osmosis and nervous system

• Osmosis


  Diffusion of water through a membrane in response to a solute concentration, More solute = less water, Water moves to dilute more concentrated side
• Osmolarity


  • Total solute concentration of a solution
  • Mole versus osmole, Milliosmole (mOsm)
• Osmotic pressure


  • Reflects total solute concentration
  • Ability to "pull" water
  • Pressure that would be applied to stop any water movement
• Tonicity


  Water gradient across a membrane caused by impermeant solutes, Isotonic when it doesn't alter cell volume, Hypertonic, Hypotonic
• Epithelial solute transport


  1. Na+ pumped into interstitial fluid

  2. Osmotic pressure of interstitial fluid increases

  3. Water is osmotically pulled across the cell

  4. Water is transported via the lumen to the interstitial fluid
• Osmolarity


  Measure of solute concentration in a solution
• Tonicity


  Effect of a solution on the volume of a cell
• Isotonic


  • Cell volume remains the same
• Hypertonic


  • Cell volume decreases
• Hypotonic


  • Cell volume increases
• Transport of macromolecules across membranes


  1. Too large for carriers, channels, pumps

  2. Uses membrane compartments

  3. Endocytosis

  4. Secretory vesicles

  5. Exocytosis
• Endocytosis


  • Phagocytosis
  • Pinocytosis
  • Receptor-mediated transport
• Phagocytosis allows particles to enter the cell
• Pinocytosis allows extracellular fluid to enter the cell
• Receptor-mediated endocytosis uses receptor proteins and clathrin to bring in specific molecules
• Exocytosis releases the contents of secretory vesicles out of the cell
• Apical membrane


  Faces the lumen of a body cavity
• Basolateral membrane


  Faces the internal environment and interstitial fluid
• Tight junctions join adjacent epithelial cells
• Epithelial solute transport


  1. Na+ pumped into interstitial fluid

  2. Osmotic pressure of interstitial fluid increases

  3. Water is osmotically pulled across the cell

  4. Water is transported via the lumen to the interstitial fluid
• Transcytosis involves the transport of macromolecules across an epithelial cell via endocytosis and exocytosis
• Afferent neurons


  Carry sensory information to the CNS
• Efferent neurons


  Carry motor information from the CNS
• Neurons


  • Excitable cells that send and receive electrical signals rapidly and over long distances
• Glial cells


  • Support cells in the nervous system
• Parts of a neuron


  • Cell body (soma)
  • Dendrites
  • Axon
• Axon hillock


  Region of the cell body where the axon originates and action potentials are initiated
• Axon terminal


  Contains mitochondria and vesicles with neurotransmitters, releases neurotransmitters
• Synapse


  Site of communication between two neurons or a neuron and an effector organ
• Axonal transport


  1. Anterograde transport (from soma to axon terminal)

  2. Retrograde transport (from axon to soma)
• Structural classification of neurons


  • Multipolar
  • Bipolar
  • Pseudounipolar
  • Anaxonic
• Functional classification of neurons


  • Afferent
  • Efferent
  • Interneurons
• Afferent (sensory) neurons


  • Carry information from sensory receptors
• Interneurons


  • Lie within the CNS
  • Interconnecting neurons
  • Complex branching (communication)
• Efferent neurons


  • Somatic (skeletal muscle)
  • Autonomic (smooth muscle)
• Sensory neuron types


  • Interoceptors
  • Exteroceptors
  • Proprioceptors
• Interoceptors


  • Monitor internal systems (digestive, respiratory, CV, urinary, reproductive)
  • Internal senses (taste, deep pressure, pain)
• Exteroceptors


  • External senses (touch, temperature, pressure)
  • Distance senses (sight, smell, hearing)
• Proprioceptors


  • Monitor position and movement
  • Skeletal muscles and joints
• Interneurons


  • Most are located in brain, spinal cord, and autonomic ganglia
  • Between sensory and motor neurons
  • Responsible for distribution of sensory information, coordination of motor activity, involved in higher functions (memory, planning, learning)