Nerve impulses

• Neural communication involves nerve impulses and osmosis.
• Neuron action potential physiology involves the cell membrane, which separates the electrical charges between the outside of the cell and inside of the cell.
• The cell membrane is composed of two layers of phospholipids molecules, with embedded protein molecules that some chemicals can pass.
• The protein molecules that chemicals can pass are called ion channels.
• Ion channels are very selective.
• Types of Ion Channel include Leaky/Passive Channels, which are always open, and Gated Channels, which could be opened or closed based on signals.
• Types of Gated Channels include Voltage-gated channels, which open and close in response to changes in membrane potential (charges), Ligand-gated channels, which open when a neurotransmitter latches onto the receptor, and Mechanically-gated channels, which open in response to physically stretching of the membrane.
• When neurons are stimulated, they fire electrical charges down the axon, which regenerates an impulse at each point and the impulse travels along the axon without weakening.
• Electrical charges have only one strength but may vary in frequency or speed.
• A weak stimulus triggers less frequent action potential, while a strong stimulus triggers more frequent action potential.
• Resting Membrane Potential (RMP) is the voltage difference across the cell membrane when the cell is at rest, with the cell at rest being slightly negative and polarized, resulting in a RMP of -70MV.
• The Sodium-Potassium Pump works by 3 Na+ getting out, 2 K+ getting in, causing the cell to become a little negative and generating a concentration gradient, the difference in distribution of ions across the membrane.
• Diffusion is the tendency for molecules to distribute themselves equally within a medium such as air or water.
• NA+ in the cell, NA+ gets in the cell.
• K+ in the cell, K+ gets out of the cell.
• Leaky Potassium Channels allow K+ to get in and out of the cell freely.
• Cell is more negative inside the cell than outside the cell.
• Electrical charges have only one strength but may vary in frequency or speed.
• Leaky Sodium Channels allow NA+ to get in and out of the cell freely.
• Information in various areas of the cell contact other neurons.
• Refractory Period is the time when the cell resists the production of further action potentials.
• Local Neuron are small neurons without axons, they exchange information with only their closest neighbors, they do not follow all-or-none law.
• Graded Potential is the change in voltage across the cell membrane due to the presence of a ligand-gated channel.
• Strong stimulus triggers more frequent action potential.
• Sodium voltage-gated channels close at +30MV → no NA+ comes in.
• Sodium voltage-gated channels are activated at threshold ( - 55MV) → NA+ comes in and cell becomes more positive (+30MV).
• Information in local neuron is sent as graded potential to adjacent areas of the cell, in all directions.
• Diffusion pressure moves molecules along a concentration gradient from areas of high concentration to areas of low concentration.
• Resting Membrane Potential (RMP) is the voltage difference across the cell membrane when the cell is at rest.
• Relative Refractory Period is the second phase of refractory period, a stronger-than-usual stimulus is necessary to initiate an action potential.
• Weak stimulus triggers less frequent action potential.
• Absolute Refractory Period is the first phase of refractory period, the membrane cannot produce another action potential, regardless of the stimulation.
• The all-or-none law states that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it, provided that the stimulus reaches the threshold.
• Potassium voltage-gated channels are activated at +30MV → K+ opens much slower.
• Presynaptic → Neurotransmitter → Excites the ligand-gated channel → gates open → ions get in → voltage goes up ( - 55MV) or voltage goes down ( - 90MV).
• K+ is bound to Anion (A-), when it goes out, it leaves the anion.