Neuro

• Afferent division of the peripheral nervous system

  Conveys sensory information
• Efferent division of the peripheral nervous system


  Conveys motor information
• Major types of senses

  • Somatic
  • Visceral
  • Special senses
• Visceral senses


  Senses that we are not consciously aware of, such as blood gas levels, blood pH, blood pressure, etc.
• Special senses


  Senses that are difficult to categorize as "visceral" or "somatic", including taste, hearing, vision, equilibrium and smell
• Major types of motor output

  • Somatic
  • Visceral
• Somatic motor output


  Leads to actions that you have conscious control of, going to skeletal or voluntary muscle
• Visceral motor output


  Goes to all other organs/tissues outside of skeletal muscle and leads in actions that you have no conscious control over
• Afferent division of the peripheral nervous system conveys sensory information, efferent division conveys motor information
• Sensory neurons are unipolar, motor neurons and interneurons are multipolar

  
• The spinal cord has dorsal roots for afferent (sensory) division and ventral roots for efferent (motor) division of the peripheral nervous system

  
• Gray matter is made up of neuron cell bodies and synapses, its main function is to process and integrate information
• White matter is made up of myelinated axons, its main function is to transmit signals between neurons
• Neuron


  Single cell
• Nerve


  Collection of myelinated axons in the peripheral nervous system
• Ganglia


  Collection of cell bodies and synapses in the peripheral nervous system
• Ascending tracts convey sensory information, descending tracts convey motor information
• Spinal nerves


  • Cervical (8 pairs)
  • Thoracic (12 pairs)
  • Lumbar (5 pairs)
  • Sacral (5 pairs)
  • Coccygeal (1 pair)

  
• The small size of the ventral horns in the thoracic spinal cord suggests less motor output to the thorax/upper abdomen, as these organs do not undergo complex movements
• Intracellular and extracellular ion concentrations

  • Na+ (15 mM ICF, 145 mM ECF)
  • K+ (150 mM ICF, 5 mM ECF)
  • Ca2+ (0.0002 mM ICF, 2 mM ECF)
  • Cl- (5 mM ICF, 115 mM ECF)

  
• Sodium, calcium, and chloride diffuse from ECF to ICF, potassium diffuses from ICF to ECF based on their concentration gradients

  
• Sodium-potassium ATPase mechanism


  1. 3 Na+ bind from ICF, ATP hydrolyzed, Na+ moved to ECF

  2. 2 K+ bind from ECF, ATPase dephosphorylated, K+ moved to ICF
• Sodium-potassium ATPase


  Maintains intracellular and extracellular concentrations of sodium and potassium
• Sodium-potassium ATPase uses ATP to move ions against their concentration gradients
• Chemical gradient


  Difference in concentrations of a solute between extracellular and intracellular fluids

  
• Electrical gradient


  Difference in charge between extracellular and intracellular fluids

  
• Ions move across the membrane based on both chemical and electrical gradients, unlike non-polar small molecules

  
• Movement of a calcium ion into the cell increases the intracellular charge and creates an electrical gradient that drives calcium out of the cell
• Cotransporters


  Move a solute against its concentration gradient along with an ion moving down its electrochemical gradient
• Antiporters


  Move a solute against its concentration gradient in the opposite direction of an ion moving down its electrochemical gradient
• Secondary active transport


  Uses energy generated by an ion moving down its electrochemical gradient to move another solute against its chemical/electrical gradient
• Equilibrium potential


  Membrane potential at which an ion is at electrochemical equilibrium, where chemical and electrical gradients are equal and opposite
• The Goldman-Hodgkin-Katz equation accounts for the relative permeability of different ions across the membrane
• Relative ion permeability


  Represents the permeability of the membrane to different ions

  
• Membrane potential closer to potassium equilibrium potential than sodium equilibrium potential


  Cell is far more permeable to potassium than sodium
• Sodium channels open


  Membrane potential becomes less negative
• Adding potassium to extracellular solution

  Membrane potential becomes less negative
• Graded potentials


  The amplitude (size) of a graded potential is directly proportional/related to the intensity (size) of the stimulus
• Types of transduction channels

  • Thermoreceptors (temperature stimulus)
  • Chemoreceptors (chemical stimulus)
  • Photoreceptors (light stimulus)
  • Nociceptors (painful stimuli)
• Leak ion channels


  • Do not have any type of gating, are always open, found in the entirety of the neuron, play a significant role in maintaining the resting membrane potential