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What is the role of the Cornea?
- Responsible for refraction
- Anterior Tunic of eye, continual with Sclera
- Na+ pump removes excess H2O
- Triggers blink Reflex
What is the role of the Iris?
- Regulates pupil diameter via constrictors (parasympathetic) and dialators (sympathetic)
- Occulomotor Nerve initiates Pupillary reflex
What is the role of the Aqueous Humor?
- Similar to Plasma
- Drains from Canal of Schlemm
- Disruption results in glucoma (excess fluid)
What is the role of the Retina?
Sensory Tunic arranged in Photoreceptors - Bipolar Cells - Innermost Ganglia - Optic Nerve
What are Cones?
- R G B sensing photoreceptors
What are Rods?
Black and White
What is Dark Adaptation?
- Rhodopsin that is continually produced is broken down in light (bleaching)
- When in the dark, Rhodopsin accumulates again ~30 minutes
What is Light Adaptation?
- Rhodopsin is broken down (bleached) in light
- Retinal Sensitivity decreases
- Retinal Neurons switch to cones ~ 60 sec
What is the visual Pathway?
- Photoreceptors - Bipolar Cells - Ganglia - Optic Nerve - fibres cross giving aspects from the other eye - Thalamus (sorts and sharpens information) - Primary Visual Cortex, Occipital Lobe (Processes basic contrast)
- Temporal and Parietal - What and Where?
What are the 3 sections of the ear?
- Outer Ear - Hearing
- Middle Ear - Hearing
- Inner Ear - Hearing and Equilirium
How is sound heard? (Processes/Locations)
- 1.Tympanic Membrane Vibrates
- 2. Auditory Ossicles Transmit and Amplify (Malleus, Incus, Staples) to the Oval Window of Cochlea
- 3. Upper Chamber (Scala Vestibuli) receives pressure waves in fluid medium
- 4. Cochlear Duct (Scala Media) transmits
- 5. Lower Chamber (Scala Tympani) transmits waves to Organ of Corti (hair cells)
- 6. Cilia move toward or away from basal body, opening mechanically gated ion channels
- 7. CNVIII transmits sound
How is frequency detected?
- 1.Location - Closer to Oval Window - High Frequencies, Further from Oval Window - Low Frequencies
- 2. Degree of stiffness/length
How is Pitch detected?
'Where' the hair cells vibrating are located
How is Loudness detected?
Different cell thresholds for the same frequency
How is Localisation detected?
Difference in loudness and timing
What is the difference between Conduction deafness and Sensoneural deafness?
Conduction impacts on conduction to middle ear while Sensoneural is damage to neural structures
What is Equilibrium?
Subconscious sense of movement with input from eyes, stretch receptors and vestibular apparatus
What is the Vestibular System?
- 2 membranous sacs, Saccule (up and down), Utricle (Side to Side) - House maculae
- 3 semicircular ducts - House Ampullae
What are the Macullae?
Hair cells with Kinocilium knob in a gelatinous otolithic membrane which bend according to gravity
What are the Ampullae?
Mounds of crista in semicircular canals with a tuft of vestibular hair. Movement of endolymph fluid deflects the ampulla
Where does the Vestibular system project to?
- Vestibular Nuclei in Brain stem
- Motor centres that control eye, neck, limb and trunk reflexes