulation of volume of flow through changing resistance [Flow = ΔP / Resistance] BP Control and Maintenance – to ensure proper flow to appropriate organs to maintain metabolism (Rapid way to deliver blood to an organ is through nervous system regulation of BP) • Short term regulation– driven by nervous reflexes o NEURAL – (Blood vessels are innervated by
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