Olfaction and the Sense of Smell

Sensory neurons in the nose that detect odors.

Tissue lining the superior nasal cavity, containing olfactory receptors.

Enlarged ends of olfactory neurons' dendrites.

Chemical substances that stimulate the sense of smell.

Cilia embedded in mucus, receiving odorants.

The sense of smell, responsible for detecting odors in the environment.

It's found in the superior part of the nasal cavity, specifically in the olfactory region.

There are approximately 10 million olfactory neurons.

They are enlarged ends of the olfactory neurons' dendrites, which are specialized for receiving odorant molecules.

These are cilia (tiny hair-like projections) on olfactory neurons, embedded in mucus.

Odorants dissolve in mucus and bind to receptors on the olfactory hairs. This initiates a series of events that lead to depolarization and action potentials in the olfactory neurons.

A single olfactory receptor can respond to more than one type of odorant, allowing for complex scent perception.

Basal cells continuously replace the olfactory neurons, ensuring a constant supply of functional receptors.

There are approximately 1000 different odorant receptor molecules, each reacting to specific sizes, shapes, and functional groups of odorants.

Olfactory receptors utilize multiple intracellular pathways involving G proteins, adenylate cyclase, and ion channels.

Olfactory receptor cells are replaced every 2 months from basal cells in the olfactory epithelium.

Olfactory sensory neurons in the olfactory epithelium pass through the cribriform plate to the olfactory bulb, where they synapse with tufted and mitral cells. These cells project to the olfactory tract and synapse with association neurons, ultimately reaching the olfactory cortex.

Association neurons along the olfactory pathway receive input from the brain, modifying olfactory information before it reaches the cortex.

Olfactory information reaches the olfactory cortex in the frontal lobe without passing through the thalamus, unlike other major senses.

The olfactory cortex includes the piriform cortex, amygdala, and orbitofrontal cortex. These areas process olfactory information for perception, emotional response, and autonomic control.

The majority of neurons in the olfactory tracts project to the central olfactory cortex areas in the temporal and frontal lobes.

A cluster of taste receptor cells and supporting cells found in the tongue. Taste cells have microvilli called taste hairs that extend into taste pores.

The most numerous and filament-shaped papillae on the tongue. They lack taste buds and primarily function in texture sensation.

Large, circular papillae located at the back of the tongue, containing taste buds. There are only 8 to 12 of these.

Leaf-shaped papillae found on the sides of the tongue. They contain the most sensitive taste buds, but their number decreases with age.

Mushroom-shaped papillae that are scattered across the surface of the tongue, containing taste buds and appearing as small red dots.

Sensory cells within taste buds that detect taste molecules. They are replaced every 10 days.

Detected by taste receptors on the sides of the tongue. Sourness is triggered by acids.

Detected by taste receptors on the tip of the tongue. Triggered by sodium ions.

The five primary tastes: sweet, sour, salty, bitter, and umami.

Humans are most sensitive to bitter tastes, likely due to their association with potential toxins.

While all taste buds can detect all five tastes, they are usually more sensitive to one specific taste.

The pathway that carries taste information from taste buds to the brain.

The process of relaying taste information from the medulla oblongata to the thalamus and then to the taste areas in the cerebrum.

The regions in the cerebrum responsible for processing taste information.

The deep groove that separates the temporal and parietal lobes of the brain, where the taste areas are located.

The tough, white outer layer of the eye that maintains its shape, protects internal structures, and provides attachment points for muscles.

The transparent, dome-shaped front part of the eye that helps focus light entering the eye. It's avascular and continuous with the sclera.

The colored part of the eye, responsible for controlling the amount of light entering the pupil.

The black circular opening in the center of the iris that allows light to enter the eye.

A ring of muscle tissue surrounding the lens that controls its shape and produces aqueous humor.

The thin, pigmented layer of the eye that provides blood supply to the retina and absorbs scattered light.

The light-sensitive inner layer of the eye that converts light into electrical impulses that are sent to the brain for interpretation. Consists of two layers: pigmented and neural.

A transparent, biconvex structure that helps focus light onto the retina.

A small yellow spot on the retina, responsible for sharp, central vision.

A tiny pit within the macula, holding the highest concentration of photoreceptor cells, resulting in the sharpest vision.

A blind spot on the retina where the optic nerve leaves the eye, lacking photoreceptor cells.

The cornea is the transparent outer layer that helps focus light onto the retina.

The lens is a flexible, transparent structure that further focuses light, adjusting its shape for near and far vision.

The retina converts light into electrical signals that are then transmitted to the brain for interpretation.

The retina converts light into electrical signals that are then carried by the optic nerve, which connects to the brain.

The full range of electromagnetic radiation, including visible light, radio waves, and X-rays.