SENSES

Senses

• Receptors detect environmental change and send nerve impulse to brain

• General senses- receptors throughout body- touch- skin, joints, organs

• Special senses- confined to head- eyes, ears, smell, taste

Receptor Types= 5

1. Chemoreceptors- change in concentration of chemical subs. – smell/taste

2. Pain receptors- (nociceptors) respond to tissue damage

3. Thermoreceptors- sensitive to temp change

4. Mechanoreceptors- sense mechanical forcesProprioceptors-change in tension of muscles/tendonsBaroreceptors- in blood vessels, detect changes in blood pressureStretch receptors- in lungs, sense degree of inflation

5. Photoreceptors- eyes, respond to light

• Sensation- receptors send info to brain• Perception- how brain interprets info

• Projection- process where the cerebral cortex causes a feeling to stem from a source (eyes, ears)

• Sensory Adaptation- sensory receptors stop sending signals when they are repeatedly stimulated

1. General Senses

• Exteroreceptive- change at body surface– touch, pressure, temp, pain

• Visceroreceptive- change in viscera– Stretching blood vessels, ingested meal

stimulating pH receptors• Proprioceptive- associated with changes in

muscles/ tendons/ body position

Touch and Pressure Senses

• Free nerve endings- sensation of itching• Tactile (meissner’s) corpuscles- hairless areas

of skin (lips, fingertips)• Lamellated(Pacinian) corpuscles- deep

pressure (tendons, joints)

Why do we need receptors to send signals about pressure or touch to our brain?

Pressure sores

Temperature Senses

• Warm receptors- detect warm temps– 77°F -113°F become unresponsive at 113

• Cold receptors- detect cold temps– 50°F and 20°F – if below 10 °C pain receptors stimulated

Sense of Pain

• Pain receptors do not adapt, prompts a person to take action to avoid stimulus

Visceral Pain

• Occurs in visceral tissues• Heart, lungs, intestine• Referred pain- feels as though it is coming

from a different part • Ex: heart attack

Pain Nerve Pathways

• Acute pain - Originates from skin, usually stops when stimulus stops (needle prick)

• Chronic Pain-dull aching sensation

Regulation of Pain Impulses

• Inhibitors of Pain• natural brain chemicals can be mimicked by

drugs such as morphine• Inhibitors released by brain- – Enkephalins– Serotonine– Endorphins

2. Special Senses

• Smell olfactory organs• Taste taste buds• Hearing ears Equilibrium• Sight eyes

What did the right eye say to the left eye?

Between you and me, something smells!

SMELL- Olfactory Receptors

• Chemoreceptor sensitive to chemicals dissolved in liquids

• 75%-80% of flavor comes from smell

Olfactory Organs

• Odor molecules enter nasal cavity as gas molecules• 500 dif olfactory receptors• Odors must dissolve in mucus

• Odor molecule • olfactory receptor cell • olfactory bulb • olfactory tract • limbic system

Taste

• Taste bud– surface of tongue, roof of mouth, cheeks– Papillae- tiny elevations

Taste Bud

Taste cells- function as receptors in taste bud• 10,000 taste buds- house 50-150 taste cells• Taste pore- spherical opening • Taste hairs- tiny projections• Chem. Must dissolve in saliva

• Taste receptors cranial nerves medulla oblongata thalamus parietal lobe of cerebrum

Hearing

• Outer External Ear- • Auricle-outer ear, collects sound waves• External acoustic meatus- S shaped tube• Tympanic membrane- ear drum• Hair/Wax keep large objects out of ears

(insects)

Ear

Mid Ear

• Mid Ear-tympanic cavity• Auditory ossicles- three small bones– Malleus– Incus – Stapes– Transmit vibrations to amplify the signal

• Auditory Tube- connects the mid ear to the throat– Maintains air pressure

Inner (Internal) Ear

• Labyrinth-communicating chambers and tubes– Osseous Labyrinth-bony canal in temporal bone – Membranous Labyrinth-tube in osseous labyrinth

• Perilymph and Endolymph- fluidsOsseous Labyrinth

PerilymphMembranous Labyrinth

Endolymph

Labyrinths Parts

• Cochlea-function in hearing, snail shell• Semicircular canals -3- function in equilibrium• Vestibule-house membranous structures for

hearing/equilibrium

• Round window- membrane covered opening in the wall of inner ear

• Organ of Corti- contains 16,000 hearing receptor cells• Hair cells- receptor cells

• Sound- detecting vibrations• 20-20,000/sec• Greatest Sensitivity – 2,000-3,000 Vibrations/Sec

Sense of Equilibrium

• Static equilibrium-sense the position of the head, maintain stability and posture

• Dynamic Equilibrium-(semicircular canals) – balance the head during sudden movement

• Cerebellum- interprets impulses from the semicircular canals and maintains overall balance and stability

Sight

• The eye is in the orbit of the skull for protection.

• Within the orbit are 6 extrinsic eye muscles, which move the eye.

• There are 4 cranial nerves: Optic (II), Occulomotor (III), Trochlear (IV), and

Abducens (VI).

• Epicanthic Fold- People of Asian descent

Visual Accessory Organs

• Eyelid• Conjuctiva• Lacrimal Gland• Extrinsic Muscles

Eye lid

• Covers/protects eye• Thinnest skin on body• Will not protect against intense radiation-

wear goggles in tanning bed

Conjunctiva

• Mucous membrane that lines inner surface of eyelids

• Transparent• Pink eye= conjunctivitis

Lacrimal Apparatus

• Lacrimal gland- secretes tears• Tears drain to nasal cavity via lacrimal duct• Function: moisten/lubricate eyes, contains

enzymes that kill bacteria living in moist/warm conditions

Extrinsic muscles

• Move eyeball– Superior rectus– Inferior rectus– Medial rectus– Lateral rectus– Superior oblique– Inferior oblique

Outer Tunic

• Cornea - transparent, focuses light rays• Sclera – continuation of cornea, going toward

the back of the eye (white of the eye)– Protection

• Optic Nerve – exits at the optic disk and transmits visual information from the eye to the brain.

Mid Tunic

• Choroid Coat – contains blood vessels• Ciliary Body – holds the lens in place• Lens – focusing• Iris – colored portion of the eye• Aqueous humor – liquid surrounding the lens• Pupil – opening for light to enter

Inner Tunic

• Retina - visual receptor cells• Fovea Centralis - region of the sharpest vision

(aka, macula)• Optic Disc – where nerve fibers leave the eye,

creating the blind spot• Vitreous Humor – supports internal parts, fluid

Retina

• on top of the choroid layer.• made up of PHOTORECEPTORS, which are

sensors for light• Photoreceptor-– Rod- see light/dark– Cone-see colorRetinal neuronsform optic nerves optic chiasma

thalamus visual cortex of occipital lobe

Eyes

• Accommodation- the lens changes shape to focus on objects

• Light Refraction- the bending of light around an object

Images viewed by eye are upside-down, our brains interpret it properly

• We have difficulty interpreting info upside down

• Which is the correct Mona Lisa?

Eye problems

Fun Fact

• When you look at someone you love your pupils dilate, when you are looking at someone you hate your pupils dilate

Problem with Eyes

• Clouding of the lens leads to a clinical condition known as CATARACTS.

• Treatment is to remove the lens and replace it with a plastic one

• If the lens yellows, you can’t see the color blue. After surgery, can see blue again.

Iris

• The function is to constrict or dilate the pupil (opening) to allow light in.

• Therefore, it regulates the amount of light passing to the visual receptors of the eye.

• If there is a lot of pigment, eye is brown; a medium amount = green, small amount = blue, no pigment = pink (albino).

Fun facts• Why are all babies born with blue eyes?• Melanin is a brownish pigment that adds color to your hair, eyes, and

skin. At the time babies are born, melanin hasn't yet been "deposited" in the eyes' iris. Hence, they appear blue.

• After about six months, eyes change color depending on the amount of melanin. If you have a lot of it, your eyes will turn brown or black. If you have little, they'll stay blue. And if you have no melanin, your eyes may appear pink. Interestingly, as the site notes, human beings aren't the only creatures with freaky color-morphing eyeballs. Kittens experience the same phenomenon.

• How can someone have two different colored eyes?• Eye color is a polygenic trait. Many babies are born with blue eyes.

Their eyes change color later as they begin to produce more melanin.

Blind Spot

• The region where the optic nerve and blood vessels goes in and out of the eye has no photoreceptors = BLIND SPOT.

• Hold your hands out at 45° and that’s the location of the blind spot.

• You can still see your hands because the other eye sees it. Close your right eye and look for your right hand and you’ll find the blind spot.

Test for colorblindness

Problems with vision

• FLOATERS are when a capillary breaks and cells break off. Floaters don’t actually move, the eye just tries to track them.