AP Bio Unit 4: Day 1 Notes Homestasis, Feedback loops, Thermoregulation

AP Bio Unit 4: Day 1 Notes

Homestasis, Feedback loops, Thermoregulation

Homeostasis: maintenance of dynamic internal consistency; provide optimal internal environment to support body functions



Feedback Loops

Mechanisms that help maintain homeostasis

→ step point - “the norm”



Negative feedback

**Are actual loops

Counteracts original stimulus to bring body back to set point

– maintains homeostasis 

ex. 

  • blood pressure

→ too low: constrict blood vessels and increase pressure

  • body temperature

  • ion concentration

  • H20 concentration

→ ADH signal received from kidneys (keep water). it will get released when you're dehydrated and can put water back into the blood stream. If you're hydrated, kidney will choose to put the excess water into the bladder for excretion (less concentrated pee **light color)

**How does the structure of water help evaporation cooling?

→ connection to unit 2



Positive feedback

Amplifies the stimulus, does NOT maintain homeostasis but important

ex.

  • clotting factors

  • childbirth

  • milk secretion/lactation



To differentiate between positive and negative feedback: identify stimulus, and whether it counteracts the stimulus to return to homeostasis and how its done



Thermoregulation: ways in which heat is exchanged with the environment

  • metabolism: chemical reactions generate heat as a byproduct (brown fat)

  • evaporation: sweating cools body by taking heat away

  • convection: panting moves air to facilitate heat transfer (countercurrent heat exchange)

  • radiation: emission of energy (sun)

  • conduction: heat transference between surfaces







**Bigger ears - increase surface area to volume ratio that allow heat to cool them

Smaller ears - tinier surface area and allows heat to stay 



Endotherms: “warm-blooded”

No matter the heat outside, they should maintain body temperature using metabolism

→ instead of turning metabolism into energy (ATP), they can turn it into heat (brown fat)

Positive correlation 


Ectotherms: “cold blooded”

They have temperature that changes with the temperature of their environment

→ lizards sunbathe on rocks that absorb heat to get warm





Line A is an endotherm because in lower temperatures, like 10C, the oxygen consumption rate is higher due to the animal’s body requiring more oxygen to facilitate cellular respiration to produce energy for heat. In higher temperatures, like 40C, the animal doesn’t need as much energy to produce heat as its body temperature is already maintained



Line B is an ectotherm because their internal temperatures move along the external temperatures. As the temperature decreases, so does the internal temperature of the lizard or animal. This is why they like to sit on hot things or require heat lamps to maintain an ideal temperature.