Olfaction: Sense of Smell – Physiology | Lecturio Nursing

Summary

This lecture introduces the special senses, focusing on the sense of smell (olfaction). The human nose contains millions of olfactory receptors located in the olfactory epithelium, which detect chemical odorants. The lecture explains the role of three types of cells in olfaction: olfactory receptor cells, supporting cells, and basal cells. It also covers how odorant molecules bind to receptors, leading to a series of chemical reactions and depolarization, which generates an action potential. This process sends signals to the brain for odor interpretation and emotional responses, involving areas like the temporal and frontal lobes.

Takeaways

• 👃 The special senses include smell, taste, vision, hearing, and equilibrium.
• 👃 Smell, or olfaction, is a chemical sense involving 10 to 100 million receptors in the olfactory epithelium.
• 👃 The olfactory epithelium is located in the superior nasal cavity, covering the cribriform plate of the ethmoid bone.
• 👃 Three types of cells are involved in olfaction: olfactory receptor cells, supporting cells, and basal cells.
• 👃 Olfactory receptor cells are first-order bipolar neurons that detect smells and send signals to the olfactory bulb.
• 👃 Supporting cells nourish olfactory receptor cells, while basal cells are stem cells that generate new olfactory cells.
• 👃 Olfactory glands, also called Bowman's glands, produce mucus that dissolves odor molecules for detection.
• 👃 Olfactory transduction occurs when an odorant binds to a receptor, triggering a chemical reaction that leads to depolarization.
• 👃 The signal from olfactory receptors travels through the olfactory nerve to the cerebral cortex for interpretation.
• 👃 Some olfactory signals reach the limbic system, which is responsible for emotional responses to certain odors, like happiness from smelling cookies.

Q & A

What are the five special senses discussed in the lecture?

The five special senses discussed in the lecture are smell, taste, vision, hearing, and equilibrium.

Where are olfactory receptors located in the human body?

Olfactory receptors are located in the olfactory epithelium, which is in the superior part of the nasal cavity.

What are the three types of cells responsible for olfaction?

The three types of cells responsible for olfaction are olfactory receptor cells, supporting cells, and basal cells.

What role do olfactory receptor cells play in the sense of smell?

Olfactory receptor cells are first-order bipolar neurons that detect odor molecules and send signals to the olfactory bulb for processing.

How do basal cells contribute to the olfactory system?

Basal cells are stem cells that can undergo mitosis to replace old and dead olfactory receptor cells.

What is the function of the olfactory glands (Bowman's glands)?

Olfactory glands produce mucus, which helps dissolve odor molecules (odorants) so that they can be transduced by olfactory receptor cells.

What happens during olfactory transduction?

Olfactory transduction occurs when an odorant binds to an olfactory receptor protein, triggering a chemical reaction that leads to the depolarization of the olfactory receptor cell.

How does the olfactory signal reach the brain for interpretation?

Olfactory signals travel via the olfactory nerve to the primary olfactory area of the cerebral cortex, where they are processed. Some signals also reach the limbic system, influencing emotional responses to odors.

What is the role of cyclic AMP (cAMP) in olfactory transduction?

Cyclic AMP (cAMP) is generated after odorant binding and opens cation channels in olfactory receptor cells, allowing sodium and calcium ions to enter, causing depolarization.

How do olfactory receptors contribute to odor identification and discrimination?

Each olfactory receptor responds to a specific set of odorants, and signals from different receptors are processed in the olfactory cortex to identify and discriminate between different odors.