taste buds are small sensory organs located on the tongue and other parts of the mouth that are responsible for detecting the five basic tastes sweet salty sour bitter and Umami each taste bud contains clusters of specialized cells called gustatory cells which have hairlike structures called microvilli that extend into the surrounding saliva these microvilli contain receptors that combine to specific molecules in food allowing the taste buds to detect different tastes when these receptors are stimulated by the presence of certain molecules they trigger electrical signals that are sent to the brain via gustatory nerves allowing us to perceive and differentiate between different flavors so Beginning by describing taste which is also known as gustation and taste is known as a chemical sense in that taste sensations arise from the interaction of molecules with taste receptors or taste buds to bind to our taste buds the molecules must be dissolved in saliva despite the large number of different molecules that exist taste is a relatively simple sensation with only five primary tastes able to be distinguished these are sour Sweet Bitter salty and Umami with Umami described as a meaty or a Savory flavor alongside those five tastes individually a taste sensation can also arise from a combination of the primary five tastes as well as olfaction or smell and from tactile or touch Sensations indeed Alf faction or our smell is much more sensitive than gustation and explains why when you have a cold or a suffering uffing from allergies you can often not taste your food The receptors for taste are located in taste buds most of our taste buds are located on the tongue but some are found on the soft palette which is the soft back part of the roof of your mouth the fenx which is your throat and the epig glotus which is the flap of cartilage that covers your tracha or your windpipe when you swallow so each taste bud consists of an oval body and three kinds of cells supporting cells gustatory receptor cells and basil cells the supporting cells provide structural support for the taste buds helping to maintain their shape and organization within the tongue and the mouth they play a role in maintaining the right chemical environment within tastebuds and are also capable of dividing and differentiating to replace damaged or dying gustatory cells around 50 gustatory receptor cells are present in each taste bot microvilli or little extensions project from each gustatory receptor cell to the external surface of the mouth through a taste pole which is just an opening of the taste bud the basil cells are stem cells which are found at the base of the taste bu and basil cells produce supporting cells which then develop into gustatory receptor cells each gustatory receptor has a lifespan of only about 10 days which is why the basil cells and the supporting cells are continually dividing and differentiating into the receptor cells it also explains why it doesn't take long to recover your taste after you've burnt or damaged your tongue on the the tongue taste buds are found on elevations called pil the pil act to increase the surface area of the tongue as well as provide a rough texture to make it easier for the tongue to move food around the oral cavity and so to show you what that looks like and here we have an illustration of a tongue you can see that the tongue is covered in pillo looking closer at the pill so if we're looking in this image here and the pill are just raised regions of the tongue which increase the surface area so increase the opportunity for the food molecules to actually interact with the taste buds and they also act to provide texture to the tongue so that you can grip your food and move it around your mouth the taste bud is this image here so it's an oval shape and it contains three different types of cells we have the basil cells which you can see down the bottom these will develop into supporting cells the supporting cells are these gray ones here so these provide structural support and a bit of protection to the gustatory receptor cells but then they can also divide and develop into our gustatory receptor cells to replace old receptor cells our gustatory receptor cell are these blue ones along here these contain microvilli or little extensions that come out of the taste pore so the taste pore is just this little hole to the external portion of the mouth or the tongue these microvilli are the parts that actually interact with the food molecules which are dissolved in the saliva so the food molecules that stimulate gustatory re receptors are called tastants once a tastant is dissolved in saliva it combind to receptors on the plasma membrane of the gustatory microvilli and it it's this that's the site of taste transduction or the conversion of the chemical signal into a neural or electrical signal upon binding of a tastant The receptors undergo a structural change what leads to the opening of ion channels in the cell membrane and this allows ions such as sodium potassium and calcium to flow into the cell a receptor potential to be generated and an action potential to travel along the sensory neuron the receptor Potentials in the gustatory receptor cells arise differently for the different tastings for example the sodium ions in salty food enter gustatory receptor cells via sodium channels in the plasma membrane and so it's this accumulation of sodium inside the cell that causes depolarization the hydrogen ions in sour tast also flow into the gustatory receptor cells via hydrogen channels and they cause depolarization but the tastant responsible for stimulating Sweet Bitter and Umami tastes do not actually enter the gustatory receptor cells themselves rather they bind to receptors in the plasma membrane these receptors are linked to G proteins the G proteins then activate several different chemicals known as secondary Messengers which are inside the receptor cell and then cause that receptor potential to be generated so they activate the taste buds indirectly following a receptor potential being generated in the taste bud A first order sensory neuron will be stimulated three cranial nerves carry Sensory neurons that innovate the tastebuds these are the facial nerve or cranial nerve 7even this carries nerve impulses from The Taste spods in the anterior 2/3 of the tongue the glosso faral nerve which innovates the posterior 1/3 of the tongue and then the vagus nerve or cranial nerve number 10 which carries nerve impulses from the taste buds in the throat and the epig glotus from these cranial nerves the nerve impulses travel to the gustatory nucleus in the medula of blong from the medula some axons carrying taste signals project to the lyic system some project to the hypothalamus and others project to the thalamus those that actually project to the thalamus and then our primary gustatory area are the ones that will give us conscious sensation of taste