Power Point Lecture Outlines to accompany Holes Human

Power. Point Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Tenth Edition Shier w Butler w Lewis Chapter 10 Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 12 -1

Chapter 10 Somatic and Special Senses Sensory Receptors • specialized cells or multicellular structures that collect information • stimulate neurons to send impulses along sensory fibers to the brain 12 -2

The Body Senses • Skin Senses: there are three basic skin sensations: touch, temperature, and pain. • Vestibular Sense: sense of body orientation with respect to gravity and three-dimensional space – The semicircular canals provide the brain with balance information. • Kinesthetic Sense: sensory system for body posture, orientation and movement – Kinsethetic receptors are found throughout the muscles, joints, and tendons of the body.

Receptor Types Chemoreceptors • respond to changes in chemical concentrations Pain receptors • respond to tissue damage Thermoreceptors • respond to changes in temperature Mechanoreceptors • respond to mechanical forces Photoreceptors • respond to light 12 -3

Sensory Impulses • stimulation of receptor causes local change in its membrane • a graded electrical current is generated that reflects intensity of stimulation • if receptor is part of a neuron, the membrane potential may generate an action potential • if receptor is not part of a neuron, the receptor potential must be transferred to a neuron to trigger an actin potential • peripheral nerves transmit impulses to CNS 12 -4

Sensation and Perception • Sensation is the process of receiving, converting, and transmitting information from the outside world. – Sensory organs contain receptors that transduce sensory energy into nerve impulses that are carried to the brain.

Sensation/Perception • Transduction: sensory receptors convert a physical energy into nerve impulses

Sensory Reduction • Sensory reduction involves the filtering and analyzing of incoming sensations before sending a neural message to the cortex. – If the reticular formation decides that information is important, it is passed on to alert the cerebral cortex.

Sensory Thresholds • Each sensory system has a threshold level of energy that is required to activate that sense. – Absolute threshold: The smallest amount of energy that can be detected by a system. – Difference threshold: The smallest difference in sensory energies that can be detected. • Different people can have widely varying sensory thresholds. • Thresholds can change within a person over time and as a function of hormone status. – Olfactory sensitivity during pregnancy – Ability to taste foods as we get older

Modification of Sensation • A key function of sensory systems is to detect change within the environment. – Movement in the peripheral aspects of the eye may signal food or danger. – Constant pressure of an object on the skin may not be important. • A stimulus that moves across the skin may be a snake or a spider. • The skin adapts to constant pressure.

Sensory Adaptation • Sensory adaptation refers to the fact that repeated or constant stimulation decreases the number of sensory messages sent to the brain, which causes decreased sensation.

Touch and Pressure Senses Meissner’s corpuscles • abundant in hairless portions of skin • detect light touch Pacinian corpuscles • common in deeper subcutaneous tissues, tendons, and ligaments • detect heavy pressure 12 -7

Touch and Pressure Senses 12 -8

Temperature Senses Warm receptors • sensitive to temperatures above 25 o. C (77 o F) • unresponsive to temperature above 45 o. C (113 o. F) Cold receptors • sensitive to temperature between 10 o. C (50 o. F) and 20 o. C (68 o. F) 12 -9

Referred Pain • may occur due to sensory impulses from two regions following a common nerve pathway to brain 12 -11

Pain Nerve Fibers Acute pain fibers • thin, myelinated • conduct impulses rapidly • associated with sharp pain • well localized Chronic pain fibers • thin, unmyelinated • conduct impulses more slowly • associated with dull, aching pain • difficult to pinpoint 12 -12

Special Senses • sensory receptors are within large, complex sensory organs in the head • smell in olfactory organs • taste in taste buds • hearing and equilibrium in ears • sight in eyes 12 -16

Smell Olfactory Receptors • chemoreceptors • respond to chemicals dissolved in liquids Olfactory Organs • contain olfactory receptors • cover parts of nasal cavity and a portion of the nasal septum 12 -17

Olfactory Receptors 12 -18

Taste Buds • organs of taste • located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx Taste Receptors • chemoreceptors • taste cells – modified epithelial cells that function as receptors • taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells 12 -20

Taste Receptors 12 -21

Taste Sensations Four Primary Taste Sensations • sweet – stimulated by carbohydrates (sugars, saccharine, and some amino acids) • sour – stimulated by acids • salty – stimulated by salts; metal ions • bitter – stimulated by many organic compound; alkaloids Spicy foods activate pain receptors 12 -22

Do you taste food when are congested? Why?

Hearing Ear – organ of hearing 3 Sections • External • Middle • Inner 12 -24

Anatomy of the Ear (Sound Waves)

Audition • Receptors within the ear are tuned to detect sound waves (changes in sound pressure level). – Sound waves vary in terms of: • Frequency: corresponds to pitch • Amplitude: corresponds to loudness • Sound loudness is measured in decibels.

Sound Loudness (d. B)

External Ear • auricle (pinna) • collects sounds waves • external auditory meatus (canal) • lined with ceruminous glands • carries sound to tympanic membrane • terminates with tympanic membrane • tympanic membrane (aka eardrum) • vibrates in response to sound waves 12 -25

Middle Ear *begins at the eardrum and ends at the windows * must maintain a certain amount of pressure for hearing • tympanic cavity • air-filled space in temporal bone • auditory ossicles • vibrate in response to tympanic membrane • Smallest bones in the body • malleus, incus, and stapes (hammer, anvil, and stirrup) • oval window • opening in wall of tympanic cavity • stapes vibrates against it to move fluids in inner ear 12 -26

Auditory Tube • (AKA) eustachian tube • connects middle ear to throat • helps maintain equal pressure on both sides of tympanic membrane • always closed except for yawning and swallowing 12 -27

Inner Ear • complex system of labyrinths (behind the eye) • osseous labyrinth • bony canal in temporal bone • filled with perilymph • membranous labyrinth • tube within osseous labyrinth • filled with endolymph 12 -28

Inner Ear 3 Parts of Labyrinths • cochlea • functions in hearing • Houses Organ of Corti • semicircular canals • fxns in main-taining balance, sensing mvmt, & rotation • (3 looped tubes @ rt. angles • Vestibule • Fxn in equilibrium • Btwn cochlea & semicircular canals 12 -29

Organ of Corti • group of hearing receptor cells (hair cells) • different frequencies of vibration move different parts of membrane • particular sound frequencies cause hairs of receptor cells to bend • nerve impulse generated • “snail” 12 -32

Pathway of sound through the ear • • • External auditory canal Eardrum Ossicles Fluid of inner ear Cochlea Brain

Summary of the Generation of Sensory Impulses from the Ear 12 -35

Mechanisms of Hearing • High pitch sounds disturb receptor cells close to the oval window and low pitch sounds stimulate cochlea. • Since sound usually reaches your ears at two different times, we hear “in stereo. ” This helps determine where the sound comes from. • Auditory receptors adapt or stop responding to sound that keep reaching the ears. • Hearing is the last sense to leave our awareness before sleep, anesthesia (or death), and is the first to return.

Hearing Loss • Conduction deafness: Middle-ear deafness resulting from problems with transferring sound waves to the inner-ear. – Causes can be earwax buildup, fusion of ossicles, ruptured eardrum, & otitis media • Sensorineural deafness: Inner-ear deafness resulting from damage to the cochlea, hair cells, or auditory nerve. – Causes can be extended listening to loud sounds >90 d. B

• Equilibrium problems include nausea, dizziness, and being unable to maintain balance. • Vertigo – sensation of spinning causing nausea and vomiting; in severe cases you cannot stand up • Motion sickness – cause is abnormal and irregular body motions that disturb the organs of equilibrium; symptoms include nausea, vomiting, dizziness, headache, and prostration

Equilibrium Static Equilibrium • vestibule( specifically the maculae) • sense position of head when body is not moving Dynamic Equilibrium • semicircular canals (crista ampullaris) • sense rotation and movement of head and body 12 -36

Macula • responds to changes in head position • bending of hairs results in generation of nerve impulse 12 -38

Crista Ampullaris 12 -40

Sight Visual Accessory Organs (accesory organs are those not directly related to the vision process but are important in maintaining eye health) • eyelids • lacrimal apparatus • extrinsic eye muscles 12 -41

Eye brain proxomity • Can you see : • the optic nerve bundle? • Spinal cord?

Eyelid • composed of four layers • skin • muscle • connective tissue • conjunctiva • orbicularis oculi - closes • conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball 12 -42

Eye disorders • Conjunctivitis – inflammation of the conjunctiva • Pinkeye – inflammation of the conjunctiva caused by bacteria/virus; very contagious

Lacrimal Apparatus • lacrimal gland • lateral to eye • secretes tears • lacrimal sac • collects from canaliculi • nasolacrimal duct • collects from lacrimal sac • empties tears into nasal cavity 12 -43

• Tears contain lysozymes for cleansing and protecting the eyes. • Too many tears are secreted (in crying) = congestion in the nasal cavity • During a cold, inflammation can “stop up” the canals or ducts, tears do not drain from the eyes = “watery eyes” • “Cross eyed” – results from unequal pulls by external eye muscles. Treatment ; exercise, glasses, or surgery.

Extrinsic Eye Muscles Superior rectus • rotates eye up and medially Inferior rectus • rotates eye down and medially Medial rectus • rotates eye medially 12 -44

Structure of the Eye • hollow • spherical • wall has 3 layers • outer fibrous tunic • middle vascular tunic • inner nervous tunic 12 -46

Outer Tunic Cornea • anterior portion • transparent • light transmission • light refraction • sensitive to touch • many nerves • no blood vessels Sclera • posterior portion • “white if eye” • opaque • protection 12 -47

Middle Tunic Iris • anterior portion • pigmented • controls light intensity Ciliary body • anterior portion • pigmented • holds lens • moves lens for focusing Choroid coat • provides blood supply • pigments absorb extra light 12 -48

Iris • composed of connective tissue and smooth muscle • pupil is hole in iris • dim light stimulates radial muscles and pupil dilates • bright light stimulates circular muscles and pupil constricts 12 -53

**The iris is made of two pigments** • 1. front layer - varying amounts of melanin based on genetics • 2. back layer – blue pigment

Anterior Portion of Eye • filled with aqueous humor 12 -49

Lens • transparent • biconvex • lies behind iris • largely composed of lens fibers • elastic • held in place by suspensory ligaments of ciliary body 12 -50

Accommodation • changing of lens shape to view objects 12 -52

Eye Disorders • Cataracts – lens becomes hard and opaque; causes blindness • Astigmatism – caused by an imperfect curvature in the cornea or lens; makes changing what you are trying to focus on difficult; corrected with glasses

Ciliary Body • forms internal ring around front of eye • ciliary processes – radiating folds • ciliary muscles – contract and relax to move lens 12 -51

Controlling light levels • Your eye are very sensitive and can be damaged by harsh light. • Your iris controls light allowed into the eye by changing the size of the pupil

Aqueous Humor • fluid in anterior cavity of eye • provides nutrients • maintains shape of anterior portion of eye 12 -54

Inner Tunic • retina • contains visual receptors • continuous with optic nerve • composed of several layers • fovea centralis –produces sharpest vision • optic disc – blind spot; contains no visual receptors • vitreous humor – thick gel that holds retina flat against choroid coat 12 -55

Retina – receives the image • Full of light receptors which are sensitive to: • Colour • Light levels • Massive blood supply is also needed Fovea is the main focal point and has greatest density of light receptors

Pathway of light through the eye • • Cornea Aqueous humor Lens Vitrous humor Retina Optic nerve Brain (occipital lobe)

Light Refraction • bending of light • occurs when light waves pass at an oblique angle into mediums of different densities 12 -57

Types of Lenses Convex lenses cause light waves to converge Concave lenses cause light waves to diverge 12 -58

Focusing On Retina • as light enters eye, it is refracted by • convex surface of cornea • convex surface of lens • image focused on retina is upside down and reversed from left to right 12 -59

Visual Receptors Cones Rods • contain light sensitive pigments called pigment called rhodopsin erythrolabe, chlorolabe, • hundred times more and cyanolabe sensitive to light than cones • provide vision in bright • provide vision in dim light • produce colorless vision • produce sharp images • produce outlines of objects • produce color vision 12 -60

Disorders of the eyes • Night blindness – problem with rod fxn. Caused by a Vit. A deficiency • Color blindness – lack of all cones (total); lack of one cone (partial) • Glaucoma – results from unequal pressure which compresses on the retina and optic nerve; can result in blindness; progresses slowly which no early symptoms

Stereoscopic Vision • provides perception of distance and depth • results from formation of two slightly different retinal images 12 -63

Visual Pathway 12 -64

Developmental Aspects • Formed very early in embryonic development • Eyes are developed by 4 th week • Vision is the only sense not fully functional at birth • Eyeballs grow until age 8 -9 • Newborns only see in gray tones • Lacrimal glands are not fully developed • until about 2 weeks old, the baby is tearless 12 -65

Life-Span Changes Age related hearing loss due to • damage of hair cells in organ of Corti • degeneration of nerve pathways to the brain • tinnitus Age-related visual problems include • dry eyes • floaters (crystals in vitreous humor) • loss of elasticity of lens • glaucoma • cataracts • macular degeneration 12 -65

Clinical Application Refraction Disorders • concave lens corrects nearsightedness • convex lens corrects farsightedness 12 -66