ANS Flashcards
Sympathetic system
adrenal medulla
release norepinephrine neurotransmitter
Parasympathetic system
loacted in brain stem
release acetyl coline neurotransmitter
decrease in activation nodes = lower HR
Increase HR onset of exercise
due to parasympathetic withdrawal
End-diastolic volume
volume of blood in the ventricles at the end of diastole
Average aortic blood pressure
pressure the heart must pump against to eject blood
mean arterial pressure
Strength of ventricular contraction enhanced by
circulating epinephrine and norepinephrine
direct sympathetic stimulation of heart
Frank-starling mechanism
greater EDV results in a more forceful contraction
due to stretch ventricles
dependent on venous return
Venous return increased by:
- venoconstriction - via SNS
- skeletal muscle pump - rhythmic skeletal muscle contractions force blood in extremities towards the heart
- respiratory pump - changes in thoracic pressure pull blood towards heart
Cardiac output
amount of blood pumped by the heart each minute
Q = HR x SV
Systolic pressure
pressure generated during ventricular contraction
Diastolic pressure
pressure in the arteries during cardiac relaxation
Pulse pressure
difference between systolic and diastolic
Mean arteial pressure (MAP)
average pressure in the arteries
~100 mmHg
Factors that determine MAP
cardiac output
total vascular resistance (sum of resistance to blood flow)
MAP equation
cardiac output x total vascular resistance
Short term regulation
SNS
baroreceptors in aorta and carotid arteries
increase in BP = decrease SNS
decrease in BP = increase SNS
Long term regulation
kidneys via control of blood volume
Increase metabolic need for oxygen/blood to exercising skeletal muscle via
increased cardiac output
redistribution of blood flow from inactive organs to working skeletal muscle
What direction is the increase of CO to metabolic rate required to perform exercise
dircetly proportional
Changes in blood pressure depends on
type, intensity and duration of exercise
environ conditions
emotional influence
training history
Onset of exercise
rapid increase HR, SV, CO
plateau in submaximal below lactate threshold exercise
During recovery
decrease in HR, SV and CO towards resting levels
Incremental exercise HR and CO:
increase linearly with increasing work rate
reaches plateau at 100% VO2max
Incremental exercise BP:
MAP increases linearly
systolic BP increases
diastolic BP remain constant
Intermittent exercise
near maximal HR values
Recovery of heart rate and blood pressure between bouts depend on
fitness level
temperature and humidity
duration and intensity of exercise
Prolonged exercise at a constant work rate
CO maintained
Gradual decrease in SV
due to dehydration and reduced plasma volume
Cardiovascular drift
gradual increase in HR during prolonged exercise in heat
Stroke volume
difference between end-diastolic volume and end-sytolic volume
SV = EDV - ESV
Determine SV
- preload (venous return)
- contractility of ventricular muscle
- afterload (aortic pressure during systole)
Frank Starling law
end-diastolic volume increased = stroke volume increased up to max
if increased more = SV decline
Neurotransmitter PNS
acetylcholine
Neurotransmitter SNS
norepinephrine
epinephrine
= adrenaline
2 major adjustments in blood flow to meet increased demands O2
increase cardiac output
redistribution blood flow from inactive tissues to skeletal muscels
Pulse presure
difference between systolic and diastolic blood pressure
Heart rate variability
time interval between heart beats
epidemiological studies suggest that low HRV = predict mortality
increases in response to regular aerobic exercise training
influenced by the balance between PNS and SNS
