OCT1172

What neurological structures are involved in experiencing/perceiving odour?

Chemoreceptors
Olfactory nerve (CN1)
Primary olfactory area

What neurological structures are involved in identifying/naming an odour and making a decision about the odour (good, bad, what it is)

Temporal lobe/association area
Frontal lobe/association area

What neurological structures are involved in emotional experience when smelling an odour?

Limbic system
Amygdala

What neurological structures are involved in connecting an odour to a memory?

Hippocampus

What neurological structures are involved in triggering a physiological/bodily response to a smell?

Hypothalamus - plays a key role in regulating the autonomic system

What are main functions of sense of smell?

Alert us to danger
Helps us to identify objects or people in environment
Stimulates memory
Stimulate emotion
Allows us to read other's emotions
Main contributor to taste

What are secondary functions of sense of smell?

Pheromones and sexual attraction
Detection of immunotypes
People more charitable when exposed to pleasant smells and aromas

What is top of nasal cavity lined with? What is within the lining?

Olfactory epithelium
There are mucosal cells within the olfactory epithelium

What extends from the olfactory epithelium?

Small neurons

Explain how the primary olfactory neurons reach the olfactory bulb

Around 40/50 neurons group together and pass through the cribiform plate of the ethmoid bone that separates the brain from the nasal cavity
These nerves make up cranial nerve one, projecting to the olfactory bulb

What bone separates the brain from nasal cavity

Ethmoid bone

What are embedded in mucus from the mucosal cells

Cilia

How are odorants picked up in the nasal cavity?

They get trapped by mucus, the cilia embedded in the mucus have chemoreceptors that pick up the odorants
This causes the neuron to fire, with the AP travelling towards the olfactory bulb through the olfactory nerves

Explain the 4 steps from odorant entering nasal cavity to projecting to olfactory cortex

1. Odorants bind to primary olfactory neurons, resulting in the depolarization of the cell
2. Signals transduced to the second-order neurons in the glomeruli of olfactory bulb. Primary olfactory neurons synapse with mitral and tufted cells
3. Periglomerular cells and granule cells from inhibitory synapses enhance contrast through lateral inhibition of mitral and tufted cells from adjacent glomeruli
4. Axons of mitral and tufted cells project to the olfactory cortex

What are the second order neurons of the olfactory pathway?

Mitral and tufted cells

Where does the synapse of first order and second order neurons occur in the olfactory pathway?

The glomeruli of the olfactory bulb

What is the function of periglomerular cells?

Mediate contact between glomeruli

What is the function of granule cells?

Mediate contact between two mitral or two tufted cells originating from different glomeruli
Receive input from cortical areas and modulate the afferent input to the olfactory system based on cortical input

What is the outcome of the function of granule cells?

Help you become habituated to smells, tell you that you don't need to focus too much on certain smells

What makes up the primary olfactory cortex?

Piriform area + part of amygdala

What structures make up the piriform area?

Uncus, entorhinal area, limen insulae

What is the orbitofrontal cortex responsible for?

Conscious awareness of odour
Cognitive decision making re: olfaction

What does the olfactory tract/bulb separate into?

Medial and lateral olfactory stria

Where do the olfactory tracts project?

1. Via medial olfactory stria to the contralateral olfactory bulb
2. Via the lateral olfactory stria to the primary olfactory cortex

Where do the connections from the olfactory areas go?

Orbitofrontal cortex
Hypothalamus
Hippocampus

Functions of the orbitofrontal cortex for smell?

Odor perception, discrimination, learning and attention
Information about the identity, reward value and response planning towards odours

Function of hypothalamus for smell?

Where smell may control autonomic and endocrine functions like hunger/nausea to food, thirst, body temperature, blood pressure, heart rate, sexual activity

Function of hippocampus/other limbic system structures for smell?

Smell impacts on motivation, emotion and memory

What is anosmia?

Loss of smell

What causes anosmia?

Head injury that causes sheering of nerves
Fracture of nasal cavity
Tumors/Cortex Damage
Congenital anosmia
Aging
Colds/sinus infection
Alzheimer's

What are the functional impacts of Anosmia?

Affects safety
Affects taste/desire to eat
Difficulty with personal hygiene
Mental health

Common way to screen for olfaction

Have 5-6 different scents
Test each nostril separately by having client occlude one at a time
Present substance with vision occluded
Have client take 2 sniffs, indicate if they smell anything at all and if so if they can indicate what they are smelling
Scoring: 0 if no smell, + if detect and identify, - if detect but not identify

What happens with loss of taste?

1. Lose ability to identify spoiled food
2. Decreases stimulation of saliva and swallowing, saliva is required to distribute tastants
3. Decreased food enjoyment - extreme forms can lead to malnutrition or overeating of certain things
4. Loss of memories and altered mood due to limbic connection

Where are taste receptors found?

Tongue, soft palate, pharynx, glottis and epiglottis

What are taste buds made of?

Taste cell receptors grouping together, typically 50-150 per bud

What are groups of taste buds called?

Papillae

How are taste cell receptors stimulated?

Chemically stimulated when liquidated food comes in contact with cells by entering pore of taste bud

What are the types of taste buds?

Circumvallate, foliate and fungiform

What are the basic tastes?

Sweet, sour, salty, bitter and umami

What other physical factors contribute to perception of flavour?

Temperature, texture, levels of acidity, smell

Other than physical attributes of food, what else can influence flavour/flavour perception?

Appearance of food, socialization, maturity of taste buds, degree of hunger, personal experience (cultural, genetic)

What is the Facial nerve responsible for in terms of taste?

Innervates taste buds on anterior 2/3 of tongue and palate
Believed to be involved in food selection

What is the Glossopharyngeal nerve responsible for in terms of taste?

Innervates taste buds on posterior 1/3 of tongue
Believed to play a role in reflexes and swallowing

What is the Vagus nerve responsible for in terms of taste?

Innervates pharynx, epiglottis and glottis
Believed to initiate reflexes that protect airway

What is ageusia?

Loss of taste

What is hypoageusia?

Hypersensitive taste

Who develops ageusia/hypoageusia?

Older adults, damage to cranial nerves, head injury, medications that can cause hypersensitivty, stroke affecting VPM nucleus of thalamus or primary gustatory cortex

How do clinicians test for gustation?

Test with 4 solutions to test sour, sweet, bitter and salt
1.Client protrudes tongue, apply cotton swab to remove saliva
2. Salt can be applied to all areas, sweet to side front of tongue, sour to side middle, bitter to side back
3. Water given to rinse out mouth between items

What are the steps of the conscious appreciation pathway of gustation?

Taste receptors > Cranial nerves VII, IX, X > gustatory nucleus > ventral posterior medial nucleus of thalamus > primary gustatory cortex

Steps of swallowing, salivation, gagging, digestion and respiration pathway?

Taste receptors > Cranial nerves VII, IX, X > gustatory nucleus >brainstem

Steps of pathway associated with desire to eat and control of eating

Taste receptors > Cranial nerves VII, IX, X > Gustatory nucleus > hypothalamus

Steps of pathway associated with taste and smell integration

Taste receptors > Cranial nerves VII, IX, X > gustatory nucleus > orbitofrontal cortex

What separates external ear from middle ear?

Tympanic membrane

How many auditory ossicles are there? What are their names?

3 ossicles
Malleus, incus, stapes

What does the bony labyrinth contain?

Perilymph

What does the membranous labyrinth contain?

Endolymph

Where are vestibular receptors located?

1. Ampulla of each semicircular canals: crista ampullaris
2. Utricle and saccules (together = maculae)

Where do CNVII and CNVIII enter the skull?

Through the internal acoustic meatus

What movements does the Utricle detect?

Movements such as head tilts to right or left and rapid lateral displacements (affects horizontal semicircular canal therefore called horizontal acceleration)

What movements does the Saccule detect?

Detect movements such as up and down (ex. being on an elevator) or head tilts forward/backward (vertical acceleration)

What is the function of aqueous humor?

Provide nutrition to the lens and back of cornea

Function of vitreous body?

A gelatinous mass of the eye posterior to the lens, filled with gel like substance called the vitreous humor.
Main function is to keep shape and integrity of the eye - keeps the eye sphere shaped and applies pressure to the retina to keep it pushed against the side of the eyeball

Functions of ciliary body

Produces and circulates fluid between cornea and iris, contains ciliary muscle that changes shape of lens

What happens when ciliary muscle is relaxed

The choroid acts like a spring, pulling back on the lens via the zonule/zonular fibers (part of suspensory ligament)
Causes lens to flatten

What happens when ciliary muscles of the eye contract

The choroid becomes stretched, which releases tension on the lens
Lens becomes thicker

How does the ciliary muscle change the diameter of the lens of the eye

Via the choroid and suspensory ligaments

What surfaces in the eye are involved in the refraction of light?

Cornea, aqueous fluid, vitreous humor, lens

Explain the fovea centralis

- A small pit within the macula lutea that has the highest concentration of cones
-Ideally fovea of both eyes focus on an object; bifoveal fixation
- No rods

Explain importance of macula lutea

Pigmented portion of the retina for central vision; concentration of both rods and cones
2nd highest concentration of cones; lowest concentration of rods

What is the optic disc

Region where axons from ganglion cells converge to form the optic nerve; lacks photoreceptors and is the "blind spot" in our FOV

Function of the optic nerve

Receives signals from the retina - relaying information to the primary visual cortex in the occipital lobes of the brain
- Can be involved in pathology like Glaucoma and Optic neuritis

Names of the two types of photoreceptor cells

Cones and Rods

What are the three types of cones and what colours do they detect?

L-type, detect red spectrum wavelengths
M type - detect green spectrum wavelengths
S type - detect blue spectrum wavelengths

Explain the function and location of the cone photoreceptors

Sensitive to colour due to containing iodopsin
Densely organized in the central portion of eye (fovea and macula)
Responsible for daytime vision
Allow for better resolution and visual acuity
Primarily a 1:1 connection with bipolar cells

Explain function and location of rod photoreceptors

Sensitive to light due to containing Rhodopsin
Found in peripheral retina; enable peripheral vision
Densely organized outside macula; concentration increases as distance from macula increases
Responsible for night time (scoptoptic) vision
Primarily 2:1 or 3:1 connection with bipolar cells

What area of eye has poor light sensitivity but excellent colour resolution?

Fovea

Another name for primary visual pathway

Retinogeniculate pathway

Steps of retinogeniculate pathway

1. Contralateral visual field projects onto the temporal or lateral portion of the retina. Ipsilateral visual field projects onto the nasal or medial portion of retina
2. Optic nerve carries all information from ipsilateral eye
3. Nasal retina fibers cross in optic chiasm
4. Optic tract contains fibers from contralateral visual field
5. Optic radiations are the projections from the lateral geniculate body to the primary visual cortex

What are the optic reflexes?

Accommodation, Pupillary light reflex, Pupillodilator Reflex, Corneal Blink reflex

What is the accommodation reflex?

Mechanism by which eyes adjust to enable visual focusing on nearby objects

What 3 processes are required to occur for the accommodation reflex?

1. Eyes must converge via activation of bilateral medial rectus muscles
2. Refractive power of lens increases; anterior-posterior diameter of lens increases via contraction of ciliary muscles and ciliary body
3. Pupils constrict via activation of constrictor pupillae muscles within the iris

What is the pupillodilator reflex

Sympathetic activation results in dilation of the pupil; occurs during a strong emotional response

What is the corneal blink reflex

If either cornea is touched, both eyes blink; protective blinking reflex that protects the cornea by contact with foreign objects; lubricates cornea to help remove foreign particles

What visual acuity would indicate legal blindness?

20/200 in best eye

What are top 3 tasks affected by decreased visual acuity?

Reading, writing/using technology for texting or computer use, driving

What can indicate someone has acuity deficits?

Squinting when looking at objects (squinting helps change shape of lens), adjust distance of objects from eyes to improve clarity, slowing navigating environment, giving up hobbies (reading, needlework)

What can an OT do for reduced visual acuity?

Make referrals, adapt activities (increase print, use magnifiers), adapt environment (reduce clutter, optimize lighting), optimize use of other sense, provide verbal cues

What is contrast sensitivity?

Ability to distinguish foreground from background/shades of colour

What would someone with difficulties with contrast sensitivity struggle?

Difficulty with depth perception (stairs), discriminating between objects in cluttered environment, driving

What can an OT do for issues with contrast sensitivity?

Optimize colour contrast in environment, optimize light sources; reduce glare

What is emmetropia?

Normal vision - no refractive errors. Light entering eye meets at focal point on retina and fovea, creating a clear and sharp image

What is ammetropia? What are the 3 kinds?

Vision with refractive errors, mismatch between axial length of eye and refractive power of the lens/cornea
3 kinds - myopia, hyperopia, astigmatism

What is myopia?

Near-sightedness, axial length of the globe of the eye is too long. Foveation occurs before retina

What is hyperopia?

Far-sightedness - axial length of eyeball is too long. Focal point occurs after retina

What is astigmatism?

Deviation of the lens shape from perfect sphere.

What is presbyopia?

Age-related changes which cause the lens to become harder and less elastic, making it difficult for eye to focus on close-up objects
Bifocals can help

What visual pathology is caused by proteins in lens breaking down and clumping together, with the clump causing cloudy areas on the lens?

Cataracts

What is glaucoma?

Group of eye conditions that damage the optic nerve. Damage often caused by abnormally high pressure in the eye. Characterized by a particular pattern of progressive damage to optic nerve that generally begins with a subtle loss of peripheral vision if left untreated as damage occurs on thinner areas of retina first which are the peripheral parts of eye

What can occur if glaucoma is left untreated?

Continuous pressure can eventually compress and kill the axons from the glial cells that are travelling from the eye

What can occur when macula lutea is damaged, causing central vision loss while peripheral vision remains unaffected?

Age-related macular degeneration