Lecture 10 Flashcards
Lecture objective:
To define the physiological term adaptation and to describe its usage.
ADAPTATION: Changes that reduce the physiological strain produced by stressful components of the total environment. This change may occur within the lifetime of an organism (phenotypic) or be the result of genetic selection in a species or subspecies (genotypic).
In thermal physiology field, the use of the term adaptation does not require specification of the climatic component of the total environment to which the organism adapts, but the most obvious component is often denoted (e.g., adaptation to heat).
There are no distinct terms that relate genotypic adaptations to the climate or particular components of climate.
Lecture objective:
To describe and give examples of the 3 types acclimation/acclimatization to cold environments
1) Metabolic adaptation
- Refers to elevated metabolic responses in cold acclimated animals (varied results for humans)
- Tcore changes depend on extent of cold stress
- E.g. greater BMR post acclimation, enhanced shivering thermogenesis, enhanced NST
2) Hypothermic adaptation
- Greater fall in core temp after acclimation
- Tsk maintained or dec
- Small increase or decrease in metabolic response to cold stress pre vs. post cold acclimation
- Redistribution of circulation to periphery to give warmer skin or resetting of thermostat
- Associated with reduced NE response indicating this is a habituation rather than an acclimation
3) Insulative adaptation
- an insulative adaptation could develop due to a more pronounced vasoconstriction or improved peripheral countercurrent heat exchange as seen by Hong in Korean women divers
Lecture objective:
To explain the main physiological adaptations evident for each of the 3 types of cold acclimation/acclimatization.
a
Lecture objective:
To explain if and how cold acclimation influences human exercise performance.
a
Acclimation and acclimatization are ____ indistinguishable
etymologically
Define acclimation
Physiological or behavioral adaptive changes in response to experimentally induced changes of particular climatic factors such as ambient temperature and humidity in a controlled environment. Acclimation relates to PHENOTYPIC adaptations to specified climatic components.
Define acclimatization
Physiological or behavioral adaptive changes that occur within an organism that reduce strain caused by stressful changes in the natural climate (e.g., seasonal or geographical).
Define adaptation
Changes that reduce the physiological strain produced by stressful components of the total environment. This change may occur within the lifetime of an organism (phenotypic) or be the result of genetic selection in a species or subspecies (genotypic).
How is the term adaptation used thermal physiology field?
In thermal physiology field, the use of the term adaptation does not require specification of the climatic component of the total environment to which the organism adapts, but the most obvious component is often denoted (e.g., adaptation to heat).
How is the term genotypic adaptation used thermal physiology field?
There are no distinct terms that relate genotypic adaptations to the climate or particular components of climate, although they do occur
Define habituation
a desensitization or damping of the normal responses to a stressor
Slide 5 Describe the different types and amount of heat loss avenues during 1) Severe cold 2) Mild cold 3) Thermoneutral 4) Heat
X axis is power. Rate of enrg or heat exchange. Pos values are heat liberation or heat production, neg values are heat loss. Both for hot and cold environment. In severe cold, added to the basometabolic rate (clear bar), we can add to that wet heat loss and heat related thermogenesis. Likely the nrg cost of thermoregulation. Cost of producing sweat and transporting fluid to sweat glands. When looking at extreme cold we have shivering and non shiverint themogenesis. Non shivering thermo is the bit above the basil. Assessing non shivering thermogenesis is difficult in someone whos shivering. 27 watts for non shivering and above is shivering.I
Mild cold we eliminate shivering and we have NST. Mass of BAT.
Slide 6
Take home is that cold water immersion does little to influence tissue insulation.
Slide 7
Mild cold exposure and looking at metabolism and insulation. Instead of more aggressive cold where u have dec inc core temp looking at metabolic and insulative changes. People are fighting over whether cold exposure influences BAT (is non shivering thermogenesis in JUST BAT or are the UP expressed in other tissues)
What are the 3 types of cold acclimation/acclimatization?
1) Metabolic adaptation
2) Hypothermic adaptation
3) Insulative adaptation
Draw a diagram and explain how to figure out what type of cold acclimation/acclimization would take place?
- With Chronic or repeated cold stress -> determine if there’s “Body heat loss?”
- If NO for #1 -> Cold habituation
a) Blunted shivering
b) Blunted cutaneous vasoconstriction - If YES for #1 -> Increased metabolic heat production sufficient to defend body temp?
- If YES for #3 -> Metabolic acclimatization/acclimation
a) Enhanced shivering thermogenesis
b) Enhanced NST (?) - If NO for #3 -> Insulative acclimatization/acclimation
a) Enhanced cutaneous vasoconstriction
b) Improved muscle BF toward subcutaneous shell
What is metabolic adaptation and give examples
- Elevated metabolic responses in cold acclimated animals, but varied results for humans
- E.g. greater BMR post acclimation, enhanced shivering, or enhanced NST
- Tcore changes depend on extent of cold stress
- Varied results in human studies, more recent studies are on NST and BAT in humans
Example of hypothermic adaptation?
Individuals lower the core temp that they defend
Example of insulative adaptation?
- Enhanced cutaneous vasoconstriction
2. Improved muscle BF toward subcutaneous shell
Provide 3 points of evidence supporting the existence of SBC in humans
a
Slide 10, is this acute shivering or NST?
1960’s mice. These mice established colonies living in meat lockers in britain. Animals living in these conditions at -10 degrees. 3 strains of mice. They’re being exposed to either 21 degrees (dotted bar) or -3 degrees (taller line bars). 3 types of mice are diff strains (AG2, C67BL and then cross). Kcal/100grams/hour, likely indirect calorimetry. Based on mean O2 consumption. They were living in cold conditions. There are enhanced metabolic rate. Diff strains gives diff elevation. Cold exposure repeatedly can inc metabolic rate. Well before they could quantify BAT thermogenesis. Is this acute shivering or non shivering thermo? Animals exposed to long time to cold they don’t shiver, but they still have —-. Earlier study.
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