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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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
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
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
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