Cardiovascular Changes Associated with Physical Activity

Why does cardiovascular system change during physical activity

Alterations to meet demands of increased physical activity - nutrient and oxygen delivery, waste removal, regional changes to blood flow, thermoregulation
Changes to co, bp and blood flow, requires coordination of nervous system, heart and vasculature

Local changes as exercise begins

Increase in oxygen consumption, glucose demands, carbon dioxide production, metabolite production
Skeletal stretch receptors and local muscle receptors feed back to medulla informing of increase in activity, skeletal muscle capillary beds and arterioles vasodilate to increase blood flow = active hyperaemia

Vascular redistribution

Vascular beds not vital during exercise experience a decrease in blood flow - renal, dermal and abdominal viscera blood flow decreases - activation of adrenergic receptor causes vasoconstriction, blood flow is redistributed by ans

Cardiac output at rest

Typically 5-6L/min, product of hr x sv - both increase during exercise

Factors affecting co

Sympathetic innervation raises co = chronotropic (rate) and ionotropic (contractility) increases, adrenaline and noradrenaline

Cardiac reserve

Difference between resting and maximal co, higher in trained atheletes

Venous return

Increase in sv = increased amount of blood available to pump, preload and end diastolic volume

Venus return to right side of the heart

Facilitated by contraction of working muscles, venoconstriction, changes in thoracic pressure during deeper inspiration - more blood returned to the heart to pump back out

Pressure changes

Changes dramatically due to general systemic arterio-constriction for blood redistribution, causes rise in tpr

Pressure changes during intense exercise

Systolic and diastolic pressures increase = both co and tpr increase = map increases

Blood distribution during intense physical activity

No decrease to brain, increase to heart to meet co demands, significant decrease to abdominal viscera and kidneys, eventual increase to skin to maintain homeostasis, significant increase to skeletal muscle