Week 3- the autonomic nervous system Flashcards
What does the release of acetylcholine do to heart rate?
Decreases HR
What causes low resting heart rate?
Parasympathetic tone
What is the initial increase in HR due to?
parasympathetic withdrawal
What is end diastolic volume (EDV)?
Volume of blood in the ventricles at the end of diastole (‘preload’)
What is the average aortic blood pressure?
Pressure heart must pump against to eject blood (‘afterload’)
What does an increase in cardiac afterload cause?
decrease in SV during resting where the influences on cardiac contractility are not at play
What is the strength of the ventricular contraction enhanced by?
-circulating epinephrine and norepinephrine
-direct sympathetic stimulation of the heart
What does a greater end diastolic volume result in?
A more forceful contraction due to strength of ventricles but is dependent on the rate of venous return
What is venous return increased by?
-vasoconstriction
-skeletal muscle pump
-respiratory pump
What is cardiac output?
amount of blood pumped by the heart each minute
What is the cardiac output equation?
Q = HR x SV
What factors regulate cardiac output?
-PNS decreases Q
-SNS increases Q
-Stoke volume decreases Q
When is systolic pressure generated?
during ventricular contraction
What is diastolic pressure?
pressure in the arteries during cardiac relaxation
What is pulse pressure?
The difference between systolic and diastolic blood pressure
What is mean arterial pressure (MAP)?
Average pressure in the arteries
What are the determinants of mean arterial pressure?
-cardiac output
-total vascular resistance (sum of resistance to blood flow)
-MAP=Q x total vascular resistance
What are the short term regulators of mean arterial pressure?
-SNS
-Baroreceptors in aorta and carotid arteries
What are the long term regulators of mean arterial pressure?
Kidneys via a control of blood volume
How is the blood flow delivery to exercising muscles increased?
-cardiac output increase
-redistribution of blood flow from inactive organs to working muscles
What do changes in HR and BP depend on?
Type, intensity, duration, environmental conditions, emotional influence pre-exercise and during submaximal exercise due to increased SNS
