Lecture 10 Flashcards
Define homeostasis.
Any self-regulating process by which biological systems maintain stability by adjusting to environmental changes.
Examples of factors that need to be controlled?
Temperature, O2 concentration, sugar concentration, waste, hydration.
What is a dynamic equilibrium?
The internal environment is stable but not static. Continuous change occurs but relatively uniform conditions prevail.
Why must a steady state be maintained?
Because external environments vary, some external conditions could be lethal to some cells and internal processes require certain conditions.
What are some examples of internal processes requiring certain conditions?
Enzymes are often heat activated, chemical reactions are affected by temperature and proteins may denature at high temperatures.
What is the sequence of control mechanisms?
Stimulus (pH, temperature etc.),
Perceived by receptor that sends a signal to
Control centre that sends a signal via the, endocrine/nervous system to the,
effector which re-establishes the normal conditions.
Define feedback.
Return of output to the input part of the system.
Define negative feedback.
Most homeostatic systems E.g. body temperature rise where an effect is counteracted by its own influence on the process giving rise to it.
Define positive feedback.
Rare in biological systems and always part of a larger negative feedback system where an effect is enhance by its own influence on the process giving rise to it.
Give an example of positive feedback.
Birth in mammals where oxytocin hormone stimulates contractions which then leads to more oxytocin being released.
What are some examples of variability among species in homeostatic mechanisms?
Platypuses have a body temperature of 32 degrees whereas Emperor penguins have a temperature of 39 degrees.
Why do naked mole rats not regulate their body temperature?
They live in stable underground conditions and homeostatic mechanisms are costly so if they aren’t used they are lost.
Describe torpor in hummingbirds.
At night/during cold weather, body temperature falls from 38-40 degrees down to 18-20 degrees and heart rate falls from 1,200 to 50 BPM. This is to reduce energy loss as their small bodies lose a lot of heat.
What effects can doping have?
Build muscle mass, increase O2 delivery, mask pain/injury, decrease weight, hide other drugs.
What are the side effects of doping?
The body tries to return itself to a normal, steady state.
