Responses to Exercise Flashcards
(41 cards)
What is the Fick equation?
VO2 = Q x a-vO2 difference
Where Q is central and a-vO2 is peripheral
Why does heart rate increase during exercise?
- Vagus withdraws (aka parasympathetic tone withdraws)
2. Sympathetic activity is increased with NE binding to Beta 1 on SA node and having the Baroreflex reset
What happens to Stroke Volume during exericse?
Stroke volume increases due to contractility, preload, and a decrease in afterload
Trained individuals Stroke Volume increases more because the heart is bigger itself
What causes decrease in TPR?
Vasodilation to get more blood to muscle with metabolites and nitric oxide
Afterload almost diminishes
Redistribution of blood flow during exercise
Muscle receives more blood with increased exercise intensity
Takes blood from kidneys/gut, and the skin
Won’t take from the heart and brain
Cardiac volumes at rest
Cardiac output = 5 L/min
Heart rate = 70 bpm
Stoke Volume = 70 mL/beat
Ejection Fraction = 55-60%
Cardiac volumes during maximal exercise in an untrained individual
Cardiac output = 22 L/min
Heart rate = about 200 bpm
Stroke Volume = about 110 mL/beat
Ejection Fraction = 80%
What is the biggest factor affecting stroke volume during exercise?
Preload
a-vO2 difference during exercise
avO2 will get bigger as exercise intensity increases
Arteriolar stays the same b/c already fully saturated
Venous decreases b/c unloading more at the tissues
What does peripheral extraction of oxygen depend on?
How much blood is perfusing the tissue and perfusion pressure
Basically how much can the system feed the greedy bastards
Blood pressure during exercise
- SBP increases
- DBP stays the same b/c TPR decreasing
- MAP increases modestly during exercise
How does muscle blood flow increase?
- Sympathetic nervous system (peripheral)
a. Baroreflex setting
b. central command
c. exercise pressor reflex - Mechanical - muscle pump causes dilation
- Autoregulation (local) - takes over sympathetic
Metabolic Autoregulation
Trumps sympathetic nervous system and causes vasodilation
This is how blood flow increases to muscle
Cardiovascular Drift
Heart rate increases throughout exercise
Cardiac output remains the same
Strove volume decreases
Why? B/c of dehydration decreasing plasma volume which decreases venous return, decrease stroke volume, increase heart rate to compensate
What do hormones do during exercise?
Increase with intensity and duration
Includes Epinephrine, Norepinephrine, Glucagon, Growth Hormone, Cortisol
What does insulin do during exercise?
Decreases with intensity and duration
What does insulin do in the body?
Decreases glucose levels 4 ways
- increase glucose uptake into cells
- increase glycogen synthesis
- Inhibit glucose formation
- Catecholamines inhibit formation
Where does insulin come from in the body?
Secreted from pancreatic Beta cells when plasma glucose levels are elevated (aka hyperglycemia)
How does the body inhibit insulin?
Release EPI or NE –> bind to alpha adrenergic recpetor on Beta cell in pancreas –> inhibit insulin
What does Glucagon do in the body?
Bring glucose levels back up 4 ways
- increase liver glycogenolysis
- increase liver gluconeogenesis
- Hepatic Glucose Production (HGP)
- Stimulated by catecholamines
How does the body stimulate the release of glucagon?
Release EPI or NE –> bind to Beta adrenergic receptor on Alpha cell in pancreas –> stimulate release of glucagon
What happens to glucose uptake during exercise?
Increases due to muscle contraction moving GLUT 4 channels that allow more glucose into the cell
Why does insulin need to be inhibited during exercise?
It will allow more glucose to leave the system and cause problems during exercise….like hitting the wall
What do carbs do during exercise?
provide fuel for exercise while maintaining blood glucose levels
retain or spare muscle glycogen for as long as possible
