badger anatomy & physiology - olfaction: sense of...
TRANSCRIPT
Olfaction: Sense of Smell
By: Olivia Deering, Erica Czosnyka, Taylor Craig, Lara
Anatomy of the Olfactory System:
-Big components are:
● Olfactory receptors
● Olfactory bulbs
Olfactory Receptors:
● Located in:- Olfactory mucosa- Region: olfactory epithelium
● Olfactory receptor cells- neurons with hair like projections (cilia)- These extend into a thick layer of mucosa of the olfactory epithelium
Olfactory Receptors:● Each olfactory neuron has:- One odor receptor- They are bipolar- Transmit olfactory info centrally
● Olfactory nerve:- Capable of regeneration- ^product new neurons - Rebuild function in CNS- Unmyelinated- Covered by schwann cells
Olfactory Bulbs:
● Part of the brain connected by nerves to the olfactory epithelium - Right above olfactory epithelium - Separated by bone called cribriform plates
Structures that make up the Olfactory System:
● Basal cells: - New stem cells where new olfactory cells develop- Capable of division...olfactory epithelium replaced every 2-4 weeks
Structures that make up the Olfactory System:
● Vestibules:- Forward section within and above each nostril- Nose has 2 cavities separated by a septum
Structures that make up the Olfactory System:
● Dendrites:- Project from nerve cells into nasal cavity-covered by thin layer of moisture- When moisture dissolves, it stimulates olfactory nerve cells
Structures that make up the Olfactory System:● Mitral Cells- Neurons that are apart of this system- Located in the olfactory bulb- Receive info from axons of olfactory receptor neurons, forming synapses
Structures that make up the Olfactory System:
● Neural Glial Cells (Sustentacular Cells)- Supporting cells- Metabolic and physical support- Have microvilli and webs- Nuclei of these cells are located in other- olfactory epithelial cells
Structures that make up the Olfactory System:● Bowman’s Glands- Secrete mucus- Immunoglobulins are secreted
here providing defense and enzymes that break down organic chemicals
● Nasal mucosa:- Allows olfactory receptor
neurons to have direct access to odorant molecules
Extra Important Info:
● Sinus cavities- Located: bony skull on both sides of nose
● Olfaction is a form of chemoreception- Chemicals activate olfactory system-odorants
Overview:
Physiology of smell:
-Begins nasal cavity (specific odor receptors found upper roof with cilia)
-Receptor sensibility (mechanics of airflow) is involved
-Odor dissolves on the mucous membrane on the cilia, this activates a G-Protein that releases calcium, AP is generated
-After sti, odor is destroyed
Interpretation:
- Brain interprets patterns in electric activity as odors- The only other chemical system that can identify, make sense of and memorize
is the immune system
- Associative learning
Pathway of Olfactory:1st pathway: Olfactory mucosa (nasal cavity)
- Lines upper and posterior parts of nasal cavity and olfactory nerve
- Fibers collect to form up to 20 bundles
Cells:
- Mitral Cells: neurons located in olfactory bulbs/ receive info from the axons of receptors forming synapses called glomeruli
- Granule/periglomerular: are formed off of mitral cells
Pathway of Olfactory:
2nd pathway: Olfactory bulb
- Oval structure that lies about cribriform plate
- Olfactory tract: nerve that synapses with the second order neurons and continues as another structure
- Olfactory receptor fibers synapse with neurons in the olfactory bulb (cranial nerve I)
- Impulses are interpreted in olfactory cortex- Glomerulus: cluster of nerve endings
The Olfactory Receptors:
Olfactory Receptors:
- Transduction occurs in receptors located on cilia at the ends of neurons
- Passive pathway: molecules reach olfactory mucosa from inhaled air
- Assisted pathway: molecules attach to an olfactory binding protein that transports them directly to receptors
Olfactory Receptors Extra Info:
- 10 - 100 million olfactory receptors contained within the olfactory epithelium- Olfactory epithelium lies in the superior part of each nostril- Olfactory membrane has a surface area of 2.4 square centimeters
Olfactory epithelium:
- Olfactory receptors- Sustentacular cells: structural support cell- Basal cells: stem cells capable of division of olfactory cells
How common are smell disorders?
❏ One to two percent of North Americans report problems with their sense of smell.
❏ In one study, nearly one-quarter of men ages 60–69 had a smell disorder, while about 11 percent of women in that age range reported a problem.
❏ Interactions with other senses:Many people who have smell disorders also notice problems with their sense of taste.
Smell Disorders : Hyposmia
❏ Reduced ability to detect odors.❏ Most common of nasal disorders❏ Causes: allergies, nasal polyps, viral infections and head
trauma❏ Treatment: treating the underlying cause of your
hyposmia is enough to treat the hyposmia.
Smell Disorders: Anosmia
● Anosmia is the complete inability to detect odors. In rare cases, someone may be born without a sense of smell.
● Up to 4 million people in the United States have hyposmia or anosmia.● Causes: Nasal congestion, nasal polyps, injury to the nose and smell
nerves, exposure to toxic chemicals, or old age.● Treatment: Decongestants may help to open up your nasal passages if it is just
congestion; however, if nasal polyps are the cause surgery may be needed.● Nasal polyps are small noncancerous growths in the nose and sinuses that
block the nasal passage.
Smell Disorders: Parosmia
● Parosmia is a change in the normal perception of odors a. Ex) when the smell of something familiar is distortedb. Ex) when something that normally smells pleasant now smells foul
● Causes: most as a result of upper respiratory tract infections and exposure to harmful solvents causing the damage to olfactory receptor neurons
● Treatment: symptoms decrease over time, people will not be affected for their lifetime
● Diagnosing: techniques are used to help deduce whether a specific case is attributed to just one stimulating odor or to a group of odors
Smell Disorders: Phantosmia
● The sensation of an odor that isn’t there● Can occur in one nostril or both● Causes: head injury or upper respiratory infection● Treatment:usually goes away on its own or when
illness associated with it resolves● Nasal saline drops or antidepressant medications may
be recommended
Works Cited
● https://www.utmb.edu/otoref/Grnds/smell-2012-01/smell-pic-2012-0130.pdf● https://www.nidcd.nih.gov/health/smell-disorders ● https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0025088/● https://www.kenhub.com/en/library/anatomy/the-olfactory-pathway● http://neuroscience.uth.tmc.edu/s2/chapter09.html ● http://ucalgary.ca/pip369/mod8/smell/pathways ● http://teachmeanatomy.info/head/cranial-nerves/olfactory-cni/ ● http://www.ablongman.com/html/psychplace_acts/olfaction/anatomy.html● https://www.britannica.com/science/nose#ref145153● http://teachmeanatomy.info/head/cranial-nerves/olfactory-cni/● http://flipper.diff.org/app/items/3370