The Sensory System Hearing General Senses RAD 101 Chapter 10.

The Sensory SystemHearing

General SensesRAD 101

Chapter 10

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


Involved in hearing only

Structures of the external ear Pinna

(auricle)

External auditory canal

Figure 8.12

The External Auditory CanalThe External Auditory Canal


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

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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


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


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


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


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


A maze of bony chambers within the temporal bone

Cochlea

Vestibule

Semicircular canals

Figure 8.12

Organs of HearingOrgans of Hearing

Slide 8.27a


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


Figure 8.13

Mechanisms of HearingMechanisms 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

Mechanisms of HearingMechanisms of Hearing


Figure 8.14

Organs of EquilibriumOrgans of Equilibrium

Slide 8.30a


Receptor cells are in two structures

Vestibule

Semicircular canals

Figure 8.16a, b

Organs of EquilibriumOrgans of Equilibrium

Slide 8.30b


Equilibrium has two functional parts

Static equilibrium

Dynamic equilibrium

Figure 8.16a, b

Static EquilibriumStatic 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

Function of MaculaeFunction of Maculae


Figure 8.15

Dynamic EquilibriumDynamic Equilibrium

Slide 8.33a


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


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


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


Figure 8.17

The Sense of TasteThe 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

The Tongue and TasteThe Tongue and Taste


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


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


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


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


Formed early in embryonic development

Eyes are outgrowths of the brain

All special senses are functional at birth

The General SensesThe 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

Sense of temperatureSense 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

Sense of PositionSense 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

Sense of PainSense of Pain


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

Sensory AdaptationSensory Adaptation

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

The Sensory System Hearing General Senses RAD 101 Chapter 10.

Documents

Transcript of The Sensory System Hearing General Senses RAD 101 Chapter 10.