Sensory Receptors - detect environmental changes and trigger nerve impulses
Somatic Senses Touch, pressure, temperature, pain
Special Senses Smell, taste, vision, equilibrium
SENSES
Chemoreceptors – respond to chemical stimuli ex) coratid artery for carbon dioxide
Pain receptors – “nociceptor” usually reacts to tissue injury
Thermoreceptors – different nerve endings for cold & heat; cutaneous & mucosal
Mechanoreceptors – touch, pressure, sound, muscular contraction causing tension
Photoreceptors – rods & cones in the retina – used only in vision
Receptors and Sensations
Sensation = feeling that occurs when a brain interprets a sensory impulse
Projection = a connection between the cerebral cortex and other parts of the nervous system or organs of special sense.
Sensory adaptation = sensory receptors stop sending signals when they are repeatedly stimulated (does not apply to pain receptors)
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Sensations
Sensory Nerve Fibers epithelial tissue, pain and pressure
Meissner's corpuscles hairless areas of skin (lips, fingertips, tongue)
Pacinian corpuscles deep pressure (tendons, joints)
Temperature Senses warm and cold receptors
Nociceptors Sense pain
Somatic Senses
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Visceral Pain - occurs in visceral tissues such as heart, lungs, intestine
Referred pain - feels as though it is coming from a different part
Acute Pain - originates from skin, usually stops when stimulus stops
Chronic Pain - dull aching sensation
Sense of Pain
Inhibitors of Pain natural brain chemicals can be mimicked by
drugs such as morphine Serotonin Endorphins
Regulation of Pain
Smell = OLFACTORY ORGANS Taste = TASTE BUDS Hearing & Equilibrium = EARS Sight = EYES
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Special Senses
Olfactory organs contain olfactory receptors = “chemoreceptors”
Pathway Odor molecule enters nose Cilia on olfactory receptor cells sense the
chemicals Olfactory bulb – receptor cells synapse with
Mitral Cells Nerve impulse sent through the Olfactory Tract Limbic system in the brain “associates” or
processes the information9
Pathway of Smell Sensation
“Gustatory” sense Taste buds contain chemoreceptors
Around 10,000 Four Kinds of Papillae: Fungiform,
Filiform, Foliate, Circumvallate FIVE Tastes: Sweet, Sour, Salty,
Bitter, Umami MISCONCEPTION: different taste areas
on the tongue!11
Sense of Taste
Pathway of Taste Sensation Taste receptors in the papillae Sensation sent to cranial (facial) nerves Medulla Oblongata Thalamus Parietal Lobe of Cerebrum makes final
association
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Sense of Taste
External Ear Auricle (pinna) - outer ear External Auditory Meatus
Sense of Hearing
Middle Ear – Tympanic Cavity Tympanic membrane Auditory Ossicles
Malleus Incus Stapes
Eustachian (Pharyngotympanic) Tube
Sense of Hearing
Inner Ear Labyrinth - communicating chambers and
tubes Osseous Labyrinth and Membranous
Labyrinth Perilymph and Endolymph
fluids within the labyrinth
Semicircular Canals - sense of equilibrium Cochlea - sense of hearing Organ of Corti - contains hearing receptors,
hair cells detect vibrations
Sense of Hearing
Inside the cochlea are special neurons called HAIR CELLS
The stapes is attached to the OVAL WINDOW vibrations cause the perilymph to vibrate the hair cells here transmit this vibration
Therefore the HAIR CELLS in this region are RECEPTORS for hearing.
Inner Ear: Cochlea
Steps in Hearing
1. Sound waves enter external auditory meatus 2. Eardrum vibrates 3. Auditory ossicles (malleus, incus, stapes)
amplify vibrations 4. Stapes hits oval window and transmits
vibrations to cochlea 5. Organs of corti contain receptor cells (hair
cells) that deform from vibrations 6. Impulses sent to the vestibulocochlear nerve 7. Auditory cortex of the temporal lobe
interprets sensory impulses 8. Round window dissipates vibrations within
the cochlea
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
Sense of Equilibrium
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