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Home , Chemoreceptor, Mechanoreceptor, Sense of smell, Stimulus (physiology), Thermoreceptor

The eg. individual sensitivities, eg colorblindness we spend our in an ocean of sensory stimuli: ! unusual pathways, eg light gravity electrical currents vibrations time our survival depends on our ability to perceive, interpret and respond to these signals

Reception vs

Reception is the mechanism and involved in detecting and transmitting sensory information

our body has millions of sensory receptors

All sensory receptors are “connected to” our CNS by way of sensory

these neurons travel through the Cranial or Spinal to the or

Perception is the conscious of sensory stimuli

is a higher level process of integration and interpretation

depends on how the brain processes the signals it is receiving & : The Senses; Ziser, Lecture Notes 2010.3 1 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 2

photoreceptor - light Reception of a - chemicals - bending, , touch Reception of a sensation is determined by: - – salt/water conc 1. Source of Sensory Stimuli - fluid pressure each sensory is designed to transduce we can classify receptors by their location or only one kind of stimulus regardless of the source of the stimulus they respond to: how it is stimulated

a. exteroceptors eg hard hit on ! “see stars” near surface of body eg. spicy food monitor external environment eg. menthol cough drop most special senses 3. Density of Receptors & Size of Receptive b. visceroceptors (interoceptors) Field deep monitor internal environment 99% of receptors in body not evenly distributed over surface of body

c. proprioceptors most tip of (specialized kind of visceroceptor) lips monitors relationship of external to internal fingertips environment position and movement back of orientation wrt gravity least back of neck

2. Kind of Transducer () braille exploits high tactile acuity of fingertips 4. Intensity of stimulus sensory receptors are transducers

! receptors convert one form of energy into another increase in stimulus intensity that the brain can interpret ! increased frequency of firing sensory receptors are designed to respond best to a single kind of stimulus: if over stimulated – become receptors

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 3 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 4 5. Duration of Stimulus eg. pain receptors, some touch, heat, cold, pressure, smell tonic receptors = the sensory fires as long as it is being stimulated B. Encapsulated Receptors (=corpuscular receptors) eg. , pain, body position, chemicals in a simple receptor encapsulated in layers of connective phasic receptors = continuous of receptors eventually results in loss of eg. Meissners Corpuscles egg shaped response just beneath in dermal papillae especially lips and tips !sensory exteroceptors – light pressure

important in detecting changes in eg. Pacinian Corpuscles stimuli, not duration of the deep subcutaneous tissues and viscera same stimulus deep pressure and vibrations largest simple receptor cells (2mm, naked ) mechanoreceptors eg. smell, touch, temperature

6. of Sensory Receptor receptors for special senses are more complex C. Receptor Cells that with Sensations can be produced by very simple kinds of receptors or complex organs eg. taste receptors receptors for General Senses are relatively simple D. Complex Sense Organs

Receptor Cells are part of more complex sense A. Free Endings

Direct stimulation of sensory neurons components of rather elaborate sense organs eg. eye, , etc the sensory neuron is also the receptor ! of sensory neurons Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 5 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 6

Cutaneous Sensations 5. Temperature free nerve endings (=”Touch”) heat and cold are separate receptors the skin possesses ~200,000

“touch” is a combination of from a variety 6. Pain of simple receptors nocioceptors in almost every tissue of body located in skin, connective tissue and all receptor types, if overstimulated, become pain receptors mucous membranes

may be free nerve endings or enclosed in capsule of epithelial tissue or connective tissue

!~64 million receptors in skin

they deliver more kinds of information than any single receptor of the special senses

Elements of Sense of Touch

1. Touch Meisner’s corpuscles esp fingertips, palms, soles, tongue, lips, , penis

2. Pressure Pacinian corpuscles

3. Vibration Pacinian corpuscles

4. and Tickle free nerve endings

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 7 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 8 The Nose & since they are neurons, they are replaced only very The Physiology of Smell slowly and not as quickly as they are lost both our senses of taste and smell are based mainly on ! some replacement ! but overall, we loose ~1%/yr ! loose as we get older smell ! detects airborne chemicals that enter nasal olfactory receptors are extremely sensitive cavity we are able to detect >10,000 different chemicals a chemical can be smelled only if it is volatile (most: 2000 – 4000) (=ie. able to become airborne)

mostly small molecules we have ~350 distinct kinds of receptor proteins

long range ! seem to be grouped into 15 – 30 “families” of receptors are located in roof and walls of nasal some can detect a single molecule of certain chemicals passages eg. can smell mercaptans (skunks) 1pt in 30 Billion 10-20 Million olfactory neurons in in an area about the size of a postage stamp women are more sensitive to smells than are men receptors are free nerve endings though very sensitive, they adapt quickly !dendrites of bipolar neurons olfactory signals can reach the cerebral cortex neurons pass through cribiform plate and connect to () before they pass through the on anterior ventral surface of brain olfactory neurons are the only neurons in the body some applications of olfactory physiology: directly exposed to external environment eg. Morning Sickness ! span of only ~60 days

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 9 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 10

during pregnancy sense of smell becomes much more acute due to action of estrogen which increases during pregnancy Taste Buds & ! may lead to morning sickness The Physiology of Taste almost all stimuli for are odors also due to chemoreceptors: esp smell of cooking foods, esp meats and bacon ! detects certain chemicals in foods and drink sometimes also coffee, , cigarette smoke, petroleum products, etc must be water soluble eg. Military use of smell for crowd control eg. starch powder in insoluble ! has no taste

short range; requires direct contact with “food”

taste receptors are much less sensitive than smell receptors

taste receptors located in tastebuds

!4000 - 10,000 taste buds

!most on tongue ! on papillae each papilla contains up to 200 taste buds

some on soft palate and in throat, cheeks

each is a cluster of 50-150 spindle shaped taste cells

taste cells with sensory neurons

taste cells are replaced every 7-10 days

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 11 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 12 !continually replaced throughout life also, many depend on smell each taste bud acts as a chemoreceptor ! taste is up to 80% smell

! presence of specific chemical initiates nerve hold nose to take impulse older people complain of lost taste but actually are losing smell ! most taste buds respond to 2-4 taste modalities interaction of all these kinds of receptors produces Flavors detected by taste receptors: all the flavors of food and drink

sweet - respond to sugars, some amino acids sour - respond to acids bitter - respond to alkaloids (eg. quinine, nicotine, caffeine) salty - respond to inorganic salts and metal - (=’delicious, savory’) respond to meaty , glutamate, aspartate, MSG all primary taste sensations are detected in all areas of the tongue

in spite of “taste maps” of the tongue: tonic receptors ! don’t adapt quickly the sense of taste also involves additional receptor types:

thermoreceptors (spicy hot, menthol)

mechanoreceptors (texture)

nocioceptors (spicy)

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 13 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 14

The Eye & The Physiology of Vision contains numerous blood vessels highly pigmented eye might be considered our most important sense organ anteriorly is modified into 2 sphincter muscles: of all the nerve fibers making up the 12 pairs of cranial iris – smooth muscle in doughnut shape nerves: pupil – opening in center of iris 38% of them are contained in the ciliary body – ring of muscle behind iris we usually use data from our other senses only to supplement visual information lens – held in place by ciliary body

Structure flattened, tightly compressed cells=lens fibers the eyeball is spherical 3. consists of 3 layers: innermost coat of eyeball

1. sclera only in posterior portion of eyeball

tough white fibrous connective tissue tissue of retina arranged in three layers

anterior portion is clear = actual visual receptors = rods and cones

no blood vessels in cornea cones – densest at fovea (10,000 cones, no rods) in rear of eye, less numerous at periphery 2. choroid rods – most dense at periphery, less numerous middle layer toward fovea Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 15 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 16 Accessory Eye Structures: neurons from rods and cones converge to form optic nerve extrinsic eye muscles 3 pairs of muscles that move eye at the point of convergence there are no rods or cones eyebrows ! creates a “blind spot” in each eye nonverbal may also protect from sweat and glare The eyeball contains two cavities: eyelids & eyelashes anterior cavity (=segment) close to moisten eye with tears and in eyelashes are guard that help keep debris out of eye extends from cornea to lens contains a clear watery fluid conjunctiva = aqueous humor transparent mucous membrane that covers innersurface of eyelid and outer surface of eyeball, except cornea richly innervated, highly sensitive to pain aqueous humor circulates heavily vascular ! bloodshot

increased pressure in aqueous humor lacrimal apparatus = glaucoma lacrimal glands & ducts protects and lubricates eye produces and drains tears that lubricate and rinse eyeball and posterior cavity (segment) remove and kill

behind lens Physiology of Vision fills most of eyeball contains gelatinous vitreous humor light is electromagnetic energy (=vitreous body) !spectrum of energies (400nm to 700 nm)

maintains pressure to prevent eyeball from what we “see” is the light that bounces off of various collapsing objects and enters our

ie. light that is not absorbed by an object

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 17 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 18

a clear image is formed on the retina by following processes: also helps absorb excess light

1. Control of Light Intensity albinos ! no pigment in choroid layer ! difficulty in daylight amount of light entering eye must be regulated to allow enough in to stimulate receptors 2. Refraction of Light Rays

while preventing too much that might cause as light passes through materials of different overstimulation density and curvatures it is bent (=refracted)

eg. spoon in glass of water A. Pupillary Constriction and Dilation light rays are bent as they pass through cornea, pupil = opening in center of iris muscle aqueous humor, lens, vitreous humor

iris acts as “f-stop” of camera if everything is normal the eye is designed to cause image to converge on the back of the allows appropriate amount of light to enter eye eyeball in many the eyeball is not shaped properly to get prevents overstimulation of retina in daytime image to converge on retina:

nearsightedness ! prevents extraneous rays that cannot farsightedness be focused from entering eye astigmatism – bump or depression on cornea or lens that refracts light rays incorrectly ! or reduces the amount of stimulation of retina 3. Accommodation of Lens

allows adequate light in at night in order to be able to focus on near or far objects the lens must change shape (similar to B. choroid layer adjusting lenses on camera)

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 19 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 20 normal eyes can adjust focus by changing shape of lens to see both near and far 5. Stimulation of Photoreceptors

accomplished by ciliary muscle and suspensary >130 Million photoreceptors in each eye ligaments: two types of photoreceptors: rods 130M/retina contraction cones 6.5 M/retina ! release tension on lens ! lens thickens for near vision rods: contain pigment = rhodopsin (derived from vitamin A) relaxation when light strikes pigment ! pulls suspensary ligaments and pulls on lens ! causes chemical change ! causes lens to thin for far vision ! triggers nerve impulse

4. Depth Perception (Convergence of Eyes) >1000 rods are connected to single neuron in optic nerve ! helps to amplify dim image extrinsic eye muscles and centers in brain ! lose acuity allow individual eyes to converge on same object cones: also contain pigments three kinds of cones: would produce double vision if both eyes are not focused on same scene combinations of the three produce color vision those with crossed eyes learn to suppress one image most cones are individually connected to neuron ! poor for dim light produces depth (3-D) perception ! much greater acuity

! both eyes are looking at same scene but switching between 2 different receptors can cause temporary blindness from slightly different angle eg. turn off or on lights ! receptors must adapt those with only one eye have no depth perception

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 21 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 22

in daytime, rods “bleach” out & shut down Disorders of the Eye at night – not enough light to stimulate cones

an American goes blind every 11 minutes (AAS 1994) Rods Cones b/w vision color vision 100’s x’s more sensitive less sensitive to light Macular Degeneration ! takes less light to ! takes more light to loss of central field of vision; sometimes loss of side vision stimulate them stimulate them usually both eyes night time, low light vision day time, high light vision inability to see clearly near or far less acute vision more acute vision in advanced stages objects seem bent or distorted (many rods/ neuron) (1 cone/ neuron) periphery sharpest vision fovea sharpest vision colors may look different

supporting tissue around macula degenerates associated with arteriosclerosis, hereditary factors, eye trauma most common for Caucasians, people >60; rare among blacks

diagnosed early ! laser treatments may prevent further degeneration

Glaucoma slow loss of peripheral vision, no pain in early stages later may be pain and blindness

due to increased pressure in eye leads to damage to optic nerve

blacks at much higher risk; also diabetics those with eye injuries or eye surgeries or very near sighted

if diagnosed and treated early may be no injury; but half with glaucoma don’t know they have it

Floaters small spots seen occasionally in field of view; spots appear as dots, threads or cobwebs that move as eye moves

caused by shrinkage of vitreus, which detaches from retina causing bleeding sometimes result from eye injury or disease

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 23 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 24 those >40 more susceptible, also those with cataract surgery The Ear & The Physiology of Diabetic Retinopathy progressive disease of blood vessels supplying retina ear is a multiple sense organ ! small blood vessels weaken and break or are blocked

esp in diabetics; more common in long term diabetics(>15 yrs) in hearing: mechanoreceptors convert vibration of air pregnancy, high BP and smoking can exacerbate condition molecules (= waves) into nerve impulses Cataracts Structure clouding of lens blurred or double viison, spots, ghost images, impression of a film over eyes, problems with lights ear is divided into 3 regions: may develop rapidly over a few months or very slowly over period outer ear of years exact cause unknown middle ear age related, diabetics, some medications and eye injury may increase risks; may be genetic component 1. Outer Ear treatment: cataract surgery – quick outpatient procedure; then lens implant, contact lenses or cataract eyeglasses pinna = external flap of tissue

ear canal = external auditory meatus passes through the temporal bone

protects

maintains more constant temp and humidity for optimal performance

also collects & amplifies sound waves and directs them to eardrum

ceruminous glands along ear canal Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 25 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 26

are modified sweat glands a. bony labyrinth ! secrete waxy cerumen b. membranous labyrinth traps particles may block ear between the two is a cushion of fluid 2. Middle Ear =perilymph

separated from outer ear by ear drum within the membranous labyrinth is =tympanum endolymph; similar to ICF

contains 3 bones: a. bony labyrinth

malleus (hammer) the actual cavity in temporal bone that incus (anvil) contains the soft tissue of the inner ear stapes (stirrup) vestibule - chamber just inside oval window auditory tube (=eustachian tube) connects the middle ear to throat - coiled canal attached to vestibule equalizes pressure to protect eardrum semicircular canals - 3 “U” shaped tubes at 3. Inner Ear right angles branching from vestibule

communicates with middle ear by two small b. membranous labyrinth membranes: inside the bony labyrinth oval window - stapes pushes on oval window the soft membranes and sacs that comprise the functional structures of the inner ear round window – below oval window utricle & saccule - within vestibule consists of two series of fluid filled sacs and cochlear duct - within cochlea passageways: semicircular ducts - within SC canals Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 27 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 28 6. On floor (=basilar membrane) of cochlear duct is cochlear duct is only portion of inner ear actually (actual organ of hearing) involved in sense of hearing contains mechanoreceptors (= cells) it forms shelf across cochlea dividing it into 3 sections: their ‘hairs’ press against tectorial membrane

scala vestibuli as endolymph sloshes it causes the cells to rub on cochlear duct tectorial membrane

scala tympani as hairs bend initiates nerve impulses Physiology of Hearing Qualities of Sound 1. outer ear collects and amplifies vibrations can vary in: eg. megaphone loudness = measured in decibels 2. causes eardrum to vibrate very small vibrations “normal sound” ~ 60 db

3. ear bones resting on eardrum also vibrate pitch (frequency of vibrations) amplify sound human ear can perceive pitch between ! has been converted from vibrations of air to 16 – 20,000 Hz (cps) vibrations of solid bone sound waves are relatively low energy waves bone conducts sound much more strongly ! much of the anatomy of the ear is designed to amplify them 4. Stapes pushes in and out on oval window detecting loudness of sound 5. This sets fluid of inner ear in motion greater bending of hair cells also causing round window to bulge in and out

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! greater frequency of nerve impulses Proprioceptors = perception of loudness equilibrium and balance are maintained by complex detecting pitch of sound interactions between simple receptors and complex proprioceptor organs and vision different hair cells respond to different pitch simple receptors embedded in deep tissues; cells near beginning of CD respond to high muscles, , joints, etc pitched sounds eg. Pacinian corpuscles cells near end (apex) of CD respond to low eg. joint receptors pitched sounds they monitor

7. nerve impulses travel through vestibulocochlear !slight changes in pressure as we shift positions nerve for processing in temporal lobe of !stretching of various internal organs ! positions of limbs wrt rest of body more complex proprioceptor organs are found in the inner ear as part of special senses

!inner ear is a multiple sense organ

in addition to hearing also has receptors for equilibrium

static equilibrium

! orientation wrt gravity: position, orientation

dynamic equilibrium

! changes in movement Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 31 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 32 movement of fluid in these canals causes bending of Static Equilibrium crista ampullaris within vestibule of inner ear is fluid filled sac ! detect acceleration and deceleration = utricle ! detect turning, changes in motion ! detect direction of the change contains patches of hair cells = macula continuous movement in same direction cannot be detected embedded in gelatinous matrix (membrane) eg. we are spinning on surface of earth at ~1000 mph eg. elevator also in gelatinous material are small particles of carbonate = otoliths as head moves these otoliths shift positions and stimulate different hair cells tells position and orientation

Dynamic Equilibrium semicircular canals branch off vestibule

fluid filled

each canal is oriented along a different plane ! at right angles to each other

at bases of each are swelling = ampulla

each ampulla contains a patch of hair cells = crista ampullaris

Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 33 Human Anatomy & Physiology: The Senses; Ziser, Lecture Notes 2010.3 34