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• Sensory reception involves the structure and function of the human eye, ear, and other sensory receptors.

• The human eye consists of various parts such as the cornea, lens, retina, rods and cones, fovea centralis, pupil, iris, and optic nerve.

• The human ear consists of parts like the pinna, auditory canal, tympanum, ossicles, cochlea, organ of Corti, auditory nerve, semicircular canals, and Eustachian tube.

• Humans also sense their environment through olfactory receptors, taste receptors, and touch receptors.

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• Sensation occurs when neural impulses generated by sensory receptors reach the cerebral cortex.

• Perception of sensation varies among individuals based on how their cerebral cortex interprets the sensory information.

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• Sensory adaptation is the brain's ability to filter out redundant sensory information to prevent over-stimulation.

• Individuals with autism may have difficulties filtering out redundant sensory information, leading to increased sensitivity and overstimulation.

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• There are four general categories of sensory receptors: photoreceptors, chemoreceptors, mechanoreceptors, and thermoreceptors.

• Photoreceptors are stimulated by light, chemoreceptors by chemicals, mechanoreceptors by pressure, and thermoreceptors by heat/cold.

• Dysfunction of these receptors can result in the inability to perceive pain.

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• Vision is associated with the stimulation of photoreceptors in the retina by light energy.

• Rods and cones in the retina convert light energy into electrochemical impulses that the brain uses to form an image.

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• The eye has various parts such as the cornea, iris, lens, retina, optic nerve, ciliary muscles, aqueous humor, vitreous humor, sclera, choroid layer, fovea centralis, and blind spot.

• Light enters the eye through the cornea, and the iris controls the amount of light entering through the lens.

• The lens helps focus light on the retina, which contains rods and cones that relay sensory impulses to the occipital lobe of the brain.

• The size of the pupil is controlled by the ciliary muscles, and the aqueous humor and vitreous humor provide nutrients and maintain the shape of the eye.

• The sclera protects the eye, and the choroid layer contains blood vessels that nourish the retina.

• The fovea centralis has a high concentration of cones, while the blind spot does not contain rods or cones.

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• Myopia (nearsightedness) is the inability to see objects at a distance, caused by an elongated eyeball. Concave lenses can help focus light on the retina.

• Hyperopia (farsightedness) is the inability to see objects at close range, caused by a shortened eyeball. Convex lenses can help focus light on the retina.

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• The retina contains two types of light-sensitive cells: rods and cones.

• Rods detect low-intensity light and are responsible for black and white vision.

• Cones detect high-intensity light and are responsible for color vision.

• Rods contain a light-sensitive pigment called rhodopsin, which is a form of vitamin A.

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• Colorblindness is a genetic condition caused by a lack of specific cones or color receptors.

• Most color blind individuals lack cones that respond to red-green wavelengths, resulting in an inability to perceive those colors.

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• The development of the eye and brain structures is only partially complete at birth.

• The lens projects an upside-down image on the retina, and the brain re-inverts the image to perceive it as right-side-up.

• Newborns initially see the world upside down until their brain learns to interpret the information correctly.

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• Hearing is associated with small fluctuations in air pressure called sound waves.

• Mechanoreceptors in the inner ear convert sound waves into electrochemical impulses that the brain perceives as sound.

Page 67: Anatomy of the Outer/Middle Ear

• Sound waves are directed by pinna to the auditory canal

  • Sound waves strike the tympanum (eardrum), generating vibrations within the middle ear

• Vibrations of the tympanum are passed on and amplified by the three neighbouring ossicles (malleus, incus, and stapes)

• Vibrations are concentrated on the oval window, causing changes in pressure within the organs of the inner ear

Page 68: Anatomy of the Inner Ear

• Changes in pressure cause waves in the fluid of the semicircular canals

  • Semicircular canals maintain dynamic equilibrium (balance during movement) by triggering the movement of tiny hair cells

• Changes in pressure also stimulate the movement of hair cells within the cochlea (organ of Corti)

  • Generates an action potential within the auditory nerve

• Action potential is carried to the temporal lobes by the auditory nerve for processing and interpretation of sound information

• Cilia from the hair cells in the cochlea play a role in maintaining static equilibrium (balance when stationary)

• The Eustachian tube connects to the throat, allowing air pressure to equalize

Page 69: Hearing Loss

• Hearing loss may be caused by various factors

  • Birth defects: Improper development of hearing organs can lead to deafness (sometimes treated with cochlear implants)

  • Ear infections: Swelling of the middle ear can prevent sound waves from reaching the cochlea and cause permanent damage

  • Noise: Loud noises can damage hair cells in the cochlea or rupture the tympanic membrane

Page 70: Balance Disorders

• Balance disorders result from damage to the semicircular canals

  • Leakage of inner ear fluid after head injury or changes in air pressure can cause dizziness and nausea

  • Failure of canals to flex properly in response to a change in head position can cause dizziness (vertigo)

  • Increase in fluid volume can lead to ringing or buzzing and a feeling of fullness in the ear

Page 71: Chemoreception: Taste

• The tongue contains chemoreceptors for taste

• Impulses from taste buds travel to the parietal lobe for taste perception

• Five major types of taste receptors: sour, sweet, salty, bitter, umami

Page 72: Chemoreception: Smell

• Humans can distinguish between over 10,000 different odors

• Odor particles fit into specific chemoreceptors in the nasal cavity called olfactory cells

• Olfactory cells transmit signals to the olfactory bulb in the brain, leading to the sensation of smell

• Dogs have a larger olfactory bulb than humans, explaining their heightened sense of smell