Lecture 7 - January 28th Flashcards
What is homeostasis?
The body’s condition as balanced. The body is always trying to achieve this state.
What are environmental stressors that can disrupt homeostasis?
- Fear
- Hunter
- Predation
- Environmental conditions, catastrophes
- Food
- Pathogens
What are the two main types of responses to environmental challenges?
- Adjustments (behavioral, acclimatization, developmental plasticity)
- Genetic adaptations
Define behavioral adjustments in the context of human adaptability.
Cultural mediated responses to an environmental stressor in an effort to maintain homeostasis.
* not genetically inherited
* short to long term change
* on the population level
What is acclimatization?
Physiological response of individual organisms to different conditions.
* individual level
* short term
* reversible
What is adaptation?
- population level
- long term (genetic)
- not reversible
What is the normal human body temperature?
37C
What physiological response occurs in the body during cold stress?
When the body temp falls below 35C, the hypothalamus becomes impaired and struggles to maintain homeostasis.
What happens to the human body when temperatures exceed 40C?
The hypothalamus has difficulty regulating body temperature responses.
Define the hunting phenomenon.
The acclimatization to cold temperatures, person goes through a cycle of vasoconstriction and vasodilation which promotes blood flow. It mitigates cold and is a behavioral adjustment, ie it’s not genetically inherited and on population level.
Define genetic adaptation.
Heritable genetic changes that develop in populations over long periods of time.
What is the significance of Bergmann’s rule?
Larger body sizes are better for heat retention in colder climates.
What does Allen’s rule state?
Animals in colder climates will have shorter limbs/appendages than those in warmer climates.
What are some examples of climate adaptation in human groups?
- African groups may have longer limbs
- Dutch are the tallest people in the world
What is hypoxia?
A condition where the body doesn’t get enough oxygen, often occurring at high altitudes.
What physiological changes occur during acclimatization to high altitude?
- Increase in red blood cell numbers
- Hemoglobin releases more oxygen
- Increase in cardiac output
- Increase in capillary network
What is altitude sickness?
- Hyperventilation
- Changed breathing and sleeping patterns
- Increased urination
- Headache
- Loss of appetite
- Nausea
- Fatigue
What are some long-term adaptations to high altitude?
- Increased RBC volume and hemoglobin concentration (Andes)
- Faster breathing and blood vessel expansion (Tibet)
- Improved oxygen uptake and delivery (Ethiopia)
What is the EPAS1 gene associated with?
A mutation that allows for decreased hemoglobin/catecholamine release at high altitude, related to adaptation.
What is developmental plasticity?
Anatomical/physiological changes occurring during growth and development that are difficult to reverse.
What is the critical window for growth and development?
The first 1000 days from conception.
What are typical characteristics of populations with long-term high altitude cultures?
- Grow more slowly
- Physically mature later
- Shorter stature
- Larger lung and heart capacity
- Smaller birth weight
What are the 4 mechanisms of thermoregulation?
- Convection
- Conduction
- Evaporation
- Radiation
Define convection.
When a warm body is surrounded by a cooler fluid (ie air or water) heat will be transferred from the warmer body to the cooler fluid.
Define conduction.
Heat will move from a warmer body to a cooler one through direct contact.
Define evaporation.
Occurs when a liquid, such as water within our bodies is converted to gas, ie sweating.
Define radiation.
Mechanism of heat transfer involving electromagnetic energy being emitted from an object.
Why do we shiver?
It is a short term physiological response to the cold to stimulate increased muscle activity.
What is vasoconstriction? Why does it happen?
The constriction of the capillaries (smallest blood vessels) in the skin. Its purpose is to constrict, which prevents heat from reaching the surface and retains body heat.
