Flashcards in Bergdahl- Chapter 24 and 25 Deck (99):
what are the 4 stages of response to extreme exposition ?
1) acute reaction
4) evolutionary adjustments
what is an acute emergency reaction like ?
maximal use of reserves, non-specific stress response
cannot be sustained permanently
what is exhaustion like ?
what happens when the exposure is too long or strong
eg Titanic sinking victims
what is adaptation like ?
selective strengthening of the most advantageous specific means of defense. however, it has limits
eg winter swimming, but even winter swimmers would not have survived the sinking of the Titanic
what are evolutionary adjustments ?
species/population change for many generations
eg Inuit are more resistant to cold
what elevations are considered high altitude ?
10 000 ft- 18 000 ft above sea level
what is altitude's physiologic challenge ?
decreased ambient PO2
how does air density change with altitude ?
it decreases progressively as one ascends above sea level
what is acclimatization ?
adaptations produced by changes in the natural environment
what is acclimation ?
adaptations produced in a controlled laboratory environment which simulates high altitude
how does sport performance change in altitude (anaerobic and aerobic)?
when sports are anaerobic, the altitude doesn't matter
however, for aerobic sports, makes a difference
how does the oxygen transport cascade differ at high altitudes ?
begins lower and ends a bit lower
what are the two important immediate responses to altitude exposure ?
2) increase in blood flow during rest and submax exercise
explain how the hyperventilation as an immediate response to altitude exposure comes about
reduced arterial PO2
peripheral chemoreceptors sensitive to reduced O2
therefore, inspiratory activity stimulates alveolar ventilation
what are the three immediate effects of high altitude ?
2) increase in submax heart rate and cardiac output
3) catecholamine response
how does cardiovascular response immediately increase at high altitude ?
- increase in submaximal heart rate
- increase in submaximal cardiac output
- increase in submaximal blood flow
- SV and max CO don't change
what is the catecholamine response that is immediate in high altitude ? :)
it will progressively increase for NE and stay the same for E during rest and exercise
(plateau, then upward slope, then plateau at new concentration)
describe the fluid loss in high altitudes
body water evaporates since ambient air is cool and dry
leads to moderate dehydration
what is the purpose of long term adjustments in high altitude ?
improve tolerance to relative hypoxia
what are the 3 main long term adjustments in high altitude ?
1) regulation of acid-base balance of body fluids altered by hyperventilation
2) synthesis of hemoglobin and RBC
3) elevated SNS activity reflected by increased NE that peaks within 1 week
what is the main action of ventilation ?
breathing out too much CO2
in high altitude, explain the process of hyperventilation and how it'll change the blood pH
hypoxia, so induce hyperventilation. this will get rid of a lot of CO2.
therefore, there is not enough CO2 in the blood, which will shift the reaction to the left. bicarbonate (HCO3-) and H+ will become carbonic acid and become CO2. this causes a decrease in H+ concentration, meaning it causes alkalosis
what kind of pH condition will high altitude bring ?
alkalosis, pH increases
until an altitude of 3048m, does hemoglobin's percentage saturation really change ?
how does performance in anaerobic events change in high altitude ?
altitude does not impair short-term anaerobic energy system
rather, it may even improve because of the lower air density
as an immediate response to altitude exposure, what compensates for arterial desaturation ?
the increased submaximal flow
what is the most important long term adjustment to high altitude ?
increase in blood's oxygen-carrying capacity
what are the two factors that account for the blood's increased O2 carrying capacity as a long term adjustment ?
1) decrease in plasma volume (so increase in hematocrit)
2) increase in RBC and Hb synthesis
basically, larger O2 amount is going to tissues even though the O2 bound to Hb is lower than in normal conditions
what is polycythemia ?
increase in total amount of RBC (what happens in high altitude)
long-term, what happens to the HCO3- (bicarbonate) ?
it is excreted via the kidneys
what are the 6 different ways that the body adjusts long-term to better bring blood to the tissues ?
1) increased cardiac output- more oxygenated blood moved
2) increased RBC, so there is a higher oxygen carrying capacity
3) 2,3-DPG levels are higher
4) more capillarization
5) increased myoglobin, meaning there is more O2 locally available
6) increased urine output is a temporary way to concentrate blood
what is acute mountain sickness ?
probably due to hypoxia
what is a high altitude pulmonary edema ?
fluid accumulates in brain and lungs
reversible if you go to a lower altitude
what is a high altitude cerebral edema ?
neurologic syndrome that can develop in those with acute mountain sickness
how much time does it take to adapt to altitudes up to 2300 m ?
how much time does it take to acclimatize to a 610 m altitude increase when we're above 2300 m?
an additional week
to minimize detraining effects, when should athletes who compete at altitude begin training ?
immediately during acclimatization
after how much time do acclimatization adaptations dissipate after return to sea level ?
what is the relationship between decline of VO2 max and altitude ?
what happens long term with VO2 max ? why ?
after several months, VO2max still remains below sea-level values, even with increases in Hb
this is because reduced circulatory capacity (due to lower maximum heart rate and stroke volume) offsets the benefits of Hb
long term what happens to maximum cardiac output ?
short term what happens to maximum cardiac output ?
doesn't really change, or decreases slightly
in submaximal exercise, what is the immediate altitude response ?
increase cardiac output
however, this diminishes as acclimatization progresses and does not improve with prolonged exposure
what happens to cardiac output in submax exercise ?
progressive decrease in heart's SV will decrease CO
how does submax VO2 change with high altitude ?
lower CO, but submax VO2 stays stable through an expanded a-v(mixed) O2 difference
what are 3 changes in the muscles that occur with hypoxic exposure ?
1) increased muscle effiency at mitochondrial level
2) greater muscle buffering
3) ability to tolerate lactic acid production
what happens to endurance during acclimatization ? what are the 3 factors that contribute to this ?
1) more minute pulmonary ventilation
2) increased arterial oxygen saturation and cellular aerobic functions
3) blunted blood lactate response in exercise
what 2 changes offset adaptations that could improve exercise performance ?
1) muscle mass loss and reduced MHR and SV do not enhance performance
2) reduction in CO offsets benefits in the increase in the blood's oxygen carrying capacity
what is more important- the CO reduction or the increase in the blood's oxygen carrying capacity in terms of change ?
decrease in CO offsets the other
does endurance training at altitude improve subsequent sea level exercise performance ?
altitude acclimatization improves capacity for exercise at altitude
what adaptations could improve subsequent sea level performance ?
local circulation and metabolism
compensatory increases in blood's oxygen-carrying capacity
(live high, train low)
how must absolute workload be adjusted depending on the altitude ?
high altitude : absolute workload must be lowered to perform aerobic exercise at the same relative intensity
how high should an athlete live and train ? 3 rules
1) the elevation must be high enough to raise EPO (erythropoietin) levels to increase total RBC volume and VO2max
2) athlete must respond positively with increased EPO output
3) training must take place at an level low enough to maintain training intensity and exercise oxygen consumption at near sea level values
what is the Gamow Hypobaric Chamber ?
at-home acclimatization technique
a person rests and sleeps in it for 10 hrs/day, and the chamber's total air pressure decreases to simulate altitude exposure
how is it possible to simulate altitude at sea level by playing around with nitrogen ?
if you increase nitrogen percentage and live there for a little while
what is temperature ?
represents the mean kinetic energy of a substance's atoms as they move
what kind of declines and increases in body temperature can humans tolerate ?
decline of 10, increase of 5
when does heat conservation occur in blood flow ?
when blood shunts rapidly to the deep body cavities and muscle mass
what brain area controls temperature
how does hypothalamus turn heat on and off
it cannot turn off the heat
it can only initiate responses to protect the body from buildup of heat or cold
what provides the greatest contribution against cold ?
what are two ways to generate heat ?
shivering and physical activity
how does heat redirect to specific body parts ?
- stimulation of cutaneous cold receptors
- constrict peripheral blood vessels
- reducing flow of warm blood to surface, redirecting it to the core
what is the main duty of the body's thermoregulatory mechanisms ?
protecting against overheating
what are the 4 ways heat can leave the body. explain them
1) radiation : sun's effect on Earth
2) conduction : direct heat transfer from one molecule to another through a liquid, solid, or gas, eg immersing body in cool water
3) convection: air currents
4) vapor : sweat, vaporization in respiratory passages
what is the main heat loss mechanism we use ?
what are the three factors that influence the total amount of sweat vaporized from the skin and pulmonary surfaces ?
1) surface exposed
2) temperature and relative humidity of the ambient air
3) convective air currents around body
what is the main factor in determining the effectiveness of evaporative heat loss ?
relative humidity (ratio of water in ambient air at a particular temperature compared to total quality of moisture)
how does the circulatory system work to maintain thermal balance ?
at rest in the heat, the HR and CO increase while superficial arterial and venous blood vessels dilate to divert warm blood to the body periphery
how does sweating (evaporation) work to maintain thermal balance ?
begins within several seconds of exercise
effective when it is combined with large cutaneous blood flow
what hormones are released in response to cold stress ?
E, NE, thyroxine
how do hormonal adjustments work to maintain thermal balance while sweating?
sweating makes people lose water and electrolytes
stimulates release of aldosterone to increase sodium reabsorption and to decrease sweat sodium concentration to further conserve electrolytes
also, vasopressin is released to facilitate fluid retention
describe the competitive cardiovascular demands on the body during heat
arterial blood diverting to periphery to cool body down cannot deliver the O2 to the active muscle
how do HR and SV look in heat for submax
lower SV, causing higher HR
in maximal exercise in heat, what happens to cardiac output ?
HR increase cannot offset SV decrease so CO decreases
how does dependence on anaerobic metabolism change in heat in submax exercise ?
submax exercise will rely more on anaerobic system which means there will be earlier lactate buildup, glycogen reserves use, early fatigue in prolonged exercise
what are 2 factors that increase blood lactate accumulation in heat in submax ?
1) decreased lactate uptake by the liver due to reduced hepatic blood flow (since the blood is going to the periphery)
2) less muscle catabolism of circulating lactate
how does fatigue coincide with temperature ?
fatigue generally coincides with a higher core temperature, which directly impairs muscle activation from a higher brain temperature
moderate exercise for more than 1 h produces what volume of sweat ?
what 5 factors do fluid loss in heat coincide with ?
1) decreased plasma volume
2) reduced skin blood flow for a given core temperature
3) reduced stroke volume
4) increased near-compensatory HR
5) general deterioration of efficiency in exercise
what must fluid replacement focus on ?
maintaining plasma volume
how does ingesting fluid change blood flow ?
it increased blood flow to skin for more effective cooling
at what rate should one replace one's water losses from sweating ?
at a rate close to or equal to sweating rate
how can sodium benefit rehydration ?
moderate to high amounts of sodium in rehydration drink can help
how can potassium affect rehydration ?
enhances water retention in intracellular space and reestablishes potassium excretion that accompanies sodium retention
what is the recommended amount of g Na / L fluid
0.5-0.7 g/ L fluid
by how much should ingested fluid exceed sweat loss ?
25-50% since kidneys also continually form urine regardless of hydration status
what are 5 factors that modify heat tolerance ?
2) training status
5) body fat level
what are heat cramps ?
severe involuntary, sustained, and spreading muscle spasms occur during or after intense physical activity, usually in active muscles
what is heat exhaustion ?
caused by ineffective circulatory adjustments- depletion of extracellular fluid, principally plasma volume, from excessive sweat
what is heat stroke ?
failure of the heat-regulating mechanisms from an excessively high core temperature
how do body fat difference influence physiologic function in the cold ?
additional body fat = more insulation
eg good for swimmers
a child has a distinctly large ratio of body surface area to mass. what are the implications of that ?
it's good and facilitates heat loss in warm environment
however, also means that in cold body dissipates rapidly
how do children rely (2 ways) on adjustments in body to tolerate cold during exercise ?
1) augmented energy metabolism
2) more effective peripheral vasoconstriction
do we have more capacity for cold or heat exposure ?
how will cold adaptation occur ?
with regular, prolonged exposure
in severe cold, what happens to the brain ?
temperature decreases, reducing O2 needs
CNS benefits from blood redistribution from tissues that will compromise their supply to save the brain
does cold ambient air pose a danger to respiratory passages ? why ?
because incoming air will warm