Homeostasis Flashcards
Homeostasis
A stable internal environment (kept stable through feedback loops)
Negative Feedback Loop
A feedback loop that brings you closer to the target set point (regulate)
Ex. Thermoregulation, blood glucose level
Positive Feedback Loop
A feedback loop that takes you over and away from the target set point (amplify)
Ex. Childbirth, apple ripening
Thermoregulation
Hypothalamus - Too hot: Vasodialate, sweat, thyroid - Too cold: Vasoconstrict, shiver, thyroid
Feedback Loop
Receptor: Sensory organ, Stimulus, Effector: Organ that acts in response, Response
Blood Glucose Level
Pancreas (islets of langerhans) (90mg/100ml) - Too high: Beta cells (insulin), (liver) cells store as glycogen - Too low: Alpha cells (Glucagon), cells release
Blood Calcium Level
Thyroid/parathyroid (10mg/100ml) - Too high: Calcitonin, kidneys excrete, bones deposit - Too low: PTH, kidneys retain, bones release, intestines pull from food
Osmolarity
Hypothalamus (300 mOsmol/L) - Too high (dehydrated): Pituitary gland (Antidiuretic Hormone), kidney/nephron retains water - Too low: less ADH, kidney releases water
Homeostasis hugs
Arteries and veins for heat (countercurrent heat exchange), capillaries and alveoli for oxygen, kidneys
Counter current gas exchange
Fish gills, blood flows in one direction water in the other. Able to get 80% of oxygen, gradient between water and lamella capillaries, 80%/20% to 50%/50%
Kidney steps (nephron)
- Filters: Glomerulus (small molecules)
- Secretes: Large molecules/other unwanted (proximal and distal tubule)
- Reabsorbs: Active transport, wanted materials like water and sodium
- Excrete: Waste
Ectotherm
Same temperature as external environment
Endotherm
Regulate their internal temperature
