Taste and Smell
Anatomy Atlases: Atlas of Microscopic Anatomy: Section Special Senses It is estimated that one vallate papilla of the tongue contains taste buds on its . the relationship of the tectorial membrane, which overlies the organ of Corti. Here we review this recent research on odor/taste integration, and propose a model of flavor processing that depends on prior experience with. Human cognition is rooted in the senses. Sight, hearing, taste, smell, touch all come together to equate to our perception of the world around us. Whether in a.
Separate senses with their own receptor organs, taste and smell are nonetheless intimately entwined.
This close relationship is most apparent in how we perceive the flavors of food. Actually, what is really being affected is the flavor of the food, or the combination of taste and smell. However, interactions between the senses of taste and smell enhance our perceptions of the foods we eat. Tastants, chemicals in foods, are detected by taste budsspecial structures embedded within small protuberances on the tongue called papillae.
Other taste buds are found in the back of the mouth and on the palate. Every person has between 5, and 10, taste buds. Each taste bud consists of 50 to specialized sensory cells, which are stimulated by tastants such as sugars, salts, or acids. When the sensory cells are stimulated, they cause signals to be transferred to the ends of nerve fibers, which send impulses along cranial nerves to taste regions in the brainstem.
From here, the impulses are relayed to the thalamus and on to a specific area of the cerebral cortexwhich makes us conscious of the perception of taste. Airborne odor molecules, called odorants, are detected by specialized sensory neurons located in a small patch of mucus membrane lining the roof of the nose.
Axons of these sensory cells pass through perforations in the overlying bone and enter two elongated olfactory bulbs lying against the underside of the frontal lobe of the brain.
The organ of vision is the eye; accessory structures include the eyelids, lacrimal glands, and the extrinsic eye muscles. The eye has been compared to a camera. Whereas structurally the two are similar, the camera lacks the intricate automatic control mechanism involved in vision.
As an optical instrument, the eye has four functional components: The protective coat is the tough, opaque sclera, which covers the posterior five sixths of the eyeball; it is continuous with the dura mater around the optic nerve. The anterior one sixth is covered by the transparent cornea, which belongs to the dioptric system.
The nourishing coat is made up of the vascular choroid, which supplies nutrients to the retina and, because of its rich content of melanocytes, acts as a light-absorbing layer. Anteriorly, this coat becomes the ciliary body and iris. The iris ends at a circular opening, the pupil.
The Atlas of Senses - Republic Nanu
The dioptric system includes the cornea, the lens, the aqueous humor within the anterior eye chamber, and the vitreous body. The dioptric system helps focus the image on the retina.
The greatest refraction of incoming light takes place at the air-cornea interface. The lens is supported by the suspensory ligament from the ciliary body see Plates andand changes in its shape permit change of focus.
This is a function of the ciliary muscle, which is supplied by the parasympathetic nervous system. In late middle age, the lens loses its elastic properties and a condition known as presbyopia results, wherein accommodative power is diminished, especially to near vision. The amount of light entering the eye is regulated by the size of the pupil. Pupillary size is controlled by the action of the constrictor and dilator smooth muscles of the iris.
The constrictor muscle is supplied by the parasympathetic nervous system, and the dilator by the sympathetic nervous system. The receptive integrating layer is the retina, which is an extension of the brain, to which it is connected by the optic nerve.
The rods and cones are the sensory retinal receptors see Plates to The rods are about 20 times as numerous as the cones. The rods and cones differ in their distribution along the retina. At all other points along the retina, rods greatly outnumber cones. Rods function best for peripheral vision and during dim light vision; cones function for central vision, during bright light vision, and in color discrimination. The outer segments of rods and cones contain the visual pigments, rhodopsin and iodopsin cone opsinrespectively.
Light falling on these pigments results in a series of chemical changes leading to depolarization of the receptor cell membrane receptor or generator potential and the formation of an action potential, which is then conducted to the brain.
Audition The organ of hearing the organ of Corti is located in the scala media cochlear duct of the inner ear and is separated from the underlying scala tympani by the basilar membrane see Plates and Sound waves reaching the tympanic membrane will initiate vibrations that are transmitted through the bony ossicles of the middle ear to the oval window. Vibrations of the oval window are transmitted to the perilymph in the scala vestibuli and across the vestibular membrane to the endolymph of the cochlear duct see Plate Such induced pulsations in the endolymph will displace the basilar membrane on which the organ of Corti lies see Plate and alter the relationship of the tectorial membrane, which overlies the organ of Corti, to the hairs of the hair cells.
Thus, bending or stretching of the hairs acts as a stimulus to the hair cells, causing release of a chemical neurotransmitter, generation of a receptor potential, and subsequent development of an action potential in the peripheral processes of bipolar neurons of the spiral ganglion see Plate The central processes of bipolar neurons constitute the auditory component of the eighth cranial nerve, which projects centrally to the cochlear nuclei.
Taste and Smell
In man, the cochlea and the organ of Corti follow a spiral course of two and one half turns. The lower turns are wider than the apical turns. It is believed that the hair cells in the lower turns respond best to high frequency sounds, whereas those of the upper turns respond best to low-frequency sounds.
Exposure to excessively loud sound as occurs in discos and around jet engines results in damage to hair cells in the lower turns of the cochlea high-tone deafness. Position and Movement Vestibular Sensations The receptor organ of posture and equilibrium is a composite one located in the semicircular canals, the utricle, and the saccule of the inner ear.
The utricle and saccule are located in the main cavity of the bony labyrinth, the vestibule; the semicircular canals, three in number, are extensions from the utricle. The dilated ends of the semicircular canals ampullae contain the cristae see Platewhich constitute the neurosensory epithelium that responds to changes in rotational or angular acceleration.
The apical processes of receptor cells are embedded in a dome-shaped, gelatinous protein- polysaccharide mass, the cupula see Plate The cupula swings from side to side in response to currents in the endolymph bathing it. Movement of the cupula bends or deforms the hairs of receptor cells embedded within it and thus modifies the rate of impulse discharge from these receptor cells.
Each crista is stimulated by movements occurring in the plane of its semicircular canal.Body Atlas #3 taste & Smell Sex & the food machine
The neuroepithelial component of the utricle and saccule macula; see Plate provides information regarding static equilibrium and position of the head in space. The macula is similar in structure to the crista of the semicircular canals. The apical processes of receptor cells in the macula project into a gelatinous mass, the otolithic membrane. It is flat and contains numerous small crystalline bodies, the otoliths or otoconia, composed of calcium carbonate and protein.
Gravitational pull acts on the otoconia on the surface of the macula, and the hair tufts of underlying neuroepithelial hair cells are thus stimulated.