Basic anatomy and physiology
Taste buds are located mainly on the tongue but are also on the palate, cheeks and epiglottis. The taste buds contain different cells responding to different tastes and are more dominant in certain areas. For instance, bitter taste is at the back of the tongue and salty taste is towards the tip. Other taste sensations are sweet, sour, and umami (meaty). The umami buds also pick up breast milk and mature cheese. The taste buds convert chemical stimuli into electrical waves which then go to the brain in the frontal lobe. There are many cranial nerves that are involved in taste. The 7th, the 9th and the 10th even the 5th cranial nerve (trigeminal) is involved as it serves sensation to the tongue.
The effects of smell
This is the first cranial nerve and any decrease in smell will effect taste. We saw this during COVID. With swallowing food vapours pass from the back of the nose to the smell fibres. Smell is essential for taste of for instance, chocolate, coffee and strawberries.
The causes of abnormal taste
Taste can be effected either permanently or temporarily. There are a number of causes for instance, medication (anti-depressants), decreased zinc, damage to the nerve which may occur in the ear or the mouth. After a head injury, the temporal bone may be fractured resulting in damage to the nerve of taste in the ear which will then lead to abnormal taste sensation. Other causes of abnormal taste as mentioned above, are a blocked nose and COVID viral infections. One can also get a dry mouth from certain auto-immune conditions and post radiotherapy which will obviously effect the taste perception. Damage to the taste nerves often give rise to a bland, metallic or even a putrid taste.