EXPH 386 Leary Notes Pages 3-4 PDF

○ Decreases as the circulating blood moves away from the heart through arteries ○ BP has its greatest decrease in the small arteries and arterioles ○ BP continues to decrease as the blood moves through the capillaries and back to the heart through veins Blood Pressure...

○ Decreases as the circulating blood moves away from the heart through arteries ○ BP has its greatest decrease in the small arteries and arterioles ○ BP continues to decrease as the blood moves through the capillaries and back to the heart through veins Blood Pressure ○ Systolic blood pressure ○ Diastolic blood pressure Mean Arterial Pressure ○ MAP is the perfusion pressure of the organs ○ MAP < 60 mmHg for an appreciable amount of time the end organ will get insufficient blood flow and become ischemic ○ MAP = DBP + [ ⅓(SBP-DBP)] ○ Example: BP= 120/80 80 + [⅓(120-80)] = 93 Hypertension ○ Hardened arteries and neural hyperactivity causes increased resistance ○ 95% of cases are idiopathic (etiology unknown) Factors that influence arterial BP ○ MAP = CO * TPR where CO= HR x SV ○ Increased BP with increased: Blood volume Heart rate Stroke volume Blood viscosity Total peripheral resistance ○ TPR = diameter, length, viscosity Vessel length does not change by the time you are an adult The way TPR is changed is through the diameter of the vessel If we have a large vessel and we vasoconstrict it that severely decreases the blood flow How does altering CO change MAP? ○ With constant flow in and out of the vessel we maintain a constant MAP ○ If you increase your heart rate with exercise which increases your SV which increases your flow so your pressure will increase Flow cannot go farther faster in the vessel so the pressure therefore increases By changing the resistance of the end of the vessel that is how we maintain MAP Our body can adjust resistance on the ends of vessels to maintain MAP MAP needs to stay in our normal healthy range  If cardiac output goes down, TPR must increase to maintain MAP Total Peripheral Resistance ○ The body uses blood vessel diameter to help regulate BP ○ Nerves controlling the muscle fibers can cause the vessel to contract Vasoconstriction or Vasodilation Cardiac Output = HR x SV ○ CO is the amount of blood that is ejected by one ventricle in one minute ○ At rest, CO= 5 L/min ○ To increase CO Increase HR, SV, or both ○ When arterioles are relaxed, blood flows freely. This is similar to the free flow of water in a garden hose when the spray nozzle is removed. The spray nozzle adds resistance and a pressure build up Cardiac Output and TPR ○ MAP = CO x TPR or TPR = MAP/CO ○ MAP = DBP + [⅓ (SBP-DBP)] ○ TPR = DBP + [⅓ (SBP-DBP)]/ CO ○ At rest SBP = 126 DBP = 80 CO = 5 L/min TPR = 19 mmHg/L Steady Rate Exercise ○ During the first few minutes of exercise increased blood flow (CO) during steady rate exercise rapidly increases SBP ○ Vasodilation (active muscles) decreases TPR to increase blood flow to the peripheral vasculature ○ As exercise continues, SBP gradually decreases because the arterioles (in active muscles) continue to dilate which decreases TPR ○ Muscle contraction and relaxation “milks” blood back to the heart (venous return) Graded Exercise ○ SBP increases rapidly at the start of exercise, the SBP increases linearly with exercise intensity ○ DBP remains unchanged or decreases slightly ○ Max SBP may reach 200+ mmHg despite reduced TPR This level of blood pressure most likely reflects the heart’s large CO during maximal exercise by individuals with high aerobic capacity Blood Pressure Response to Exercise ○ Resistance exercise