L12 NPB 101 - Lecture 12 •  SmartSite: – ...

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Unformatted text preview: Lecture 12 •  SmartSite: –  Lecture 12 Notes –  Sample ques5ons •  Review –  Visual System •  Announcements: –  Sample Ques5ons Online •  Reading: –  Vision: Relevant por5ons of Chapter 6 (Recommended) –  Taste & Smell: Chapter 6, pg. 227 ­232 (Required) –  ANS: Relevant por5ons of Chapter 7 (Recommended) •  Visual System •  Autonomic Nervous System 1 REV: On ­ and Off ­Ganglion Cells Na+ channel open in dark NT release in dark NT closes Na+ channel Note: “ ­” and “+” refer to the sign of the synapse at these loca5ons. Thus, Photoreceptor  ­ + Bipolar Cell NT opens Na+ channel + + Ganglion Cell 2  ­ = Inhibitory (ISPS) + = Excitatory (EPSP) REV: On ­ and Off ­Ganglion Cells LIGHT Na+ channel open in dark NT release in dark IN Dark: NT closes Na+ Channel In Light: Na+ Channel opens Photoreceptor Na+ channel closed in light No NT release in light Depolarizing On ­Center Bipolar Cell  ­ + Hyperpolarizing Off ­Center Bipolar Cell + On ­Center Ganglion Cell + Off ­Center Ganglion Cell In Dark: NT opens Na+ Channel In Light: Na+ Channel closes 3 Re5nal Convergence •  As many as 100 photoreceptors may converge onto a bipolar cell –  ~ 108 receptors •  Several bipolars converge onto a single ganglion cell –  ~ 106 ganglion cells Fig. 6 ­21, pg. 199 4 Proper5es of Rod & Cone Vision Table 6 ­3, pg. 207 5 Recep5ve Fields of Ganglion Cells 6 Recep5ve Fields of Ganglion Cells •  •  •  The recep5ve field of a ganglion cell is a circle of photoreceptors in the re5na. A ganglion cell may depolarize or hyperpolarize depending on where light is shone in the recep5ve field. We can classify them according how they respond to light shined within the center circle of the recep5ve field –  On ­center, off ­surround –  Off ­center, on ­surround •  When an image is projected upon the re5na, it is analyzed by many, many ganglion cells (both On ­ and Off ­center) See Fig. 6 ­28a, pg. 207 7 What’s the Point? •  We are presented significantly complex visual s5muli, made up of contras5ng light to dark edges; in other words, the contours of an object •  By analyzing the input from On ­center and Off ­center ganglia, the visual cortex detects contours, borders, and edges 8 Contrast Detec5on •  The brain analyzes input from MANY ganglion cells that respond to the image. + + + + + 9 Visual System Anatomy Fig. 6 ­31, pg. 211 10 The Visual Cortex Analyzes Characteris5cs of the Image •  Cor5cal cells are organized to process informa5on about –  Lines –  Orienta5on –  Color –  Binocular processing •  It does not form a picture in the brain, per se. 11 Visual Percep5on is a Product of Organiza5on of Sensa5ons •  We perceive par5cular images based on several clues that are provided to the brain. –  The brain uses these clues to determine what is signal and what is noise –  It ignores the noise and pays amen5on to the signal 12 Signal versus Noise? 13 The Autonomic Nervous System 14 PNS: Efferent Division •  Communica5on link by which CNS controls ac5vi5es of muscles and glands •  Two divisions of PNS –  Autonomic nervous system (ANS) •  Involuntary branch of PNS •  Innervates cardiac muscle, smooth muscle, most exocrine glands, some endocrine glands, and adipose 5ssue –  Soma5c nervous system •  Subject to voluntary control •  Innervates skeletal muscle 15 ANS •  Autonomic nerve pathway –  Extends from CNS to an innervated organ –  Two ­neuron chain •  Preganglionic fiber (synapses with cell body of second neuron) •  Postganglionic fiber (innervates effector organ) Fig. 7 ­1, pg. 238 16 Two ANS Subdivisions Table 7 ­5, pg. 245 17 Autonomic Efferent Neuron Organiza5on Fig. 7 ­2, pg. 239 18 Structures Innervated by SympatheKc and ParasympatheKc Nervous Systems Fig. 7 ­3, pg. 241 19 ANS •  Most visceral organs innervated by both sympathe5c and parasympathe5c fibers •  In general produce opposite effects in a par5cular organ •  Dual innerva5on of organs by both branches of ANS allows precise control over organ’s ac5vity SNS PNS 20 ANS •  Sympathe5c system dominates in emergency or stressful (“fight ­or ­flight”) situa5ons –  Promotes responses that prepare body for strenuous physical ac5vity •  Parasympathe5c system dominates in quiet, relaxed (“rest ­and ­digest”) situa5ons –  Promotes body ­maintenance ac5vi5es such as diges5on 21 ...
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