smell 3 Flashcards
what is anosmia
A condition that causes a person to partially or completely lose his or her sense of smell
Most commonly, anosmia is caused by:
The common cold, Influenza (flu), Sinus infections (acute sinusitis), Hay fever
There are other causes of anosmia, too. When the nasal passageways are obstructed in some way, the ability to smell can be affected.
In addition, the olfactory pathways, which send messages between the nasal passages and the brain, can become impaired from age and from certain medications. Also, certain medical conditions can dull or diminish the sense of smell.
how do molecules in the air give rise to electrical signals in olfactory neuron
Odorant Molecules Detection: odorants enter the nasal cavity, they dissolve in the mucus lining the nasal epithelium.
-Olfactory receptors detect specific odorant molecules. Each olfactory receptor neuron typically expresses only one type of olfactory receptor. Still, there are hundreds of different types of olfactory receptors in total, allowing for a wide range of odor detection.
- Binding of odorant molecules to their corresponding olfactory receptors activates a signaling cascade within the olfactory sensory neuron. This cascade involves the activation of G-proteins and the production of cyclic AMP (cAMP).
-The activation of the signaling cascade leads to the generation of an action potential, an electrical signal, in the olfactory sensory neuron.
-Action potentials travel along the axons of olfactory sensory neurons, which bundle together to form the olfactory nerve. These action potentials are then transmitted to the olfactory bulb
- In the olfactory bulb, the electrical signals from the olfactory sensory neurons are integrated and processed by various neurons. The processed information is then transmitted to higher brain regions, including the olfactory cortex, where odor perception and interpretation occur.
how is the sense of smell carried from the nasal mucosa to the cerebrum
Olfactory Receptor Neurons (ORNs): Each olfactory receptor neuron expresses a specific type of olfactory receptor protein, allowing it to detect particular odorant molecules.
Olfactory Nerve (Cranial Nerve I): The axons of olfactory receptor neurons bundle together to form the olfactory nerve. This nerve extends from the olfactory epithelium through the cribriform plate of the ethmoid bone and into the olfactory bulb of the brain.
Olfactory Bulb: The olfactory nerve fibers synapse in the olfactory bulb, which is located at the base of the brain. the incoming signals are processed and relayed to higher brain regions
Olfactory Tract: From the olfactory bulb, the processed olfactory information is transmitted via the olfactory tract, which extends from the olfactory bulb to several regions of the brain, including the primary olfactory cortex, the orbitofrontal cortex, and the amygdala.
Primary Olfactory Cortex: The primary olfactory cortex, located in the temporal lobe of the cerebrum, receives input from the olfactory tract. It plays a crucial role in processing and analyzing olfactory information, contributing to the perception of smell.
Secondary Olfactory Areas: In addition to the primary olfactory cortex, olfactory information is also transmitted to secondary olfactory areas in the brain, including the orbitofrontal cortex and the amygdala. These regions are involved in further processing olfactory information, associating it with emotions, memories, and other cognitive functions.
where along the olfactory pathway can pathology occur
