Introduction to Physiology

Question 1

The August Krogh Principle

Answer 1

• States that for every question in biology, there is an ideal system in which to study it
• Ex: hibernation is better studied in small animals like squirrels rather than in bears, because squirrels decrease their body temperature much more than bears, leading to them having a lowered metabolic rate and being less likely to become aroused while being studying (compared to bears).

Question 2

Branches of Comparative Physiology

Answer 2

1. Mechanistic physiology
2. Evolutionary physiology
3. Environmental physiology

Question 3

Adaptive Significance

Answer 3

• Is any given physiological mechanism a specific adaptation to a given environmental condition or challenge?
• Could be that a trait evolved 1000s of years ago to deal with a different challenge, and just so happened to be useful again for a new reason

Question 4

Structure-Function Relationships

Answer 4

• How does the physical structure or anatomy of an organ allow it to fulfill its physiological function?
• Ex: Fish gills are great at getting oxygen out of water, are optimally designed for gas exchange, are more efficient than mammalian and bird lungs

Question 5

Acclimatisation

Answer 5

• A physiological change caused by moderate to long-term exposure to certain environmental stimuli
• Ex: Over 9-10 days in high altitudes where there are lower oxygen levels, changes occur in certain parts of the brain to make breathing more efficient (“acclimatising” to the low oxygen levels)

Question 6

Adaptation

Answer 6

• Physiological mechanisms that have developed over long periods of time (i.e., generations; evolutionary time scale) due to constant exposure of a population to a specific environmental condition
• Ex: populations who have lived at high altitudes for several generations have changes in the molecular structure of hemoglobin, making it more efficient at binding oxygen

Question 7

Feedback Control System

Answer 7

• A physiological response to changing conditions (usually internal) to restore homeostasis
• Ex: insulin released in response to high blood glucose (sugar) to allow glucose to move out of the blood and enter cells

Question 8

Feedforward Control System

Answer 8

• A physiological response in anticipation of changing conditions
• Ex: insulin being released prior to blood glucose levels rising; secretes in response to food (carbohydrates) in the intestine, which will later be broken down into glucose

Question 9

Conformity

Answer 9

• The internal (body) level of any given variable matches that of the environment that the animal is in
• Ex: For temperature, conforming means body temp will change with environmental temp, which is done by poikilotherms and ectotherms (cold-blooded animals)

Question 10

Regulation

Answer 10

• The internal (body) level of any given variable is kept at a value different from that of the environment in which the animal is in
• Ex: For temperature, regulating means that body temp will stay relatively consistent (unless it’s too cold or too hot to do so)
• Endotherms (warm-blooded animals) are temperature regulators

Question 11

Time Domains of Physiological Change

Answer 11

1. Acute changes (fight or flight; neural/endocrine response; ex: touching hot stove)
2. Chronic changes (acclimatisation)
3. Evolutionary changes (adaptation)
4. Developmental changes
5. Circadian rhythms

Question 12

Circadian Rhythm

Answer 12

• A biological (physiological) change that occurs over a ~24 hour period or in association with day/night or light/dark

Question 13

Developmental Change

Answer 13

• Changes that occur over the lifespan
• Ex: amphibian development
• Frogs start as tadpoles with gills, then have an intermediate form with both gills and lungs, and finally mature into adult frogs with lungs

Question 14

Environmental Physiology

Answer 14

• Examines how animals live in harsh environments and cope with extreme abiotic factors
• Important factors considered:
  
  • Oxygen and carbon dioxide levels
  • Temperature
  • Water salinity (in aquatic systems)
  • Water availability
  • Toxic conditions

Question 15

Terrestrial Environment

Answer 15

• Lots of O2 and not a lot of CO2 at sea level (base depth level)
• Generally, terrestrial animals don’t lack for oxygen

Question 16

Aquatic Environments

Answer 16

• Much less O2, with levels fluctuating during the day and night because of aquatic plants performing photosynthesis (day) and respiration (day and night)

Question 17

High Altitude Environments

Answer 17

• Low levels of O2 due to low atmospheric pressure (“thinner” air)
• Temp decreases as altitude increases

Question 18

Underground Burrows

Answer 18

• Can be very low in O2 and high in CO2, reaching CO2 levels that may be lethal to humans

Question 19

Deserts

Answer 19

• Defined by dryness, not temp
• Have very little water
• Can very in temp greatly from very hot during the day to very cold at night

Question 20

Water Salinity

Answer 20

• Osmosis affects fish
• Freshwater fish lose ions and gain water
• Seawater fish lose water and gain ions
• Fish need a way to regulate this so that they stay healthy

Question 21

Hydrothermal Vents

Answer 21

• Found deep on ocean floor
• Heated by volcanic magma, they release extremely heated, pressurized water, and are generally inhospitable environments (hot, high pressure, no oxygen, no light, and toxic H₂S released)
• Still, some animals live here, such as the giant tube worm