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Andisha

Conjuctival disorder

QuestionAnswer
What is the role of sensory cells? Allow conversion of chemical, electromagnetic and mechanical stimuli into action potentials
Describe the olfactory epithelium? Needed to smell total area of 5cm2 Covers superior nasal cavity and cribriform plate Contains 10-100million olfactory receptors cell
What is the process that allows us to smell? 1. Olfactory receptor cells (Bipolar neurons) detect inhaled chemicals 2. Synapse with olfactory bulb neurones in olfactory pathway 3. Conscious awareness of smell occurs in the primary olfactory area of the cerebral cortex
What causes emotional or memory-evoked responses? Axons of olfactory tract also project to the limbic system and hypothalamus - cause emotional and memory-evoked responses
How are we able to taste different things m, e.g sweet or salty? • Receptors are located in taste buds • Found on tongue, soft palate, larynx and epiglottis • Have around 10,000 – but declines with age • Receptor cells have a lifespan of about 10 days – replaced by differentiation of basal cells
What is the process whereby we can taste? • Conscious awareness of taste occurs in the primary gustatory area of the cerebral cortex •Some axons carrying taste signals also project to the limbic system and hypothalamus - cause emotional and memory-evoked responses
What is the orbital cavity? A Bony orbital cavity that protects eyes from injury Nerves & vessels transmitted through ‘spaces’ within the bone
What are the accessory organs for sight? Extrinsic Eye Muscles - Co-ordinate eye movements Eyebrows - Prevent sweat running into the eye Eyelids - Form the anterior protection for the eye The Lacrimal Apparatus - Lacrimal gland secretes lacrimal fluid (tears)
What are the extrinsic eye muscles ? Co-ordinate eye movements. Arise from bony walls of orbit & attach to the sclera ● Superior rectus ● Inferior rectus ● Medial rectus ● Lateral rectus ● Inferior oblique ● Superior oblique
What is the role of the eyelid and how is it specialised for this role? • Form the anterior protection for the eye • Blink frequently • Corneal reflex – eyelids close instantly if an object approaches or touches the eye • The eyelashes have a protective function • Lined by the conjunctiva
Describe the lacrimal apparatus? •Lacrimal gland secretes lacrimal fluid (tears) •Movement of tears across the eye assisted by blinking •Ultimately drains into nasolacrimal duct •Contains water, salts, mucus and lysozyme
What are the three layers of the eyeball & their components? 1. Outer fibrous coat •Sclera •Cornea 2. Middle vascular coat •Choroid •Ciliary body •Iris 3. Inner nervous coat •Retina
Describe the sclera? •Dense connective tissue •Provides shape and protection •Site of attachment of extrinsic muscles •Extends along optic nerve posteriorly
Describe the cornea? •Transparent •Curved to focus light •Avascular •Continuous with sclera
Describe the choroid? •Lines internal surface of sclera •Firmly attached in region of optic nerve •Dense capillary network – provide nutrients to retina •Dark brown (melanocytes) – absorbs stray light
Describe the ciliary body ? ontinuous with choroid Secretes aqueous humour Attached to the lens by zonular fibres (suspensory ligament) Contains smooth muscle Alters shape of lens – change focus
Describe the iris? •Suspended between the cornea and the lens •Attached to the ciliary process •Eye colour determined by levels of melanin in iris •Contains circular and radial smooth muscle Function: •Regulates amount of light entering eye
How does the iris control the amount of light entering the eye ? Pupils constrict as circular muscles of the iris contract (parasympathetic response)—response to bright light Pupils dilate as the radial muscles of the iris contract (sympathetic) — response to dim light
Describe the retina and its components? •Lines the choroid (posterior three quarters of eyeball) •Specialised light sensing cells •Rods •Cones ~Macula •Centre of posterior region of retina ~Fovea •Contains only cones •Point of most accurate vision ~Optic disc •Blind-spot
Describe rods and cones? Photosensitive pigments that concert light into nerve impulses. Cones are needed for colour vision and are more sensitive to bright light. Rods are needed for black& white vision and are more sensitive to low light.
What is the optic nerve? •Form at the optic disc •Leave orbital cavity through the optic foramen •Medial nerves cross in the optic chiasm
What are the contents of the eye? ➢Aqueous humour •Between lens & cornea. Secreted by ciliary body. Supplies nutrients to cornea & lens ➢Lens •Elastic, Suspended from ciliary body by suspensory ligament ➢Vitreous humour •Jelly-like, maintains shape of eye& Helps keep the retin
What is needed to allow vision ? ➢Intrinsic muscles •Focus lens •Alter diameter of iris (controlling ambient light) ➢Extrinsic muscles •Global movement of the eye ➢Retina •Contains light receptors (i.e. rods & cones) ➢Optic nerve •Relays information to sensory cortex of
Components of the external ear? ➢Pinna (auricle) •Upper elastic fibrocartilage •Lower adipose & connective tissue ➢External auditory canal •About 2.5cm long •Lies in temporal bone ➢Tympanic membrane (ear drum) •Fibrous tissue coated with epithelium
What is the middle ear? Small air filled cavity ➢Ossicles: 3 small bones (smallest in body). Joined by synovial joints ➢Connects with •Outer ear via the tympanic membrane •Inner ear via the oval and round windows •Eustachian tube
What are the components of the inner ear? Bony labyrinth •Series of cavities in temporal bone filled with perilymph Membranous Labyrinth •Series of epithelial sacs&tubes within the bony labyrinth filled with endolymph 1. Semi-circular canals Superior, lateral, posterior Balance + position
How are sound waves transmitted? Vibrations are transmitted through: •Tympanic membrane •The ossicles •The oval window •Into cochlea duct causing wave motion in the perilymph and endolymph
What is needed to convert mechanical to electrical signals? ➢ Frequency Basilar membrane fibres changes in length and stiffness – each section resonates at a different pitch ➢ Amplitude Louder sounds stimulate more hair cells to move
What is the vestibular apparatus? Utricle and saccule •contain macula •Provide information on position and detecting linear acceleration/deacceleration Three semi circular ducts •Contain ampullae •Detection of rotational acceleration/deacceleration Macula and ampullae contain
How is the vestibular apparatus used for equilibrium? Changes in head position Cause movement of perilymph and endolymph Leads to movement of hair cells ➢ Resultant nerve impulses transmitted by vestibular nerve ➢ Combined with input from eyes and receptors within joints and muscles
Created by: hifsah
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