MODULE 5-8

• Homeostasis


  The steady state or internal balance of an organism regardless of the external environment
• Environment is dynamic
• It is important for a living organism to survive through homeostasis
• To have homeostasis, we need a variable/stimulus
• Receptor


  • Detects current stimulus
• Control Center


  • Processes information sent by receptor and decides response
• Effector


  • Responds depending on decision of control center
• Setpoint value


  The normal state that the variable returns to
• Negative feedback


  Part of homeostasis, reduces the original stimulus to return a variable to normal range
• Positive feedback


  Opposite of negative feedback, amplifies or increases the stimulus, does not contribute to homeostasis
• Circadian rhythm


  Physiological changes that occur every 24 hours in response to light and dark
• Circadian rhythm cannot be controlled
• Circadian rhythm regulates the sleep-wake cycle of an individual
• Thermoregulation


  The process by which animals maintain an internal temperature within a tolerable range
• Endotherms


  • Warmed by heat generated by their metabolism, maintain stable internal body temperature
• Ectotherms


  • Gain heat through external sources like the environment, consume less food, increase body temperature through behavior
• Acclimatization


  Physiological adjustments of animals to changes in their external environment
• Four physical processes of heat exchange in animals

  • Radiation
  • Evaporation
  • Convection
  • Conduction
• Tissue


  A group of cells with similar structures and functions
• Four types of tissues

  • Epithelial
  • Nervous
  • Muscle
  • Connective
• Types of epithelial tissues based on number of layers

  • Simple
  • Stratified
• Shapes of epithelial cells

  • Squamous
  • Cuboidal
  • Columnar
• Loose connective tissue (areolar)


  • Found beneath the epidermis layer of the skin
• Adipose tissue


  • Cells are adipocytes or fat cells, contain large amounts of lipids
• Dense connective tissue


  • Found in tendons, ligaments, and dermis of the skin
• Three types of cartilage

  • Hyaline
  • Fibrocartilage
  • Elastic
• Bone


  • Consists of osteocytes, the mature bone cells
• Blood


  Liquid connective tissue containing plasma, red blood cells, white blood cells, and platelets
• Three types of muscle tissue

  • Skeletal
  • Smooth
  • Cardiac
• Skeletal muscle


  • Attached to the skeleton, contracts with the bones, striated cells, multi-nucleated, voluntary contractions
• Smooth muscle


  • Forms walls of hollow organs, fusiform shape, no striations, uni-nucleated, involuntary contractions
• Cardiac muscle


  • Muscle of the heart, cylindrical cells, branched and connected by intercalated discs, striated, uni-nucleated, involuntary contractions
• Neurons


  Cells important for conducting action potentials and transmitting impulses, consist of cell body, dendrites, and axon
• Neuroglia


  Supporting cells that do not transmit impulses like neurons
• The skeleton provides a rigid structure to which muscles attach
• Skeletons function in support, protection, and movement
• Three types of skeletons

  • Hydrostatic
  • Exoskeleton
  • Endoskeleton
• Hydrostatic skeleton


  • Consists of fluid held under pressure in a closed body compartment, simplest form of skeletal system
• Exoskeleton


  • Hard encasement deposited on the surface of an animal, found in most molluscs and arthropods
• Endoskeleton


  • Components are cartilage and bones, found in sponges, echinoderms, and vertebrates