Topic 11:

Sensory Receptors

 Part of the nervous system that detects a stimulus  A sensory receptor could be: o o o  Types of Sensory Receptors: o Chemoreceptors: detects chemicals ( ) o Photoreceptors: detects light (found in ) o Thermoreceptors: detects changes in . Bulb of Krause: sensitive to temperatures o Mechanoreceptors: detect movement ( ) . Meissner’s corpuscles: sensitive to . Pacinian corpuscles: sensitive to . Ruffini corpuscles: senses changes in o Pain receptors ( ): detects tissue damage o Osmoreceptors: detects changes in the

Sense of Touch:

o Tactile corpuscles: touch receptors found in the of skin and around hair follicles  Senses of pressure: located in tissues beneath the skin, near joints, muscles and other deep tissues  of Temperature: free endings found distributed within the skin o Separate receptors for hot and cold  Sense of Position o Propioceptors: receptors that maintain muscle tone and good posture in order to coordinate movements  Sense of Pain o o o

o

o

How Pain is Perceived

How to Manage Pain

 Endorphins: naturally released chemicals that impair the flow of pain signals  Aspirin: slows the production of pain signaling molecules  Morphine: mimics endorphins

Sense of Taste

 Taste: chemoreceptors that detect chemicals dissolved in fluid (tastebuds)  Five Main Flavors: o o o o o

Sense of Smell (Olfaction)

 Chemoreceptors that bind to specific substances  Olfactory nerve carries impulses from the smell receptors to the and  Vomeronasal organ: sensitive to

Sense of Sight

 Protected by: o o o o o  Structure of the o Outer layer: . : . :

o Middle layer: . :

. :

. Cilary body:

. :

o Inner layer: . :

. Aqueous humor:

. Vitreous humor:

.  Rods: receptors for

 Cones: receptors for

 Macula lutea: an area that contains the o Fovea centralis: largest concentration of cells that has the sharpest vision  : leads to , which in turn sends signals to the cortex

 How Photoreceptors Work o Rods: disks which consist of : a light absorbing pigment made up of (protein) and Retinal Vitamin A, which helps to manufacture pigments for the rods o Cones: three types that are sensitive to , and light  o Connect to photoreceptors to receive, process and integrate visual signals o Different neurons inside the brain respond to different visual patterns o Region where the optic nerve exists in the eye is known as the .

: the shape of the lens adjusts so that incoming light rays fall on the retina o Curvature of the lens determines the extent to which light rays will bend . Flat: focuses on objects . Rounder: focuses on objects

 Light Pathway  Light waves (bend) once they enter the eye.  Muscles of the adjust the pupil  Muscle adjusts the lens ( )  Light stimulates receptor cells of the  Optic nerve transmits impulses to the brain  lobe interprets the impulse

Disorders of the Eye

1. Hyperopia: (light focuses beyond the retina) 2. Myopia: (light focuses before the retina) 3. Astigmatism: irregular curvature of the 4. Strabismus: lack of eyeball coordination a. Convergent: eye deviates toward the b. Divergent: eye deviates 5. Conjunctivitis: infection of the 6. Cataract: cloudiness of the lens a. Surgery can remove the lens and implant an artificial one 7. Glaucoma: excess pressure of the a. Can lead to destruction of some optic nerve fibers 8. Retinal detachment: retina detaches from the layer 9. : deterioration of the central area of the

Sense of /Balance

 Structure of the : adapted to gather sound . Pinna: projecting from the side of the head that collects sound waves and directs them into the canal  : amplifies and transmits air waves to the . Ear drum ( ): vibrations transmit sound waves to middle ear . (bones)  Mallus 

 Inner ear: contains the . Vestibule: two bony chambers that contain receptors for

. : 3 projecting bony tubes containing cells which are stimulated by fluid movements in canals . : looks like a snail shell and contains 2 fluid filled compartments and receptors for  How do we hear?  : contains ciliated receptor cells inside the cochlea . Sound waves enter the and cause vibrations in the

. The , and transfer the vibrations to the . Vibrations of the oval window are transferred to the canal, which contains the organ of Corti . The organ of Corti contain hairs that transfer impulses to the nerve which then carries the impulse to the brain  How do we maintain balance?  Macula: mechanoreceptors in the vestibule detect movement in and planes  Cristae: mechanoreceptors in the semicircular canal detect and movement  : calcium carbonate granules found within special membranes that stimulate the hair cells to detect position  Disorders of the Ear  Otits Media: bacterial or viral infection of the ear  Externa: “swimmer’s ear” – an infection of the auditory canal caused by a fungus or bacterium  Conductive : results from the inability of sound waves to pass from the outer to the inner ear . May be a result of an obstruction within the or blockages of the or damage to the tympanic membrane . Otosclerosis: hereditary disorder which prevents the vibration of the stapes may also cause  Presbycusis: slow progressive hearing loss associated with age  : feeling of dizziness due to an inflammation of the bony labyrinth  : ringing, roaring, clicking or hissing sound in the due to: . . .

Sensory

 Phenomenon in which receptors adjust themselves to a continuous stimulus so that the sensation becomes less acute  Receptors adapt at different rates: o Receptors for temperature and pressure adapt rapidly o Receptors for pain do not adapt