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Chapter 8 Special Senses

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Presentation on theme: "Chapter 8 Special Senses"— Presentation transcript:

1 Chapter 8 Special Senses
Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 8 Special Senses Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

2 The Senses General senses of touch Special senses Temperature Pressure
Pain Special senses Smell Taste Sight Hearing Equilibrium Slide 8.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

3 The Eye and Vision 70 percent of all sensory receptors are in the eyes, only see 1/6th of eye 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 Slide 8.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

4 Accessory Structures of the Eye
Eyelids Meets at medial and lateral canthus Eyelashes Figure 8.1b Slide 8.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

5 Accessory Structures of the Eye
Eyelashes =Meibomian glands modified sebacious glands produce an oily secretion to lubricate the eye Figure 8.1b Slide 8.3b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

6 Accessory Structures of the Eye
Ciliary glands – modified sweat glands between the eyelashes Figure 8.1b Slide 8.3c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

7 Accessory Structures of the Eye
Conjunctiva Membrane that lines the eyelids Connects to the surface of the eye Secretes mucus to lubricate the eye Slide 8.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

8 Accessory Structures of the Eye
Lacrimal apparatus Glands, ducts, (eye), canals, sac, nasolacrimal duct Tears: antibodies, lysozymes, stress? Figure 8.1a Slide 8.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

9 Extrinsic Eye Muscles Muscles attach to the outer surface of the eye
Produce eye movements Figure 8.2 Slide 8.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

10 Structure of the Eye The wall is composed of three tunics
Sclera&Cornea fibrous outside layer Choroid – middle layer Sensory tunic – (retina) inside layer Figure 8.3a Slide 8.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

11 The Fibrous Tunic Sclera Cornea 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 Slide 8.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 Slide 8.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

13 Sensory Tunic (Retina)
Contains receptor cells (photoreceptors) Rods Cones Signals pass from photoreceptors and leave the retina toward the brain through the optic nerve Slide 8.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14 Neurons of the Retina Slide 8.11 Figure 8.4
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 Slide 8.12a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

16 Neurons of the Retina and Vision
Cones – 3 types detect different colors Densest in the center of the retina Fovea centralis – area of the retina with only cones Lack of one type = color blindness No photoreceptor cells are at the optic disk, or blind spot Slide 8.12b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

17 Lens Biconvex crystal-like structure
Held in place by a suspensory ligament attached to the ciliary body Figure 8.3a Slide 8.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

18 Internal Eye Chamber Fluids
Aqueous humor in Anterior Segment 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 Blocked drainage = glaucoma Slide 8.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

19 Internal Eye Chamber Fluids
Vitreous humor in Posterior Segment Gel-like substance behind the lens Keeps the eye from collapsing Lasts a lifetime and is not replaced Slide 8.15b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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 Slide 8.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.9

21 Correcting the Eye Correct Focus = emmetropia Nearsightedness = myopia
Focus of light in front of retina Eyeball too long or lens too strong Distant objects are blurry Farsightedness = hyperopia Focus of light beyond the retina Short eyeball or lazy lens Near objects are blurry.

22 Emmetropia

23

24 Hyperopia

25 Astigmatism Unequal curvatures in cornea & lens

26 The Ear Houses two senses Receptors are mechanoreceptors Hearing
Equilibrium (balance) Receptors are mechanoreceptors Slide 8.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

27 Anatomy of the Ear The ear is divided into three areas
Outer (external) ear Middle ear Inner ear Figure 8.12 Slide 8.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

28 The External Ear Involved in hearing only
Structures of the external ear Pinna (auricle) External auditory canal Figure 8.12 Slide 8.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

29 The External Auditory Canal
Narrow chamber in the temporal bone Lined with skin Ceruminous (wax) glands are present Ends at the tympanic membrane Slide 8.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

30 The Middle Ear or Tympanic Cavity
Air-filled cavity within the temporal bone Only involved in the sense of hearing Slide 8.24a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

31 The Middle Ear or Tympanic Cavity
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 Slide 8.24b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

32 Bones of the Tympanic Cavity
Three bones span the cavity Malleus (hammer) Incus (anvil) Stapes (stirrip) Figure 8.12 Slide 8.25a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

33 Bones of the Tympanic Cavity
Vibrations from eardrum move the malleus These bones transfer sound to the inner ear Figure 8.12 Slide 8.25b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

34 Inner Ear or Bony Labyrinth
Includes sense organs for hearing and balance Filled with perilymph Figure 8.12 Slide 8.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

35 Inner Ear or Bony Labrynth
A maze of bony chambers within the temporal bone Cochlea Vestibule Semicircular canals Figure 8.12 Slide 8.26b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

36 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 Slide 8.27a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

37 Organs of Hearing Slide 8.27b Figure 8.13
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

38 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 Slide 8.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

39 Mechanisms of Hearing Slide 8.29 Figure 8.14
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

40 Organs of Equilibrium Receptor cells are in two structures Vestibule
Semicircular canals Figure 8.16a, b Slide 8.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

41 Organs of Equilibrium Equilibrium has two functional parts
Static equilibrium – sense of gravity at rest Dynamic equilibrium – angular and rotary head movements Figure 8.16a, b Slide 8.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

42 Static Equilibrium - Rest
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 Slide 8.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

43 Function of Maculae Slide 8.32 Figure 8.15
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

44 Dynamic Equilibrium - Movement
Crista ampullaris – receptors in the semicircular canals Tuft of hair cells Cupula (gelatinous cap) covers the hair cells Figure 8.16c Slide 8.33a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

45 Dynamic Equilibrium Action of angular head movements
The cupula stimulates the hair cells An impulse is sent via the vestibular nerve to the cerebellum Figure 8.16c Slide 8.33b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

46 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 Slide 8.34 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

47 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 Slide 8.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

48 Olfactory Epithelium Slide 8.36 Figure 8.17
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

49 The Sense of Taste Taste buds house the receptor organs
Location of taste buds Most are on the tongue Soft palate Cheeks Figure 8.18a, b Slide 8.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

50 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 Slide 8.38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

51 Structure of Taste Buds
Gustatory cells are the receptors Have gustatory hairs (long microvilli) Hairs are stimulated by chemicals dissolved in saliva Slide 8.39a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

52 Structure of Taste Buds
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 Slide 8.39b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

53 Anatomy of Taste Buds Slide 8.40 Figure 8.18
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

54 Taste Sensations Sweet receptors Sour receptors Bitter receptors
Sugars Saccharine Some amino acids Sour receptors Acids Bitter receptors Alkaloids Salty receptors Metal ions Slide 8.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

55 Developmental Aspects of the Special Senses
Formed early in embryonic development Eyes are outgrowths of the brain All special senses are functional at birth Slide 8.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings


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