the sensory system hearing general senses rad 101 chapter 10
TRANSCRIPT
Anatomy of the EarAnatomy of the Ear
Slide 8.21Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The ear is divided into three areas Outer
(external) ear
Middle ear
Inner ear
Figure 8.12
The External EarThe External Ear
Slide 8.22Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Involved in hearing only
Structures of the external ear Pinna
(auricle)
External auditory canal
Figure 8.12
The External Auditory CanalThe External Auditory Canal
Slide 8.23Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Narrow chamber in the temporal bone
Lined with skin
Ceruminous (wax) glands are present
Ends at the tympanic membrane
The Middle Ear or Tympanic CavityThe Middle Ear or Tympanic Cavity
Slide 8.24a
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Air-filled cavity within the temporal bone
Only involved in the sense of hearing
The Middle Ear or Tympanic CavityThe Middle Ear or Tympanic Cavity
Slide 8.24b
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Two tubes are associated with the inner ear
The opening from the auditory canal is covered by the tympanic membrane
The eustachian (auditory) tube connecting the middle ear with the throat
Allows for equalizing pressure during yawning or swallowing
This tube is otherwise collapsed
Bones of the Tympanic CavityBones of the Tympanic Cavity
Slide 8.25a
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Three bones span the cavity
Malleus (hammer)
Incus (anvil)
Stapes (stirrip)
Figure 8.12
Bones of the Tympanic CavityBones of the Tympanic Cavity
Slide 8.25b
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Vibrations from eardrum move the ossicles
These bones transfer sound to the inner ear through the oval window
Figure 8.12
Inner Ear or Bony LabyrinthInner Ear or Bony Labyrinth
Slide 8.26a
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Includes sense organs for hearing and balance
Filled with perilymph
Figure 8.12
Inner Ear or Bony LabrynthInner Ear or Bony Labrynth
Slide 8.26b
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A maze of bony chambers within the temporal bone
Cochlea
Vestibule
Semicircular canals
Figure 8.12
Organs of HearingOrgans of Hearing
Slide 8.27a
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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
Organs of HearingOrgans of Hearing
Slide 8.27b
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Figure 8.13
Mechanisms of HearingMechanisms of Hearing
Slide 8.28Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
Mechanisms of HearingMechanisms of Hearing
Slide 8.29Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 8.14
Organs of EquilibriumOrgans of Equilibrium
Slide 8.30a
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Receptor cells are in two structures
Vestibule
Semicircular canals
Figure 8.16a, b
Organs of EquilibriumOrgans of Equilibrium
Slide 8.30b
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Equilibrium has two functional parts
Static equilibrium
Dynamic equilibrium
Figure 8.16a, b
Static EquilibriumStatic Equilibrium
Slide 8.31Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
Function of MaculaeFunction of Maculae
Slide 8.32Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 8.15
Dynamic EquilibriumDynamic Equilibrium
Slide 8.33a
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Cristae – receptors in the semicircular canals
Function when the body is spinning or moving in different directions
An impulse is sent via the vestibular nerve to the cerebellum
Figure 8.16c
Chemical Senses – Taste and Chemical Senses – Taste and SmellSmell
Slide 8.34Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
Olfaction – The Sense of SmellOlfaction – The Sense of Smell
Slide 8.35Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
Olfactory EpitheliumOlfactory Epithelium
Slide 8.36Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 8.17
The Sense of TasteThe Sense of Taste
Slide 8.37Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Taste buds house the receptor organs
Location of taste buds Most are on
the tongue
Soft palate
Cheeks Figure 8.18a, b
The Tongue and TasteThe Tongue and Taste
Slide 8.38Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The tongue is covered with projections called papillae
Taste buds are found on the sides of papillae
Structure of Taste BudsStructure of Taste Buds
Slide 8.39a
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Gustatory cells are the receptors
Have gustatory hairs (long microvilli)
Hairs are stimulated by chemicals dissolved in saliva
Structure of Taste BudsStructure of Taste Buds
Slide 8.39b
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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
Taste SensationsTaste Sensations
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Sweet receptors (tip of tongue) Sugars Saccharine Some amino acids
Sour receptors (laterally on the tongue Acids
Bitter receptors (posterior part of tongue) Alkaloids
Salty receptors (anterior sides of the tongue) Metal ions
Developmental Aspects of the Developmental Aspects of the Special SensesSpecial Senses
Slide 8.42Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Formed early in embryonic development
Eyes are outgrowths of the brain
All special senses are functional at birth
The General SensesThe General Senses
Slide 8.42Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Touch
Tactile receptors found in the dermis of the skin
Sensitivity varies with number of touch receptors
Pressure
Receptors for deep touch located in the subcutaneous tissue
Sense of temperatureSense of temperature
Slide 8.42Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Free nerve endings widely distributed in the skin
Separate receptors for heat and cold
Temperature receptors in the hypothalamus help to adjust body temperature
Sense of PositionSense of Position
Slide 8.42Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Proprioreceptors located in muscles, tendons and joints
Relay impulses that help to judge position and changes in location of body parts
Inform the brain of muscle and tendon tension
Aided by equilibrium receptors in the internal ear
Kinesthesia Sense of body movement
Sense of PainSense of Pain
Slide 8.42Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Receptors are widely distributed nerve endings
Two pathways to brain
Sharp acute pain
Slow, chronic pain
Pain ReliefPain Relief
• Analgesic drugs• Nonnarcotic analgesics
• Act locally to reduce inflammation• Non-steroidal antiflammatory drugs (NSAIDS)
• Ibuprofen, naproxen
• Narcotic• Act on the CNS to alter the reception and response to pain
• Anesthetics• Prevent pain during surgery• Used to prevent chronic pain
• Endorphins
Pain ReliefPain Relief
• Endorphins• Released naturally from certain areas of the
brain• Associated with pain relief
• Applications of heat and cold• Relaxation or distraction techniques