The autonomic nervous system & cardiovascular control during exercise Flashcards
What is the first stage of increasing HR during exercise?
Parasympathetic withdrawal - gets HR up to 100BPM.
This is followed by activation of sympathetic nervous system
What 3 factors regulate Stroke Volume ?
- End-diastolic volume (EDV)
- Average aortic blood pressure
-Strength of ventricular contraction (contractility)
What is EDV,and the principle variable that regulates it?
Volume of blood in ventricles at the end of diastole (preload).
- Principle variable that regulates EDV is the rate of venous return to the heart (can be different between TRN and UT)
What is average aortic BP?
Pressure the heart must pump against to eject blood (afterload)
- MAP
- Increase in cardiac afterload = decrease SV during resting conditions where influences on cardiac contractility (sympathetic stimulation + Frank-Starling law) are not at play.
What is strength of ventricular contraction enhanced by?
- Circulating epinephrine and norepinephrine
- Direct sympathetic stimulation of the heart
In simple terms, what is the frank-starling mechanism?
Greater EDV = more forceful contraction. This is due to stretch of ventricles
What increases venous return?
- Venoconstriction (via SNS)
- Skeletal muscle pump (+1-way valves in veins prevent backflow of blood)
- Respiratory pump (changes in thoracic pressure pull blood toward heart)
What does it mean if someone has a high arterial pressure?
Their cardiac output is restricted
What are systolic, diastolic, and pulse pressure?
Systolic pressure - pressure generated during ventricular contraction
Diastolic pressure - Pressure in the arteries during cardiac relaxation
Pulse pressure - difference between systolic and diastolic.
MAP = average pressure in the arteries
MAP = DBP + 0.33 (SBP-DBP)
- equation can only be used when someone is at rest
What is the (classic) MAP equation?
MAP = Cardiac Output x Total Vascular Resistance (sum of resistance to blood flow)
What is the short-term regulation of blood pressure?
SNS - baroreceptors in aorta and carotid arteries.
- Increase in BP = decrease SNS activity
- Decrease in BP = increase SNS activity
What is the long-term regulation of blood pressure?
Kidneys (via control of blood volume)
What do changes in HR and blood pressure during exercise depend on?
- Type, intensity, duration
- Environmental conditions
- Emotional influence pre-exercise and during submaximal exercise
What does recovery rate depend on?
- Duration and intensity of exercise
- Training state of subject
