Transcript of Chapter 40! The Mouth!
THE MOUTH Chemoreceptors are responsible for taste and smell by being sensitive to chemicals in food, liquids, and air Chemoreception is found universally in animals; it is thought to be the most primitive sense. In mammals, receptors for taste are in the mouth, and receptors for smell are in the nose. In amphibians, chemoreceptors are located in the nose, mouth, and all over the skin. Crustacea have chemoreceptors on their antennae and appendages. Insects, such as houseflies, taste with their feet. Chemoreceptors are present all over a planarian but concentrated in the auricles at the side of the head. Human taste buds are located primarily on the tongue, along the walls of papillae (the small elevations on surface of the tongue). Isolated ones are present on the surfaces of the hard palate, pharynx, and epiglottis. Taste buds are embedded in tongue epithelium and open at a taste pore, which have supporting cells and elongated taste cells that end in microvilli. Microvilli bear receptor proteins for certain chemicals. Molecules bind to receptor proteins and impulses are generated in associated sensory nerves. Nerve impulses go to the brain cortical areas which interpret them as tastes. Humans have four primary types of taste buds, which are each concentrated in particular regions: Sweet receptors are most plentiful near the tip of the tongue; Sour receptors occur primarily along the margins of the tongue; Salty receptors are most common on the tip and upper front portion; Bitter receptors are located near the back of the tongue. The brain appears to take an overall weighted average of taste messages as the perceived taste.Full transcript