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The General & Special Senses

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Presentation on theme: "The General & Special Senses"— Presentation transcript:

1 The General & Special Senses
Chapter 18

2 Introduction Senses – our perception of what is “out there” 2 groups
General senses Includes senses that are not specific Pass information through spinal nerves Special senses Found within complex sense organs to cerebral cortex Pass information through cranial nerves to cerebral cortex

3 Sensory receptors are transducers
Change stimuli into electro-chemical impulses Specific receptors can transduce only certain types of stimuli

4 Receptors

5 Interpretation of Sensory Information
Occurs in cerebral cortex Depends on the area of the cerebral cortex that receives the information

6 Central Processing and Sensory Adaptation
Sensory adaptation – the loss of sensitivity after continuous stimulation Occurs in some types of receptors Role – prevents brain from being overloaded with unimportant information

7 Receptors of the General Senses
Pain Referred pain Phantom pain Thermoreceptors detect changes in temperature Mechanoreceptors respond to pressure & touch Chemoreceptors detect chemicals in solution Blood composition (Smell) (Taste)

8 Referred Pain

9 The Special Senses

10 Olfaction (the nose) Olfactory receptors
Can detect at least 50 different primary smell Located in the roof of nasal cavity Molecules dissolve in the mucus or lipids of the epithelium Olfactory neurons pass through the roof of the nasal cavity and synapse in the olfactory nerve Olfactory tracts go directly to the cerebral cortex

11 Olfactory Receptors

12 Olfactory Receptors

13 Taste receptors are in the taste buds
Taste (the tongue) Taste receptors are in the taste buds Can detect 4 primary tastes Sweet, sour, salty, bitter Located in papillae on the surface of the tongue Taste buds contain the taste receptors Molecules dissolve in saliva Cranial nerves relay sensory impulses to the cerebral cortex

14 Taste Areas of the Tongue

15 Taste Buds

16 Taste Bud

17 Equilibrium & Hearing (the ear)
External ear The auricle directs sound waves into the external auditory meatus to the tympanic membrane Middle ear Contains the auditory ossicles Malleus, incus, stapes Connected to throat by the eustachian tube Inner ear

18 The Ear

19 The Middle Ear

20 The Inner Ear Separated from the middle ear by the oval window Consists of a series of canals filled with fluid

21 The Inner Ear Semicircular canals Cochlea
Contains receptors for head position Cochlea Contains the organ of Corti, the organ of hearing

22 The Inner Ear

23 The Semicircular Canals
Detects balance Arranged at right angles to each other Contain hair cells are embedded in gelatinous material with fluid over it Detect movement of the head Bends the hairs, creating nerve impulses

24 Hair Cells in the Semicircular Canals

25 Consists of hair cells on a basement membrane
The Organ of Corti Detects sound waves Consists of hair cells on a basement membrane Tips of hairs touch the tectorial membrane When the basement membrane vibrates, the hair cells are bent, sending a nerve impulse

26 Organ of Corti

27 Organ of Corti

28 Summary of Hearing Sound waves enter the external auditory meatus
Tympanic membrane vibrates Auditory ossicles vibrate Oval window vibrates Fluid in inner ear vibrates Basement membrane moves Hairs rub against the tectorial membrane Nerve impulse is sent along the auditory nerve to the brain

29 Vision (the eye) Accessory structures Eyelids protect the eye
Conjunctiva lines the eyelid Lacrimal gland produces tears Extrinsic muscles move the eyeball

30 The Eye

31 Consists of 3 tunics (layers)
Structure of the Eye Consists of 3 tunics (layers) Outer tunic – outermost layer Includes the cornea & sclera Middle tunic Includes the choroid coat, ciliary body, and lens, iris & pupil Inner tunic (retina) – inner layer Contains the rods & cones (photoreceptors) Includes the optic disc (blind spot),

32 The Eye

33 Tunics of the Eye

34 Inner Tunic

35 The lens separates the interior of the eye into 2 cavities
The Cavities of the Eye The lens separates the interior of the eye into 2 cavities Anterior cavity in front of the lens Contains aqueous humor Glaucoma Posterior cavity behind the lens Contains vitreous humor

36 Cavities of the Eye

37 Contains many blood vessels & nerves
The Vascular Tunic Contains many blood vessels & nerves The iris controls the size of the pupil Suspensory ligaments attach the lens to the ciliary body Controls the shape of the lens Allows focusing on near & distant objects Cataract

38 The Pupil

39 Cones allow for sharp color vision in bright light
The Retina Cones allow for sharp color vision in bright light 3 types, each with a different pigment

40 Rods provide for vision in dim light
The Retina Rods provide for vision in dim light Most dense at the periphery of the retina Contain the pigment rhodopsin

41 Visual Receptors

42 Summary of Vision Light rays enters through the pupil Light rays cross in the lens Retina receives reversed & upside down image Rods & cones are stimulated Optic nerve carries impulse to the brain

43 Abnormal Vision Myopia Hyperopia Presbyopia Astigmatism

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