Senses Flashcards
What comprises the outer layer of the eye?
Cornea and sclera
What is the cornea?
Transparent dome front surface
Protection and focus of light
What is the sclera?
Fibrous, white surface
Structural support and muscle attachment
What is the uvea?
The middle section of the eye comprising of the pupil, iris, ciliary body and choroid
What is the iris?
Coloured section surrounding pupil
Muscles control pupil size and how much light enters
What is the pupil?
Black centre
Changes shape using muscles in the iris to allow varying amounts of light in
What is the ciliary body?
Ring behind the iris
Muscles control the lens to adjust focus
What is the choroid?
Vascular layer supplying oxygen and nutrients
Absorbs excess light
What structures comprise the inner eye?
Retina, macula and optic nerve
What is the retina?
Thin tissue layer that lines the back of the eye
Abundant photoreceptors that convert light to chemical signals (rods and cones)
What are rods and cones?
Photoreceptor cells found in the retina
Rods detect in dim light and peripheral vision
Cones detect bright light and colour vision
What is the macula?
A small region on the retina with an abundance of cone photoreceptors for central vision and fine detail. The fovea area gives us the sharpest vision
How are electrical signals transmitted from the retina to the brain?
Via the optic nerve - optic chiasma - occipital lobe
What is the lens?
An auxiliary structure behind the iris that focuses light onto the retina. It’s shape is controlled by the ciliary muscles
What is humorus?
Fluid that maintains the shape of the eye and provides nutrients
Aqueous humour is in the front chamber
Vitreous humour is behind the lens
What is the sequence of events which turns light into ‘vision’?
Light enters eye via cornea
Light travels through the pupil (controlled by iris)
Light reaches the lens which changes shape (controlled by ciliary body) to focus on the retina
Light hits cones + rods in retina causing phototransduction to create an electrical signal
Optic nerve carries signal via chiasma to the occipital lobe
What is decussation?
When visual information crosses over at the optic chiasma
(Lateral vision does not cross over)
What is the purpose of taste?
Identify nutritious food
Respond to bodily demand
Recognise harmful food
Create memory to remember the above
Describe the structure of the tongue?
Skeletal muscle covered in mucus membrane
Surface covered in papillae which contain taste buds
Taste buds contain gustatory cells
What are the regions of the tongue?
Apex, body and root
What are the 5 tastes?
Sweet (detect sugar)
Sour (detect acid)
Salty (detect sodium and minerals)
Bitter (detect unpleasant)
Umami (savoury flavour linked to glutamate amino acid)
Describe the structure of the olfaction system?
Olfactory mucosa is covered in a mucus layer
Olfactory mucosa contains olfactory receptor cells with cilia that project into the mucus layer
Olfactory nerve carries electrical signals to the olfactory bulb and onto the brain
How does smell occur?
Odorous chemicals enter the nose and dissolve into the mucus layer
Olfactory cell cilia detect and are stimulated by these chemicals
An electrical signal is created and sent to the brain
What is anosmia?
Loss or altered sense of smell
What is ageusia?
Loss of taste
What is hypogeusia?
Reduced taste
What type of receptor detects touch?
Mechanoreceptor
What are meissners corpuscles?
Mechanoreceptors that detect fine touch, vibration and texture
Found in finger tip, lip and palm
What are Merkel cells?
Mechanoreceptors that detect light touch and shape
Found in finger tip and lip
What are pacinian corpuscles?
Mechanoreceptors that detect deep pressure and vibration
Found in deeper skin structures
What are Ruffini endings?
Mechanoreceptors that detect skin stretch, continuous pressure and body movements
Found throughout the skin
What are fine nerve endings?
Mechanoreceptors that detect pain and temperature
Found throughout the skin
Which area of the brain processes touch?
Somatosensory cortex
What is a dermatome?
An area of skin supplied by a single spinal nerve
What is hyposthesia?
Reduced or lost sense of sensory stimulus caused by peripheral nerve damage
What structures comprise the outer ear?
Pinna/auricle
Ear canal/external auditory meatus
What is the auricle?
The visible external ear
Collected sound waves
What is the external auditory meatus?
The ear canal
Carries and amplifies sound to the middle ear
Contains small hairs and glands
What structures comprise the middle ear?
Tympanic membrane
Ossicles
Eustachian tube
What is the tympanic membrane?
The ear drum
Cone shaped membrane separating the outer and middle ear
Vibrates when hit with sounds waves
What are ossicles?
The 3 middle ear bones: malleus, incus and stapes
Form a chain to amplify and transmit sound to inner ear
What is the Eustachian tube?
Narrow tube connecting middle ear to back of throat
Equalises middle ear pressure to external environment to ensure accurate sound
What is the oval window?
Membrane separates middle and inner ear
What structures comprise the inner ear?
Cochlea and organ of corti
What is the cochlea?
A spiral, fluid-filled structure that contains the organ of corti that converts sound into electrical signal
What is the organ of corti?
In the cochlea
Lined with lots of cilia
Fluid in the cochlea moves which stimulates the cilia and an electrical signal is created
Which nerve carries nerve impulses from the cochlea to the brain?
Auditory nerve
What is equilibrioception?
Balance
The ability to sense and maintain stability and orientation
Constant system of position detection - feedback - adjustment
Input from inner ear, eyes, musculoskeletal and brain
What is the vestibular system?
Located in inner ear
3 semicircular canals (anterior, posterior and horizontal)
Filled with fluid and lined with cilia
Detects head movement
What are the otolithic organs?
Utricle and saccule
Membranous sacs in vestibule that are lined with hair cells to detect linear acceleration, head position relative to gravity and head tilt
How do electrical signals get carried from the vestibular system to the brain?
Vestibular nerve
What is macular degeneration?
Thinning macular tissue or fluid leak in the retina
Progressive loss of central vision
What is glaucoma?
Impaired drainage of aqueous humour
High ocular pressure damages optic nerve
What is a cataract?
Proteins in the lens clump together creating cloudy patches
Interference of light occurs
What is diabetic retinopathy?
High blood sugars damage small blood vessels in the retina leading to damage
What is retinal detachment?
Retina separates from the underlying tissue
What optic issues would require transport to ED?
Penetrating injury
Sudden loss of vision
Cover and keep moist
What are the 3 types of hearing loss?
Conductive, sensorineural and mixed
What is conductive hearing loss?
Transmission of sound waves is disrupted before reaching inner ear
Result is reduced volume or clarity
Ear wax, fluid, abnormal anatomy
What is sensorineural hearing loss?
Damaged or dysfunctional cochlea or auditory nerve
Result is reduced volume AND clarity
Age, medication, noise damage
What is mixed hearing loss?
Has both conductive and sensorineural factors
Genetics, traumas or infection
What is industrial deafness?
Prolonged exposure to loud noise causes damage to cilia in inner ear
SX: progressive hearing loss, difficulty hearing speech in noisy areas, tinnitus and noise sensitivity
What is vertigo?
False sense of spinning/movement with dizziness and reduced balance
SX: spinning, dizzy, light head, N+V, unsteady
TX: mild to GP; severe to ED (consider prochlorperazine)
What is BPPV?
Benign paroxysmal positional vertigo
Calcium crystals (otoconia) dislodge from inner ear disrupting movement of fluid
What is Menieres Disease?
A build up of fluid in the ear creating vertigo, reduced hearing, tinnitus and pressure
What is vestibular migraine?
Migraine causing vertigo
Triggered by stress, food or hormones
What is labyrinthitis?
Infection causing an inflamed labyrinth
