november 12

Functions of the Cardiovascular System

To transport nutrients and remove metabolic waste.

Vascular Loop

A closed system through which blood flows.

Arteries

Large, muscular, and elastic vessels, largest being the aorta; transport blood away from the heart.

Arterioles

Smallest branching blood vessels, critical for controlling circulation and referred to as resistance vessels.

Resistance (to blood flow)

Opposition to blood flow within the vessels due to vessel diameter changes, affecting pressure and flow.

Vasoactive Responses

Control by the sympathetic nervous system through smooth muscle modulation; vasodilation increases radius, vasoconstriction decreases radius.

Cardiac Output (CO)

Critical measure representing blood flow per minute. Formula: $CO = \text{Heart Rate} \times \text{Stroke Volume}$

Resting Heart Rate

Approximately 70 beats per minute.

Stroke Volume (SV)

Approximately 60 to 80 mL per beat. Formula: $SV = \text{End Diastolic Volume} - \text{End Systolic Volume}$

End Diastolic Volume

Blood volume in the ventricles before contraction.

End Systolic Volume

Blood volume remaining in the ventricles after contraction.

Total Blood Volume (average adult)

About 5 liters circulating.

Blood Distribution at Rest

Liver and kidneys receive about 50% of cardiac output; skeletal muscles receive about 15-20%.

Blood Flow During Exercise

Redistribution of blood flow to working muscles, which can receive 80% or more of cardiac output for increased oxygen delivery and waste clearance.

Thermoregulation in Exercise

Increased blood flow to the skin to release heat via sweating, maintaining stable body temperature.

Vasoconstriction

Narrowing of blood vessel diameter to decrease blood flow.

Vasodilation

Widening of blood vessel diameter to increase blood flow.

Capillaries

One-cell-thick walled vessels, the primary site of gas exchange (unloading oxygen, loading CO2 and nutrients).

Venules

Blood vessels that collect deoxygenated blood from tissues.

Veins

Largest blood vessels returning blood to the heart, including the vena cava.

Pressure Differences (blood flow)

Key factor in blood flow, generated by heart contractions, with higher pressure in arteries compared to veins.

Formula for Resistance (blood flow)

$R = \frac{\text{viscosity} \times \text{length}}{\text{radius}^4}$

Mechanisms to prevent blood pooling in veins