a & p holes' senses ppt

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Hole’s HumanAnatomy and Physiology

Eleventh EditionModified by Mrs. Fiser

Shier Butler Lewis

Chapter

10 Little Book

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

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Smell

Pain, Touch

Taste

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General Senses• receptors that are widely distributed throughout the body• skin, various organs and joints

Special Senses• specialized receptors confined to structures in the head • eyes and ears

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Chemoreceptors• respond to changes in chemical concentrations

Pain receptors (Nociceptors)• respond to tissue damage

Thermoreceptors• respond to changes in temperature

Mechanoreceptors• respond to mechanical forces

Photoreceptors• respond to light

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• stimulation of receptor causes local change in its receptor potential

• 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 action potential

• peripheral nerves transmit impulses to CNS where they are analyzed and interpreted in the brain

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Projection process in which the brain projects the sensation back to the apparent source it allows a person to pinpoint the region of stimulation

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• ability to ignore unimportant stimuli (clothes)

• involves a decreased response to a particular stimulus from the receptors (peripheral adaptations) or along the CNS pathways leading to the cerebral cortex (central adaptation)

• sensory impulses become less frequent and may cease

• stronger stimulus is required to trigger impulses

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Free nerve endings• common in epithelial tissues• simplest receptors• sense itching

Meissner’s corpuscles• abundant in hairless portions of skin; lips• detect fine touch; distinguish between two points on the skin

Pacinian corpuscles• common in deeper subcutaneous tissues, tendons, and ligaments• detect heavy pressure and vibrations

Touch and Pressure Receptors

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Warm receptors• sensitive to temperatures above 25oC (77o F)• unresponsive to temperature above 45oC (113oF)

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

Pain receptors• respond to temperatures below 10oC• respond to temperatures above 45oC

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• free nerve endings • widely distributed

• nervous tissue of brain lacks pain receptors

• stimulated by tissue damage, chemical, mechanical forces, or extremes in temperature

• adapt very little, if at all

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• pain receptors are the only receptors in viscera whose stimulation produces sensations

• pain receptors respond differently to stimulation

• not well localized

• may feel as if coming from some other part of the body• known as referred pain

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

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Acute pain fibers• A-delta fibers •thin, myelinated• conduct impulses rapidly• associated with sharp pain• well localized

Chronic pain fibers• C fibers •thin, unmyelinated• conduct impulses more slowly• associated with dull, aching pain• difficult to pinpoint

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Thalamus • allows person to be aware of pain

Cerebral Cortex • judges intensity of pain • locates source of pain• produces emotional and motor responses to pain

Pain Inhibiting Substances• enkephalins• serotonin• endorphins

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• 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

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Olfactory Receptors• chemoreceptors• respond to chemicals dissolved in liquids

Olfactory Organs• 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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Once olfactory receptors are stimulated, nerve impulses travel through

• olfactory nerves olfactory bulbs olfactory tracts limbic system (for emotions) and olfactory cortex (for interpretation)

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• olfactory organs located high in the nasal cavity above the usual pathway of inhaled air

• olfactory receptors undergo sensory adaptation rapidly

• sense of smell drops by 50% within a second after stimulation

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Taste Buds• organs of taste• located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx•Each has from 50-150 taste cells.

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

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Five Primary Taste Sensations• sweet – stimulated by carbohydrates• sour – stimulated by acids• salty – stimulated by salts• bitter – stimulated by many organic compounds•umami- stimulated by certain amino acids

Spicy foods activate pain receptors

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Sensory impulses from taste receptors travel along• cranial nerves to • medulla oblongata to• thalamus to • gustatory cortex (for interpretation)

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Ear – organ of hearing

Three Sections• External• Middle• Inner

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• auricle• collects sounds waves

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

• tympanic membrane • vibrates in response to sound waves

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

• vibrate in response to tympanic membrane• malleus, incus, and stapes

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

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• eustachian 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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• complex system of labyrinths• osseous labyrinth

• bony canal in temporal bone• filled with perilymph

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

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Three Parts of Labyrinths• cochlea

• functions in hearing• semicircular canals

• functions in equilibrium

• vestibule• functions in equilibrium

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

Scala tympani• lower compartment• extends from apex of the cochlea to round window• part of bony labyrinth

Cochlea

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Cochlear duct• portion of membranous labyrinth in cochlea

Vestibular membrane• separates cochlear duct from scala vestibuli

Basilar membrane• separates cochlear duct from scala tympani

Organ of Corti

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• group of hearing receptor cells (hair 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

Organ of Corti

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

Dynamic Equilibrium• semicircular canals• sense rotation and movement of head and body

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

• Saccule• communicates with cochlear duct

• Mucula• hair cells of utricle and saccule

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

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• three canals at right angles• ampulla

• swelling of membranous labyrinth that communicates with the vestibule

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

Crista Ampullaris

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The eye, the organ that contains the visual receptors, provides vision with the assistance of :

Visual Accessory Organs• eyelids• lacrimal apparatus• extrinsic eye muscles

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They are housed within the orbital cavity,or orbit of the skull.Each orbit contains fat, blood vessels, nerves and connective tissue

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• palpebra• composed of four layers

• skin• muscle • connective tissue• conjunctiva

• orbicularis oculi - closes• levator palpebrae superioris – opens• tarsal glands – secrete oil onto eyelashes• conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball

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• lacrimal gland• lateral to eye• secretes tears

• canaliculi• collect tears

• lacrimal sac• collects from canaliculi

• nasolacrimal duct• collects from lacrimal sac• empties tears into nasal cavity

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Superior rectus• rotates eye up and medially

Inferior rectus• rotates eye down and medially

Medial rectus• rotates eye medially

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Lateral rectus• rotates eye laterally

Superior oblique• rotates eye down and laterally

Inferior oblique• rotates eye up and laterally

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• hollow• spherical• wall has 3 layers

• outer fibrous tunic• middle vascular tunic• inner nervous tunic

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Cornea• anterior portion• transparent• light transmission• light refraction

Sclera• posterior portion• opaque• protection

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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

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• filled with aqueous humor

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

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

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• changing of lens shape to view objects

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• 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

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• fluid in anterior cavity of eye• secreted by epithelium on inner surface of the ciliary body• provides nutrients• maintains shape of anterior portion of eye• leaves cavity through canal of Schlemm

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

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• contains vitreous humor – thick gel that holds retina flat against choroid coat

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• receptor cells, bipolar cells, and ganglion cells - provide pathway for impulses triggered by photoreceptors to reach the optic nerve• horizontal cells and amacrine cells – modify impulses

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

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Convex lenses cause light waves to converge

Concave lenses cause light waves to diverge

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• 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

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Rods• long, thin projections• contain light sensitive pigment called rhodopsin• hundred times more sensitive to light than cones• provide vision in dim light• 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

Rods and Cones

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Rhodopsin• 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• erythrolabe – responds to red• chlorolabe – responds to green• cyanolabe – responds to blue

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• provides perception of distance and depth• results from formation of two slightly different retinal images

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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

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Refraction Disorders

• concave lens corrects nearsightedness

• convex lens corrects farsightedness