CH1 (HOMEOSTASIS - BODY CAVITY)

• Homeostasis


  Maintenance of constant internal environment despite fluctuations in the external or internal environment
• Variable


  Measures of body properties that may change in value
• Examples of variables


  • Body temperature
  • Heart rate
  • Blood pressure
  • Blood glucose levels
  • Blood cell counts
  • Respiratory rate
• Normal range


  Normal extent of increase or decrease around a set point
• Set point


  Normal, or average value of a variable overtime, body temperature fluctuates around a set point
• Negative feedback


  1. Detection of deviation away from set point

  2. Correction of deviation toward set point and normal range
• Positive feedback


  Mechanisms occur when the initial stimulus further stimulates the response<|>System response causes progressive deviation away from set point, outside of normal range<|>Not directly used for homeostasis<|>Some positive feedback occurs under normal conditions, e.g. childbirth<|>Generally associated with injury, disease<|>Negative feedback mechanisms unable to maintain homeostasis
• Components of feedback


  • Receptor
  • Control center
  • Effector
• Anatomical position


  Person standing erect with face and palms forward<|>All recreational descriptions based on the anatomical position, regardless of body orientation
• Directional terms


  • Superior: above
  • Inferior: below
  • Anterior: front (also: ventral)
  • Posterior: back (also: dorsal)
  • Medial: close to midline
  • Lateral: away from midline
  • Proximal: close to point of attachment
  • Distal: far from point of attachment
  • Superficial: structure close to the surface
  • Deep: structure toward the interior of the body
• Body planes


  • Sagittal plane: separates the body into right and left parts
  • Median plane: a sagittal plane along the midline that divides body into equal left and right halves
  • Transverse plane: a horizontal plane that separates the body into superior and inferior parts
  • Frontal plane: a vertical plane that separates the body into anterior and posterior parts
• Body regions


  • Upper limbs: upper arm, forearm, wrist, hand
  • Lower limbs: thigh, lower leg, ankle, foot
  • Central region: head, neck, trunk
• Body cavities


  • Thoracic cavity: space within chest wall and diaphragm, contains heart, lungs, thymus gland, esophagus, trachea
  • Mediastinum: space between lungs, contains heart, thymus gland, esophagus, trachea
  • Abdominal cavity: space between diaphragm and pelvis, contains stomach, intestines, liver, spleen, pancreas, kidneys
  • Pelvic cavity: space within pelvis, contains urinary bladder, reproductive organs, part of large intestine
• Serous membranes


  • Visceral serous membrane: covers organs
  • Parietal serous membrane: is the outer membrane
  • Cavity: a fluid-filled space between the membranes
• Three sets of serous membranes and cavities

  • Pericardium around heart, pericardial cavity
  • Pleura around lungs, pleural cavity
  • Peritoneum around abdominopelvic cavity and its organs, peritoneal cavity
• Pleura


  Visceral pleura: covers lungs<|>Parietal pleura: lines inner wall of thorax<|>Pleural cavity: reduces friction, adheres lungs to thoracic wall
• Pericardium


  Visceral pericardium: covers heart<|>Parietal pericardium: thick, fibrous<|>Pericardial cavity: reduces friction
• Peritoneum


  Visceral peritoneum: covers, anchors organs, double layers called mesenteries<|>Parietal peritoneum: lines inner wall of abdominopelvic cavity<|>Peritoneal cavity: reduces friction