the general & special senses chapter 18. introduction senses – our perception of what is...
TRANSCRIPT
The General & Special Senses
Chapter 18
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
Receptors
• Sensory receptors are transducers – Change stimuli into electro-chemical impulses – Specific receptors can transduce only certain
types of stimuli
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-01
Receptors
Interpretation of Sensory Information
• Occurs in cerebral cortex
• Depends on the area of the cerebral cortex that receives the information
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
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)
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-02
Referred Pain
The Special Senses
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
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-06a
Olfactory Receptors
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-06b
Olfactory Receptors
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
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-07a
Taste Areas of the Tongue
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-07b
Taste Buds
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-07c
Taste Bud
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
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Figure 18-09
The Ear
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-10b
The Middle Ear
The Inner Ear
• Separated from the middle ear by the oval window
• Consists of a series of canals filled with fluid
The Inner Ear
– Semicircular canals• Contains receptors for head position
– Cochlea • Contains the organ of Corti, the organ of hearing
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-12b
The Inner Ear
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
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-12c
Hair Cells in the Semicircular Canals
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
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-16d
Organ of Corti
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-16e
Organ of Corti
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
Vision (the eye)
• Accessory structures– Eyelids protect the eye
• Conjunctiva lines the eyelid
• Lacrimal gland produces tears
– Extrinsic muscles move the eyeball
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-18b
The Eye
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),
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-20b
The Eye
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-20a
Tunics of the Eye
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-22c
Inner Tunic
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
Cavities of the Eye
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-23
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
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-20c
The Pupil
The Retina
• Cones allow for sharp color vision in bright light– 3 types, each with a different pigment
The Retina
• Rods provide for vision in dim light– Most dense at the periphery of the retina– Contain the pigment rhodopsin
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-22a1
Visual Receptors
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
Abnormal Vision
• Myopia
• Hyperopia
• Presbyopia
• Astigmatism