Mouth Watering Science

 Have you ever wondered why your mouth waters when you see a delicious dish or smell a mouthwatering aroma? Well, in this blog post, I will explain the science behind this phenomenon and how it is related to your appetite and digestion.

Saliva is a fluid that is produced by the salivary glands in your mouth. It has many functions, such as

• moistening your food.
• helping you swallow.
• protecting your teeth from decay.
•  aiding in digestion. 

Saliva also contains enzymes that break down starches and fats in your food.

Saliva on a baby's lips

But what triggers the production of saliva? And why does it increase when you see or smell something tasty?

The answer lies in the nervous system. There are two types of nerves that control salivation: the parasympathetic and the sympathetic. The parasympathetic nerves are responsible for stimulating salivation, while the sympathetic nerves inhibit it.

The parasympathetic nerves are activated by various stimuli, such as taste, touch, smell, sight, and even thought of food. These stimuli send signals to the salivatory nuclei in the brainstem, which then send signals to the salivary glands to secrete saliva.

The most powerful stimulus for salivation is sour taste. This is because sour foods stimulate the taste buds on the sides of the tongue, which have a direct connection to the salivatory nuclei. Sour foods can increase salivation up to eight times more than other tastes.

Another strong stimulus for salivation is smell. When you smell something appetizing, your brain activates the appetite centre in the hypothalamus, which then stimulates the salivatory nuclei. This is why you may drool when you smell your favourite food.

Sight and thought of food can also trigger salivation. This is because these stimuli activate the cerebral cortex, which is involved in memory and imagination. The cortex can recall the taste and texture of food and send signals to the hypothalamus and the salivatory nuclei. This is why you may salivate when you see a picture of a cake or think about a pizza.

Salivation can also be influenced by reflexes from the stomach. When you eat something spicy or irritating, your stomach sends signals to the brainstem to increase salivation. This is because saliva can help neutralize the acidity and protect the esophagus from damage. This is also why you may salivate more when you feel nauseous.

Salivation is not only a physiological response, but also a psychological one. It can be conditioned by learning and association. This was demonstrated by the famous experiment of Ivan Pavlov, a Russian physiologist who studied salivation in dogs.

Ivan Pavlov

Pavlov noticed that dogs would salivate when they saw food or heard a bell that signalled feeding time. He decided to test whether he could make them salivate without food or bell by pairing a neutral stimulus with food. He chose a light as the neutral stimulus and turned it on before giving food to the dogs. After several trials, he found that the dogs would salivate when they saw the light even without food.

This showed that salivation can be conditioned by associating a stimulus with food. The light became a conditioned stimulus that elicited a conditioned response of salivation. The food was an unconditioned stimulus that elicited an unconditioned response of salivation.

One of Pavlov's dogs with a surgically implanted cannula to measure salivation.

Salivation is an amazing process that involves many parts of your nervous system and helps you enjoy and digest your food. It can also be influenced by your emotions, memories, and expectations. So next time you feel your mouth water at the sight of tasty foods, remember that it is a sign of your appetite and curiosity.