CARDIOVASCULAR CARDIOVASCULAR REGULATIONREGULATION

Homeostatic mechanismsHomeostatic mechanisms regulate cardiovascular ac tivity to regulate cardiovascular ac tivity to ensure that tissue ensure that tissue perfusion, perfusion, or or blood flow through tissues, blood flow through tissues, meets the demand for oxygen meets the demand for oxygen and nu trients. and nu trients.

The three variable factors areThe three variable factors are: : (1) Cardiac out put, (1) Cardiac out put,

(2) peripheral resistance, and (2) peripheral resistance, and (3) blood pressure. (3) blood pressure.

The goalThe goal of cardiovascular of cardiovascular regulation is to ensure that these regulation is to ensure that these blood flow changes occur blood flow changes occur

(1) at an appropriate time, (1) at an appropriate time, (2) in the right area, and (2) in the right area, and (3) without drastically changing (3) without drastically changing

blood pressure and blood flow to blood pressure and blood flow to vital organs.vital organs.

FactorsFactors involved in the involved in the regulation of cardiovascular regulation of cardiovascular function include function include

1.1. local factors, local factors,

2.2. neural mechanisms, and neural mechanisms, and

3.3. endocrine mechanismsendocrine mechanisms..

A. Local factors:A. Local factors: Local factors Local factors change the pattern of blood flow change the pattern of blood flow within capillary beds in response to within capillary beds in response to chemical changes in interstitial fluids. chemical changes in interstitial fluids. AutoregulationAutoregulation occursoccurs at the tissue at the tissue level when each tissue controls the level when each tissue controls the amount of its blood supply according amount of its blood supply according to its need through controlling the to its need through controlling the tone of the blood vessel supplying it. tone of the blood vessel supplying it. If autoregulation fails to normalize If autoregulation fails to normalize conditions at the tis sue level, neural conditions at the tis sue level, neural mechanisms and endocrine factors mechanisms and endocrine factors are activated.are activated.

B. Neural mechanismsB. Neural mechanisms. . Neural mechanisms respond to Neural mechanisms respond to

changes in arterial pressure or changes in arterial pressure or blood gas levels at spe cific blood gas levels at spe cific sites. When those changes sites. When those changes occur, the cardiovascu lar occur, the cardiovascu lar centers of the autonomic centers of the autonomic nervous system adjust cardiac nervous system adjust cardiac output and peripheral resistance output and peripheral resistance to maintain blood pressure and to maintain blood pressure and ensure adequate blood flow.ensure adequate blood flow.

C. Endocrine mechanismsC. Endocrine mechanisms. . The endocrine system releases The endocrine system releases hormones that enhance short-hormones that enhance short-term adjustments and direct term adjustments and direct long-term changes in long-term changes in cardiovascular performance.cardiovascular performance.