Think, Pair, Share Flashcards
What are the sources of fuel that support metabolism in skeletal muscle?
CHO-4 kcals/g
Fat-9 kcal/g
Protein- 4 kcals/g
What factors determine how much energy is associated with these sources of fuel?
The number of hydrogen atoms
The chemical energy contained in bonds
How is chemical energy in nutrients converted to useable energy?
Via oxidation and reduction
Role of enzymes?
Regulate the speed at which a reaction occurs
Do not CAUSE reaction to occur
Affected by pH and temperature
Muscle has limited storage capacity for fat and carbs, the 2 most important fuels for contracting muscle. Thus, during exercise, muscle uses carbs and fat stored from other organs. What are these other organs?
Liver- provides carbs in the form of glucose
Fat- adipose tissue (subcutaneous and visceral) provides lipids in the form of fatty acids
(also secretes hormones and cytokines that can affect metabolism in liver and muscle) PREDOMINANT SOURCE comes from this
Nervous system- does not provide fuel, but needs constant supply of glucose; competes with muscle for glucose
Where are carbohydrates
stored in the body?
Muscle glycogen
Liver glycogen
Plasma glycogen (comes from liver glycogen)
What is the relative abundance of carbs stored in their different compartments?
Muscle glycogen is the largest storage depot, liver is second, and very little is stored in plasma
What is the role of glycogen in the muscle?
Provides fuel to be oxidized, supplying energy for muscular contraction.
What is the role of glycogen in the liver?
Provides temporary storage for glucose; produce new glucose when body (e.g. muscle) glycogen stores are compromised.
Exercise uses ATP. How is this tank refilled?
- ) Anaerobic Metabolism- the immediate energy system (phosphates system) or Glycolysis
- ) Aerobic Metabolism- Kreb’s and Electron Transport chain
Can you think of a way to increase the size of the immediate energy tank and glycolytic tank?
Exercise training that stresses these tanks will lead to an increase in their size (immediate energy system-more CP storage, faster activity of enzyme activity) (Glycolytic energy system-process of depleting glycogen stores during exercise causes glycogen stores to expand and training enhances enzyme activity)
Nutritional strategies-(immediate energy system:creatine loading) (glycolytic energy system:carb loading)
What are the primary signals that contribute to the regulation HR at rest and during exercise?
At rest: activity of SA node and autonomic nervous system
During exercise: feedback from signals in brain and periphery
At start of exercise, HR rapidly increases due to
Decreased PNS stimulation
Activation of central command
Activation of mechanoreceptors
As duration of exercise continues, HR is “fine tuned” by signals from
Increased SNS stimulation
Chemoreceptors
Baroreceptors
Describe 2 ways that SV can be increased during exercise.
Increase the amount of blood in the LV before it contracts (at the end of diastole/start of systole) (increased EDV/Pre-load)
Eject more blood from the LV with each beat (Greater systolic emptying (decreased after load)
SV is highest when preload is high and after load is low
Performing regular, high intensity exercise appears to maintain diastolic function. How might exercise training improve diastolic function?
Reduces fibrosis and collagen accumulation
Improved myosin-actin cross bridge cycling
Allows heart to keep stretching and be elastic
Nerve endings of the SNS directly innervate the LV. What effect will increasing SNS activity have on CO? Why?
CO=HRxSV
Exercise increases SNS activity
SNS activity increases both HR and SV;SV is increased because force of contraction increases
Result is dramatic increase in CO (more than would occur with just an increase in HR)
Facts about CO
CO is proportional to whole body O2 consumption
CO increases proportionally to the amount of external work being performed
Maximal CO is the most important determinant of VO2max
List some ways which exercise training may increase cardiac output
More blood in ventricle prior to systole (increases pre-load and EDV) (increased stretch, increased filling and increased blood volume)
Less blood in ventricle after systole (Decreased after load, ESV) (greater ventricular emptying during exercise due to increased force of contraction and less resistance in vascular system)
Consider two individuals (trained, untrained) of similar age, sex, and body weight. How would CO, HR, and SV compare under the following situations?
Rest (Cardiac output ~5L/min)
Submaximal exercise at same absolute workload (e.g. 150 watts); assume this requires a cardiac output of 15 L/min
Maximal exercise (VO2max)
Epi/norepi are released into the circulation during exercise, and higher amounts are released at higher exercise intensities
However, Epi/norepi causes systemic vasoconstriction- it will causes all vessels in system to constrict even more than they do at rest
How can blood flow to active muscles be increased if episodes/norepi are causing vasoconstriction?
During exercise- various substances are released from local exercising muscle, blocking signal from SNS, causing vasodilation and increasing blood flow to exercising muscle
Also regulated by temp and PO2
(increased temp and decreased PO2 causes vasodilation
