AI: Chapter 10: Sensory Reception and the Special Senses

What are the two ways sensory receptors can be divided?

Visceral vs. Somatic Senses, General vs. Special Senses

What do visceral receptors monitor?

The internal environment of the body

What are visceral receptors sometimes called?

Interoceptors

What are examples of visceral senses?

Nausea and hunger

What do somatic senses monitor?

The external environment and the external body

What are the two types of somatic senses?

Exteroceptors and Proprioceptors

What are examples of somatic senses?

Sensation of air temperature and muscle strain

What are examples of general senses?

Touch, pressure, temperature, pain

How is the location of the stimulus determined in mammals for general senses?

By the sensory cortex

What are the two types of general senses?

General Somatic and General Visceral senses

What are examples of special senses?

Sight, smell, taste, hearing, equilibrium

How is the location of the stimulus determined in mammals for special senses?

By the sensory cortex

What are the two types of special senses?

Special Somatic and Special Visceral senses

How can sense reception be handled?

By dendritic endings of sensory neurons or by an entire receptor cell

What are the two forms of dendritic endings?

Encapsulated Dendritic Endings and Free Dendritic Endings

What is the purpose of encapsulated dendritic endings?

To increase surface area for increased sense perception

What are examples of senses detected by dendritic endings?

General senses

What are examples of senses detected by receptor cells?

Special senses

What can complete cell receptor cells be?

Neurons or specialized cells

What are neuroepithelial cells?

Specialized epithelial cells derived from neural crest ectoderm.

What is the function of neuroepithelial cells?

To conduct an impulse to a sensory neuron.

What are stereocilia?

Hair-like structures on the apical surface of neuroepithelial cells.

Why are neuroepithelial cells sometimes referred to as 'hair cells'?

Due to the hair-like appearance of stereocilia.

What are neuromast organs?

Organs composed of neuroepithelial cells.

What is the typical arrangement of neuromast cells?

Neuromast cells are associated with columnar epithelial cells called sustentacular or supporting cells.

What is the function of the stereocilia in neuromast cells?

To detect stimuli.

What is the cupola?

An acellular glycoprotein in which the stereocilia of neuroepithelial cells are embedded.

What is the role of sensory dendrites in neuromast cells?

To carry the impulse from the neuroepithelial cells to the CNS.

What stimuli do neuromast cells primarily monitor in fish and aquatic amphibians?

Mechanical stimuli from water.

What are the two types of neuromasts?

External and internal neuromasts.

Where are external neuromasts located?

In shallow pits or grooves on the body surface.

What is the primitive state neuromast?

The external neuromast.

Where are internal neuromasts found?

Embedded to some extent within the body.

Where are the most specialized internal neuromasts located?

In the membranous labyrinth of the inner ear in all gnathostomes.

Where can neuromasts be found in jawed fishes?

In a number of locations, including pit organs.

What are pit organs?

Fluid-filled pits located beneath the epidermis.

What is the function of pit organs?

To house internal neuromasts embedded in the skin.

What is the function of neuromasts in agnathans, larval amphibians, and aquatic urodeles?

To monitor mechanical stimuli from water.

What are Ampullae of Lorenzini?

Internal neuromasts of sharks located deep beneath the skin.

How do Ampullae of Lorenzini open up onto the surface?

By means of a long duct.

What is the gelatinous material called that surrounds the neuromasts?

Jelly.

Who produces the jelly around the neuromasts?

Supporting cells of the neuromast.

Where are Ampullae of Lorenzini primarily located?

On the head.

What is the function of Ampullae of Lorenzini?

Electroreceptive and aid in the detection of prey.

What are the Lateral Line and Cephalic Canal Systems?

Shallow grooves on the surface of the head and a single groove extending along the lateral line to the tail on both sides.

What are the neuromasts of the lateral line and cephalic canal systems in their primitive state?

External neuromasts.

What happens to the lateral line and cephalic canal systems in larval amphibians?

They are lost during metamorphosis into the adult, terrestrial form.

What are the neuromasts of the lateral line and cephalic canal systems in jawed fishes?

Internal neuromasts.

What happens to the lateral line canal in most teleosts?

It sinks below the surface and is embedded in the dermal bone.

What forces do the lateral line and cephalic canal systems respond to?

Mechanical forces such as water currents.

What functions do the lateral line and cephalic canal systems serve?

Avoiding predators, detecting prey movements, schooling, orientating in flowing streams, and other functions.

Can the lateral line and cephalic canal systems respond to electrical signals?

Yes, in some species.

What are the innervations of the lateral line and cephalic canal systems in fish, larval aquatic amphibians, and adult aquatic amphibians?

CN 8, CN ALL, and CN PLL.

What remains innervated by CN 8 in amniotes?

Internal neuromasts in the ear.

What is the Membranous Labyrinth of the Ear?

The structure of the ear that contains the sensory organs for hearing and balance.

What is the membranous labyrinth?

The membranous labyrinth is a structure found in all vertebrates, located within a bony or cartilaginous labyrinth in the otic capsule of the neurocranium.

What is the function of the membranous labyrinth in most fishes?

In most fishes, the membranous labyrinth serves only in the detection of equilibrium.

What is the function of the membranous labyrinth in some fishes and all tetrapods?

In some fishes and all tetrapods, the membranous labyrinth detects both audition and equilibrium.

What is the basic structure of the skeletal and membranous labyrinths?

The membranous labyrinth is located within a skeletal labyrinth composed of either cartilage or bone.

What are the two portions of the skeletal labyrinth in all gnathostomes?

The two portions of the skeletal labyrinth in all gnathostomes are the semicircular canals and the vestibule.

How many portions does the skeletal labyrinth have in mammals and birds?

The skeletal labyrinth in mammals and birds has three portions: semicircular canals, vestibule, and cochlea.

What is the cochlea?

The cochlea is a structure that developed from an outpocketing of the vestibule in fish and amphibians called the Lagena.

What is the fluid between the skeletal and membranous labyrinths called?

The fluid between the skeletal and membranous labyrinths is called perilymph.

What is the space that encloses the perilymph called?

The space between the two labyrinths, which encloses the perilymph, is called the perilymphatic space.

How many regions does the membranous labyrinth have in most gnathostomes?

The membranous labyrinth has two regions in most gnathostomes.

How many regions does the membranous labyrinth have in mammals?

The membranous labyrinth has three regions in mammals.

What are the semicircular ducts?

The semicircular ducts are located within the semicircular canals.

How many semicircular ducts and canals do gnathostomes have?

Gnathostomes have three semicircular ducts and canals, one in each plane of motion.

How many semicircular ducts and canals do agnathans have?

Agnathans have two semicircular ducts and canals.

What are the two connected portions of the membranous labyrinth within the vestibule called?

The two connected portions of the membranous labyrinth within the vestibule are the utricle and saccule.

Where is the cochlear duct located?

The cochlear duct is located in the cochlea of birds and mammals.

What is the fluid within the membranous labyrinth called?

The fluid within the membranous labyrinth is called endolymph.

What do most vertebrates have extending from the vestibule and ending in a blind sac?

Most vertebrates have an endolymphatic duct extending from the vestibule and ending in a blind sac called the endolymphatic sac.

Where do the endolymphatic ducts open in elasmobranchs?

In elasmobranchs, the endolymphatic ducts open onto the surface of the chondrocranium and are located in depressions termed the endolymphatic fossae.

What structures do mammals have in addition to the endolymphatic sacs?

In mammals, in addition to the endolymphatic sacs, there is also a set of...

What are perilymphatic sacs?

Sacs located in the subarachnoid space.

Where are the receptors of static equilibrium located?

Utricle and saccule of the vestibular portion of the bony labyrinth.

What is the function of the receptors of static equilibrium?

Provide sensory information about head orientation and help maintain posture.

Where are the maculae located?

On the wall of the utricle and saccule.

What are the two classes of epithelial cells in the maculae?

Supporting cells and hair cells.

What are the characteristics of hair cells?

Have long stereocilia and extend into an overlying acellular membrane called the otolith membrane.

What do the supporting cells secrete?

The otolith membrane, a gelatinous glycoprotein.

What are otoliths?

Calcium carbonate crystals found in the otolith membrane.

What causes the movement of otoliths?

Movements of the head.

How do otoliths affect the otolith membrane?

Their mass moves the otolith membrane.

What happens when the otolith membrane presses down on the stereocilia?

It triggers a nerve impulse.

Where is the impulse transmitted to?

Cerebral cortex via the vestibular branch of CN 8.

Where are the receptors of dynamic equilibrium located?

Ampulla of the semicircular canal portion of the bony labyrinth.

What is the function of the receptors of dynamic equilibrium?

Provide sensory information about head orientation during movement.

How are the semicircular ducts positioned in mammals and birds?

At right angles to one another, allowing detection of dynamic equilibrium along three planes.

Which semicircular canal handles the frontal plane?

Superior semicircular canal.

What is the function of the posterior semicircular canal?

Handles the sagittal plane.

What is the function of the lateral semicircular canal?

Handles the transverse/lateral plane.

What is the sensory organ for dynamic equilibrium called?

Crista Ampullaris.

What are the two classes of epithelial cells in the sensory organ for dynamic equilibrium?

Supporting Cells and Hair/Receptor Cells.

What is the gelatinous membrane that the hair cells are embedded in called?

Cupola.

What happens when the head moves?

Endolymph flows in the semicircular ducts and pushes against the cupola, stimulating the hair cells.

Where is the cochlea located?

Anterior to the vestibule.

What are the three canals internally divided in the cochlea?

Scala Vestibuli, Scala Tympani, and Scala Media.

What is the scala media also known as?

Cochlear Duct.