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

3 Pages
Unlock Document

KN 252
Marone Jane, Michael Jones

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
More Less

Related notes for KN 252

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.