EXP 18 – MODALITIES OF SOMATIC SENSATIONS
Sensory modalities requires specific receptors receptors and they are only present on a specific organ unlike the general somatosensory modalities. Some general somatosensory are touch, temperature, pressure, vibration, and stretch. CLASSIFICATION OF RECEPTORS BASED ON LOCATION ▪ Exteroceptor - Located at or near body surface - Provide information about external environment ▪ Interoceptor or V isceroceptors - Located in blood vessels, visceral organs, muscles, & nervous system - Provide information about internal environment - Impulses usually not consciously perceived ▪ Proprioceptor - Located in muscles, tendons, joints, inner ear - Provide information about body position, muscle length and tension, position and motion of joints, equilibrium CLASSIFICATION BASED ON TYPE OF STIMULUS DETECTED ▪ Mechanoreceptors – mechanical pressure, touch sensations, pressure, vibration ▪ Thermoreceptors – changes in temperature temperature ▪ Nocireceptors – physical/chemical damage to tissue (pain) ▪ Photoreceptors – detect light that strikes the retina ▪ Chemoreceptors – chemical in mouth (taste), nose (smell) and body fluids EXP 19 – ANATOMY OF THE EYE
Parts of the Eye
A. EXTRAOCULAR STRUCTURES Eyebrows – protects the eye from sweat Eyelashes – filtering particulate matters lodged in the eyes such as dust particles Eyelids – (superior and inferior palpebrae) covers the eye and protects eye from intense glare; wiper *Eyelids close starting from lateral cantus and then swipes the tears towards median cantus Lacrimal gland – found in the superolateral portion of the eye; it produces tears Lacrimal apparatus – lubricates and keeps it moist Palpebral fissure – slit where eyeball is found
Caruncle – found at the median cantus, fleshstructure at the midline *Superior and inferior to caruncle, there are two apertures: superior and inferior aperture of nasolacrimal apparatus Nasolacrimal sac – where secreted tears are drained and going down to nasolacrimal duct draining into inferior meatus in the nasal cavity
EXTRAOCULAR EXTRAOCULAR MUSCLES - Extraocular muscles are innervated by cranial nerve III (oculomotor nerve) includes levator palpebrae superioris - Orbicularis is innervated by cranial nerve VII - Insertion is at the lateral rectus and superior oblique
▪ Levator palpebrae superioris - elevates the superior eyelids - innervated by cranial nerve III (oculomotor) ▪ Superior rectus - pull eyeballs superomedially to the nasal side - innervated by cranial nerve III (oculomotor) ▪ Lateral rectus - moves the eye to the temporal side - deviates the eye laterally - innervated by cranial nerve VI (abducens) ▪ Medial rectus - deviates to nasal side - innervated by cranial nerve III (oculomotor) ▪ Inferior rectus - pull eyeballs inferomedially - innervated by cranial nerve III (oculomotor) ▪ Superior oblique - swings back to insert into the eye obliquely - moves the eye inferolaterally - innervated by cranial nerve IV (trochlear) ▪ Inferior oblique - when it contracts it moves the insertion towards the origin superolaterally - innervated by cranial nerve III (oculomotor)
B. Eyeball - Located in the orbital fossa, bordered by cranial bones and facial bones - Has three layers: I. Fibrous tunic – outermost layer a. Cornea – transparent portion b. Bulbar conjunctiva – continuous with palpebral conjunctiva c. Sclera – posterior part which can’t be seen II. Middle layer – has blood vessels a. Choroid – contains the blood vessels b. Uvea – anterior, vascular tunic – comprised of the: ▪ Iris – Iris – colored portion of eye; causes dilation & constriction of the pupil ▪ Ciliary body – forms aqueous humor ▪ Suspensory ligament – attached to the lens, causes accommodation accommodation ▪ Lens – transparent and elastic; refraction and focusing onto the retina III. Nervous layer – innermost layer a. Retina – third part of the eye wall; contains rods and cones; light rays are focused on it ▪ Optic disc – on the nasal side, area where optic nerve and retinal vessels enter ▪ Macula – area without any blood vessels where retinal vessels travelling temporally eventually converge – area of sharpest vision ▪ Fovea centralis – point in macula, only has cones, sharpest color vision
Anterior chamber – filled with aqueous humor Posterior chamber – filled with vitreous humor which is a gel-like substance
Visual Pathway ↓ Optic nerve ↓ Optic chiasm ↓Optic tract ↓ Superior colliculus ↓ Thalamus ↓ Optic radiation ↓ Visual cortex – occipital lobe
EXP 21 – OLFACTORY STRUCTURES
Olfactory sensation has very low threshold (parts per million) and has fast accommodation accommodation
A. Olfactory epithelium - is on the roof of nasal cavity; will have the: a. Olfactory neuron which has olfactory hair *Olfactory hair – apical modification like a cilla – Olfactory neuron is supported by sustentacular cells (supporting cells) and basilar cell which are like basal cell which mitotically divide Olfactory neuron is the receptor and synapses with olfactory nerve Olfactory nerve (dendrites) rises up and traverse and olfactory foramina On the cribriform plate, there is the olfactory bulb → olfactory tract (axon) → the olfactory cortex
EXP 22 – GUSTATORY STRUCTURES
Gustatory sensation or taste is subserve by the tongue Taste buds – chemoreceptor of gustation – seen in the lingual papilla – also located on the pharynx, palette, and lips
LINGUAL PAPILLA Circumvallate – junction of anterior 2/3 and posterior 1/3 of the tongue Fungiform – mushroom like structure, has taste buds which has gustatory neuron with gustatory hair Filiform – doesn’t have taste buds, triangular structure, enhance the taste because they can detect texture and temperature temperature Foliate – have taste buds embedded in their surfaces
I. Tympanic Membrane - is concaved externally hence when light is shone it produces cone of light which point to where the handle of malleus is attached to the ear drum II. Ossicles Malleus (Hammer) Incus (Anvil) Stapes (Stirrup) III. Windows Oval window – foot process of stapes is in contact with Round window – inferior to it IV. Mastoid air cells – above the middle ear, ceiling, used for sound resonance, lightens the weight of skull V. Auditory tube / Eustachian – equalizes the pressure of the middle ear and external ear – If it’s not equalized, the concave ear drum will be sucked out – it opens up to nasopharynx ∙
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CRANIAL NERVES THAT SUBSERVE GUSTATION Cranial nerve VII – anterior 2/3 of the tongue Cranial nerve IX – posterior 1/3 of the tongue Cranial nerve X – epiglottis
EXP 20 – ANATOMY OF THE EAR Ear – for hearing and balance
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C. Otic interna – inner ear – a cast of the middle ear – has bony and membranous labyrinth
A. Otic externa – outer ear – includes the pinna/auricle pinna/auricle to ear drum I. Pinna Helix – outermost fold Lobule – inferior to helix, for earrings Anti-helix – second fold Anti-tragus – terminal protrusion Tragus – can cover the meatus, opp of anti-tragus Umbo – depression External auditory meatus/canal Outer 1/3 – cartilaginous Inner 2/3 – bony ∙
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I. Vestibule – stapes steps on the oval window of the vestibule which also has round window II. Semicircular canal – supposed to detect position in a 3-dimnesional 3-dimnesional manner Anterior (Superior) Posterior Lateral III. Cochlea – is a fluid-filled, snail shaped cavern – translates sound into nerve impulses IV. Vestibulocochlear nerve ∙
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B. Otic media – middle – lateral wall is the tympanic membrane
