ANS and Cardiovascular system W3 Flashcards
What is cholinergic?
Acetylcholine
What is adrenergic?
Norepinephrine
What causes the initial increase of heart rate at the onset of exercise?
Initial increase due to parasympathetic withdrawal
What causes the later increase of heart rate at the onset of exercise?
Due to SNS outflow
What is end-diastolic volume (EDV)?
Volume of blood in the ventricles at the end of diastole (“preload”)
What is average aortic blood pressure?
Pressure the heart must pump against to eject blood (“afterload”)
Mean arterial pressure
What regulates stroke volume?
End-diastolic volume
Average aortic blood pressure
Strength of the ventricular (contractility)
What is the strength of the ventricular (contractility) enhanced by?
Circulating epinephrine and norepinephrine
Direct sympathetic stimulation of heart
What is end-diastolic volume dependent on?
Venous return
How is venous return increased?
Vasoconstriction
Skeletal muscle pump
Respiratory pump
What is frank starling mechanism?
Greater EDV results in a more forceful contraction
(due to stretch of ventricles)
How is vasoconstriction increased?
Via SNS
How is skeletal muscle pump increased?
Rhythmic skeletal muscle contractions force blood in the extremities toward the heart
One-way valves in veins prevent backflow of blood
How is respiratory pump increased?
Changes in thoracic pressure pull blood towards the heart
What is cardiac output?
The amount of blood pumped by the heart each minute
What is formula for cardiac output?
Q= HR x SV
HR= Cardiac Rate
SV= Stroke Volume
What is systolic pressure?
Pressure generated during ventricular contraction
What is diastolic pressure?
Pressure in the arteries during cardiac relaxation
What is pulse pressure?
Difference between systolic and diastolic
What is mean arterial pressure (MAP)?
Average pressure in the arteries
What are determinants of Mean Arterial Pressure?
Cardiac Output
Total Vascular resistance
What is total vascular resistance?
Sum of resistance to blood flow
What is the formula for MAP?
MAP= Cardiac Output x Total Vascular Resistance
What is short-term regulation for arterial blood pressure?
Sympathetic nervous system
Baroreceptor in aorta and carotid arteries
How does blood pressure influence SNS activity?
Increase in BP= Decreased SNS activity
Decrease in BP= Increased SNS activity
What is long-term regulation for arterial blood pressure?
Kidneys (via control of blood volume)
What mechanisms increase blood flow delivery to exercising skeletal muscle?
Increased cardiac output
Redistribution of blood flow from inactive organs to the working skeletal muscle
What is cardiac output increase during exercise directly proportional to?
The metabolic rate required to perform the exercise
What are circulatory responses to exercise dependent on?
Type, Intensity, Duration of Exercise
Environmental Conditions
Emotional influence pre-exercise and during submaximal exercise
What are the circulatory responses to exercise?
Changes in heart rate
Changes in blood pressure
What happens at the onset of exercise?
Rapid increase in heart rate, SV, Cardiac output
Plateau in submaximal exercise (below lactate threshold)
What happens during exercise to recovery stage?
Decrease in HR, SV and Cardiac Output toward resting levels
Depends on duration/intensity of exercise and training state of subject
What happens to heat rate and cardiac output during incremental exercise?
Increases linearly with increasing work rate
Reaches plateau at 100% VO2 max
What happens to blood pressure during incremental exercise?
Mean arterial pressure increases linearly
- Systolic BP increases
- Diastolic BP remains fairly constant
What happens to cardiac output during prolonged exercise at a constant work rate?
It is maintained
Gradual decrease in stroke volume= due to dehydration and reduced plasma volume
What happens to heart rate during prolonged exercise?
Gradual increase in heart rate during prolonged exercise (cardiovascular drift)
