PHIS 206 1st EditionLecture 5Outline of Last Lecture I. Diffusion and Transport ReviewII. Nervous System―UnitsIII. Glial Cells―4 TypesIV. NeuronsV. Electrical Properties of MembranesOutline of Current Lecture I. Electrical Properties of Membrane (cont’d)II. NeuronsIII. Myelinated and NonmyelinatedIV. NeurotransmittersCurrent LectureI. Electrical Properties of Membrane (cont’d)-All-or-nothing: either generate action potential or do not-Graded potentials: only occur in the soma (body)-Refractory period: resistance to responding to a stimulus Consequences: limits the # of action potentials in a nerve-Voltage gated channels: embedded in neurons; can be open or closed for a specific ionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. The voltage gradient across the membrane determines whether it is open (when threshold is reached) or closed-When it becomes more (-), it means the neuron is further from the threshold. Therefore, it is harder to stimulate up to the threshold. (hyperpolarize)II. Neurons-Inhibited neuron: becomes MORE (-) and harder to reach threshold with a stimulus-Excited neuron: becomes LESS (-) and easier to reach threshold with a stimulus-Action potentials CAN TRAVEL. Rate at which they travel affects the rate at which information is transferred.-Slowest creators of action potentials: NONMYELINATED axons (faster as diameter of axon increases; approx. 1-3 ft/s)-Myelinated axons: can transmit action potentials faster; approx. 30-50 ft/sIII. Myelinated and Nonmyelinated-If we depolarize in the soma, there will be a diffusion gradient.-Action potentials can only go AWAY from the soma!-In myelinated axons, it is directly in contact with the membrane, so it sets the rate for diffusion.-synapse: where axon terminal (pre-synaptic) of one neuron comes into contact with thedendrites or soma of another neuron (post-synaptic) specialized structure with receptors on the post-synaptic neuronIV. Neurotransmitters-One neuron only releases one neurotransmitter-Most common neurotransmitter: Acetylcholine (ACh)-ACh in the synapse binds to receptors in the post-synaptic cell-Simulatenously, the enzyme in the cytoplasm AChase breaks acetylcholine: Stimulation decreases Acetate and Choline get actively transported and re-synthesized (RECYCLED) cholynergic neurons: includes motor neurons; release ACh to help muscle cellsAcetylcholine Acetate +
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