Sensory System

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Chapter 13
Sensory System
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Overview
.Receptors .Sensation gtComponents
gtCharacteristics .Types of senses gtGeneral
senses gtSpecial senses
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• The Senses
• Sensory system detects environmental change
• Environmental change initiates nerve impulse
  (stimulus)
• Stimulus interpreted by cerebral cortex
• Sensation experienced

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• Sensory Receptors
• Classifying sensory receptors
• Structure
• Free dendrite of sensory neuron
• End-organ on dendrite of afferent neuron
• Specialized cell associated with afferent neuron
• Stimuli
• Chemoreceptors
• Photoreceptors
• Thermoreceptors
• Mechanoreceptors

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• Special and General Senses
• Distribution of sense receptors
• Special senses in sense organ
• Vision
• Hearing
• Equilibrium
• Taste
• Smell
• General senses throughout body
• Pressure, temperature, pain, touch
• Sense of position

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General senses
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• The General Senses
• Receptors scattered throughout the body sense
• Touch
• Pressure
• Heat
• Cold
• Position
• Pain

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• Sense of Touch
• Tactile corpuscles
• Found mostly in dermis of skin and around hair
  follicles
• Sensitivity varies with the number of receptors

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• Sense of Pressure
• Receptors for deep touch located
• In subcutaneous tissues
• Near joints, muscles, and other deep tissues

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• Sense of Temperature
• Temperature receptors
• Are free nerve endings
• Are widely distributed in the skin
• Are separate for heat and cold
• Occur in hypothalamus of brain
• Help to adjust body temperature according to
  temperature of circulating blood

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• Sense of Position
• Proprioceptors (position receptors)
• Are located in muscles, tendons, joints
• Relay impulses of body parts in relation to each
  other
• Send impulses to the cerebellum for coordination

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Checkpoint 12-1 What are examples of general
senses? Checkpoint 12-2 What are proprioceptors
and where are they located?
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• Sense of Pain
• Pain receptors
• Are free nerve endings
• Are found in skin, muscles, joints and (to a
  lesser extent) in most internal organs
• Pain relief
• Analgesic drugs
• Anesthetics
• Endorphins
• Heat or cold
• Relaxation or distraction techniques

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Other Special Sense Organs Taste and smell sense
organs respond to chemical stimuli
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• Sense of Taste
• Taste receptors (buds) on tongue
• Stimulated by substance in solution
• Basic tastes
• Sweet
• Salty
• Sour
• Bitter
• Other tastes
• Water
• Alkaline
• Metallic
• Umami
• Cranial nerves
• Facial (VII)
• Glossopharyngeal (IX)

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Special senses that respond to chemicals. (A)
Organs of taste (gustation) and smell
(olfaction). (B) A taste map of the tongue.
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• Sense of Smell
• Smell receptors in nasal cavity
• Stimulated by substances in solution in nasal
  fluids
• Smells stimulate appetite and flow of digestive
  juices
• Olfactory nerve (cranial nerve I)

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Checkpoint 12-3 What are the special senses that
respond to chemical stimuli?
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• The Eye and Vision
• Eye protection structures
• Eye cavity bones
• Eyelids
• Eyelashes and eyebrow
• Conjunctiva
• Lacrimal glands

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Visual accessory organs
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Checkpoint 12-4 What are some structures that
protect the eye?
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• Coats of the Eyeball
• Eyeball has three separate coats (tunics)
• Sclera
• Choroid
• Retina

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The eye. Note the three tunics, the refractive
parts of the eye (cornea, aqueous humor, lens,
vitreous body), and other structures involved in
vision.
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Checkpoint 12-5 What are the names of the tunics
of the eyeball?
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• Pathway of Light Rays and Refraction
• Transparent parts of the eye that refract light
• Cornea
• Aqueous humor
• Crystalline lens
• Vitreous body

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Checkpoint 12-6 What are the structures that
refract light as it passes through the eye?
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• Function of the Retina
• Pigmented layer
• Sensitive to light
• Rods
• Function in dim light
• Shades of gray
• Blurred images
• Cones
• Function in bright light
• Color sensitive
• Sharp images
• Connecting neurons

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Checkpoint 12-7 What are the receptor cells of
the retina?
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How you see
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Structure of the retina. Rods and cones form a
deep layer of the retina, near the choroid.
Connecting neurons carry visual impulses toward
the optic nerve.
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Muscles of the Eye Two muscle groups adjust eye
so retina can receive clear image
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• The Extrinsic Muscles
• Outer surface of eyeball
• Voluntary
• Control convergence for three-dimensional vision

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Extrinsic muscles of the eye. The medial rectus
is not shown. ZOOMING IN What characteristics
are used in naming the extrinsic eye muscles?  
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Checkpoint 12-8 What is the function of the
extrinsic muscles of the eye?
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• The Intrinsic Muscles
• Within eyeball
• Iris regulates amount of light entering eye
• Ciliary muscle shapes lens for near and far vision

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The ciliary muscle and lens (posterior view).
Contraction of the ciliary muscle relaxes tension
on the suspensory ligaments, allowing the lens to
become more round for near vision.  ZOOMING IN
What structures hold the lens in place?
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Checkpoint 12-9 What is the function of the
iris? Checkpoint 12-10 What is the function of
the ciliary muscle?
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• Errors of Refraction and Other Eye Disorders
• Hyperopia
• Myopia
• Astigmatism
• Strabismus
• Convergent
• Divergent
• Amblyopia
• Infections
• Conjunctivitis
• Inclusion conjunctivitis
• Ophthalmia neonatorum
• Injuries
• Cataract
• Glaucoma
• Disorders involving the retina
• Diabetic retinopathy
• Macular degeneration

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• The Ear
• Sense organ for hearing and equilibrium
• Outer ear
• Middle ear
• Inner ear

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The ear. Structures in the outer, middle, and
inner divisions are shown.
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• The Outer Ear
• Pinna (auricle)
• Directs sound waves into ear
• External auditory canal (meatus)
• Ceruminous glands
• Tympanic membrane
• Vibrates as sound waves enter ear

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• The Middle Ear and Ossicles
• Middle ear cavity contains ossicles (small bones)
  that amplify sound waves and transmit sounds to
  inner ear
• Malleus (hammer)
• Incus (anvil)
• Stapes (stirrup)

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Checkpoint 12-11 What are the ossicles of the
ear and what do they do?
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• Eustachian Tube
• Connects middle ear cavity with throat (pharynx)
• Allows pressure to equalize on both sides of
  tympanic membrane
• Continuous mucous membrane from pharynx to middle
  ear cavity

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• The Inner Ear
• Bony labyrinth
• Vestibule
• Semicircular canals
• Cochlea
• Perilymph fluid
• Membranous labyrinth
• Vestibule
• Semicircular canals
• Cochlea
• Endolymph fluid

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The inner ear. The vestibule, semicircular
canals, and cochlea are made of a bony shell
(labyrinth) with an interior membranous
labyrinth. Endolymph fills the membranous
labyrinth and perilymph is around it in the bony
labyrinth.
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• Hearing
• Organ of Corti
• Located in membranous cochlea (cochlear duct)
• Ciliated receptor cells
• Tectorial membrane

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Cochlea and the organ of Corti. The arrows show
the direction of sound waves in the cochlea.
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How you hear
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Checkpoint 12-12 What is the name of the organ
of hearing and where is it located?
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• Equilibrium
• Ciliated equilibrium sensory receptors are
  located in vestibule and semicircular canals
• Types of equilibrium
• Static
• Maculae receptors
• Otoliths fluid
• Dynamic
• Cristae receptors

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Balance
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Checkpoint 12-13 Where are the receptors for
equilibrium located? Checkpoint 12-14 What are
the two types of equilibrium?
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• Otitis and Other Disorders of the Ear
• Otitis media
• Otitis externa
• Hearing loss
• Conductive hearing loss
• Sensorineural hearing loss
• Presbycusis