Weekend 2 lecture 3 Flashcards
Cell Respiration and Bioenergetics What is the immediate requirement of exercise
The most immediate requirement of exercise is the release of the terminal phosphate bond in ATP to fuel the contractile and related demands of the muscle at a rate which is matched to the task being performed
3 Mechanisms for ATP Generation
Aerobic oxidation of substrates
Provides major source of ATP and becomes the only source during sustained moderate intensity exercise
Anaerobic hydrolysis of phosphocreatine
Used in the early phase of exercise; serves as an immediate source of ATP regeneration (ADPATP)
Anaerobic breakdown of glycogen or glucose to lactic acid
The amount of energy produced is relatively small for the amount of glycogen and glucose consumed
Aerobic oxidation briefly describe
When regeneration of ATP is aerobic, O2 is consumed and CO2 is produced in proportion to the ratio of the CHO to fatty acid in the substrate being oxidized in the muscle cells
Anaerobic hydrolysis of phosphocreatine
When PCR is split, it is converted to Cr and Pi. Cr is neutral in water while PCr reacts like a relatively strong acid, therefore, the hydrolysis of Pcr decreases cell acidity.
This reaction retains CO2 in the tissues as bicarbonate and reduces the net CO2 produced by aerobic metabolism
Anaerobic glycolysis describe
When high energy phosphat is generated from anaerobic glycolysis, the H+ produced with lactate is buffered primarily by the bicarbonate (HCO3-)
This adds CO2 to that produced by aerobic processes
Normal Coupling of External to Cellular Respiration
Does HR increase when you increase the exercise and what happens if it doesn.t what is this a sign of?
The circulation must increase at a rate which is adequate to supply O2 to the cells
Cardiac output increases in proportion to the metabolic rate in normal subjects (approximately 6L/min of CO per liter of O2 consumed)
CVD is often characterized by the failure of O2 uptake to increase. This is associated with lactic acidosis
how much CO2 is in the body at a certain defined walking speed?
Does the elmination of CO2 have to be quick and precise? What happens if it is not?
Total H+ in the body is only on the order of 3.4 micromoles
Total H+ equivalent produced per minute from metabolism in the form of CO2 even for moderate walking speeds is about 40,000 micromoles per minute
Elimination of the increased CO2 must be accomplished quickly and precisely
In order to regulate arterial pH closely, ventilation must be closely linked to CO2 production during exercise
Physical Activity is a major Challenge to homeostasis of the cellular environme
How much does the oxygen content change when you start walkinghg at roughly 3.0 mph and how long does it take the body to reach the full enery requirements
Walking at 3mph requires a 16-20 fold increase in O2 consumption of the muscles of locomotion. The rate of acid production, in the form of CO2 increases by a similar amount.
Normally this is accomplished with such precision that the blood is reoxygenated with little or no changes in PO2, PCO2, and pH.
This is because the response of the transport systems can increase the rate of O2 delivery to meet all the energy requirements within 3 minutes
Respiratory Quotient (RQ) what is this and I think we already have this on another deck somewhere
The ratio of increase in VCO2 relative to VO2 in the steady-state
Respiratory Exchange Ratio what is it for fat and what is it for carbs
Theoretical gas exchange from carbohydrate and fee fatty acid oxidation far a standardized exercise bout requireing an O2 uptake of 1 L/min
CHO: 1.0 ; VO2: 1L/min; VCO2: 1 L/min
Free fatty acid: 0.7; VO2: 1L/min; VCO2: .7 L/min
Anaerobic Threshold (AT) what is it
When the VO2 does not achieve a steady state by 3 minutes, lactate increases in the body; thus, the work rate is above the subject’s anaerobic threshold (AT).
VCO2 increases relative to VO2 when lactate increases because bicarbonate is the principle buffer of the newly formed lactic acid, the VCO2 rises to a level higher that VO2
If the work rate is not too high above the AT, VO2 may reach a constant value before the subject fatigues, otherwise, VO2 progressively increase until the subject is forced to stop from fatigue.
Why do we measure components of external respiration (VO2 & VCO2)?
Increases in external respiration are intimately and predictably linked to the increases in cellular respiration.
The linkage is through the circulation.
The contribution of aerobic and anaerobic metabolism can often be inferred from measurements of external respiration.
Why does VCO2 increase in the body and what happens if the match for the VCO2 is meet
There is an accompanying increase in VCO2 in excess of VO2 due to the CO2 release from bicarbonate as it buffers the lactic acid
In contrast, when work is done in a true steady-state in which all the O2 required by the muscle is provided to and utilized by the muscle, the VO2 increases rapidly and no lactic acidosis develops
Factors limiting exercise
fatique, dyspena, pain
Exact mechanisms of muscle fatigue remain controversial
Intracellular consequences of lactic acidosis
Low cellular pH
Increased inorganic phosphate
Impaired calcium release from the sarcoplasmic reticulum
Decreased levels of ATP
the consistent physiological signal for impending fatigue during exercise is
is the failure of the VO2 to reach a steady-state**
Who is at risk and what is dyspnea
Subjective complaint of shortness of breath
Normal sedentary subjects usually experience fatigue rather than dyspnea as their limiting symptom during exercise
Three types of normal subjects seem to be prone to dyspnea
Females
Elderly
Some athletes
What is the number one sign of CAD
What is claudication
Anginal pain is the most common symptom of CAD
Claudication: imbalance in the O2 supply/demand in the exercising muscles
VO2 Non-steady state
The continued slow increase in VO2 observed after 3 minutes during constant work rate exercise is only seen for work rates that are associated with lactic acidosis
five reasons for slow VO2 rising after 3 mintues of exercise
Progressive vasodilation to thelocal muscle untis by metabolic vasodilators produced in response to relative low O2increased O2 flow and consumption at the O2 debt sites
Acidemia facilitating O2 unloading from hemoglobin by shifting the oxyhemoglobin dissociation curve downward for a given PO2
O2 cost of conversion of lactate to glycogen in the liver, as the lactate concentration rises
Increase in VO2 needed to satisfy the increased work of the muscles of respiration and the heart at high ventilatory and cardiac output states
Reduced muscular efficiency during heavy work either by recruiting more low efficiency “fast twitch” muscle fibers or by calling into play additional groups of muscles (ie more forceful pulling on handlebars)
Increased catecholamine levels
Increased body temperature at high work rates
At what level does the Lactate start to increase in a healthy a individual
What about a sedentary inddividual
Lactate does not start to increase in normal subjects who are relatively physically active until VO2 has increased to as much as 10 times the resting metaboic rate
Lactate starts to increase in sedentary subjects when VO2 has increased only 4x the resting level
The VO2 at which lactate starts to increase in normal subjects is on average 50-60% of their VO2 max
note that this can be considerably higher in aerobically fit subjects***
What happens when the individual is above the AT anaorbic thershold and what happens when it’s below
Above AT, VE increases in proportion to the increased CO2 output (VE/VCO2 is constant or decreases slightly)
Above AT, the VE/VO2 increases
If the work rate is further increased while above AT, the VE starts to increase even more rapidly than the CO2 output (increase in the VE/VCO2)
Fiver factors that affect O2 delievery
Five factors
Cardiac output
Distribution of perfusion to the tissues in need of O2
Partial pressure of O2 in the capillary blood
Hemoglobin concentration
Hemoglobin’s affinity for O2
How does CO increase in realtion to VO2 during exercise? and is it immediate
SV increases almost immediately
At approximately 50% of the VO2, further increases in cardiac output come from increases in the heart rate
What determines the mechanism by where blood is suppose to flow think ANS
If the increase in CO is not distributed appropriately to the sites of O2 requirement, supply is compromised.
The mechanism by which blood flow is distributed during exercise depends on the response of the ANS and local humoral control
Hemoglobin and Arterial O2 content
What determines the level of O2 in the arteries
The arterial O2 content depends on the arterial PO2 and the hemogloin concentration that is free to take up O2
Any condition which reduce the O2 content will result in a more rapid decrease in capillary PO2 than normal
Ventilatory Coupling to Metabolism What happens in the lungs 3 things one is get rid of CO2
The blood passing through the lungs must:
Eliminate the added CO2
Replenish the O2 consumed
Achieve a homeostatic pH (7.35-7.45
What is minute ventilaion?
Minute ventilation (VE) normally increases at a rate required to remove the CO2 added to the capillary blood by metabolism and minimize the increase in H+ concentration Below AT, the VE increase is generally so precise that arterial PCO2 and pH are regulated at resting values
Describe phase 1 of the gas exchange during exercise
The immediate increase n gas exchange at the start of exercise. It lasts for about 15 seconds
Reflects an abrupt increase in pulmonary blood flow consequent to the increase in heart rate and stroke volume at the start of exercise
Because the composition of the blood was determined under conditions of rest, it is usually the same as rest (period before blood from exercising muscles has reached the lungs
Describe phase 2 and its time frame
Lasts from 15 seconds after onset of exercise until the 3rd minute of exercise. It reflects the period of major increase in cellular respiration.
If exercise is below the AT, a steady-state in VO2 is achieved by 3 minutes
If exercise is above the AT, the steady state in VO2 is delayed or not achieved before the subject fatigues
Phase3 describe and when does it start
Starts 3 minutes after the exercise onset, and reflects the start of the VO2 steady state period if the work rate is below the AT
If the work rate is above the AT, the rate of increase in VO2 correlates with the magnitude of the lactate increase
O2 Deficit what is this about
Traditionally computed as the difference between the total oxygen uptake during the exercise bout and the product of the steady-state VO2 and the exercise duration
If the true steady-state value for VO2 is not reached by the time exercise is stopped, the calculated O2 deficit will be less than the true O2 deficit
What is the level 02 debt
The difference between the total oxygen uptake in excess of the resting oxygen uptake during the recovery period
Once VO2 reaches a steady state during exercis the oxygen debt no longer increases, regardless of the exercise duration. In this case O2 debt is repaid within five minutes of recovery
If the work rate is above the AT, the O2 debt can be quite high and may not be repaid for an hour or more.
The degree of O2 debt is linked to the increase in blood lactate concentration
CO2 Output Kinetics
Below AT, VCO2 has slower kinetics than VO2
The time of peak reduction in R (gas exchange ratio) identifies a time period in which CO2 produced aerobically is not being entirely eliminated by the lungs, accounting for the slower CO2 kinetics
This time is between 30-45 seconds
Maximal Oxygen Uptake (VO2max) and Maximum Oxygen Uptake (peak VO2) and
determinants
The body has an upper limit for O2 utilization at a particular level of fitness/training.
Determinants:
the maximal CO
Arterial O2 content
Fractional distribution of the CO to the exercising muscle
Ventilatory capacity is of importance in the upper limit of VO2 when the ventilation is insufficient to eliminate the CO2
what is peak VO2
The upper limit in VO2 may be determined in a progressively increasing exercise test, when a decreasing rate of increase in VO2 is observed just before the subject fatigues
Sometimes the subject cannot sustain the work rate to the point of oxygen limitation, and a flattening of the VO2-work rate relationship is not seen. This is called the peak VO2
Pattern of Work Rate Increase and VO2 response
how does the VO2 test work I guess what the guy is going for.
VO2 increases smoothly when cycle ergometer work rate is increased in a continuous ramp pattern or in equal steps of 1 minute duration
This type of protocol has advantages in the ease with which the patient perceives the addition of work rate during the testing
Because the time constant for VO2 at work intensities below the AT is 35-45seconds in healthy subjects, steps at 1 minute increments give smooth increases in VO2
