Responses to Exercise Flashcards
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
What puts glucose back into the system?
The liver through glycogenolysis and gluconeogenesis which are stimulated by glucagon
What does blood glucose do during short, high intensity exercise?
Increases due to immediate muscle and liver glycogenolysis from increased catecholamines
What does blood glucose do during long, low intensity exercises?
Blood glucose is maintained
Increase HGP
What do catecholamines do for metabolism?
- Increase glucagon
- decrease insulin
- Increase glycogenolysis in muscle
- Increase lipolysis from fat for fat oxidation
What does calcium do for metabolism?
Increases glycogen phosphorylase for supporting glycogenolysis
Glycogen phosphorylase mobilizes glycogen so it can be used in glycoysis
Liberated from sarcoplasmic reticulum during contraction
What does cortisol do for metabolism?
Liberates fuels during exercise
1. Breaks fats down into fatty acids
2. Breaks proteins down into amino acids
Cortisol is the reason there is a baseline for 2-3% metabolism during exercise
Very slow in responding!
What does lactate inhibit?
Lipolysis
What do growth hormones increase?
lipolysis, especially when exercise becomes prolonged
Where does all glucose come from?
Glucose 6 phosphate (G6P)
Where does glycogen synthesis take place?
- Liver - anaerobic pathway during exercise from lactate or glucose post-meal
- Skeletal muscle - occurs from blood glucose that comes from G6P
What is the best VO2 to burn fat?
50% VO2 max is optimal
moderate exercise for a longer period of time is better for fat oxidation
What is the fuel type as exercise duration and intensity increases?
Fats first and then start to rely on blood glucose and muscle glycogen (stored form of glucose)
Fats cannot be exclusively burned during rest nor exercise
What causes fatigue in the muscles?
Glycogen stores being used
Lactate production
Where are ketones produced?
primarily in the liver but the liver can’t utilize them
How are ketones created?
Acetyl CoA can bind to itself when there is not enough OAA available to make the Kreb’s cycle turn.
Acetyl CoA binding to itself creates Ketone bodies
When can Ketones be good?
- A fuel source during prolonged exercise
- Used as fuel source in the brain during starvation
- Don’t need ATP to synthesize ketones
When are Ketones bad?
- Ketoacidosis - when Ketones accumulate in blood and decrease pH
- Secreted by kidney to urine - lead to kidney failure
- Changes in BMR (decreases)
