CV changes in exercise Flashcards
What are the 4 mechanisms of controlled response to increased physical activity?
Local
Neural
Hormonal
Mechanical
What are the local responses to exercise?
Increased metabolites in cardiac muscle and skeletal muscle increase blood flow
Decreased blood flow to splanchnic and renal circulations
Vasodilation in skin to release heat
Increased CO2, H+, and 2,3-DPG favors unloading O2
What will shift the hemoglobin dissociation curve to the right?
Increased CO2
Increased H+ (decreased pH)
Increased 2,3-DPG
What does is mean if the hemoglobin dissociation curve is shifted to the right?
Favors oxygen unloading and increased oxygen extraction by tissues
What is the neural response to exercise?
Increased SyNS
Decreased PsNS
What is the response of circulation to increased SyNS during exercise?
Increased HR and contractility –> increased SV
Vasodilation of vessels supplying cardiac muscle and skeletal muscle
Venoconstriction of capacitance vessels –> increases VR
Vasoconstriction of renal and splanchnic vessels
What is the hormonal response to exercise?
Increased epinephrine –> vasodilation in muscles and renal vasoconstriction
What is the mechanical response to exercise?
Skeletal muscle pump and thoracic pump increase VR
Sustained muscle contraction impedes flow –> significant increase in HR, SBP, DBP, and MAP
What are the changes in SBP and DBP in moderate isotonic exercise?
Increase SBP
DBP unchanged
What are the changes in SBP and DBP in severe isotonic exercise?
Significant increase in SBP
Decreased DBP
What are the changes in SBP and DBP in isometric exercise?
Both increase
What occurs during rhythmic exercise?
Blood vessels dilate in active muscles
Muscles pump the blood to circulate faster
Increased blood flow increases SBP initially and then it will level off
DBP does not change significantly
Similar response in conditioned and unconditioned individuals
What occurs during resistance exercise?
Strained muscle activity compresses peripheral arteries –> significant resistance to blood flow and both SBP and DBP increase
Dangerous in HTN and heart disease pts
What are the equations for estimated HRmax?
HRmax = 220 - age in years
HRmax = 208 - (0.7 x age in years)
What is the steady-state HR?
Point of plateau, the optimal HR for meeting circulatory demands at a submaximal intensity
What are the changes in SV seen with exercise?
It will increase with increased intensity up to 40-60% of VO2max, from there is plateau until exhaustion
SV during maximal exercise is about double standing SV, but only slightly higher than supine SV
What are changes in CO seen during exercise?
Increases with increasing intensity and plateaus near VO2max
What are normal values of CO during rest, untrained Qmax, and trained Qmax?
5 L/min at rest
Untrained Qmax = 20 L/min
Trained Qmax = 40 L/min
What is the purpose of the Fick principle?
Calculation of tissue O2 consumption depends on blood flow and O2 extraction
What are the equations related to the Fick principle?
VO2 = CO x (a-v)O2 difference
VO2 = HR x SV x (a-v)O2 difference
What are the changes in MAP during endurance exercise?
MAP increases
What is cardiovascular drift associated with?
Increased core temperature and dehydration
What are the cardiovascular drifts?
SV drifts down
Skin blood flow drift up
Plasma volume drifts down, from sweating
VR/preload drifts down
HR drifts up to compensate
What are the arterial blood oxygen contents at rest compared to at max exercise?
Rest: 6 mL O2/100 mL blood
Max exercise: 16-17 mL O2/100 mL blood
What is the normal mixed venous blood oxygen content?
Greater than or equal to 4 mL O2/100 mL of blood
What is the first priority of cardiovascular responses?
Maintenance of BP
What is the O2 debt?
About 11.5L of additional O2 that must be consumed after exercise to restore ATP and process lactic acid
How much of the O2 debt is used to remove lactic acid?
About 8 L
What is the definition of VO2max?
The maximum amount of oxygen an individual can use during intense/maximal exercise
What can VO2max be used to assess?
CV fitness and aerobic endurance
What is the primary limiting factor of VO2max?
Maximal CO, particularly maximal SV
What is concentric hypertrophy?
Sarcomeres added in parallel in ventricle wall creating decreased ventricular compliance
When is concentric hypertrophy seen?
Increased afterload conditions like aortic stenosis and HTN
Static exercise
What other conditions are associated with concentric hypertrophy?
Diastolic dysfunction first then systolic dysfunction later
S4 heart sound
What is eccentric hypertrophy?
Sarcomeres added in series in ventricle wall creating decreased ventricular compliance
When is eccentric hypertrophy seen?
Volume overload conditions
Pregnancy
Physiologic hypertrophy in athletes
