Sensing the World - Chemical Senses

Olfaction

The sense of smell, where odorants interact with the epithelium in the nose, captured by mucus, and recognized by specific receptors in the cilia.

Taste

The detection of chemical compounds in the mouth by chemoreceptors on the tongue and roof of the mouth, leading to the perception of flavours.

Olfactory receptors

Receptors in the cilia that recognize and bind with odorants, activating sodium and calcium channels in neurons, causing action potentials to fire.

Shape-Pattern Theory

Theory that scent has a specific shape that activate (fit) a unique receptor in the epithelium. The various arrays produce firing patterns of neurons (in the olfactory bulb) that determine which scent we perceive.

Difference in Olfaction between humans and dogs

Dogs can detect up to 100x less concentrated odors as they have 100x more olfactory receptors.

Functions of the Nose

• To warm and humidify air going into the lungs (primary)

• Olfaction: Mucus in the epithelium captures odorants

3 types of Epithelium Cells

• Supporting cells

• Basal cells

• Olfactory sensory neurons (detectors of odours)

Odors

Key in detecting potential dangers and opportunities for food or social interactions.

What is Olfaction affected by?

• Gender

• Training

• Age

Olfactory Fatigue

Where smell detection stops during continuous exposure to odorant.

Flavour

The combination of taste (sweet, salty) and olfaction (smell) that contributes to the overall perception of food. This helps in identification of specific foods and food quality, and support learning associations between tastes and emotional events.

Taste buds

Structures containing taste receptor cells, specialized with microvilli and receptor proteins, detecting different tastes like sweet, salty, sour, and bitter.

Retronasal olfactory sensation

Perception of odorants while chewing and swallowing.

Outline the different types of taste receptor cell?

• Type 1: support function

• Type 2: detect bitter, sweet and umami

• Type 3: detect sour

Salt

A taste detected by animals, with high concentrations leading to dehydration, detected by ENaC (Sodium) channels.

Sour

Taste coming from acidic substances, which at high concentrations can cause damage.

Sweet

Taste evoked by sugars, detected by T1R receptors, initiating seeking behavior for food.

Bitter

Taste associated with potentially poisonous substances, like quinine, detected by T2R receptors, signaling harmfulness.

Taste-mediated behaviors

Responses to tastes that help in finding food, with sweet and salty tastes initiating seeking behaviour, while bitter tastes signal potentially poisonous food and sour tastes may indicate harmfulness.