Biology 2

• Homeostasis


  The regulation of conditions to maintain an Optimum internal environment in response to either internal or external change
• Things homeostasis works to control in humans

  • Body temperature
  • Blood glucose concentration
  • Water levels
• Homeostasis control


  Nervous system and the hormonal or endocrine system through cyclical processes
• Homeostasis cycle


  1. Receptors detect changes (stimulus)

  2. Coordinators process information

  3. Effectors respond to bring about change
• Nervous system


  Made up of the central nervous system (brain and spinal cord) and nerves that transmit electrical impulses
• Reflex action


  Unconscious response involving only 3 neurons (sensory, relay, motor)
• Reflex actions


  • Knee jerk response
  • Pupil response to light
  • Blinking
  • Coughing and sneezing
  • Moving body part away from pain
• Reflex arc


  Sensory neuron (receptor) -> Relay neuron (spinal cord) -> Motor neuron (effector)
• Synapse


  Gap between two neurons where a chemical is released to trigger an electrical impulse
• Measuring reaction time


  1. Ruler drop test

  2. Computer program
• Factors affecting reaction time

  • Practice
  • Sleep
  • Caffeine
  • Distractions
  • Sex and age
• Cerebral cortex


  Controls conscious thoughts, language, memory, intelligence
• Cerebellum


  Coordinates muscle contractions and helps with balance and body control
• Medulla oblongata


  Controls unconscious behaviors like heart and breathing rate
• Studying the brain


  • Studying people with brain damage/injury
  • Electrical stimulation
  • Imaging techniques (EEG, MRI)
• Ethical issues with studying people with brain damage
• Eye


  Sense organ containing receptors that detect changes in light intensity and color
• Parts of the eye

  • Optic nerve
  • Retina
  • Sclera
  • Iris
  • Pupil
  • Cornea
  • Ciliary muscles
  • Suspensory ligaments
  • Lens
• Functions of the eye

  • Adapt to different light intensities
  • Accommodate to focus on near or far objects
• Hyperopia


  Long-sightedness, lens too flat to refract light enough
• Myopia


  Short-sightedness, lens too curved refracting light too much
• Thermoregulatory center


  In the brain, detects blood and skin temperature
• Thermoregulation when too cold

  1. Vasoconstriction

  2. Muscle contraction/shivering

  3. Hairs standing up
• Thermoregulation when too hot

  1. Vasodilation

  2. Hairs lying flat

  3. Sweating
• Endocrine system


  System of glands that secrete hormones directly into the bloodstream
• Endocrine glands


  • Pituitary
  • Adrenal
  • Pancreas
  • Ovary
  • Testes
  • Thyroid
• Negative feedback


  Process where a change in the body is reversed
• Controlling blood glucose


  1. Receptors detect high/low glucose

  2. Pancreas releases insulin/glucagon

  3. Liver/muscle cells absorb/release glucose
• Regulation of blood glucose levels


  1. Receptors in pancreas detect increase in blood glucose

  2. Pancreas releases insulin

  3. Insulin binds to liver and causes absorption of glucose

  4. Blood glucose levels decrease
• Regulation of blood glucose levels (reverse)

  1. Receptors in pancreas detect decrease in blood glucose

  2. Pancreas releases glucagon

  3. Glucagon causes liver to release glucose

  4. Blood glucose levels increase
• Negative feedback cycle


  Insulin and glucagon go up and down in response to blood glucose levels to keep them stable
• Type 1 diabetes


  Not enough or no insulin produced by pancreas, treated with insulin injections
• Type 2 diabetes


  Insulin receptors on target cells do not respond to insulin, treated with low carb diet, exercise, and sometimes glucose lowering medication
• Obesity is a risk factor for type 2 diabetes
• Water balance


  Water levels in body fluids need to match cell cytoplasm to prevent osmosis and cell damage
• Excretion of water, ions, and urea

  1. Lost through sweat, exhalation, and urine

  2. Urea filtered by kidneys and excreted in urine
• Deamination


  Excess amino acids converted to ammonia in liver, then to less toxic urea
• Kidneys


  • Filter blood to remove urea, water, and excess ions
  • Reabsorb useful substances like glucose and some ions
• Dialysis


  Blood is removed from body, filtered to remove urea and excess ions, then returned to body
• Kidney transplant


  Receiving a kidney from a donor, requires lifelong immunosuppressant drugs