Homeostasis and Thermoregulation | Quizlet

Regulator

Uses control mechanisms to maintain a stable internal environment.
Have more consistent enzymatic reactions but waste a lot of ATP
Ex. Otter will maintain temperature using lots of ATP

Conformer

Allows internal conditions to fluctuate with external environment.
Ex. Bass internal temperature fluctuates with the water

Homeostasis

Regulators maintain a steady state of internal conditions
Ex. Humans: body temperature, blood pH, glucose concentration, ect. are maintained at a constant level

Mechanisms of Homeostasis

Fluctuations above or bellow a set point serves as a stimulus
Detected by sensor, triggering a response, the response returns the variable to the set point

Negative Feedback Loop

Homeostasis is maintained in this way
Keeps a variable within a certain range

Positive Feedback Loop

Amplifies a stimulus, and does not contribute to homeostasis
Ex. Childbirth, contractions lead to hormone secretion, which leads to more contraction, and around and around until the baby is born

Thermoregulation

Process by which animals maintain a stable internal temperature within a tolerable range
Affected by Form, function, and Behavior

Endothermic

Animals that generate heat via metabolism
May remain active at a greater range of temperatures, but is energetically expensive
Ex. Birds and Mammals, Walrus

Ectothermic

Animals gain heat from external source
Can tolerate greater variation of internal temperature, which is cost saving
Ex. Invertebrates, Fish, Amphibians, Non- avian reptiles, Lizard

Poikilotherms

Allow their body temperature to vary with the environment
Ex. Hummingbirds (endo), hibernating reptiles (ecto)

Homeotherms

Maintain relatively constant internal body temperatures
Most endotherms and many ectotherms

Conduction

Exchange heat with the environment via physical contact with object

Convection

Exchange heat with the environment via water, or air across skin

Radiation

Exchange heat with the environment via in fared rays

Evaporation or Condensation

Exchange heat with the environment via liquid going into the gaseous phase, or gas going into the liquid phase

Integumentary System

Heat Regulation in mammals
Skin and its derivatives

Adaptations to Help Animals Thermoregulate

Insulation
Circulation
Evaporative Heat Loss
Behavior
Metabolic Heat Production

Insulation

Important for thermoregulation in mammals and birds, especially marine animals
Skin, Feathers, Blubber, all reduce heat exchange between animals and the environment.

Circulatory Adaptations

Regulation of blood flow near the body surface significantly affects thermoregulation
Animals can alter the amount of blood flowing between the body and the skin

Vasodilation

Capillaries in the skin dilate, increasing blood flow and facilitating heat loss

Vasoconstriction

Capillaries in the skin constrict, reducing blood flow and minimizing heat loss

Countercurrent Heat Exchange

Possible due to blood vessels lying in close proximity to promote heat transfer from arteries to veins, if the vessels we're far apart, heat would transfer from arteries to the environment
Allow heat to transfer between two fluids in order to reduce heat loss

Cooling by Evaporation

Many types of animals lose heat through evaporation of water from their skin
Panting increases cooling effect in birds and many mammals

Behavioral Responses

Both endoderms and ectoderms use behavior to control body temperature
Some animals adopt postures that minimize or maximize absorption of solar radiation
Ex. Dragonfly's "Obelisk Posture"

Metabolic Heat Production

Some animals regulate body temperature by adjusting the rate of metabolism
To heat up, animals can increase the metabolic rate of mitochondria or increase muscle activity, by moving or shivering
Ex. Python

Hypothalamus

The region of the brain that controls thermoregulation
Controls mechanisms resulting in heat loss or generation

Fever

The change to the set point of a biological thermostat

Metabolism

Maintaining a constant internal temperature requires energy obtained through...
After these needs are met, remaining energy can be used for: Activity, Growth and repair, Storage of fat, Reproduction

Metabolic Rate and Animal

Ectotherms have a much lower...than endotherms of a comparable size
More energy for growth, reproduction, etc.
Affected by many other factors, including size and activity

Metabolic Rate and Size

MR increases with size
Ex. Large mammals have a higher MR than small mammals, so large mammals need to eat more food
MR per kg is inversely related to body size
Smaller animals have a higher MR than larger animals, per kg of body mass

Energy Budgets

Different species use energy in food in different ways
Use of energy is partitioned to MR, activity, thermoregulation, growth, and reproduction

Topor

Physiological state in which activity is low and metabolism decreases, enables some animals to save energy

Hibernation

Long term torpor that is an adaptation to cold and food shortages

Estivation

Topor in the summer, enables animals to survive high temperatures and scarce water access

Daily Topor

Exhibited by small mammals and birds to save energy
Ex. Hummingbirds