The Special Senses - Eye, Ear and Nose

Flashcards for reviewing lecture notes on special senses - eye, ear, and nose.

General senses receptors

Temperature, pain, touch, stretch, and pressure.

Special senses receptors

Gustation, olfaction, vision, equilibrium, and audition.

External ear structures

Auricle, external auditory meatus, tympanic membrane.

Middle ear structures

Tympanic cavity, auditory ossicles (Malleus, Incus, and Stapes).

Inner ear (Labyrinth) structures

Cochlea and other structures associated with equilibrium.

Auricle

Skin covered, funnel-shaped, elastic cartilage-supported structure.

External acoustic meatus

Bony tube leading to the tympanic membrane (eardrum).

Tympanic cavity

Air-filled cavity containing the auditory ossicles.

Auditory ossicles

Malleus, Incus, Stapes

Tympanic membrane

Partitioning the external and middle ear, an epithelial sheet

Auditory ossicles function

Amplify and transmit sound waves from the tympanic membrane to the inner ear

Oval window function

Responsible for transmitting vibrations to the fluid of the inner ear and hearing receptors.

Inner ear

Houses specialized sensory apparatus for balance and hearing.

Bony labyrinth divisions

Semicircular canals, vestibule, and cochlea.

Membranous labyrinth

Fluid-filled tubes and spaces within the bony labyrinth.

Bony labyrinth

Lined with periosteum and contains perilymph.

Epithelial membranous labyrinth

Contains endolymph.

Spiral organ (Organ of Corti)

Contains hair cells that detect movement of surrounding membranes.

Organ of Corti function

Specialized sensory epithelium that transduces sound vibrations into neural signals.

Balance - 3 parts

Vestibular Apparatus: Semicircular ducts/canals, Utricle, Saccule

Utricle and Saccule

Two sacs within the vestibule connected by a small duct.

Maculae function

Provide sensory information on the position of the head in space. (Static equilibrium)

Hair cells

Sensory receptors for both equilibrium and hearing.

Vestibulocochlear nerve (CN VIII)

Carry nerve impulses from the ear to the brain.

Auditory pathway destinations

Brainstem, thalamus, cerebellum, and auditory cortex of the temporal lobe.

What are the 2 classes of receptors?

1. general senses receptors—temperature, pain, touch, stretch, and pressure
2. special senses receptors—gustation, olfaction vision, equilibrium, and audition

What is the external ear comprised of?

primarily composed of the skin covered, cartilaginous
structure called the auricle

What are some of the components of the middle ear?

• air filled tympanic cavity; bony walled

• a connection through to the nasopharynx but is normally
  closed

What are the auditory ossicles?

Auditory ossicles (three smallest bones in the body) located here that amplify and transmit sound waves from the tympanic membrane to the inner ear

Where is the inner ear located and where are some of the components?

• Located in spaces within the petrous portion of the temporal bone

• In the inner ear are specialised sensory apparatus for the sensations of balance and hearing -these are connected to the middle ear by areas the oval and round window

What is the bony labyrinth composed of?

• A set of cavities in the petrous part of the temporal bone

• Divided into three parts: semicircular canals, vestibule, and cochlea

• Lined with periosteum and filled with perilymph

What is the Membranous labyrinth composed of?

• A series of epithelial sacs and tubes located within the bony labyrinth

• Filled with endolymph

• Houses receptors for hearing and equilibrium

Where are hearing organs housed?

In the cochlea of the inner ear.

When the cochlea is cut in half/ cross section you can see it has a number of canals of the membranous labyrinth. What is it called?

cochlea duct

Frequency and intensity are measured (low frequency sounds travel
further along the cochlear duct)

Summarise some of the components of the spiral organ

Summary – The Spiral Organ (Organ of Corti):

• Located within the cochlea, between the membranes of the cochlear canals

• Contains hair cells that detect membrane movement

• Sound waves hitting the tympanic membrane create pressure waves in the cochlear fluid, which distort membranes

• The organ of Corti (spiral organ) is a specialised sensory epithelium that converts these vibrations into neural signals for hearing

What are the 2 sacs called in the vestibule of a membranous labyrinth?

the utricle and the saccule, which are connected by a small duct

What are the 3 semicircular canals that project superiorly and posteriorly from the vestibule.

The anterior, posterior, and lateral semicircular canals, which are involved in balance and spatial orientation.

What are the 3 semicircular canals innervated by?

cranial nerve VIII Vestibulocochlear

What do maculae provide?

The maculae provide sensory information on the position of
the head in space.

What happens when stereocilia is bent?

As the stereocilia is bent, the amount of NT released changes.

What do the utricle and saccule contain?

The sensory epithelium lining the two maculae (utricle and saccule)
contains hair cells and supporting cells

What are hair cells for?

Hair cells are sensory receptors for both equilibrium and hearing.

On the apical surface how many microvilli do they have and what are they called?

On their apical surface, they contain more than 50 stiff microvilli called stereocilia and one long cilium called a kinocilium

What happens when stereocilia and kinocilium are bent?

When the stereocilia and kinocilium are bent, this translates into
electrical activity sent to the brain via the vestibular nerve.

Look at the diagram of the auditory pathways

What happens when stereocilia on hair cells is bent?

Bending of stereocilia on hair cells produces a nerve impulse

During auditory pathways what cranial nerve carries the nerve impulse?

Nerve impulse is carried via the vestibulocochlear nerve (CN VIII)

What are the auditory neural pathways?

Summary – Auditory Neural Pathway:

• Sensory axons from the ear travel to the brainstem

• They synapse with secondary neurons, which project to:

  • Other parts of the brainstem

  • The thalamus

  • The cerebellum

  • And finally, the auditory cortex in the temporal lobe, where sound is consciously perceived