OTHER FACTORS AFFECTING MOVEMENT OF PARTICLES ACROSS MBRN

• Factors affecting movement of particles across the membrane:
• Particle size:

  • Ions in the body are hydrated, so although K+ is larger than Na+, hydrated Na+ is larger than hydrated K+
• Ion channels:

  • Ions cross membranes via ion channels rather than simple pores
  • Channels are passages through protein molecules, with separate Na+, K+, and Cl- channels
• Voltage:

  • The ease with which ions pass through some channels is controlled by voltage
  • Passage of Na+ through Na+ channels in excitable tissues (muscles and nerves) is greatly increased by a decrease in membrane potential
• Neurotransmitters:

  • The ease with which ions pass through some channels is also controlled by neurotransmitters
  • Neurotransmitters may bind to receptors associated with the ions