SensesCassidy McCombsClaire JohnsonSiobhan O’SheaKevin Su

Basic Definitions• General Senses: Receptors are widely distributed

through out the body (Skin/Organs/Joints)• Specialized Senses: Specialized receptors confined to

the structures of the head• Sensation: Raw form in which receptors send

information to the brain• Perception: The way the brain interprets a received

sensation• Projection: What the brain sends back to the projection

source (allows person to pinpoint the region)

Receptor Types• Chemoreceptors: Changes in concentration of

chemical substances (Senses of smell and taste; changes in blood such as oxygen, hydrogen, glucose)

• Pain Receptors: Respond to tissue damage (exposure to electrical, chemical, thermal, and mechanical energy)

• Thermo Receptors: Temperature Change• Photoreceptors: Detects light energy intensity (found in

eyes)• Mechanoreceptors: changes that deform receptors

– Proprioceptors: Muscles and Tendons– Baroreceptors: Certain blood vessels and blood pressure– Stretch Receptors: Lungs (by degree of inflation)

Apple Example

Hearing•Sound Pathway: • Auricle → External Acoustic Meatus → Tympanic Membrane →

Ossicles → Oval Window → Scala Vestibuli → Vestibular Membrane → Cochlear Duct → Hair Cells → Sensory Neurons → Temporal Lobe

External Ear•Auricle: Cone shaped,

collects sound•External Auditory

Meatus: Lined with ceruminous glands, transfers sound to tympanic membrane

•Tympanic Membrane: Vibrates as a result of sound vibrates ossicles

Middle Ear•Tympanic Cavity: air-filled

space in the temporal bone•Ossicles: Vibrates from

contact from the tympanic membrane, malleus, incus, stapes

•Oval Window: Small cavity in the tympanic cavity, stapes vibrates against it to move fluids in inner ear

Eustachian (Auditory) Tube• Eustachian tube • Part of Middle Ear• connects middle ear

to throat • helps maintain

equal pressure on both sides of tympanic membrane (think altitude-pop)

• usually closed by valve-like flaps in throat

Inner Ear• Contains two labyrinths• Osseous Labryinth: bony

canal, filled with perilymph• Membranous Labyrinth: tube

within Osseous Labyrinth, filled with endolymph

• Three parts of the Labyrinth: Cochlea, Semicircular Canals, Vestibule

• But we’ll focus on the Cochlea for now because the other two are not in the sound pathway

From the stapes in the middle ear, vibrations enter the oval window and transfer to the scala vestibuli. Different pitched sounds travel different distances along the length of the scala vestibuli. The vibrations take a u-turn then enter the vestibular membrane and pass through the membranous labyrinth. Here, the sounds are processed and sent to the brain. The sounds then pass through the Basilar membrane, then back down the cochlea through the scala tympani to be absorbed by the round window.

Cochlea

Scala vestibuli upper compartment leads from oval window to apex of spiral part of bony labyrinth

Scala tympani lower compartment extends from apex of the cochlea to round window part of bony labyrinth

group of hearing receptor cells (hair cells) on upper surface of basilar membrane different frequencies of vibration move different parts of basilar membrane particular sound frequencies cause hairs of receptor cells to bend Ca influx causes NT release onto sensory nerve

AP generated-to medulla-to thalamus-to auditory cortex (temporal)Some crossover occurs

Organ of Corti

Static Equilibrium• uses vestibule• sense position of head when body is not moving

Dynamic Equilibrium• uses semicircular canals• sense rotation and movement of head and body

Equilibrium

Vestibule

• Utricle• communicates with saccule and membranous portion of semicircular canals

• Saccule• communicates with cochlear duct

• Mucula• hair cells of utricle and saccule

• responds to changes in head position• bending of hairs results in generation of nerve impulse

MaculaStatic eq.

Crista Ampullaris

Dynamic Eq

Smell•Smell works closely with taste to aid in food

selection▫We smell food the same time we taste it▫75%-80% of flavor derives from the sense of smell

•Olfactory receptors▫used to sense smell▫Similar to chemoreceptors and taste

Olfactory Receptor Cells•Bipolar neurons surrounded by columnar

epithelial cells•Neurons have knobs at the distal ends of

their dendrites and are the sensitive portion of the receptors

•Odorant molecules stimulate olfactory receptors

•Main interpreting areas for olfactory impulses are located deep within the temporal lobes and at the bases of the frontal lobes

Olfactory Organs

•Contain the olfactory receptors and epithelial supporting cells

•Appear as yellowish brown masses surrounded by pinkish mucous membrane

•Cover upper parts of the naval cavity, the superior nasal conchae and a portion of the nasal septum

Odorant molecules•Enter the nasal cavity as gases •Must dissolve at least partially in the watery

fluids that surround the cilia before they can be detected by bonding to receptor proteins on the cilia

•Bind to about 500 types of olfactory receptors, depolarizing the olfactory receptor cells, therefore generating nerve impulses

•Signaling proteins inside the receptor cells translate the chemical signals into the electro chemical language of the nervous system

Receptors

•Sensory receptors▫respond to sensory stimuli

•Membrane receptors▫Molecules such as proteins and glycoproteins ▫Allow cells to respond to specific molecules

•Olfactory receptors ▫Respond to specific molecules and chemical

stimuli

Olfactory Nerve Pathways

• When stimulated nerve impulses travel along their axons through tiny opening in the cribriformplates of the ethmoid bone

• These fibers synapse with neurons located in the enlargements of the olfactory bulbs

• Within the olfactory bulbs the sensory impulses are analyzed and additional impulses travel along the olfactory tracts to portions of the limbic system

Olfactory Stimulation

•Biologists not certain how stimulated receptors encode specific cells

•Leading hypothesis is that each odor likely stimulates a distinct set of receptor cells that in turn have distinct sets of receptor proteins

•The brain then recognizes the particular combination as an olfactory code

Olfactory Adaptation•The sense of smell drops about 50% within a

second following stimulation•Within a minute the receptors may become

almost insensitive to a given odor•Olfactory receptor neurons are the only nerve

cells in direct contact to the outside environment▫Basal cells along the basement membrane of the

olfactory epithelium regularly divide and yield differentiated cells that replace lost neurons

Taste Receptors

• The sense of taste derives from combinations of chemicals binding specific receptors on taste hair surfaces

• This binding alters membrane polarization and generates sensory impulses on nearby nerve fibers

• The degree of change is directly proportional to the concentration of the stimulating substance

Taste Sensations

•Five primary taste sensations are sweet, sour, salty, bitter, and umami ▫Each of the flavors we experience results from

one of the primary sensations or from a combination of two or more of them

▫The way we experience flavors may also reflect the concentration of chemicals as well as the sensations of smell, texture, and temperature

Taste Nerve Pathways

•Cranial nerves conduct the impulses into the medulla oblongata

•From there the impulses ascend to the thalamus and are directed to the gustatory cortex of the cerebrum, located in the parietal lobe along a deep portion of the lateral sulcus

Anatomy of the Eye

•From outermost to innermost:•Sclera, Cornea, Aqueous humor, Iris, Pupil, Lens, Vitreous humor, Retina, Choroid coat, optic nerve

The Outer Tunic of the Eye

•The outer tunic consists of the sclera, cornea, and optic nerve. The sclera is the

white of the eye. The cornea is the “window of the eye” where light enters, it helps focus light into the eye. The optic nerve transports

stimuli from the eye to the brain.

The Middle Tunic of the Eye

•Also called the vascular tunic. Includes the chortoid coat, the ciliary body, and the iris.

The ciliary body is the thickest part. Suspensatory ligaments extend from the

back of it and connect to the lens.

The Inner Tunic of the Eye

•Contains the retina. The retina has several parts: the fovea centralis (where vision is best), the optic disc – which becomes the optic nerve, and the vitreous humor. The

vitreous humor supports the internal structure of the eye and helps it maintain its

shape.

Refraction and Focus

Refraction occurs when light enters the eye and bends in order to focus. Images appear upside down when they reach the retina, but are perceived as right side up by the brain. If the lens is normal, the light always focuses on the retina. In myopia and hyperopia the shape if the eye is slightly deformed. In myopia the eye is too long and the light focuses too far in front of the retina. It is corrected using glasses with concave lenses. In hyperopia the eye is too short and light focuses to far behind the retina, it is corrected using a convex lens.

Visual Pigments

Rods and cones contain pigments that decompose when they absorb light. Rhodopsin is found in rods, which see shapes and are not very acute. In darkness, more rods are used, and when going from darkness to somewhere light, the rhodopsin decomposes. Too little vitamin A reduces the amount of rhodopsin, causing a condition called “nightblindness”.Cones contain idopsins , which see color and vision is acute.

Stereoscopic Vision and Visual nerve Pathways

Stereoscopic vision perceives depth, height, and width. It depends on having two eyes.

Visual nerve pathways: the optic nerves in the eyes split into two, sending messages to both sides of the brain.

Bibliography• "Gustatory Receptor Cells." - WolfWikis. Web.

03 Apr. 2012. <http://wikis.lib.ncsu.edu/index.php/Gustatory_receptor_cells>.

•Shier, David. Hole's Human Anatomy & Physiology. Student Ed. Eleventh ed. [S.l.]: McGraw, 2007. Print.

• "Please Pass The Salt." Basal Science Clarified. 14 Aug. 2011. Web. 03 Apr. 2012. <http://bsclarified.wordpress.com/2011/08/14/please-pass-the-salt/>.

•Haas’s Previous Slideshows