Anatomy and Function of Neurons: From Cell Body to Action Potentials - Prof. Christopher A, Study notes of Physiology

Download Anatomy and Function of Neurons: From Cell Body to Action Potentials - Prof. Christopher A and more Study notes Physiology in PDF only on Docsity! 1/19/2011 1 January 19, 2011 (B) Pearl  Nerve and muscle  Can undergo rapid changes in their membrane  potentials  Can change their resting potentials into electrical  signals 2 Neuron Anatomy > Cell body » Dendrites » Axon ° Axon Hillock ° Axon Terminals Neuron Anatomy 1/19/2011 1/19/2011 5  Movement of ions  What causes a change in movement of ions? ◦ Opening or closing of ion channels ◦ Chemical messengers ◦ Nearby depolarizations Sti li◦ mu  Light – eye  Sound wave – ear  Mechanical Stretch – feeling, pain 9  Leak  Voltage Gated 10 Voltage Gated Na Channels VOLTAGE-GATED SODIUM CHANNEL RHR wil i ) iA Rapid I | Activation gate (ua?) opening (closing oe p triggered triggered t Inactivation gate atthreshold _ at thres! (a) Closed but (b) Open (c) Closed and not capable of opening (activated) capable of opening (inactivated) Voltage Gated K Channels VOLTAGE-GATED POTASSIUM CHANNEL Activation @ Aree ® he MINH ny tae triggered” 1/19/2011 1/19/2011 7  Graded potentials ◦ Serve as short‐distance signals  Action potentials ◦ Serve as long‐distance signals 13  Occurs in small, specialized region of excitable cell  membranes   Magnitude of graded potential varies directly with  the magnitude of the triggering event 14 1/19/2011 10  Hindrance to electrical charge movement  Greater resistance leads to less current flow  Lower resistance leads to greater current flow  Membrane has high resistance ◦ Current tends to stay on one side of the cell ◦ Will only cross through leak channels 19 20 1/19/2011 11 21  Brief, rapid, large (100mV) changes in membrane  potential   Potential actually reverses  Involves only a small portion of the total excitable  cell membrane  Do not decrease in strength as they travel from their  site of initiation throughout remainder of cell  membrane 22 1/19/2011 12  When membrane reaches threshold potential ◦ Voltage‐gated  Na+channels in the membrane undergo  conformational changes ◦ Flow of sodium ions into the ICF reverses the membrane  potential from ‐70 mV to +30 mV ◦ Flow of potassium ions into the ECF restores the  membrane potential to the resting state 23  Sodium channels open during depolarization by positive feedback.  When the sodium channels become inactive, the channels for potassium open. This repolarizes the membrane.  As the action potential develops at one point in the plasma membrane, it regenerates an identical action potential at the next point in the membrane.  Therefore, it travels along the plasma membrane undiminished. 24