PSYC 222 1st Edition Lecture 6Outline of Last Lecture • The Nervous SystemOutline of Current Lecture i. Resting membrane Potentialii. How is the resting membrane potential generated?iii. How do Drugs fit into this pic?Current Lecturei. What generates the resting membrane potential?1. The electrical characteristics of ions2. The physical forces that drive the movements of ions 3. The characteristics of the nerve cell membrane including the lipid and protein components.Characteristics of the neuronal membrane and conditions represent when the resting membrane potential is in place must be considered. The nerve cell membrane consists of a phospholid bilayer with imbedded proteins. The lipid portion of a bilayer act as a barrier to the movement of ions or polar substances.• The protein components include:1. Enzymes2. Receptors3. Channels4. TransportersEach protein component can serve as a substrate for drug action. The protein components contribute to the resting membrane potential and nerve cell excitability. ii. Under baseline or "resting" conditions:1. CI- and K+ channels are mostly open 2. Na+ channels are virtually all closed3. Na+/K+ pump actively transports some K+ into the cell but transports more Na+ out of the cellThe current of Na+ Ions flow through when a valve is opened. In a neural membrane any channel that allows Na+ to past through will allow an inward Na+ current to flow. This is how neurons change from polarized resting or baseline state to become excited or depolarized. Electrical conditions across the membrane can be recorded by electrodes. Voltage or current changes can then be measured.3 different types of electrical phenomena commonly recorded from nerve cells:1. Excitatory postsynaptic (ESPs)2. Inhibitory postsynaptic potentious (IPSPs)3. Action potentials (aka "spikes" or neuronal firing)The term potential refers to a voltage change. The term postsynaptic refers to the convention that these are recorded from the postsynaptic membrane. The EPSP is a small transient change in the positive direction. The IPSP is a small change in the negative direction. An action potentialhas 2 parts, an ascending limb and a descending limb. The excitability of a neuron depends upon the degree of popularization when stimulation is applied. The computational power of the brain is based upon1. The computational operations performed by individuals neurons in the brain2. Interactions between these networks of neurons that constantly communicate with eachother (They are chemically active)3. They release signaling molecules (neurotransmitters) that become apart of the chemical enviornment of the next cells in the circuitDifferent codes or "languages" are used at those different stagesiii. Some drugs act on the electrophysiological properties of the nerve cells. Ex: Phenytoin (Dilantin). A drug with neuronal membrane stabilizing properties used in the treatment of epilepsy. Local anesthetics act by blocking voltage gated sodium channels in neuronal
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