mechanisms

• Homeostasis


  Regulation and internal maintenance of the body
• The body works best when internal conditions are within an acceptable range; homeostasis helps to do this


  Homeostasis
• Homeo


  Meaning similar
• Stasis


  Meaning stable
• Feedback loops


  1. Feedback compares current conditions to the body's comfort levels (=Set Ranges)

  2. Negative feedback loop - counteracts change and brings the body back to homeostasis

  3. Positive feedback loop - increases change away from the set points. Needed for rapid change in the body
• Negative feedback loop


  • Control of body temperature, thermostat
• Positive feedback loop


  • Torn blood vessels stimulates the release of clotting factors to stop blood flow
• Hormones are chemical messengers that regulate various physiological processes such as growth, metabolism, reproduction, and homeostasis.
• HOMEOSTASIS EXAMPLES

  • Thermoregulation (temperature)
  • Osmoregulation (water)
  • Gas Exchange
  • Blood Glucose
  • Guard Cells
• THERMOREGULATION

  1. Hypothalamus scans temperature of blood as it passes through

  2. Too high blood vessels dilate, sweating occurs

  3. Too low blood vessels constrict, shivering
• THERMOREGULATION

  • The most in heat activates cooling mechanisms
  • Temperature sensors in skin dilate blood vessels and heat escapes
  • Sweat glands secrete sweat that evaporates, cooling body
  • Thermostat shuts off cooling mechanisms
• THERMOREGULATION

  1. Temperature increases: Blood vessels constrict, minimizing heat loss

  2. Skeletal muscles rapidly contract, causing shivering which generates heat

  3. Temperature decreases: Thermoregulation activates warming mechanisms
• OSMOREGULATION


  Regulation of the balance of water and solutes (salt, ions) in the body
• OSMOREGULATION


  • Freshwater fish take in lots of water, excrete very dilute urine to conserve solutes
  • Saltwater fish lose water to osmosis, have specialized gills to excrete excess ions
• OSMOREGULATION


  1. Hypothalamus detects higher concentration of solutes in blood

  2. Posterior pituitary releases more ADH

  3. Kidneys reabsorb less water

  4. Pituitary releases less ADH
• GAS EXCHANGE IN MAMMALS

  • Oxygen-rich air is taken in during inhalation, moves to alveoli
  • Oxygen-poor blood vessels surround the alveoli
  • Passive transport moves oxygen from alveoli into blood, CO2 from blood into alveoli
  • Oxygen delivered to cells through blood vessels, CO2 expelled during exhalation
• REGULATION OF BLOOD GLUCOSE

  1. Blood sugar too high: Pancreas releases insulin, body cells take in glucose and move it to storage in liver

  2. Blood sugar too low: Pancreas releases glucagon, stimulates liver to break down stored glycogen and release into bloodstream
• Guard Cells


  • Surround the stomata in leaves
  • Open when water abundant, close when water scarce
  • Generally open during the day for photosynthesis, close at night to prevent water loss