Senses Flashcards
Explain how the middle ear is connected to the nasopharynx.
Via the eustachian tube
Outer Ear
Describe the main role of the tympanic membrane
- The tympanic membrane [eardrum] is a thin semi transparent partition between the external auditory canal and the middle ear.
- Its role is to transmit sound from the outer ear to the auditory ossicles.
- It converts sound waves into mechanical vibration carried across the bones of the middle ear.
Middle Ear
List the THREE ‘ossicles’ found in the middle ear.
We have Malleus, Incus and Stapes.
Middle Ear:
Explain the role of the ‘stapedius’.
Stapedias is a very small muscle that dampens large vibrations and is innovated by the facial nerve
Inner Ear
Describe specifically the structure of the inner ear.
The innner ear provides information on balance and hearing.
Outer Bony labyrinth that encloses an inner membranous labyrinth.
Bony labyrinth consists of a series of cavities in the temporal bone, divided into
- 3 semi circular canals for balance
- vestibule for balance
- Cochlea for hearing
Inner Ear
Explain how loud noises can affect the inner ear.
The inner ear contains epithelial cells lined with hair cells. These are called stereocilia.
Strong movement of fluid [which occurs from very loud noise] can kill hair cells
Inner Ear
TWO main functions of the inner ear.
balance and hearing
Inner Ear
Describe how ‘stereocilia’ trigger an electrical impulse.
Fluid movement [vibration] causes stereocilia movement and initiates an electrical impulse along cranial nerve #8.
Inner Ear
Name which cranial nerve provides sensory information for hearing and balance.
8. The vestibularcochlear
Describe in specific detail how external sound waves are perceived as ‘sound’ in the cerebrum of the brain.
Step 1: Soundwaves. Outer ear
1st we need the initial sound waves. They are collected by the auricle and directed down into the auditory canal where they hit the tympanic membrane
Step 2: Mechanical Vibration Middle ear
In the middle ear the tympanic membrane vibrates and creates this mechanical vibration across the three auditory ossicles – malleus, incus and stapes
Step 3: Fluid Waves Inner ear
We then get a fluid wave in the inner ear. the bending of the sterocilia creates a receptor potential generating an action potential.
Step 4: Nerve Impulse
Finally this leads to a nerve impulse via the vestibularcochlear nerve to the brainstem carrying info about hearing to the hearing area in the cerebrum
Describe the difference between ‘pitch’ and ‘volume’ of sound waves.
Pitch refers to the frequency of sound waves and is measured in Hertz. The higher the frequency of vibration the higher the pitch.
Volume refers to the amplitude of sound waves and is measured in Decibels
Identify the decibel rating above which can contribute to hearing loss.
140dB
Prolonged over 90dB can also lead to hearing loss
Explain the main function of white noise.
White noise is a constant noise that contains all the different frequencies of sound .
It is a background noise that the brain ignores is used to mask other sounds.
This is useful to enhance privacy, for sleep and to mask tinnitus
List TWO functions of the Eustachian tube.
Connects the middle ear to the nasopharynx which is the top of the pharynx.
- It equalises pressure between the middle ear and the atmosphere.Why do we need this? Is ascential that air can escape the middle ear otherwise damage could occur with pressure changes.. eg: if you yawn or swallow you can feel your ears pop and this is opening the tube
- It functions to drain mucus.
Explain why children are more prone to middle ear infections.
The eustachian tube is a common route for infection to spread. It is more horizontal in children which makes spread easier
Inner Ear
Describe the structure of the ‘otolithic’ membrane’.
A dense layer of calcium carbonate crystals that extends over and rests on the stereocilia. it helps with balance
List THREE ways in which the cerebellum can make postural adjustments to maintain balance.
- Vestibular feedback from the inner ear
- visual feedback from the eyes
- proprioceptors in the skeletal muscles, joints and surrounding ligaments
The three sources of information are coordinated and efferent impulses passed the cerebrum and skeletal muscles
Using definitions compare the following:
a. Otitis externa
b. Otitis media
c. Otitis interna -
a. Otitis externa - also known as swimmers ear. It’s an inflammation of the outer ear associated with a bacterial infection in 90% of cases, and fungal or allergic in the remaining cases.
b. Otitis media - inflammation of the middle ear. The most common cause of earache in children because of the horizontal nature of the eustachian tube
c. Otitis interna - a balance disorder associated with the inflammation of the membranous labyrinth of the inner ear.
Explain why insufficient earwax can predispose to ear infections.
Ear wax contains lysozymes and oil that create an acidic, lubricating coat. This inhibits bacterial and fungal growth.
On the other hand excess wax causing obstruction can also predispose to ear infections.
Name TWO pathologies that increase the risk of otitis externa.
Diabetes mellitus and HIV
TWO signs and / or symptoms of otitis externa.
- Pain (especially with movement of Pinna)
- Discharge [often purulent], swelling, itchy, red, swollen auditory canal
- Hearing deficit
Otitis Media
1. List TWO causes of otitis media.
2. Explain how the tympanic membrane appears in otitis media.
- Allergy
- Infectious organisms typically spread from the nasopharynx
- You can get bulging of the tympanic membrane
Secretory Ititis Media
- Describe how ‘secretory otitis media’ can result in hearing impairment.
- Explain how a ‘grommet’ can relieve secretory otitis media.
- The gluey fluid of glue ear dampens the tympanic membrane and ossicle vibrations which leads to hearing impairment.
- A grommet is a tiny pipe inserted into the ear drum under anaesthetic and fluid is drained, air circulates in the middle ear and hearing improves.
They typically fall out within 6 to 12 months and the whole usually hears heels
Otitus Interna
Describe TWO characteristic signs and / or symptoms of otitis interna.
- Sudden and severe a vertico that is not triggered by movement
- Sudden unilateral hearing loss
- Nausea and vomiting
- tinnitus
Using definitions, compare ‘Meniere’s disease’ and ‘tinnitus’
.
Menier’s disease is a disorder of the inner ear that is caused by a change in fluid volume in labyrinth and typically affects balance and hearing. Associated with progressive distension of the membrane’s labyrinth. Tinnitus is a sign/symptom of Menieres disease
Tinnitus is the perception of sound originating from within the head when no external sound source is present. Tinnitus can be caused by underlying health conditions such as Meniere’s disease.
Meniere’s disease
- List ONE autoimmune cause of Meniere’s disease.
- List TWO signs and / or symptoms of Meniere’s disease.
- Explain why a low salt diet is recommended in Meniere’s disease.
- RA and SLE
2.
* Vertigo
* Tinnitus
* Hearing loss
- Reduce fluid build up in the inner ear. Where there’s salt there’s fluid!
List TWO causes of:
a. Objective tinnitus
b. Subjective tinnitus
Redo answer. Have not defined subjective and have not given causes for subjective
a. Objective tinnitus
Pulsatile - rhythmic or pulsating sensations or sounds related to blood flow or pressure abnormalities in the arteries or heart valves.
Muscular (spasm of Tympanic muscles)
b. Subjective tinnitus
* Ear origin (Meniere’s, ear infection, wax)
* Neurological (head injury, MS, tumour)
* infections (meningitis)
* drug-related (NSAIDs, loop diuretics)
* TMJ (jaw) dysfunction.
Describe the key difference between ‘conductive’ and ‘sensory’ hearing impairment.
Conductive: hearing impairment refers to ear canal obstructions, optical abnormalities, ruptured tympanic membrane
Sensory: Poor hair cell function - can be due to a congenital condition, infection or noise trauma
List TWO viral causes of hearing impairment.
Measles, viral meningitis, mumps (auditory nerve damage), rubella.
Name the THREE layers of the eyeball.
- Outer fibrous Layer: Sclera and Cornea
- Middle vascular Layer: Uvea (the choroid, ciliary body and Iris)
- Inner nervous tissue layer: Retina
Describe the main role of the ‘iris’.
The iris controls the amount of light reaching the retina by adjusting pupil size
Describe how the following protect the eye:
a. Eyebrows
b. Eyelids / eyelashes
c. Blinking
d. Conjunctiva
a. Eyebrows – Stop sweat and dirt from getting in
b. Eyelids / eyelashes – protect the eye, spread secretions over the eye
c. Blinking – spreads tears, close for protection
d. Conjunctiva – Thin transparent mucous membrane lining the internal eyelids and anterior eyeball. Protects the cornea
Explain how tears play an important immune role.
They contain IgA and Lysozymes that protect the eye from infection
Name the cranial nerve that controls tear secretion.
Nerve no 6: Trigeminal Nerve
List THREE ways in which clear vision is achieved by the eyes.
Light must be focused on the retina. This involves
- Refraction (bending) of the light rays
- Accommodation - adjustment of the lens. This is the ability of the eye to switch focus, enabling clear vision of objects at different distances.
- Changing the size of pupils
Refraction:
Name ONE eye component that refracts most light rays.
Primarily the Cornea, but also the retina to a lesser extent.
The refraction of light rays helps to focus the image on the retina
Refraction:
Describe in detail the difference between:
(HINT: Think ciliary muscles»_space;>suspensory ligaments»_space;> what happens to the lens)
a. Greater refraction
b. Less refraction
The lens is able to change its refractive power. This is determined by the amount of pull the suspensory muscle places on the suspensory ligaments.
a. Greater refraction
When an object is close, the ciliary muscle contracts. This reduces suspensory ligament tension and the lens becomes more convex
b. Less refraction
when an object is far away, the ciliary muscle relaxes. This increases tension on the ligament and the lens becomes less convex – flattens the lens.
Describe how the pupil size is affected by:
a. Sympathetic nervous system
b. Parasympathetic nervous system
a.
Sympathetic stimulation, dilates the iris by contracting the radial muscles.
b.
Parasympathetic stimulation constricts the pupil by contracting, the circular muscles
Accomodation?
Explain why an individual may experience ‘double vision’.
It occurs when convergence is not complete and two images are sent to the brain.
Ordinarily there is convergence between the two eyeballs so that both are directed towards the object. Extra ocular muscles move the eyes in a coordinated way.
Accomodation?
Describe what is meant by ‘binocular vision’.
The ability to perceive a single, 3 dimensional image of the environment by integrating visual input from both eyes simultaneously. Two images from two eyes are fused in the cerebrum so that only one image is perceived.
The point of which the two images crossover in the brain is called the optic chiasma
Name the location where the optic nerve crosses over in the brain.
Optic Chiasma
Explain why a pituitary tumour can cause ‘tunnel vision’.
The Optic Chiasma, where the optic nerve crosses over in the brain, is located next to the pituitary gland. If the pituitary gland has a tumour it can interfere with the function of the optic chiasma leading to tunnel vision
Name one investigative tool that can be used to view the retina.
Opthalmoscope
Retina Question:
Name the location where the optic nerve exits the eyeball.
The optic disc
Retina Question:
List TWO layers of the retina.
A pigmented later or melanin-containing epithelial cells
A layer of photoreceptors - specialised visual cells. Two types, Rod cells and Cone cells.
Retina Question:
Describe THREE differences between ‘rod cells’ and ‘cone cells’.
Rod Vs Cone
120 million cells Vs 6 Million cells
1 type Vs 3 types - blue red and green
Provide black/White and grey scale Vs Provide colour vision
More plentiful at the periphery of the retina and not found in the fovea centralis Vs Found in the Fovea Centralis
Retina Question:
Describe TWO features of the ‘fovea centralis’.
Fovea centralis is a small depression in the centre of the Macula Lutea
- It contains only cone cells
- It is the area of highest visual acuity
(The macula lutea is a yellowish spot at the exact centre of the retina)
Retina Question:
State where you would expect to find ‘rod cells’ in the retina.
The periphery of the retina. Not in the Fovea Centralis
Retina Question:
Describe how light affects photo pigments.
A photo pigment is a transmembrane protein with the discs of both rod and cone cells. When light hits the photo pigment it changes shape initiating an action potential
Essentially – It is the conversion of light signals into electrical signals that the brain can interpret as vision.
State where Vitamin A is stored in the eye.
The pigmented layer
In the retina, vitamin A is in the form of retinal and binds to a protein called opsin to produce photoprint pigments
Retina Question:
Name the protein bound to Vitamin A in the eye.
Opsin
Retina Question:
List two food sources of:
a. Pre-formed vitamin A
b. Carotenoids
a. Pre-formed vitamin A
Liver
Eggs
b. Carotenoids
Leafy greens
Pumpkin, Carrots, Mango, Squash, sweet potato
Retina Question:
Explain why carotenoids are not considered to be toxic.
Because absorption is regulated unlike preformed Vitamin A
Retina Question:
Describe how the eyes adjust in the following situations:
a. Moving from dark to light sensitivity
b. Moving from light to dark sensitivity
a. Moving from dark to light sensitivity
Light Adaption: Quite quick. The visual system adapts in seconds by decreasing its sensitivity
b. Moving from light to dark sensitivity
Happen slowly over some minutes.
Retina Question:
Explain how quickly rod and cone cells regenerate.
Rods and cones must regenerate photo pigments. Cones regenerate within the first 8 minutes, rod cells take much longer.
Using definitions compare ‘blepharitis’ with a ‘stye’.
Blepharitis is an inflammation of the eyelid margin. It can be acute or chronic.
A stye is an inflammation of the sebaceous glands
Both are often related to staphylococcus
Using signs and / or symptoms, compare ‘blepharitis’ with a ‘stye’.
Blepharitis:
* Red eyelid margins
* Sore, gritty eyes
* Scales and flakes
* Can block sebaceous glands and cause recurrent styes
Styes:
Red, swollen lump usually on the upper eyelid.
Usually upper eyelid
List ONE endocrine pathology that increases the risk of styes.
Diabetes Mellitus
What is conjunctivitis and what are the signs and symptroms?
A highly contagious (not when an allergy) inflammation of the conjunctiva.
Presents as
- red eye, irritated and uncomfortable.
- watering eye
State TWO parts of the uvea affected in uveitis.
Refers to inflammation of any part of the uvea.
There are 3 parts so it could be the Iris, ciliary body or choroid.
List ONE viral cause of uveitis.
Herpes
Other causes:
- Fungus; parasites
- Autoimmune link to HLA-B27 and ankylosing spondylitis
- Trauma to eye such as contact lenses use and hygiene
Describe THREE characteristic signs and / or symptoms of uveitis.
- Progressive broad redness in the eye with pain
- Associated with blurred vision and reduced visual accuity
- Pain sensitivity to light (photophobia)
- Watery discharge
Explain why a corneal ulcer is a medical emergency.
Can lead to loss of sight
List ONE pathology that can cause ‘strabismus’.
Strabismus is a squint.
Pathology that damage cranial nerves 3, 4, and 6 would be implicated here – no 3, the oculomotor nerve supplying extra ocular muscles. Also 4, trochlear and 6, abducens.
If nerve on one side is damaged it leads to imbalance and can pull the eyes in our out.
Stroke, Brain tumour.
Describe the difference between a healthy lens and a lens affected by cataracts.
A healthy lens is transparent due to the regular arrangement of lens fibres.
In cataracts, new fibres are produced and become disorganised within cytoplasm and you get a silvery grey appearance to the lens.
The lens sits behind the iris.
List TWO causes (not age) of cataracts.
- Diabetes Mellitus more common
- Long term steroid use – through break down of proteins in connective tissue in the lens.
- Smoking
List TWO signs and/or symptoms of cataracts
- Gradual loss of vision
- Diplopia (double visions)
Define age related macular degeneration (AMD)
Macula is the central part of the retina where we get the highest visual acuity.
The age related changes occur in the macula.
Age is relevant and we see this typically in over 55’s
List TWO causes (not age) of AMD.
- Smoking
- Family History
- Cardio vascular disease risk factors
Describe how vision is affected in AMD.
- Reduced visual acuity, particularly difficulty with near vision.
- Gradual and progressive loss of central vision
Describe how an individual experiences ‘floaters’.
Very common.
The vitreous humor is a transparent, colorless, gel-like substance located in the posterior chamber of the eye.
Little fragments form of shrunken vitreous humor. Collagen fibres to create these more condensed structures which are not transparent.
These squiggly dark shapes create shadows in the retina when the light is incoming.
Explain why floaters develop in diabetic retinopathy.
Small quantities of bleeding in the retina
Identify the following pathology:
‘Floaters in vision, flashing lights, curtains descending over vision’.
Retinal Detachment
Explain how the pathology of Retinal Detachment develops.
The retina has 2 layers - the neuro sensory layer rod and cone layer and the pigmented epithelium. These become separated and fluid builds up in the sub retinal space.
It can lead to permanent blindness, so it is an emergency.
Describe specifically how glaucoma produces eye symptoms.
It is a condition where the pressure within the eyeball builds up.
Normal pressure is 10-21 mmHg. When it gets beyond 21 it starts to compress the retina and optic nerve, causing damage. > 40 it can cause significant damage and lead to blindness.
List ONE lifestyle factor that may cause glaucoma.
Smoking
List TWO signs and / or symptoms associated with:
a. Mild acute glaucoma:
b. Severe acute glaucoma
a. Mild acute glaucoma:
- Pain and maybe pressure in the eyes
- Halos around lights
- Symptoms alleviated by sleep when draining is improved.
b. Severe acute glaucoma
- Raid deterioration of vision
- Intense eye pain
- Redness and watering of eye
- Significant sensitivity to light/
List TWO signs/symptoms of late chronic glaucoma.
Often there are no symptoms until permanent damage has occurred. Then we might see:
- loss of peripheral vision
- blurring of objects directly in front of the person
- loss of night vision
Describe the pathophysiology of diabetic retinopathy.
Diabetes is associated with hyperglycaemia. Chronic Hyperglycaemia has been associated with many complications which are predominantly vascular.
Eg: High chronic levels of blood sugar can lead to damage of very small delicate blood vessels such as those in the retina leading to diabetic retinopathy.
- Microvascular damage occurs, which occludes branches of the retinal artery, causing neovascularisation (new vessel formation in an attempt to revascularise),
- The vessel walls become physically weak, and Leeky, leading to micro haemorrhages and micro aneurisms.
- The outcome is decline in vision and floaters
Name three eye pathologies that smoking is a risk factor.
- Cataracts
- Age-related Macular degenration
- Glaucoma
Name three eye pathologies and one hearing pathology where diabetes is a risk factor.
Cataracts
Styes
Diabetic retinopathy
Otitis Externa
Name the cranial nerve responsible for sense of smell.
Olfactory Nerve
Describe how decreased sensitivity to odours occurs rapidly.
Adaption
- Decreased sensitivity to odours occurs rapidly. Olfactory receptors adapt by 50% in first second. Odours seem 80% less powerful after a few minutes of exposure.
- Prevents smelling bad odours; e.g. working near a foul odour gets to the point where olfactory adaptation is 100%.
Explain the main function of ‘olfactory adaptation’.
To protect from danger — if the scent is not a danger, olfaction re-calibrates to be able to detect other smells which might indicate harm
Name the cranial nerve which innervates the tongue.
Hypoglossal Nerve innervates the 8 muscles on the tongue
Describe the role of the following in relation to taste buds:
a. Gustatory receptor cells
b. Basal cells
- Describe the role of the following in relation to taste buds:
a. Gustatory receptor cells - Detect taste
b. Basal cells - Stem cells that produce new receptor cells
Explain what is meant by ‘papillae’.
Elevations on the tongue where we find taste buds
Describe the difference between the following:
a. Circumvallate papillae
b. Fungiform papillae
c. Foliate papillae
Describe the difference between the following:
a. Circumvallate papillae – Large in the shape of a V at the back of the tongue.
b. Fungiform papillae – Mushroom shaped and all over the tongue. Contain at least 5 taste buds each.
c. Foliate papillae - Located in small trenches at lateral margins of tongue; most degenerate in childhood. Used for tasting milk as babies.
Name FIVE tastes.
Sweet, sour, salty, umami and bitter
Name TWO cranial nerves involved in taste physiology.
Facial
Glossopharyngeal
Name TWO cranial nerves involved in
tongue sensation and touch
Trigeminal
Glossopharyngeal
