BIO 240 1st Edition Lecture 31 Outline of Last Lecture B Receptors I Peripheral Nervous System A Cranial Nerves B Spinal Nerves II Neurophysiology A Electrochemical Equilibrium Resting Potential B Anatomy of Neurophysiology Outline of Current Lecture II Neurophysiology A Electrochemical Equilibrium Resting Potential B Anatomy of Neurophysiology C Graded Potentials D Action Potential III Vision A Anatomy of the eye Current Lecture II Neurophysiology A Electrochemical Equilibrium Resting Potential i Muscles 85 mV ii Neurons 70 mV iii Inside the neurons low NA high K low Ca low Cl high Pr B Anatomy of Neurophysiology i Presynaptic neuron Neuron before the synapse ii Voltage Regulated Ca channels Channels for calcium on the presynaptic neuron iii Synaptic Vesicles Vesicles in the presynaptic neuron holding AcH iv Postsynaptic neuron Neuron after the synapse v 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 on the postsynaptic neuron These 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 When voltage 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 Vision A Anatomy of the eye i 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 place
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