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Unit 7 Special Senses

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Information about Unit 7 Special Senses
Health & Medicine

Published on February 18, 2014

Author: nionoveno

Source: slideshare.net

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PPT prepared for lecture.
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Facebook: h_noveno@hotmail.com Instagram: Nio Noveno I hope you will make good use of my slides. Enjoy learning!  Anatomy h_noveno@hotmail.com 1

UNIT 7 SPECIAL SENSES HILARIO CRUZADA NOVENO JR., MAN, MSN, RN Lecturer Tuesday, February 18, 2014 h_noveno@hotmail.com 2

THE SENSES Tuesday, February 18, 2014 • General senses of touch – Temperature – Pressure – Pain • Special senses – Smell – Taste – Sight – Hearing – Equilibrium h_noveno@hotmail.com 3

THE EYE AND VISION • 70 percent of all sensory receptors are in the eyes • Each eye has over a million nerve fibers • Protection for the eye – Most of the eye is enclosed in a bony orbit – A cushion of fat surrounds most of the eye Tuesday, February 18, 2014 h_noveno@hotmail.com 4

• Eyelids • Eyelashes • Meibomian glands – produce an oily secretion to lubricate the eye Tuesday, February 18, 2014 ACCESSORY STRUCTURES OF THE EYE h_noveno@hotmail.com 5

• Ciliary glands – modified sweat glands between the eyelashes • Conjunctiva ACCESSORY STRUCTURES OF THE EYE – Membrane that lines the eyelids – Connects to the surface of the eye – Secretes mucus to lubricate the eye Tuesday, February 18, 2014 h_noveno@hotmail.com 6

• Ciliary glands – modified sweat glands between the eyelashes • Conjunctiva ACCESSORY STRUCTURES OF THE EYE – Membrane that lines the eyelids – Connects to the surface of the eye – Secretes mucus to lubricate the eye Tuesday, February 18, 2014 h_noveno@hotmail.com 7

• Lacrimal apparatus ACCESSORY STRUCTURES OF THE EYE – Lacrimal gland – produces lacrimal fluid – Lacrimal canals – drains lacrimal fluid from eyes • Lacrimal sac – provides passage of lacrimal fluid towards nasal cavity • Nasolacrimal duct – empties lacrimal fluid into the nasal cavity Tuesday, February 18, 2014 h_noveno@hotmail.com 8

FUNCTION OF THE LACRIMAL APPARATUS • Properties of lacrimal fluid – Dilute salt solution (tears) – Contains antibodies and lysozyme • Protects, moistens, and lubricates the eye • Empties into the nasal cavity Tuesday, February 18, 2014 h_noveno@hotmail.com 9

EXTRINSIC EYE MUSCLES Tuesday, February 18, 2014 h_noveno@hotmail.com 10

STRUCTURE OF THE EYE Tuesday, February 18, 2014 h_noveno@hotmail.com 11

THE FIBROUS TUNIC • Sclera – White connective tissue layer – Seen anteriorly as the “white of the eye” • Cornea – Transparent, central anterior portion – Allows for light to pass through – Repairs itself easily – The only human tissue that can be transplanted without fear of rejection Tuesday, February 18, 2014 h_noveno@hotmail.com 12

CHOROID LAYER • Blood-rich nutritive tunic • Pigment prevents light from scattering • Modified interiorly into two structures – Cilliary body – smooth muscle – Iris • Pigmented layer that gives eye color • Pupil – rounded opening in the iris Tuesday, February 18, 2014 h_noveno@hotmail.com 13

SENSORY TUNIC (RETINA) • Contains receptor cells (photoreceptors) – Rods – Cones • Signals pass from photoreceptors via a twoneuron chain – Bipolar neurons – Ganglion cells • Signals leave the retina toward the brain through the optic nerve Tuesday, February 18, 2014 h_noveno@hotmail.com 14

NEURONS OF THE RETINA Tuesday, February 18, 2014 h_noveno@hotmail.com 15

NEURONS OF THE RETINA AND VISION • Rods – Most are found towards the edges of the retina – Allow dim light vision and peripheral vision – Perception is all in gray tones • Cones – Allow for detailed color vision – Densest in the center of the retina – Fovea centralis – area of the retina with only cones • No photoreceptor cells are at the optic disk, or blind spot Tuesday, February 18, 2014 h_noveno@hotmail.com 16

CONE SENSITIVITY • There are three types of cones • Different cones are sensitive to different wavelengths • Color blindness is the result of lack of one cone type Tuesday, February 18, 2014 h_noveno@hotmail.com 17

LENS Biconvex crystal-like structure Held in place by a suspensory ligament attached to the ciliary body Tuesday, February 18, 2014 h_noveno@hotmail.com 18

INTERNAL EYE CHAMBER FLUIDS • Aqueous humor – Watery fluid found in chamber between the lens and cornea – Similar to blood plasma – Helps maintain intraocular pressure – Provides nutrients for the lens and cornea – Reabsorbed into venous blood through the canal of Schlemm Tuesday, February 18, 2014 h_noveno@hotmail.com 19

INTERNAL EYE CHAMBER FLUIDS • Vitreous humor – Gel-like substance behind the lens – Keeps the eye from collapsing – Lasts a lifetime and is not replaced Tuesday, February 18, 2014 h_noveno@hotmail.com 20

LENS ACCOMMODATION • Light must be focused to a point on the retina for optimal vision • The eye is set for distance vision (over 20 ft away) • The lens must change shape to focus for closer objects Tuesday, February 18, 2014 h_noveno@hotmail.com 21

LENS ACCOMMODATION Tuesday, February 18, 2014 h_noveno@hotmail.com 22

IMAGES FORMED ON THE RETINA Tuesday, February 18, 2014 h_noveno@hotmail.com 23

VISUAL PATHWAY • Photoreceptors of the retina • Optic nerve • Optic nerve crosses at the optic chiasma • Optic tracts • Thalamus (axons form optic radiation) • Visual cortex of the occipital lobe Tuesday, February 18, 2014 h_noveno@hotmail.com 24

EYE REFLEXES • Internal muscles are controlled by the autonomic nervous system – Bright light causes pupils to constrict through action of radial and ciliary muscles – Viewing close objects causes accommodation • External muscles control eye movement to follow objects • Viewing close objects causes convergence (eyes moving medially) Tuesday, February 18, 2014 h_noveno@hotmail.com 25

• Houses two senses THE EAR – Hearing – Equilibrium (balance) • Receptors are mechanoreceptors • Different organs house receptors for each sense Tuesday, February 18, 2014 h_noveno@hotmail.com 26

ANATOMY OF THE EAR • The ear is divided into three areas – Outer (external) ear – Middle ear – Inner ear Tuesday, February 18, 2014 h_noveno@hotmail.com 27

THE EXTERNAL EAR • Involved in hearing only • Structures of the external ear – Pinna (auricle) – External auditory canal Tuesday, February 18, 2014 h_noveno@hotmail.com 28

THE EXTERNAL AUDITORY CANAL • • • • Narrow chamber in the temporal bone Lined with skin Ceruminous (wax) glands are present Ends at the tympanic membrane Tuesday, February 18, 2014 h_noveno@hotmail.com 29

THE MIDDLE EAR OR TYMPANIC CAVITY • Air-filled cavity within the temporal bone • Only involved in the sense of hearing • Two tubes are associated with the inner ear – The opening from the auditory canal is covered by the tympanic membrane – The auditory tube connecting the middle ear with the throat • Allows for equalizing pressure during yawning or swallowing • This tube is otherwise collapsed Tuesday, February 18, 2014 h_noveno@hotmail.com 30

BONES OF THE TYMPANIC CAVITY • Three bones span the cavity – Malleus (hammer) – Incus (anvil) – Stapes (stirrup) • Vibrations from eardrum move the malleus • These bones transfer sound to the inner ear Tuesday, February 18, 2014 h_noveno@hotmail.com 31

BONES OF THE TYMPANIC CAVITY Tuesday, February 18, 2014 h_noveno@hotmail.com 32

BONES OF THE TYMPANIC CAVITY Tuesday, February 18, 2014 h_noveno@hotmail.com 33

INNER EAR OR BONY LABRYNTH • A maze of bony chambers within the temporal bone – Cochlea – Vestibule – Semicircular canals Tuesday, February 18, 2014 h_noveno@hotmail.com 34

ORGANS OF HEARING • Organ of Corti – Located within the cochlea – Receptors = hair cells on the basilar membrane – Gel-like tectorial membrane is capable of bending hair cells – Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe Tuesday, February 18, 2014 h_noveno@hotmail.com 35

ORGANS OF HEARING Tuesday, February 18, 2014 h_noveno@hotmail.com 36

MECHANISMS OF HEARING • Vibrations from sound waves move tectorial membrane • Hair cells are bent by the membrane • An action potential starts in the cochlear nerve • Continued stimulation can lead to adaptation Tuesday, February 18, 2014 h_noveno@hotmail.com 37

MECHANISMS OF HEARING Tuesday, February 18, 2014 h_noveno@hotmail.com 38

STATIC EQUILIBRIUM • Receptor cells are in two structures – Vestibule – Semicircular canals • Equilibrium has two functional parts – Static equilibrium – Dynamic equilibrium Tuesday, February 18, 2014 h_noveno@hotmail.com 39

ORGANS OF EQUILIBRIUM Tuesday, February 18, 2014 h_noveno@hotmail.com 40

STATIC EQUILIBRIUM • Maculae – receptors in the vestibule – Report on the position of the head – Send information via the vestibular nerve • Anatomy of the maculae – Hair cells are embedded in the otolithic membrane – Otoliths (tiny stones) float in a gel around the hair cells – Movements cause otoliths to bend the hair cells Tuesday, February 18, 2014 h_noveno@hotmail.com 41

FUNCTION OF MACULAE Tuesday, February 18, 2014 h_noveno@hotmail.com 42

DYNAMIC EQUILIBRIUM • Crista ampullaris – receptors in the semicircular canals – Tuft of hair cells – Cupula (gelatinous cap) covers the hair cells • Action of angular head movements – The cupula stimulates the hair cells – An impulse is sent via the vestibular nerve to the cerebellum Tuesday, February 18, 2014 h_noveno@hotmail.com 43

CHEMICAL SENSES – TASTE AND SMELL • Both senses use chemoreceptors – Stimulated by chemicals in solution – Taste has four types of receptors – Smell can differentiate a large range of chemicals • Both senses complement each other and respond to many of the same stimuli Tuesday, February 18, 2014 h_noveno@hotmail.com 44

OLFACTION – THE SENSE OF SMELL • Olfactory receptors are in the roof of the nasal cavity – Neurons with long cilia – Chemicals must be dissolved in mucus for detection • Impulses are transmitted via the olfactory nerve • Interpretation of smells is made in the cortex Tuesday, February 18, 2014 h_noveno@hotmail.com 45

OLFACTORY EPITHELIUM Tuesday, February 18, 2014 h_noveno@hotmail.com 46

THE SENSE OF TASTE • Taste buds house the receptor organs • Location of taste buds – Most are on the tongue – Soft palate – Cheeks Tuesday, February 18, 2014 h_noveno@hotmail.com 47

THE TONGUE AND TASTE • The tongue is covered with projections called papillae – Filiform papillae – sharp with no taste buds – Fungifiorm papillae – rounded with taste buds – Circumvallate papillae – large papillae with taste buds • Taste buds are found on the sides of papillae Tuesday, February 18, 2014 h_noveno@hotmail.com 48

STRUCTURE OF TASTE BUDS • Gustatory cells are the receptors – Have gustatory hairs (long microvilli) – Hairs are stimulated by chemicals dissolved in saliva • Impulses are carried to the gustatory complex by several cranial nerves because taste buds are found in different areas – Facial nerve – Glossopharyngeal nerve – Vagus nerve Tuesday, February 18, 2014 h_noveno@hotmail.com 49

ANATOMY OF TASTE BUDS Tuesday, February 18, 2014 h_noveno@hotmail.com 50

TASTE SENSATIONS • Sweet receptors – Sugars – Saccharine – Some amino acids • Sour receptors – Acids • Bitter receptors – Alkaloids • Salty receptors – Metal ions Tuesday, February 18, 2014 h_noveno@hotmail.com 51

DEVELOPMENTAL ASPECTS OF THE SPECIAL SENSES • Formed early in embryonic development • Eyes are outgrowths of the brain • All special senses are functional at birth Tuesday, February 18, 2014 h_noveno@hotmail.com 52

UNIT 7 SPECIAL SENSES HILARIO CRUZADA NOVENO JR., MAN, MSN, RN Lecturer Thank You! Tuesday, February 18, 2014 h_noveno@hotmail.com 53

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