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Senses Notes AnaPhy
Nursing (RLE70)
Capitol University
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Senses
■ Sense:
- ability to perceive stimuli
■ Sensation:
- Is the process initiated by stimulating sensory receptors. Perception- is the conscious awareness of those stimuli.
■ Sensory receptors:
- sensory nerve endings that respond to stimuli by developing action potentials
TYPE OF SENSES
■ General senses:
- receptors over large part of body that sense touch, pressure, pain, temperature, and itch
- somatic provide information about body and environment
- visceral provide information about internal organs
■ Special senses:
- smell, taste, sight, hearing, and balance
TYPE OF RECEPTORS
■ Mechanoreceptors:
detect movement
Example, touch, pressure, vibration ■ Chemoreceptors:
detect chemicals • Example, Odors ■ Photoreceptors:
detect light ■ Thermoreceptors:
detect temp. changes ■ Nociceptors:
detect pain
GENERAL SENSES
■ Simplest and most common types of sensory receptors are FREE NERVE ENDINGS. ■ Cold Receptors- respond to decreasing temperatures but stop responding at temperatures below 12 degrees Celsius. ■ Warm Receptors- respond to increasing temperatures but stop responding at temperatures above 47 degrees Celsius.
■ BELOW AND ABOVE- only PAIN RECEPTORS are stimulated.
TYPES OF TOUCH RECEPTORS
■ Merkel’s disk:
- detect light touch and pressure ■ Hair follicle receptors:
- detect light touch ■ Meissner corpuscle:
- deep in epidermis
- localizing tactile sensations ■ Ruffini corpuscle:
- deeper tactile receptors
- detects continuous pressure in skin ■ Pacinian corpuscle:
- deepest receptors
- associated with tendons and joints
- detect deep pressure, vibration, position
PAIN
■ Pain is an unpleasant perceptual and emotional experience ■ Pain can be localized or diffuse.
■ Localized:
- sharp, pricking, cutting pain
- rapid action potential
■ Diffuse:
- burning, aching pain
- slower action potentials
PAIN CONTROL
■ Local anesthesia:
- action potentials suppressed from pain
- receptors in local areas
- chemicals are injected near sensory nerve
■ General anesthesia:
- loss of consciousness
- chemicals affect reticular formation
■ Referred Pain
originates in a region that is not source of pain stimulus
felt when internal organs are damaged or inflamed
sensory neurons from superficial area and neurons of source pain converge onto same ascending neurons of spinal cord
OLFACTION
■ Olfaction is the:
- sense of smell
- occurs in response to odorants
- receptors are located in nasal cavity and hard palate
- we can detect 10,000 different smells
OLFACTION PROCESS
- Nasal cavity contains a thin film of mucous where odors become dissolved.
- Olfactory neurons are located in mucous. Dendrites of olfactory neurons are enlarged and contain cilia.
- Dendrites pick up odor, depolarize, and carry odor to axons in olfactory bulb (cranial nerve I).
- Frontal and temporal lobes process odor.
TASTE
■ Taste buds:
- sensory structures that detect taste
- located on papillae on tongue, hard palate, throat ■ Inside each taste bud are 40 taste cells ■ Each taste cell has taste hairs that extend into taste pores
TASTE PROCESS
Taste buds pick up taste and send it to taste cells.
Taste cells send taste to taste hairs.
Taste hairs contain receptors that initiate an action potential which is carried to parietal lobe.
Brain processes taste.
TYPES OF TASTES
- Sweet
- Sour
- Salty
- Bitter
- Umami ■ Certain taste buds are more sensitive to certain tastes. ■ Taste is also linked to smell. PATHWAYS FOR THE SENSE OF TASTE
VISION
ACCESSORY STRUCTURES
■ Eyebrow:
- protects from sweat
- shade from sun ■ Eyelid/Eyelashes:
- protects from foreign objects
- lubricates by blinking
THE EYE AND ACCESSORY STRUTURES
■ Conjunctiva:
- thin membrane that covers inner surface of eyelid
■ Lacrimal apparatus:
- Lacrimal gland, nasolacrimal duct
- produces tears
■ Extrinsic eye muscles: (six)
- help move eyeball
- Superior, inferior, medial, and lateral rectus muscles.
- Superior and inferior oblique muscles.
Anatomy of Eye
■ Hollow, fluid filled sphere ■ Composed of 3 layers (tunics) ■ Divided into chambers
The Eye
The Retina
■ Macula:
- small spot near center of retina ■ Fovea centralis:
- center of macula
- where light is focused when looking directly at an object
- only cones
- ability to discriminate fine images ■ Optic disk:
- white spot medial to macula
- blood vessels enter eye and spread over retina
- axons exit as optic nerve
- no photoreceptors
- called BLIND SPOT
Chambers of the Eye
■ Anterior chamber:
- located between cornea and lens
- filled with aqueous humor(watery)
- aqueous humor helps maintain pressure, refracts light, and provide nutrients to inner surface of eye ■ Posterior chamber:
- located behind anterior chamber
- contains aqueous humor ■ Vitreous chamber:
- located in retina region
- filled with vitreous humor: jelly-like substance
- vitreous humor helps maintain pressure, holds lens and retina in place, refracts light
Functions of the Eye
■ The eye functions much like a camera. ■ The IRIS allows light into the eye, which is focused by the cornea, lens, and humors onto the retina. ■ The light striking the retina produces action potentials that are relayed to the brain. ■ Light refraction and image focusing are two important processes in establishing vision. ■ Light Refraction
Bending of light ■ Focal point:
point where light rays converge
occurs anterior to retina
object is inverted
FOCUSING IMAGES ON RETINA ■ Accommodation:
- lens becomes less rounded and image can be focused on retina
- enables eye to focus on images closer than 20 feet
Neuronal Pathway for Vision
■ Optic nerve:
- leaves eye and exits orbit through optic foramen to enter cranial cavity ■ Optic chiasm:
- where 2 optic nerves connect ■ Optic tracts:
- route of ganglion axons
Visual Defects
■ Myopia:
- nearsightedness
- image is in front of retina ■ Hyperopia:
- farsightedness
- image is behind retina ■ Presbyopia:
- lens becomes less elastic
- reading glasses required ■ Astigmatism:
- irregular curvature of lens
- glasses or contacts required to correct ■ Color Blindness:
- absence or deficient cones
- primarily in males ■ Glaucoma:
- increased pressure in eye
- can lead to blindness
■ When a person’s vision is tested, a chart is placed 20 feet from the eye, and the person is asked to read a line of letters that has been standardized for normal vision. ■ If the person can read that line, he or she has 20/ vision, which means that the person can see at 20 feet. ■ On the other hand, if the person can only read at 20 feet the line that people with normal vision see at 40 feet, the person’s eyesight is 20/40, and corrective lenses are probably needed.
The Ear
■ The organs of hearing and balance are located in the ears. ■ Each ear is divided into THREE AREAS:
- the external ear
- the middle ear
- the inner ear
The External Ear
■ Extends from outside of head to eardrum ■ Auricle:
- fleshy part on outside ■ External auditory canal:
- canal that leads to eardrum ■ Tympanic membrane:
- eardrum
- thin membrane that separates external and middle ear
The Middle Ear
■ Air filled chamber with ossicles ■ Malleus (hammer):
- bone attached to tympanic membrane ■ Incus (anvil):
- bone that connects malleus to stapes ■ Stapes (stirrup):
- bone located at base of oval window ■ Oval window:
- separates middle and inner ear ■ Eustachian or auditory tube:
- opens into pharynx
- equalizes air pressure between outside air and middle ear
The Inner Ear
■ Set of fluid filled chambers ■ Bony labyrinth:
tunnels filled with fluid
3 regions: cochlea, vestibule, semicircular canals ■ Membranous labyrinth:
inside bony labyrinth
filled with endolymph ■ Endolymph:
clear fluid in membranous labyrinth ■ Perilymph:
fluid between membranous and bony labyrinth ■ Cochlea:
snail-shell shaped structure
where hearing takes place ■ Scala vestibuli:
in cochlea
filled with perilymph ■ Scala tympani:
in cochlea
filled with perilymph ■ Cochlea duct:
in cochlea
filled with endolymph
■ Spiral organ(organ of Corti):
- in cochlear duct
- contains hair cells ■ Tectorial membrane:
- in cochlea
- vibrates against hair cells ■ Hair cells: attached to sensory neurons that when bent produce an action potential ■ Vestibular membrane:
- wall of membranous labyrinth that lines scala vestibuli ■ Basilar membrane:
- wall of membranous labyrinth that lines scala tympani
Hearing Process
- Sound travels in waves through air and is funneled into ear by auricle.
- Auricle through external auditory meatus to tympanic membrane.
- Tympanic membrane vibrates and sound is amplified by malleus, incus, stapes which transmit sound to oval window.
- Oval window produces waves in perilymph of cochlea.
- Vibrations of perilymph cause vestibular membrane and endolymph to vibrate.
- Endolymph cause displacement of basilar membrane.
- Movement of basilar membrane is detected by hair hairs in spiral organ.
- Hair cells become bent and cause action potential is created.
Balance (Equilibrium)
■ Static equilibrium:
- associated with vestibule
- evaluates position of head relative to gravity ■ Dynamic equilibrium:
- associated with semicircular canals
- evaluates changes in direction and rate of head movement
Balance
■ Vestibule:
- inner ear
- contains utricle and saccule ■ Maculae:
- specialized patches of epithelium in utricle and saccule surround by endolymph
- contain hair cells ■ Otoliths:
- gelatinous substance that moves in response to gravity
- attached to hair cell microvilli which initiate action potentials ■ Semicircular canals:
- dynamic equilibrium
- sense movement if any direction ■ Ampulla:
- base of semicircular canal ■ Crista ampullaris:
- in ampulla ■ Cupula:
- gelatinous mass
- contains microvilli
- float that is displaced by endolymph movement
Senses Notes AnaPhy
Course: Nursing (RLE70)
University: Capitol University
