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Biology 211 Anatomy & Physiology I. Special Senses. Special Senses 1. All confined to head 2. All special senses reach the central nervous system through cranial nerves 3. Consist of highly specialized cells which serve as receptors

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slide2

Special Senses

1. All confined to head

2. All special senses reach the central nervous system

through cranial nerves

3. Consist of highly specialized cells which serve as

receptors

4. These specialized receptor cells housed in sensory

organs which are also specialized for a particular

function.

slide3

Special Senses

Specialized

Receptor Cells

Specialized

Organ.....

TASTE:

SMELL:

VISION:

HEARING:

EQUILIBRIUM:

Gustatory Cells Taste Buds

Olfactory Cells Olfactory

Epithelium

Rods & Cones Eye (Retina)

Hair Cells Cochlea

Hair Cells Vestibular

Apparatus

slide4

Start with Vision:

Specialized

Receptor Cells

Specialized

Organ.....

VISION:

Other structures of eye regulate amount of light reaching retina and focus it on rod and cone cells.

slide7

The eyeball has three layers or "tunics:

Strong connective tissue

Protects the eye

Holds shape of eye

Insertion of extraoccular muscles

Contains blood vessels

Pigmented

Contains smooth muscle cells

Contains rod and cone cells

and

Other neurons to transmit visual

information to brain

slide8

Layers ("tunics") of the eyeball

Fibrous Layer

Vascular Layer

Sensory Layer

slide11

Focus:

Majority of light refraction (bending) occurs in cornea. Not adjustable

"Fine tuning" of light refraction occurs in lens:

Thicker = more refraction

Thinner = less refraction

slide18

Special Senses

Specialized

Receptor Cells

Specialized

Organ.....

TASTE:

SMELL:

VISION:

HEARING:

EQUILIBRIUM:

Gustatory Cells Taste Buds

Olfactory Cells Olfactory

Epithelium

Rods & Cones Eye (Retina)

Hair Cells Cochlea

Hair Cells Vestibular

Apparatus

slide19

Next: Hearing

Specialized

Receptor Cells

Specialized

Organ.....

HEARING

Located in inner ear. Outer ear and middle ear serve to transmit and regulate the volume of sound

slide21

The inner ear contains a complex fluid-filled structure,

the membranous

labyrinth, which

is embedded

in the

temporal

bone.

Outer ear

channels air vibrations

(sound) to the tympanic membrane (eardrum)

The middle ear is an air-filled chamber containing three ossicles: the malleus, the incus, & the stapes

slide22

Malleus

Incus

Stapes (attaches

to oval

window

of inner

ear)

Tympanic membrane

slide23

The tympanic membrane is attached to the malleus, which is attached to the incus, which is attached to the stapes, which is attached to the oval window of the membranous labyrinth of the inner ear. The membranous labyrinth is fluid-filled.

Therefore:

Vibrations of air (sound) vibrate the tympanic membrane

Which makes the ossicles vibrate

Which makes the oval window vibrate

Which makes the fluid of the membranous labyrinth

of the inner ear vibrate

This is how the vibrations get transmitted from the air of the outer ear to the receptor cells of the cochlea in the inner ear

slide24

The membranous labyrinth of the inner ear actually consists of two sets of tubes, one inside the other.

The outer tube is filled with a fluid called , while the inner tube is filled with fluid called

slide25

At one end of inner ear, these two tubes (one inside the other) coil about 2 & 2/3 times to form the

Vibrations of the oval window actually make the perilymph vibrate. This must be transmitted to the endolymph within the cochlea before the hair cells can detect it.

slide28

Vibration of oval window causes vibration of perilymph

of and which causes vibration of endolymph in

slide29

Vibration of the cochlear duct causes bending of hair cells within it.

When these hair cells bend, they send electrical signals through the vestibulocochlear nerve to the brain

slide30

Hearing involves two aspects of bending hair cells:

Which hair cells bend determines the pitch of the sound

How far hair cells bend determines volume of the sound

slide31

The membranous labyrinth of the inner ear also houses the specialized receptor cells for equilibrium - both position of the head ("static equilibrium") and movement of the head ("dynamic equilibrium").

slide32

Special Senses

Specialized

Receptor Cells

Specialized

Organ.....

TASTE:

SMELL:

VISION:

HEARING:

EQUILIBRIUM:

Gustatory Cells Taste Buds

Olfactory Cells Olfactory

Epithelium

Rods & Cones Eye (Retina)

Hair Cells Cochlea

slide33

The parts of the membranous labyrinth responsible for equilibrium are the the and three

which lie at right angles to each other.

slide34

The saccule and the utricle are responsible for detecting the position of the head ("static equilibrium").

Each of them contain a region of hair cells called a

slide35

The tips of these hair cells project into a gelatinous mass called the in which are embedded small crystals of calcium carbonate called

slide36

When the head changes position, gravity pulls on the otoliths, which causes the otolithic membrane to bend the hair cells (receptors)

When these hair cells bend, they send electrical signals to the brain through the vestibulocochlear nerve, telling it the new position of the head

slide37

A very similar situation tells your brain about movement of the head when hair cells of the semicircular canals bend.

slide38

Each semicircular canal has an enlargement, or at one end where the hair cells (receptors) are located

slide39

The tips of these hair cells in an ampulla of a semicircular canal project into a gelatinous mass called the in which are also embedded

slide40

When the head moves in any direction, movement of the endolymph in the semicircular pulls on the otoliths, which causes the cupula to bend the hair cells (receptors)

When these hair cells bend, they send electrical signals through the vestibulocochlear nerve to the brain, telling it which direction the head moved.

slide41

Special Senses

Specialized

Receptor Cells

Specialized

Organ.....

TASTE:

SMELL:

VISION:

HEARING:

EQUILIBRIUM:

Olfactory Cells Olfactory

Epithelium

Rods & Cones Eye (Retina)

Hair Cells Cochlea

Hair Cells Vestibular

Apparatus

slide42

Most, but not all, taste buds are located on projections from the surface of the tongue called papillae

Some taste buds are also located on the cheeks, the palate, and the oropharynx

slide43

Each taste bud contains three types of cells:

Each taste bud also has a small hole, or taste pore, on its free surface (facing the inside of the mouth)

slide44

Each gustatory cell has long microvillus, called a gustatory hair, which extends out of the taste pore into the saliva of the mouth.

This gustatory hair contains receptors on its plasma membrane which can detect specific chemicals in the saliva.

At the other end, each gustatory cell is surrounded by dendrites of sensory neurons

slide45

Substances must be dissolved in saliva or other liquid before they can stimulate the gustatory cells.

Each gustatory cell can respond to only one substance (sodium, glucose, etc.) BUT each taste bud contains many different types of gustatory cells.

Gustatory cells for different types of tastes are grouped on different parts of the tongue

slide46

Each gustatory cell has a separate threshold: concentrations below this do not stimulate the receptors.

In general: Sweet & Salty substances have high thresholds

Sour substances have moderate thresholds

Bitter substances have low thresholds

slide48

These afferent neurons carry information for conscious perception of tastes.

They also form afferent limbs of reflexes whose efferent limbs stimulate saliva production,

secretion of enzymes by stomach, liver,

pancreas

if necessary, gagging

vomiting

slide49

Special Senses

Specialized

Receptor Cells

Specialized

Organ.....

TASTE:

SMELL:

VISION:

HEARING:

EQUILIBRIUM:

Gustatory Cells Taste Buds

Rods & Cones Eye (Retina)

Hair Cells Cochlea

Hair Cells Vestibular

Apparatus

slide50

The olfactory epithelium (mucosa) is located high in the nasal cavity, just inferior to the cribriform plate of the ethmoid bone.

slide51

Each olfactory cell has long microvillus, called an olfactory hair, which extends into a layer of mucous on its free surface

This olfactory hair contains receptors on its plasma membrane which can detect specific chemicals in the mucous.

slide52

The axons of these olfactory cells (neurons) pass through the cribriform plate to synapse with neurons in the olfactory bulb. These axons are the olfactory nerve (C.N. I)

slide53

Substances must dissolve from the air into the mucous before they can stimulate the olfactory cells.

Each olfactory cell appears to be able to respond to many different substances.

Each olfactory cell has a separate threshold, but these are generally very low: just a few molecules of a substance may stimulate the olfactory cells.

slide54

Olfactory Pathways:

Axons of olfactory receptor cells pass through the cribriform plate of the ethmoid bone as the olfactory nerve, then synapse with afferent neurons in the olfactory bulb which lies just superior to it.

Axons of these afferent neurons pass through the olfactory tract to:

- The thalamus and the olfactory cortex on the medial

surface of the temporal lobe. This provides conscious

perception and interpretation of smells

- The hypothalamus and the brainstem. This provides

reflexes (salivation, avoidance, etc.) and "associative

responses" (activation of autonomic pathways, sexual

responses, emotional responses, etc.)

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