BIO 240 1st Edition Lecture 31Outline of Last Lecture B. ReceptorsI. Peripheral Nervous SystemA. Cranial Nerves B. Spinal Nerves II. NeurophysiologyA. Electrochemical Equilibrium - Resting Potential B. Anatomy of NeurophysiologyOutline of Current LectureII. NeurophysiologyA. Electrochemical Equilibrium - Resting Potential B. Anatomy of NeurophysiologyC. Graded PotentialsD. Action Potential III. VisionA. Anatomy of the eyeCurrent LectureII. NeurophysiologyA. Electrochemical Equilibrium - Resting Potential i. Muscles = -85 mVii. Neurons = -70 mViii. Inside the neurons: low NA, high K, low Ca, low Cl, high PrB. Anatomy of Neurophysiologyi. Presynaptic neuron  Neuron before the synapseii. Voltage-Regulated Ca channels  Channels for calcium on the presynaptic neuroniii. Synaptic Vesicles  Vesicles in the presynaptic neuron holding AcHiv. Postsynaptic neuron  Neuron after the synapsev. Synapse or synaptic cleft  Gap between two neurons. vi. Axonal hillock  Where the axon joins the cell body. If enough sodium ions reach the axonal hillock it will initiate an action potential. vii. Chemically regulated sodium channels  Channels for sodium located onthe postsynaptic neuronThese 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.viii. Voltage Regulated Na channels  Alternate along the length of the postsynaptic axon. ix. Voltage Regulated K channels  Alternate along the length of the postsynaptic axon. C. Graded Potentials i. Excitatory Post-synaptic Potential (EPSP)  *NOT an action potential. But,it is needed to achieve an action potential by approaching threshold. Threshold for nervous tissue is -55 mV. Maximum voltage an action potential can achieve (ceiling) is +30 mV. EPSP is representing sodium flowing into the postsynaptic cell making it more positive and extending towards the axonal hillock to cause an action potential. ii. Inhibitory Post-synaptic Potential (IPSP)  Pushes the neuron more negative away from threshold to make sure an action potential doesn’t occur.D. Action Potential i. Action Potential  Depolarization of the neuron; becomes more positive.Occurs as soon as the voltage regulated sodium channels on the axon open and sodium flows into the axon. When the peak is reached, voltage regulated sodium channels close and the action potential starts to fall. About halfway down, voltage regulated potassium channels on the axon open, making it become rapidly more negative. It hyperpolarizes past resting potential and then stabilizes at resting potential. Action potential is from threshold being reached to stabilization at resting potential. ii. Absolute refractory period  Left side of the action potential peak. Whenvoltage regulated sodium channels are closed and inactivated for service. Time where you cannot achieve another action potential. iii. Relative refractory period  Right side of the action potential (including hyperpolarization). A supernormal stimulus, or a secondary strong stimulus, could cause another action potential. iv. Hyperpolarization  Potassium channels are quick to open, but slow to close. So, a little too much potassium leaks out making the cell more negative before they shut. III. VisionA. Anatomy of the eyei. Choroid  Middle layer of the eye that is highly vascularized with blood vessels. ii. Retina  “Movie screen” where photoreceptors (rods and cones) are. Innermost layer of the eye. iii. Anterior cavity  Front of the cornea to the back of the lens. Contains aqueous humor.1. Anterior chamber  Front of the anterior cavity 2. Posterior chamber  Back of the anterior cavity.iv. Posterior cavity  Back of the lens to the end of the eyeball. Contains vitreous humor. v. Aqueous humor  Clear liquid. vi. Vitreous humor  Jelly like substance. Functions to press on the back of the retina to keep it smooth and without any wrinkles. vii. Optic nerve  Sticks off of posterior aspect of the eye. Receives input from the photoreceptors of the retina. viii. Optic disc (Blind Spot)  Area directly in front of the optic nerve. You can’t see anything if an image is projected here. ix. Fovea centralis  Area concentrated about optic disc embedded in the retina. Is the area of greatest visual acuity. x. Cornea  The anterior clear covering of the iris and the pupil. Is for protection. xi. Sclera  The outermost layer of the eye made of fibrous connective tissue. The white part of the eye. xii. Ciliary body and Suspensory ligaments  Work together to change the shape of the lens and hold then lens in