Physio 1

• Physiology


  The study of the function of living systems
• Cellular Physiology


  The study of how cells work encompassing the study of events at the chemical, molecular, and genetic levels
• Organ Physiology


  The study of specific organs
• Systems Physiology


  The study of the function of a specific system such as the cardiovascular, respiratory, or reproductive systems
• Levels of organization


  • Chemical level
  • Cellular level
  • Tissue level
  • Organ level
  • Organ system level
  • Organismal level
• Chemical level


  Atoms are the smallest units of matter that combine to form molecules
• Cellular level


  Cells are the smallest unit of life. They exhibit various sizes, shapes, and properties that enable them to carry out specialized functions
• Tissue level


  Tissue is a group of cells having a common structure and function
• Organ level


  Two or more tissues working for a given function form an organ
• Organ system level


  Organs work together for a common function
• Organismal level


  All of the organ systems work together to maintain homeostasis
• Milieu interieur


  The relatively constant internal environment which is the extracellular fluid where cells live
• Homeostasis


  A relatively steady state that is maintained within an animal despite a wide range of environmental conditions
• Homeostatic regulatory mechanisms


  • Autoregulation
  • Extrinsic regulation
• Autoregulation


  Regulation that occurs at either the cellular, tissue, organ or organ system level
• Autoregulation example


  • Release of cholecystokinin when the presence of tryptophan is detected in the small intestine prompting the pancreas to release digestive enzymes
• Extrinsic regulation


  Involves the coordinated action of nervous and endocrine systems
• Extrinsic regulation example


  • Release of norepinephrine, epinephrine, and corticosteroids from adrenal glands during prolonged stress prompting the increase in blood pressure and flow to the skeletal muscle
• Regulatory mechanisms


  • Receptor
  • Control center
  • Effector
• Receptor


  A specialized cell or a protein cell component that senses a change in the environment called a stimulus
• Control center


  Has a set point around which the variable is maintained
• Effector


  Induces a change in the controlled variable to bring it back to the set point
• Feedback systems


  • Negative feedback
  • Positive feedback
• Negative feedback system


  The control system initiates change that counteract the stimulus which will either reduce or eliminate the stimulus, thus, reestablishing the variable near its set point to maintain homeostasis
• Negative feedback system example

  • When body temperature rises, warmth receptors in the skin and hypothalamus sense the increase and then send a signal to the hypothalamus. The hypothalamus will then activate heat loss mechanisms such as sweating and vasodilation resulting in evaporative cooling and increased blood flow in the skin, decreasing temperature toward the set point

  
• Positive feedback system


  The animal elicits regulatory mechanisms that augment the effect of a stimulus
• Positive feedback system examples

  • Blood clotting - a damaged blood vessel secretes a factor that attracts platelets then these platelets will secrete factors that will further attract more platelets preventing blood loss
  • Childbirth - Oxytocin is produced by the fetus near the time of parturition which will initiate uterine contraction. These contractions will then cause the release of oxytocin from the hypothalamus of the mother, causing greater uterine contraction

  
• Cell


  The smallest functional unit that performs essential vital functions (metabolism, growth, movement, reproduction, and hereditary transmission)
• Cell membrane


  A double layer of phospholipid molecules with protein molecules embedded within it. It is responsible for separating the cell from its environment and controls the movement of substances in and out of the cell
• Cell membrane


  • Proteins in the cell membrane are classified into integral cell membrane proteins which act as pores/channels, carrier proteins, receptors, enzymes, and peripheral cell membrane proteins which mainly act as enzymes attached to integral proteins
  • Water-soluble substances such as ions, glucose, and urea do not easily pass through the membrane unlike fat-soluble substances such as oxygen, carbon dioxide, and alcohol which easily move in and out of the membrane
  • The glycocalyx is a loose carbohydrate coat found on the entire outside surface of the cell composed of proteoglycans glycoproteins/glycolipids. The presence of this structure brings a negative charge, serves as an attachment and receptor, and is also important to immune reactions
• Selective permeability of cell membrane


  Certain substances can easily move into the cells while other substances may require specialized transport systems
• Cell membrane transport mechanisms

  • Pores in the cell membrane
  • Diffusion
  • Active transport mechanisms

  
• Simple diffusion


  A kinetic movement of molecules or ions through a membrane opening or intermolecular spaces without any interaction with carrier proteins in the membrane
• Facilitated diffusion


  A carrier-mediated diffusion in which a substance diffuses through the membrane using a specific carrier protein
• Gating of protein channels

  Voltage gating is when the molecular conformation of the gate or its chemical bonds responds to the electrical potential across the cell membrane. Chemical (ligand) gating is when a protein-channel gates are opened by the binding of a chemical substance (a ligand) with the protein

  
• Active transport


  When the cell membrane moves molecules or ions "uphill" against a concentration gradient (or "uphill" against an electrical or pressure gradient)

  
• Active transport mechanisms


  • Primary active transport
  • Secondary active transport
• Primary active transport


  The energy is derived directly from the breakdown of ATP or some other high-energy phosphate compound
• Primary active transport examples

  • Sodium-Potassium Pump, Primary Active Transport of Calcium Ions, Primary Active Transport of Hydrogen Ions

  
• Secondary active transport


  The energy is derived secondarily from the energy that has been stored in the form of ionic concentration differences of secondary molecular or ionic substances between the two sides of a cell membrane, created originally by primary active transport