Olfaction and Odor Signal Transduction

Specialized neurons located in the olfactory epithelium, responsible for detecting odorant molecules. They are bipolar neurons, meaning they have two extensions: one that receives signals from odorants and another that transmits signals to the brain.

Stem cells in the olfactory epithelium constantly regenerating olfactory receptor neurons, which have a short lifespan.

They support and nourish olfactory receptor neurons, ensuring proper function and a stable environment for signal transduction.

Located in the olfactory epithelium, they produce mucus that traps and dissolves odorant molecules, facilitating their detection by olfactory receptors.

The first relay station in the olfactory pathway. It receives signals from olfactory receptor neurons, where they synapse with mitral and tufted cells. It then transmits the signal to other brain regions.

A bundle of axons carrying signals from the olfactory bulb to various brain regions. This pathway includes the primary olfactory cortex, limbic system, and hypothalamus.

Located in the temporal lobe, it processes olfactory information and plays a key role in perceiving smells.

Includes structures such as the amygdala and hippocampus, responsible for the emotional and memory-related aspects of olfaction.

The influx of Na⁺ and Ca²⁺ ions into the olfactory receptor cell creates a change in its electrical potential, making it more positive. This electrical signal is called a depolarising generator potential.

Microscopic structures in the tongue, soft palate, and epiglottis that contain taste receptor cells.

Papillae located on the sides of the tongue, containing many taste buds.

Papillae on the tongue that do not contain taste buds but are involved in the perception of food's texture.

Mushroom-shaped papillae scattered across the tongue, each containing a few taste buds.

Large papillae at the back of the tongue, arranged in a V-shape, containing many taste buds.

The taste sensation associated with glutamate, often described as savory or meaty.

The taste sensation associated with acidic substances, detected by ion channels responsive to H⁺ ions.

Taste signals are transmitted through cranial nerves to the brain.

The binding of tastants to GPCRs activates intracellular pathways that lead to depolarisation and neurotransmitter release.

The clear, dome-shaped outer layer of the eye that helps focus light onto the retina. Think of it as the eye's protective window.

The opening in the center of the iris that controls the amount of light entering the eye. It can dilate (expand) in dim light and constrict (shrink) in bright light.

The transparent, flexible structure behind the pupil that focuses light onto the retina. It can change shape to adjust focus, a process called accommodation.

The innermost layer of the eye containing light-sensitive cells (rods and cones) that convert light into electrical signals.

Photoreceptor cells in the retina responsible for seeing in dim light and detecting shades of gray. They provide peripheral vision.

Photoreceptor cells in the retina responsible for detecting colour and providing sharp central vision in bright light.

The pathway that light travels through the eye, starting from the cornea and ending at the retina.

The process by which light energy is converted into electrical signals in the retina. It involves photopigments in rods and cones, which change shape in response to light.

A condition where the cornea (the clear front part of the eye) thins and bulges into a cone shape, causing distorted vision.

Damage to the blood vessels in the retina (the light-sensitive layer at the back of the eye), caused by high blood sugar levels over a long time. This can lead to vision loss.

A condition where increased pressure inside the eye (intraocular pressure) damages the optic nerve, which carries visual signals to the brain, leading to vision loss.

The outer part of the ear that includes the pinna (the visible part of the ear) and the ear canal, which funnels sound waves towards the eardrum.

The part of the ear located between the eardrum and the inner ear. It contains the ossicles (malleus, incus, and stapes), which are tiny bones that amplify sound vibrations and transmit them to the inner ear.

The innermost part of the ear, containing the cochlea, semicircular canals, saccule, and utricle. It's responsible for both hearing and balance.

A spiral-shaped organ inside the inner ear responsible for converting sound vibrations into electrical signals that the brain can understand.

Three fluid-filled loops in the inner ear that detect rotational movements of the head. Each semicircular canal has an ampulla containing a crista ampullaris that senses changes in head position.

The Facial nerve (VII) is responsible for relaying taste information from the anterior two-thirds of the tongue to the brain.

The primary olfactory cortex is located in the temporal lobe.

Ciliary muscles are located in the eye and regulate the shape of the lens.

The Organ of Corti, found within the cochlea, is responsible for detecting sound frequencies.

Filiform papillae, found on the surface of the tongue, are involved in texture perception, lacking taste buds.

G-protein coupled receptors (GPCRs) play a crucial role in taste perception by binding to molecules like bitter, sweet, and umami tastants, initiating a cascade of events that ultimately lead to the generation of a signal sent to the brain.

Phototransduction in rods and cones starts with light triggering a conformational change in the retinal molecule, activating opsin. This cascade of events reduces cGMP levels, causing sodium channels to close, hyperpolarizing the photoreceptor cell. This reduces glutamate release, altering the activity of bipolar cells and eventually generating an action potential in the ganglion cells.

The taste pathway involves the transmission of taste signals from the tongue to the brain via cranial nerves, allowing us to perceive different tastes.

Meniere's disease affects the inner ear, particularly the semicircular canals and the vestibule, which are responsible for maintaining balance and hearing. An excess of fluid in these structures can disrupt the hair cells (sensory receptors), causing the symptoms of dizziness, hearing loss, and ringing in the ears (tinnitus).

The inner ear plays a crucial role in maintaining balance. The semicircular canals are three fluid-filled loops that detect head movements. The vestibule, another part of the inner ear, helps with detecting gravity and linear acceleration. Dysfunction in these structures can lead to dizziness, a sensation of spinning or unsteady movement.

Medications, such as diuretics, can help reduce fluid buildup in the inner ear. Anti-vertigo medications can reduce the symptoms of dizziness. For severe cases, surgery may be considered to improve fluid drainage or to alter the structure of the inner ear.

Medications, such as beta-blockers and prostaglandin analogs, can help reduce eye pressure. Laser therapy can be used to improve fluid drainage from the eye. In severe cases, surgery may be necessary to create a new drainage pathway.