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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