Lecture notes 4 Nervous System PHYS 205
Lecture notes 4 Nervous System PHYS 205 PHYS 205
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This 7 page Class Notes was uploaded by Samantha Decker on Monday September 21, 2015. The Class Notes belongs to PHYS 205 at Ball State University taught by in Summer 2015. Since its upload, it has received 40 views. For similar materials see Fundamentals of Human Physiology in Physiology at Ball State University.
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If Samantha isn't already a tutor, they should be. Haven't had any of this stuff explained to me as clearly as this was. I appreciate the help!
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Date Created: 09/21/15
Functional Organization of the PNS Peripheral Nervous System Consists of nerve bers that carry information between the CNS and other parts of the body Afferent division Detects encodes and transmits peripheral signals to the CNS sends information from internal and external environment to CNS To maintain homeostasis Visceral afferent Incoming pathway for information from internal viscera organs in body cavities Sensory afferent Somatic body sense sensation Sensation arising from body surface and proprioception Special senses Vision hearing taste smell Classi cation by Stimulus Type Mechanoreceptors respond to touch pressure vibration stretch and itch Thermoreceptors sensitive to changes in temperature Photoreceptors respond to light energy eg retina Chemoreceptors respond to chemicals eg smell taste changes in blood chemistry Nocioreceptors sensitive to paincausing stimuli eg extreme heat or cold excessive pressure in ammatory chemicals acu y Refers to discriminative ability In uenced by receptive eld size and lateral inhibition The Eye and Vision 70 of all sensory receptors are in the eye Nearly half of the cerebral cortex is involved in processing visual information Most of the eye is protected by a cushion of fat and the bony orbit Eye The Retina Optic disc blind spot Site where the optic nerve leaves the eye Light comes in and is absorbed by the pigmented Lacks photoreceptors layer of the retina Photoreceptors Rods More numerous at peripheral region of retina away from the macula lutea Operate in dim light has low threshold Provide indistinct fuzzy non color peripheral vision Photoreceptors Cones Found in the macula lutea concentrated in the fovea centralis Operate in bright light Provide high acuity color vision Three primary types blue yellow red Lens Biconvex transparent exible elastic and avascular no blood ow Allows precise focusing of light on the retina Lens becomes denser more convex and less elastic with age Cataracts clouding of lens occur as a consequence of aging diabetes mellitus heavy smoking and frequent exposure to intense sunlight Focusing Light on the Retina Pathway of light entering the eye cornea aqueous humor lens vitreous humor neural layer of retina photoreceptors Light is refracted At the cornea Entering the lens Leaving the lens Change in lens curvature allows for ne focusing of an image Eye Accommodation Mechanics of Accommodation Retinal Layers Light Adaptation Occurs when moving from darkness into bright light Ability to adjust strength of lens Increases strength of lens for near vision Strength of lens depends on its shape which is regulated by ciiary muscle Accomplished by action of ciiary muscle and suspensory ligaments Ciliary muscle part of ciiary body Agerelated reduction in accommodation ability presbyopia Parasympathetic looking at something near Sympathetic looking at something far Large amounts of pigments are broken down instantaneously producing glare Pupils constrict Dramatic changes in retinal sensitivity rod function ceases Cones and neurons rapidly adapt Visual acuity improves over 5 10 minutes Dark Adaptation Occurs when moving from bright light into darkness Cones stop functioning in lowintensity light Pupils dilate Chemical Senses Taste and smell olfaction Their chemoreceptors respond to chemicals in aqueous solution Physiology of Smell Dissolved odorants bind to receptor proteins in the olfactory cilium membranes Sense of Taste Receptor organs are taste buds Found on the tongue On the tops of fungiform papillae On the side walls of foliate papillae and circumvallate vallate papillae Taste Sensations There are ve basic taste sensations Sweet sugars saccharin alcohol and some amino acids Sour hydrogen ions Salt metal ions Bitter alkaloids such as quinine and nicotine Umami amino acids glutamate and aspartate The Ear Hearing and Balance Three parts of the ear External outer ear Middle ear tympanic cavity Internal inner ear Ear Consists of 3 parts External ear Consists of pinna external auditory meatus and tympanum Transmits airborne sound waves to uid lled inner ear Ampli es sound energy Middle ear Transmits airborne sound waves to uid lled inner ear Ampli es sound energy Inner ear Houses 2 different sensory systems Cochlea Contains receptors for conversion of sound waves into nerve impulses which makes hearing possible Vestibular apparatus Necessary for sense of balance Middle Ear A small air lled mucosalined cavity in the temporal bone Pharyngotympanic auditory tube connects the middle ear to the nasopharynx Equalizes pressure in the middle ear cavity with the external air pressure Internal Ear Bony labyrinth In the temporal bone Three parts vestibule semicircular canals and cochlea Filled with perilymph uid Membranous Labyrinth Series of membranous sacs within the bony labyrinth Filled with endolymph uid The Cochlea The cavity of the cochlea is divided into three chambers Scala vestibuli the top chamber which abuts the oval window amp contains perilymph Scala media cochlear duct the middle chamber which contains endolymph amp where sound is detected Scala tympani bottom chamber which is an extension of the scala vestibuli terminates at the round window contains perilymph Transmission of Sound to the Internal Ear Sound waves vibrate the tympanic membrane Ossicles vibrate and amplify the pressure at the oval window Pressure waves move through perilymph of the scala vestibuli Equilibrium and Orientation Vestibular apparatus consists of the equilibrium receptors in the semicircular canals and vestibule Chapter 7 The Peripheral Nervous System Efferent Division PNS Efferent Division Communication link by which CNS controls activities of muscles and glands Two divisions of PMS Autonomic nervous system ANS Divisions of the ANS sympathetic division dominates in emergency or stressful quotfight or ightquot situations or physical activity 1 Parasympathetic division dominates in quiet relaxed quotrestand digestquot situations Dual innervation Almost all visceral organs are served by both divisions but they cause opposite effects Divisions of the ANS Seven Responses to Increased Svmpathetic Activitv quotFight or Flightquot Heightened mental alertness Increased metabolic rate Reduced digestive and urinary functions Energy reserves activated Increased respiratory rate and respiratory passageways dilate Increased heart rate and blood pressure Sweat glands activated Divisions of the ANS Five Responses to Increased Parasympathetic Activity quotrest and digestquot Decreased metabolic rate Decreased heart rate and blood pressure Increased secretion by salivary and digestive glands Increased motility and blood ow in digestive tract P PWF Urination and defecation stimulation Control of ANS Functioning Hypothalamus main integrative center of ANS activity Other controls come from the cerebral cortex the reticular formation and the spinal cord Hypothalamic Control Control may be direct or indirect through the reticular system Centers of the hypothalamus control Heart activity and blood pressure Body temperature water balance and endocrine activity Emotional stages rage pleasure and biological drives hunger thirst sex Reactions to fear and the quot ghtor ightquot system