Chapter 22 - Homeostasis Flashcards
Define homeostasis
The maintainance of a constant internal environment in the body cells.
Describe the principles of negative feedback in homeostasis.
- Receptor cells detect changes and send a message (chemical or hormonal) to the brain.
- The brain gives new instructions
- The effectors receives the instructions and does corrective actions to bring the factor back to normal.
- The receptor cells then sends a feedback to brain on corrective actions.
- A negative message received from the receptor to effector prevents corrective actions of going too far.
Can ectothermic animals regulate body temperature? Give reason for your answers.
- They cannot generate heat from within the body.
- Relatively low metabolic rates. Metabolic rate generates insufficient heat
- Rely on a external energy source. (sun, hot rocks.)
- ecto - outside
- therm - heat
- Body temperature is directly proportional to external temperatures.
Give examples of ectothermic animals.
- Fish
- Reptiles
- Amphibians
- Crustacean
How do ectothermic animals regulate their body temperature if it is cold?
- In low temperature, they bask in the sun to absorb its radiant energy.
- Some reptiles has a black pigment melanin in cells.
- If these cells relax, the pigment becomes more visible.
- The skin becomes darker in color and more energy is absorbed.
How do ectothermic animals regulate their body temperature when it is hot?
- The cells containing melanin contracts, the pigment becomes more concentrated and invisible.
- The skin becomes lighter and more heat is reflected.
Name the 5 regulations performed by homeostasis
- It is responsible for thermoregulation ( temperature )
- Body needs to be kept between 36 - 37.5 ºC.
- Enzymes denature when too high, and become inactive when too low
- Water balance is kept at 67%, other wise consequences.
- Glucose levels are maintained by homeostasis.
- 90-100mg/100cm3 per drop of blood (0.1% of blood) - Blood pH
- Kept around 7.4, enzymes may denature at variations - Oxygen and CO2 is regulated. Shortage of O2, lower metabolic rate, excess CO2 decreases pH of blood.
State some typical behavioral patterns of an ectothermic animal in cold temperatures
- Basking in the sun
- Black pigment called melanin becomes more visible when the cells relax, absorbing more heat energy
- Therefore, solar energy is used to increase body temperature
- Hibernation in some seasons, where all body processes slow down
What happens to ectothermic animals like lizards when temperatures are high?
The cells contract, and the melanin pigments become less visible. The skin becomes lighter, reflecting more heat.
These animals also avoid unfavorable conditions by hiding under rocks or flicking sand over their bodies.
Explain the term Aestivation
A state of dormancy due to dry summer conditions, occurs in some reptiles and toads.
Define the term endothermic
Heat is generated within the body by cellular respiration high metabolism, and muscular contractions. In this way, a constant body temperature is maintained.
State the optimum temperature for enzyme activity in humans
37ºC
How is heat generated within the human body?
- Cellular respiration
- Increase in thyroxine and adrenaline secretions cause faster metabolic rate, faster respiration and more heat
- Heat can be absorbed from the environment (sun, hot drinks)
Name and explain the four processes by which the body loses heat
- Radiation: Heat lost from warm body to cold environment
- Evaporation: Fluids (sweat) absorb energy and evaporate
- Convection: Hot air heated in the body rises, making space for cold air
- Conduction: Heat lost from warm body to cold object
Name the six mechanisms which control body heat in endoderms
(These are really easy to remember, so they will not be asked seperately. Read through them in the textbook if you really want to)
- Vasoconstriction
- Vasodilation
- Hairs
- Sweat glands
- Shivering
- Exercise
