Hole’s HumanAnatomy and Physiology

Tenth Edition

Shier Butler Lewis

Chapter

12

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 12-1

Chapter 12Somatic and Special Senses

Sensory Receptors• specialized cells or ____________ structures that collect information• stimulate neurons to send impulses along sensory fibers to the brain

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Receptor Types

___________________• respond to changes in chemical concentrations

Pain receptors• respond to tissue damage

_________________• respond to changes in temperature

Mechanoreceptors• ________________________

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 _________ of stimulation• if receptor is part of a neuron, the membrane potential may generate an action potential• if receptor is not part of a ________, the receptor potential must be transferred to a neuron to trigger an actin potential• peripheral nerves transmit impulses to CNS

___________• feeling that occurs when brain interprets sensory impulse

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Sensory Adaptation

• adjustment of sensory receptors from continuous stimulation• stronger stimulus required to activate receptors• ____________ undergo sensory adaptation

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Somatic Senses

• senses associated with skin, muscles, joints, and viscera

• three groups• ______________ senses – senses associated with body surface; touch, pressure, temperature, pain• _______________ senses – senses associated with changes in muscles and tendons• _________________ senses – senses associated with changes in viscera

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Touch and Pressure Senses

Free nerve endings• common in epithelial tissues• ___________ touch and pressure

______________________• abundant in hairless portions of skin• detect light touch

__________________• common in deeper subcutaneous tissues, tendons, and ligaments• detect heavy pressure

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Touch and Pressure Senses

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Temperature Senses

Warm receptors• sensitive to temperatures above ____________• unresponsive to temperature above ______ (113oF)

______________• sensitive to temperature between 10oC (50oF) and 20oC (68oF)

Pain receptors• ________________________________• respond to temperatures above 45oC

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Sense of Pain

• ______________________ • widely distributed • nervous tissue of brain lacks pain receptors• stimulated by tissue damage, chemical, mechanical forces, or extremes in temperature• ___________________

______________• may exhibit referred pain• _________________

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Referred Pain

• may occur due to sensory impulses from two regions following a common nerve pathway to brain

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Pain Nerve Fibers

___________________ thin, myelinated

• conduct impulses rapidly• associated with sharp pain• well localized

_________________• thin, unmyelinated• conduct impulses more slowly• associated with dull, aching pain• ________________

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Regulation of Pain Impulses

Thalamus • allows person to be aware of pain

Cerebral Cortex • judges intensity of pain • locates source or pain• produces motor response to pain• produces emotions to pain

Pain Inhibiting Substances• ___________• __________• ____________

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Stretch Receptors

• proprioceptors• send information to CNS concerning lengths and tensions of muscles• 2 main kinds of stretch receptors

• _________________ – in skeletal muscles• ________________ – in tendons

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Stretch Receptors

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Special Senses

• sensory receptors are within large, complex sensory organs in the head• _________ in olfactory organs• _________ in taste buds• ______________________ in ears• sight in eyes

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Smell

Olfactory Receptors• _________________• respond to chemicals dissolved in liquids

_________________• contain olfactory receptors and supporting epithelial cells• cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum

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Olfactory Receptors

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Olfactory Nerve Pathways

Once olfactory receptors are stimulated, nerve impulses travel through

• ________________ • olfactory bulbs to • _________________ • limbic system (for emotions) and olfactory cortex (for interpretation)

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Taste

________________• organs of taste• located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx

_____________________• chemoreceptors• taste cells – modified epithelial cells that function as receptors• taste hairs –_________ that protrude from taste cells; sensitive parts of taste cells

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Taste Receptors

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Taste Sensations

Four Primary Taste Sensations• ________ – stimulated by carbohydrates• sour – stimulated by acids• _______ – stimulated by salts• bitter – stimulated by many organic compound

_________________________________

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Taste Nerve Pathways

Sensory impulses from taste receptors travel along• cranial nerves to • _____________________• __________________ • gustatory cortex (for interpretation)

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Hearing

Ear – organ of hearing

3 Sections• ________• Middle• ________

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External Ear

• _____________• collects sounds waves

• external auditory meatus• lined with ceruminous glands• carries sound to tympanic membrane• _____________________ tympanic membrane

• tympanic membrane • _________ in response to sound waves

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Middle Ear

• tympanic cavity• air-filled space in temporal bone• auditory ossicles

• vibrate in response to tympanic membrane• ________, ______, and stapes

• _____________ • opening in wall of tympanic cavity• stapes vibrates against it to move fluids in inner ear

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Auditory Tube

• ________________ • connects middle ear to throat• helps maintain equal pressure on both sides of tympanic membrane• usually closed by valve-like flaps in throat

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Inner Ear

• complex system of labyrinths• ____________________

• bony canal in temporal bone• filled with _________

• membranous labyrinth• tube within osseous labyrinth• filled with ____________

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Inner Ear

3 Parts of Labyrinths• ________

• functions in hearing• _________________

• functions in equilibrium

• vestibule• __________ in equilibrium

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Cochlea

______________• upper compartment• leads from oval window to apex of spiral• part of bony labyrinth

_____________• lower compartment• extends from apex of the cochlea to ___________• part of bony labyrinth

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Cochlea

______________• portion of membranous labyrinth in cochlea

_________________• separates cochlear duct from scala vestibuli

Basilar membrane• separates cochlear duct from scala tympani

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Organ of Corti

• group of hearing receptor cells (__________)• on upper surface of basilar membrane• different frequencies of vibration move different parts of basilar membrane• particular sound frequencies cause hairs of receptor cells to bend• nerve impulse generated

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Organ of Corti

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Auditory Nerve Pathways

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Summary of the Generation of Sensory Impulses from the Ear

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Equilibrium

Static Equilibrium• ____________• sense position of head when body is not moving

_________________• semicircular canals• sense rotation and movement of head and body

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Vestibule

• ________• communicates with saccule and membranous portion of semicircular canals

• ________• communicates with cochlear duct

• ________• hair cells of utricle and saccule

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Macula

• responds to changes in head position• bending of hairs results in generation of nerve impulse

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Semicircular Canals

• three canals at right angles• __________

• swelling of membranous labyrinth that communicates with the vestibule

• ______________• sensory organ of ampulla• hair cells and supporting cells• rapid turns of head or body stimulate hair cells

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Crista Ampullaris

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Sight

___________________• eyelids• lacrimal apparatus• extrinsic eye muscles

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Eyelid

• _____________• composed of four layers

• skin• muscle • connective tissue• conjunctiva

• _________________ - closes• levator palperbrae superioris – opens• ___________ – secrete oil onto eyelashes• _____________ – mucous membrane; lines eyelid and covers portion of eyeball

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Lacrimal Apparatus

• lacrimal gland• lateral to eye• secretes tears

• ___________• collect tears

• lacrimal sac• collects from canaliculi

• ________________• collects from lacrimal sac• empties tears into nasal cavity

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Extrinsic Eye Muscles

______________• rotates eye up and medially

_____________• rotates eye down and medially

Medial rectus• rotates eye medially

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Extrinsic Eye Muscles

Lateral rectus• ________ eye laterally

______________• rotates eye down and laterally

Inferior oblique• rotates eye up and laterally

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Structure of the Eye

• hollow• spherical• wall has 3 layers

• outer _____________• middle vascular tunic• inner ____________

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Outer Tunic

_________• anterior portion• transparent• light transmission• light refraction

Sclera• posterior portion• opaque• ________

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Middle Tunic

______ • anterior portion• pigmented• controls light intensity

____________• anterior portion• pigmented• holds lens• moves lens for focusing

Choroid coat• provides blood supply• pigments absorb extra light

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Anterior Portion of Eye

• filled with ____________

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Lens

• transparent• __________• ________________• largely composed of lens fibers• elastic• held in place by suspensory ligaments of ciliary body

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Ciliary Body

• forms internal ring around front of eye• ____________ – radiating folds• _____________ – contract and relax to move lens

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Accommodation• ____________________________

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Iris

• composed of connective tissue and smooth muscle• _______________ in iris• dim light stimulates radial muscles and pupil dilates• bright light stimulates circular muscles and pupil constricts

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Aqueous Humor

• ________________________• secreted by epithelium on inner surface of the ciliary body• provides nutrients• maintains shape of anterior portion of eye• _____________________________

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Inner Tunic

• _________• contains visual receptors• continuous with optic nerve• ends just behind margin of the ciliary body• composed of several layers• ____________ – yellowish spot in retina• ______________ – center of macula lutea; produces sharpest vision• optic disc – blind spot; contains no visual receptors• ________________ – thick gel that holds retina flat against choroid coat

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Layers of Retina

• ________________________________, and ganglion cells - provide pathway for impulses triggered by photoreceptors to reach the optic nerve• _______________________________ – modify impulses

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Light Refraction

Refraction • __________________• occurs when light waves pass at an oblique angle into mediums of different densities

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Types of Lenses

_________ lenses cause light waves to _________

_______ lenses cause light waves to _______

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Focusing On Retina• as light enters eye, it is refracted by

• convex surface of cornea• _______________________

• image focused on retina is upside down and reversed from left to right

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Visual Receptors

Rods• ______________• contain light sensitive pigment called rhodopsin• hundred times more sensitive to light than cones• _____________________• produce colorless vision• produce outlines of objects

Cones• short, blunt projections• contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe• provide vision in bright light• produce sharp images• produce color vision

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Rods

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Visual Pigments

_____________• light-sensitive pigment in rods• decomposes in presence of light• triggers a complex series of reactions that initiate nerve impulses• impulses travel along optic nerve

Pigments on Cones• each set contains different light-sensitive pigment• each set is sensitive to different wavelengths• color perceived depends on which sets of cones are stimulated• ________ – responds to red• _______ – responds to green• ________ – responds to blue

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Stereoscopic Vision• __________________________________• results from formation of two slightly different retinal images

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Visual Pathway

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Life-Span Changes

Age related hearing loss due to • ___________________________________• degeneration of nerve pathways to the brain• tinnitus

Age-related visual problems include• __________• floaters (crystals in vitreous humor)• loss of elasticity of lens• glaucoma• ___________• macular degeneration 12-65

Clinical Application

Refraction Disorders

• ___________________ nearsightedness

• ______________ farsightedness

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