week 10

• Homeostasis


  a term coined by psychologist Walter Cannon (1932)
• Homeostasis 


  refers to an organism’s ability to adjust its physiological processes to maintain a steady internal balance or equilibrium.
• Behavioral Strategies for Cold Temperatures


  • Move to a warmer place or shelter
  • Huddle with others to conserve heat
  • Curl up to decrease exposed surface area
  • Add more clothing, preferably dark colors
• Behavioral Strategies for Warm Temperatures


  • Move to cooler, shadier place or shelter
  • Stretch out
  • Wear less clothing, preferably light colors
• Internal Strategies for Cold Temperatures


  • Shivering
  • Constriction of blood vessels
  • Increased release of thyroid hormone to increase metabolic rate
  • Increased metabolism in brown fat stores
• Internal Strategies for Warm Temperatures


  • Perspiration and panting
  • Dilation of blood vessels
• ALLOSTASIS


  (from the Greek roots meaning “variable” and “standing”),
• ALLOSTASIS


  means the adaptive way in which the body anticipates needs depending on the situation, avoiding errors rather than just correcting them
• Mammals and birds are referred to as endotherms
• (“endon” is the Greek word for “within”)
• endotherms 


  due to their ability to maintain body temperature through internal metabolic activity
• Amphibians, reptiles, and fish are referred to as ectotherms
• (ektos is the Greek word for “outside”)
• ectotherms


  because they rely on external factors, such as basking in the sunlight or retreating to the shade below a rock, to maintain ideal body temperature,
• Hypothermia


  occurs when core body temperature drops below 35°C/95°F.
• the force that causes water to move from an area with lower concentration of solutes to an area with higher concentration of solutes

  osmosis
• Solutions that are lower in concentration of solutes than a reference solution are referred to as hypotonic
•  solutions that are relatively higher in concentration of solutes are referred to as hypertonic.
• osmotic thirst occurs in response to cellular dehydration that results from drops in the intracellular fluid volume.
•  hypovolemic (low volume) thirst occurs in response to drops in blood volume.
• osmotic thirst appears to be the more common mechanism
• hypovolemic thirst serves as a less frequently used emergency backup system.
• Hypovolemic thirst results when we experience a drop in the volume of interstitial fluid, blood, or both.
• antidiuretic hormone (ADH), also known as vasopressin
• renin


  a substance released by the kidneys that converts angiotensinogen into angiotensin II
• angiotensinogen


  a blood protein converted into angiotensin II by renin.
• a hormone that constricts blood vessels to maintain blood pressure and triggers the release of aldosterone.

  angiotensin II
• hormone that signals the kidneys to retain sodium.

  aldosterone
• subfornical organ (SFO),


  area of the brain, located near the junction of the two lateral ventricles, that regulates drinking.
• zona incerta


   An area of the midbrain that participates in the initiation of drinking behavior
• zona incerta


  produces drinking behavior, suggesting that this structure is responsible for initiating the motor components of drinking behavior.
•  hyponatremia


  a condition in which extracellular sodium levels drop 10 percent or more below normal
• The hormone cholecystokinin (CCK) is released when large quantities of fat are consumed.
• Heat stroke, or hyperthermia,
occurs when the body’s normal compensations (such as sweating and dilating the blood vessels close to the skin) cannot keep core temperature within normal limits.