The Sensory System Hearing General Senses RAD 101 Chapter 10

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

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

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

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

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 eustachian (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

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

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

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

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

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

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

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

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

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

Organs of Equilibrium Equilibrium has two functional parts Static equilibrium Dynamic equilibrium Figure 8.16a, b Slide 8.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Static Equilibrium 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

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

Dynamic Equilibrium 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 Slide 8.33a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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

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

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

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

The Tongue and Taste The tongue is covered with projections called papillae Taste buds are found on the sides of papillae Slide 8.38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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

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

Taste Sensations 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 Slide 8.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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

The General Senses 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 Slide 8.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Sense of temperature Free nerve endings widely distributed in the skin Separate receptors for heat and cold Temperature receptors in the hypothalamus help to adjust body temperature Slide 8.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Sense of Position 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 Slide 8.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Sense of Pain Receptors are widely distributed nerve endings Two pathways to brain Sharp acute pain Slow, chronic pain Slide 8.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Pain Relief Analgesic drugs Nonnarcotic analgesics Narcotic 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

Pain Relief Endorphins Applications of heat and cold Released naturally from certain areas of the brain Associated with pain relief Applications of heat and cold Relaxation or distraction techniques Endorphins

Sensory Adaptation When exposed to continuous stimulus, sensory receptors adjust themselves so the sensation becomes less acute