Heart and Blood Flow 101

Blood flow and the heart muscle are much interconnected, as it flows quickly through large arteries and slowly through the capillaries. Blood pressure is the force exerted by the blood against the walls of the vessels (particularly in the arteries). Vessels experience vasodilation (dilation in flow and width) within areas of the body that require more oxygenated blood, while conversely, vessels experience vasoconstriction (reduction of flow) with areas that require less oxygenated blood. To determine blood pressure, you take the product of your cardiac output and peripheral resistance (blood vessel resistance within the body). Vessels that have higher resistance or built plaque (fatty deposits) inside the wall vessel would experience higher blood pressure, which could be very detrimental to the body. However, the more the vessel can stretch when pressure increases, the higher compliance (measure of how the vessel can be deformed or expanded) the individual has.

Circulation of the blood flow increases with activity, therefore, so does the capacity to deliver blood to tissues. To regulate blood flow, our body uses individual tissues to control the flow (contingent on our metabolic demands), our nervous system adjusts the blood pressure and determines which area of the body the blood should flow, and hormonal communication signals are released by the blood tissue.  As the demand of the body increases, so does the heart.
 
Essentially, increases in cardiac output linearly increases with oxygen consumption (such as your ventilation). And as the body performs exercises that requires lifting a lot of force (such as squats), blood pressure increases. This all stimulates our metabolic functions, which increases the demand of oxygen and rate pressure product (measure of oxygen consumption); which increases our heart rate and blood flow. Something important to note is that breathing adaptions and controlled ventilation can correspond to increases in oxygen consumption. Those who train on increasing oxygen consumption and meeting the demands, through proper ventilation, can marginally perform better in tasks. 
 
Important functions and components of blood include: 

• Transportation of nutrients and oxygen
• Carries waste products and carbon dioxide away from tissues
• Carries hormones and transports enzymes to tissues
• Plays a role in pH regulation and homeostasis
• Platelets – Cells responsible for blood coagulation
• Red Blood Cells (aka Erythrocytes)– Transports oxygen and carbon dioxide to and away from tissues
• White Blood Cells – Critical in a fully functional immune system
• Plasma – Clear fluid of the blood where cells are held