Exercise Phys

Question 1

describe CNS and local response to exercise

Answer 1

• CNS: motor cortex activated, communicates with CVS control centers–reduces vagal tone, resets arterial baroreceptors to higher level, increases sympathetic activity
• Local Response: lactic acid is formed which stimulates muscle afferent nerves (muscle chemoreflex), information to CVS center increases sympathetic activity to heart and systemic resistance vessels
  
  • increased NO and vasodilators

Question 2

describe changes to enhance O2 delivery to exercising muscles

Answer 2

• SBP increases via muscle chemoreflex, diastolic remains near resting values
  
  • rise in MAP normally less than increment in CO, reflecting a decrease in peripheral vascular resistance
• distribution of blood flow related to skeletal muscle vasodilation due to local decreases in pH and PaO2, and local increases in NO, adenosine, potassium
• rightward shift (decreased O2 affinity) of oxyhemoglobin dissociation curve with acidosis increase skeletal muscle O2 extraction