homeostasis. what is homeostasis? (same) (state) regulation and internal maintenance of the body the...
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Homeostasis
What is homeostasis? (same) (state)
• Regulation and internal maintenance of the body
• The body works best when internal conditions are within an acceptable range; homeostasis helps to do this
Feedback Loops
• Homeostasis controls internal conditions with feedback loops
• NEGATIVE feedback loop – the product inhibits the process that creates them– Ex: control of body temperature, thermostat– Common homeostatic mechanism
• POSITIVE feedback loop – the product amplifies the process that creates them– Ex: labor, global warming
Feedback Loop
NEGATIVE POSITIVE
Homeostasis Examples• Thermoregulation (temperature)• Osmoregulation (water)• Gas Exchange• Blood Glucose• Other examples:
– pH– Blood pressure– Hormone levels– Metabolism
ThermoregulationORGAN IN CHARGE BRAIN
• Hypothalamus scans temperature of blood as it passes through– Too high blood
vessels dilate, sweating occurs
– Too low blood vessels constrict, shivering
Osmoregulation• Regulation of the balance of
water and solutes (salt, ions) in the body
• Aquatic Organisms:– (Freshwater) Protists – don’t
forget about the contractile vacuole!
– Freshwater fish – environment is hypotonic to the fish; fish take in lots of water
• Solution fish excrete LOTS of very dilute urine to conserve solutes
– Saltwater fish – environment is hypertonic to the fish; fish loses water to osmosis
• Solution fish have specialized gills to excrete excess ions
FRESHWATER
SALTWATER
OsmoregulationORGAN IN CHARGE BRAIN/KIDNEYS
• Terrestrial Animals– Water is constantly
being lost through evaporation, perspiration, urination• Water lost through
these avenues needs to be replaced by drinking and eating
– Concentration of urine allows solutes to be excreted while conserving water (kidneys)
Osmoregulation – Land Animals
OSMOREGULATION (Plants) ORGAN IN CHARGE LEAF
• Leaves take in CO2, release O2 and H2O through stomata
• Guard cells surround the stomata– Water abundant water
pressure in guard cells is HIGH, stomata OPEN, release water, CO2 enters
– Water scarce water pressure in guard cells is LOW, stomata CLOSED, loss of water limited
• Generally – Stomata open during the
day (photosynthesis)– Stomata closed during
the night (decreased photosynthesis, prevent water loss)
– Exceptions HOT DRY conditions may result in closed stomata during the day
Gas Exchange in MammalsORGAN IN CHARGE LUNGS
• Oxygen-rich air (poor in CO2) is taken in during inhalation; moves to alveoli
• Oxygen-poor blood (rich in CO2) vessels surround the alveoli
• Passive transport moves the oxygen from alveoli into the blood, CO2 from blood into the alveoli
• Oxygen delivered to cells through the blood vessels; CO2 expelled during exhalation
Regulation of Blood Glucose ORGAN IN CHARGE PANCREAS
• Blood sugar too high:– Pancreas releases
insulin; body cells take in glucose and moves it to long term storage in liver (glycogen)
• Blood sugar too low:– Pancreas releases
glucagon; stimulates liver to break down stored glycogen (into glucose) and release into bloodstream