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40 Cards in this Set
- Front
- Back
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What are the 3 types of encapsulated and non-encapsulated receptors? Which as rapidly adaptive (RA) and which are slowly adaptive (SA)?
Which 2 are superficial (*)? |
Encapsulated:
- Meissner's * (RA) - Pacinian (SA) - Ruffini (SA) Non-Encapsulated: - Merkel axon terminals * (RA) - Hair cell receptors - Bare/Naked/Free Nerve endings |
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Generally speaking, what type of sensory nerve fiber will have tactile, low threshold mechanoreceptors?
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All the encapsulated fibers and hair cell receptors will carry tactile information using low threshold mechano receptors.
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What types of sensory nerve fibers will carry nocioception and temperature?
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Non-encapsulated, naked nerve endings (Bare & Merkel)
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What can you say about the distribution of nerve fibers in relation to their field size?
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The smaller the field size the denser the distribution of the nerves. Thus areas with ++ dense nerves (hand, mouth genitals) will have very good discrimination.
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What type of fiber (in a mixed motor/sensory nerve) would fire the fastest?
Put the remaining 3 types of fibers in order of descending conduction speed. |
Aa or Type I fibers have the biggest diameter and fire the fastest (carry the stretch reflex)
II (AB), III (Ad) and IV (C) <-- only unmyelinated type, gamma fibers that tighten muscle spindles, detect nocioception in sensory fibers. |
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How has the nervous system encoded each of the following:
1. Intensity 2. Location of stimulus 3. Modality (ie touch, temp, etc) 4. Quality (ie warm & smooth) |
1. Intensity - frequency of AP's
2. Location of stimulus - receptive field that an axon is coming from 3. Modality (ie touch, temp, etc) - type of axon (each axon carries only 1 modality) 4. Quality (ie warm & smooth) - population of axons that are firing |
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Define each vision condition and list the type of lens required:
Emmetropia Myopia Hypermetropia Astigmatism |
Emmetropia - normal; no lens needed
Myopia - rays focus in front of retina (nearsighted). Nee Concave lenses Hypermetropia - rays focus behind the lens (farsighted) need convex lens Astigmatism - rays do not focus on fovea, need a bent lens to redirect the rays |
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What are the contents of the anterior segment of the eye?
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cornea
sclera anterior chamber Iris (& pupil) Ciliary body Lens |
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Identify the structures
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The sclera is a white collagenous structure that surrounds the eye. What covers it? What is it perforated by?
Function (2)? |
The sclera is covered by the cornea and episclera. It is perforated posteriorly by the optic nerve, at the lamina cribosa.
Functions: 1. insertion of extraocular muscles 2. blocks extraneous light from entering the globe |
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The conjuNctiva is a modified ______ that covers the ______. It is a very vascular tissue with 2 functions:
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The conjunctiva is a modified mucous membrane that covers the SCLERA. It is a very vascular tissue with 2 functions:
- PROTECTS THE GLOBE - PRODUCES PART OF TEAR FILM * conjuctiva = nonkeratinized, stratified squamous columnar epithelium w/goblet cells |
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What is the episclera?
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A vascular plexus between the conjunctiva and the sclera. It has 2 layers of vessels; superficial and deep.
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What 3 things make the cornea clear? What nerve supplies it's sensation?
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Cornea is clear because:
1. Avascular 2. uniform strucuture 3. Has ATP pumps in the endothelium (deep to Descemet's Membrane) that keep it dehydrated Nerve supply: Ophthalmic division of Trigeminal nerve (V1). |
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What are the 5 layers of the cornea?
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1. Epithelium - nonkerat stratified squamous, acts as a barrier & can regenerate
2. Bownman's membrane 3. Stroma: >90% of total thickness, orderly array of collagen, will not regenerate 4. Desecemet's Membrane 5. Edothelium: monolayer; contain ATP pumps to keep cornea dehydrated |
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Which is opaque, the cornea or the sclera? Why (i.e. what makes it opaque?)
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The sclera is opaque and the cornea is clear. This is b/c the sclera has coarse & irregular collagen while the cornea has fine & regularly arranged collagen.
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What is the innervation of the Iris constrictor muscles? Dilators?
What is the NT for each? |
Spincter muscle constrictors: parasympathetics, CN III, Cholinergics
Iris dilator muscles: Sympathetics, adrenergics |
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Have a good look at this picture and note the layers of things
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The cilliary body is a ring-like structure located behind the iris. It is very vascular. What are it's 2 functions?
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Cilliary body functions:
1. production of aqueous humor (from the 2-layered epithelium which nourishes avascular structures (cornea/lens) 2. Accomodation of lens - contraction makes lens round and allows it to focus on near things |
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Where is aqueous humor made, how does it circulate and where is it drained?
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Aqueous humor is made by the cilliary body. It circulates from the posterior chamber, through the pupil to the anterior chamber. It is then drained by the trabecular meshwork --> canal of Schlem --> episcleral venous vessels --> systemic veins
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What is the angle of the eye (ie what structures form it & what does it do?)
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The angle is formed where the Iris meets the Cornea.Fluid drains here through the trabecular meshwork (if obstructed - get Glaucoma and rising intraocular pressure).
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The "near triad" allows you to see things close-up. What does this triad involve?
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1. Lens accomodation - makes it round to converge the rays of light
2. Eyes converge to keep the near object centered on the fovea 3. Pupils constrict to decrease spherical abberation |
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What are the 3 main types of cataracts? What conditions are associated with the last 2 causes?
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1. Cortical
2. Nuclear sclerosis - aging 3. Posterior subcapsular - steroids, diabetes |
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What are the 4 components of the posterior segment?
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1. Vitreous
2. Retina 3. Choroid 4. Optic Nerve |
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The Retina has 10 layers. The inner-most of which is called the retinal pigment epithelium (RPE). What are 2 functions of the RPE?
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1. forms the blood-brain barrier
2. Supports metabolism of photoreceptors. Sits on top of the ++ vascular choroid and is impenetrable to light! |
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What is the function of the choroid?
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The choroid supplies the outer retina with much of its metabolic requirements (esp. important b/c centre of the fovea is avascular)
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What is found in each of the following holes:
- optic foramen - superior orbital fissure - inferior orbital fissure |
- optic foramen: (in sphenoid bone) optic nerve and ophthalmic artery
- superior orbital fissure: (between G & L wings of sphenoid) contains CN III, IV, V1, VI & vessels - inferior orbital fissure: sympathetics & vessels |
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What nerve and muscle are responsible for:
- lid closure - lid opening |
Lid closure
-orbicularis oculi; CN VII Lid opening: - Levator palpebrae superiorus; CN III - Mullers muscle; sympathetics |
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List the 3 layers of the tear film from the corneal epithelium outwards. For each layer list the origin and function.
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1. Mucin layer - conjuctival goblet cells; aids in adherence to cornea
2. Aqueous layer: accessory lacrimal glands; forms the bulk of tear film 3. Lipid layer: meibomian gland on lid margin; reduces tear evaporation |
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Which gland is responsible for producing reflex secretions in response to irritation, emotion or bright light?
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The lacrimal gland ( innervated by CN II)
* the accessory gland provides basal secretions |
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For each of the following muscles list it's CN and action (movement):
Lateral Rectus Medial Rectus Superior Rectus Inferior Rectus Inferior oblique Superior oblique |
LR - aBduction; CN 6
MR - aDduction; CN 3 SR - elevation; CN 3 IR - depression; CN3 IO - down & in; CN 3 SO - Up & in; CN 6 |
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What is the effect of a CN 3 palsy? CN 2?
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CN 3 palsy:
- diplopia - ptosis - dilated pupil CN2: - decrease acuity, loss of color vision and visual field defects |
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What is the difference in a CN IV and a CN VI palsy?
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They both will cause diplopia but with a CN 4 the eye will be down and out and with CN 6 the eye will have medial deviation.
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What would be the signs of a CN V and VII lesion?
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CN V:
Corneal anaesthesia (leading to ulcers) CNVII: - Ptosis (failure of lid closure) - tearing on face - ulceration d/t inability to protect the eye |
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Review the production, circulation and drainage of aqueous humor.
What is Schwalbe's line? Schlemm's canal? Anterior chamber depth is important!! < 20 deg = narrow!! |
Schwalbe's line: found on the interior surface of the cornea, and delineates the outer limit of the corneal endothelium layer (termination of Descemet's membrane).
Schlemm's canal: in front of scleral spur, encircles the eye and drains humor to ciliary veins. |
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List the muscles and nerves involved in the pupillary light response.
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1. Iris spincter muscle (smooth ring-shaped & flat) is supplied by parasympathetics, and it constricts the iris (miosis - opiods)
2. Iris dilator muscle, extend to 0,3mm of the pupillary border and is supplied by sympathetics (mydriasis - cholinergics) |
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The ciliary body consists of what 2 things?
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smooth muscle fibers which give rise to the lens zonules and ciliary processes which secrete the aqueous humor.
anterior portion = par plicata posterior portion = pars plana |
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Moving towards the vitrous humor, what are the 4 layers of the choroid?
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Suprachoroid
vascular layer & Chorio capillaries Brush's membrane |
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Moving towards the inside of the eye (vitrous humor) what are the 3 layers of the outer retina? What is it's blood supply?
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RPE - sticks to Bruch's membrane
Rods & cones - Outer plexiform layer - axons of R & C that synapse with dendrites of bipolar cells Blood supply is the choriocapillaries (under the RPE) |
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Moving from the middle of retina to the vitrous humor what are the 4 layers of the inner retina? What is it's blood supply?
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1. Inner nuclear layer - cell bodies (of bipolar, horizontal & amacrine cells)
2. Inner plexiform layer - synapses of bipolar, amacrine and ganglion cells 3. Ganglion cell layer 4. Nerve fiber layer (no myelin!) Blood supply = Central retinal artery & vein |
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What is the blood supply to the optic nerve?
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short posterior ciliary arteries & central retinal artery
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