2Sensory Receptors; specialized cells that monitor internal and external conditions. Receptors CNS for interpretationAdaptation is a decreased sensitivity to the presence of a constant stimulus.I.e. not feeling your watch; jumping into cold lake (Work of RAS)
3Your Senses can be divided into two categories General Senses – receptors for temperature, pain, touch, pressure, vibration and body positionScattered throughout the bodySpecial Senses – smell, taste, vision, balance and hearingConcentrated with specific structures, called sense organs
4General Senses Part of PNS Pain Receptors (Nociceptors) Common in the superficial portions of the skin, joint capsules, along periosteum of bones,Fast pain: carried by myelinated fibersSlow pain: carried by unmyelinated fibersReferred Pain: perception coming from other parts of body; parts of body are connected to by same spinal nerves. I.e. cardiac pain – originates in chest and left arm.
5Temperature (thermoreceptors) Nerve endings scattered beneath skin surfaceLocated in skeletal muscles, liver and hypothalamus as well. Why?Receptors RAS system (Working right now in this room!!!)
6Touch, Pressure and Position (Mechanoreceptors) Respond to stretching, compression, twisting or other distortions of the cell membrane.3 classes of MechanoreceptorsTactile (touch)Baroreceptors (pressure)Proprioceptors (position)Contain mechanically regulated ion channels that open or close in response to stretching, compression, twisting or other distortions of the cell membrane
76 Types of Touch Receptors Free NerveendingsHair PlexusMerkel’sMeissner’sPacinianRuffini’s
8Baroreceptors: monitor changes in pressure Surround the walls of hollow organs. I.e. blood vessels, lungs, stomach, bladderMonitors BP – plays a role in regulating cardiac function and blood flow to tissuesBaroreceptors in lungs determine degree of lung expansion, which is relayed to pons and medullaControls urination and defecation in urinary and digestive systems
10Proprioceptors Monitors the position of joints, tension in tendons and ligamentsState of muscle contractionLab ActivityMost information processed subconsciously
11Smell and TasteChemoreceptors respond to chemical in a water solution.Olfactory organs – provide a sense of smellConsists of olfactory epithelium, receptors, supporting cells and basal (stem) cellsOlfactory glands produce a mucus that covers epitheliumKeeps area moist and free of dust/debrisSolvent that captures and dissolves air borne moleculesConstantly replaced; flushes away old odorsNose diffuses chemicals thru mucus; mouth chemicals dissolve in salivaTissue is pseudostratified epithelium
12Olfactory Receptors: modified neurons An odor causes olfactory receptors to open Na+ channels and change membrane permeability.Research in the 1990’s suggests we have 1000 smell genesGenes only active in noseEach gene codes for an odor binding protein; these receptor proteins only allow certain odors to bind to it.Receptor cells replace themselves q 60 days. Function of basal or stem cells10-20 million receptors are packed into a 5 cm2 area; animals have much larger numbers
13Olfactory Receptors10-20 million receptor cells are packed into a 5 cm2 area.
14Olfactory Bulb: Cranial Nerve I Axons leaving bulb travel to the olfactory cortex of cerebrum, hypothalamus and part of limbic system.Elicits emotional responses to odorsSmells associated with danger (smoke, skunk)Pleasant smells cause increased secretion of saliva and gastric juiceUnpleasant smells trigger protective reflexes (sneezing/coughing)Lab ActivitySome of what we smell is really pain.Nasal cavities contain receptors that respond to irritants such as ammonia, hot of peppers, chill of menthol. Reach the CNS via the trigeminal nerve, not the olfactory bulb
15TasteTongue contains 3 types of cells: receptor, support and basal cellsTaste buds are the gustatory receptors distributed all over tongue.Basal cells replace receptors q 7-10 daysTaste hairs extend from receptor cells and are bathed in salivaDissolved chemicals touch hair (microvilli), causing Na+ channels to open → A.P.
16Four Primary Tastes Sweet – tip of tongue Salt – lateral tip Sour – sides of tongueBitter – back of tongue
17Taste Receptors respond more to unpleasant stimuli Taste buds are monitored by cranial nerve 7 (facial), 9 (glossopharyngeal), 10 (vagus).Taste is 80 % smell.Think of how food tastes when you have a cold.Try This!Cranial nerves send impulses to thalamus and then primary sensory cortex.Olfactory receptors play huge role in taste perception1000 X more sensitive to tastes when organs are functioning (Think cold)
18Vision: Eye Anatomy Eyes are hollow organs divided into two cavities. Aqueous humor – liquid inside eyeball gives the eye shapeWall of the eye contains 3 layersFibrous tunic – outer layerVascular tunic – middle layerNeural tunic – inner layer
19Fibrous Tunic Contains Functions Sclera – white of eye 6 eye muscles attachPosterior surface contains blood vessels and nervesCornea – transparent light passes thru.FunctionsMechanical support and some protectionAttachment site for 6 extrinsic eye musclesAssists in focusingFibrous TunicSclera is a layer of dense fibrous tissue that contains collagen and elastic fibersBlood vessels lie under the sclera; but are very small so you only see white fibers. Thus white eyeballCollagen fibers in cornea are arranged to allow light to pass through; gets oxygen by diffusing from air.
20Vascular Tunic Functions Provide route for blood and lymph tissue Iris – contains blood vessels, pigment cells, smooth muscleControls the size of pupil (center of iris) in response to lightCiliary body – Thickened ring of tissue surrounding lens; forms aqueous humor and muscles maintain lens shapeGlaucoma – increased pressure in eye due to imbalance of A. humorChoroid – blood vessel-rich membrane; delivers oxygen and nutrients to retinaFunctionsProvide route for blood and lymph tissueTransmits and Regulates amount of light entering eyeCirculate aqueous humor within eyeControl shape of lensSmooth muscle represents all intrinsic eye muscles; 2 layers of smooth muscleExplain dilation and constriction of pupil; controlled by autonomic nervous systemMuscles are responding to changes in light intensity
22Tunic Neural Tunic: Retina Contains Photoreceptors – respond to light Rods – light sensitiveCones – color vision3 types of cones Red/Green/Blueprovides perception of colorGive more clarity than rodsFovea – largest concentration of cones; sharpest visionVolunteers??? Anyone, Anyone!!Neural Tunic: RetinaTunicRods allow us to see in dim light; night driving. Located along sides of eyeCones are red, green, blue; each type is sensitive to different range of wavelengths
30How Do You See?LensPrimary function is to focus image on the retinal receptors in the back of eye.Focusing requires two stepsLight is bent when it passes between mediums of varying densitiesGreatest refraction occurs when light passes thru cornea.Focal point – when light bends to form a pointFocal Distance – distance between center of lens and focal point.Focusing is accomplished by changing the shape of the eyeball.Light bends 3 times cornea (most diffraction), entering and leaving lens. Doesn’t refract going thru V. humor
31Pathway to the brain eye Occipital Lobe Optic Nerve II Superior ColliculiPathway to the brainOccipital Lobe
32Depth PerceptionTwo eyes are better than one, especially when it comes to depth perception. Depth perception is the ability to judge objects that are near or farther than others.To demonstrate the difference of using one vs. two eyes to judge depth, hold the ends of two pencils, one in each hand. Hold them either vertically or horizontally facing each other at arms-length from your body. With one eye closed, try to touch the end of the pencils together. Now try with two eyes, it should be much easier. (Can use fingers if you don’t have 2 pencils.)
33What happens to the lens at close distances? Close Images – longer focal distance; lens is rounded because ciliary muscles contract.The closer the source, the longer the focal distance
34Distant Objects –Shorter focal distance and flattened lens.
35Keeping FocusedThe lens constantly changes shape to keep the focal distance constant. – Image stays focused on retina.I.e. looking at the board and then your paper.20/20 vision means a person can see details at a distance of 20 feet as clearly as the “normal population” would.
37Near sighted (myopia) 20/30 vision Images forms in front of retina Vision at close range will be normal, because lens can adjust and round up to focus.Eyeball is too deepObjects in the distance will be blurry and out of focus20/30 vision
38Corrected by wearing a diverging lens! Diverging lens increase focal distance
39Far Sighted (Hyperopia) Eyeball is too shallow Person can see distant objects; not near objectsAt close range the lens cannot provide enough refraction; point doesn’t focus at end of retina.
40Corrected by wearing converging lens! Converging lens – bends rays more.
41Astigmatism occurs when the cornea is more oval than spherical Astigmatism occurs when the cornea is more oval than spherical. The result is an unequal bending of the light which results in multiple focal points.
42Test for AstigmatismTo test your vision, stand about 20 feet from the chart. Test one eye at a time. If you see lines grey and other black you have an astigmatism.
43Ear Anatomy Ear is composed of 3 anatomical regions External Ear: Pinna – Tympanic membraneMiddle Ear: Tympanum – Auditory ossiclesInner ear: Bony Labryinth
45External Ear Organs Pinna (auricle) External Auditory Canal Functions to collect, direct sound waves to ear drum.External EarHairs prevent foreign object and insects from entering canalCerumen (ear wax) slows growth of microbes and reduces chance of infection.Ends at Tympanum
46Middle Ear Tympanum – ear drum; Auditory Tube (Eustachian tube) Cavity is filled with airAuditory Tube – equalizes pressure on either side of eardrumTympanum – ear drum; Auditory Tube (Eustachian tube)Auditory Ossicles –1. Malleus (hammer) 2. Incus (anvil) 3. Stapes (stirrup)
47Inner Ear Vestibule – provides sensations of gravity and acceleration Semicircular Canals – detect movement of headCochlea – provide sense of hearingHair Cells – receptors of inner ear for sound
49How do we hear?Sound waves cause the tympanic membrane to vibrate which moves the ossicles. Sound energy are converted to mechanical energy.Ossicles transmit the in/out vibrations from tympanic membrane to ear’s inner fluid-filled chamber.
51What about Hearing?Sounds set up vibrations in air that beat against the tympanic membrane.Vibrations push the ossicles that press fluid in the inner ear against membranes.Fluid causes forces that pull on tiny hair cells and stimulate neurons.Neurons send impulses to the brain, which interprets them.Tympanic membrane = eardrumOssicles = 3 tiny bones
55Maintaining Equilibrium: How does it work? When the head is upright, otoliths pushes the sensory hairs downward rather than side to side.By tilting the head, the otoliths move causing the sensory hairs to be distorted. This is sent to the CNS for interpretation.Within the vestibule and semicircular canals, tiny hairs are found along the membrane of these structures. Inside the canals, jellylike substance contains tiny calcium carbonate crystals called ear stones or otoliths. (o’to-lith)
56EquilibriumEar responds to various head movements.Static Equilibrium is controlled by the vestibule.Respond to straight-line changes in speed and direction, but not rotation.Dynamic Equilibrium is controlled by the semicircular canals.Respond to changes in head position; rotating the head to say no.