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Block 12 > Week 5 Ear + Eye > Flashcards

Week 5 Ear + Eye Flashcards

1
Q

3 inputs to Postural System

A
  1. Somatosensory.
  2. Visual.
  3. Vestibular (Otolith, semicircular canals).
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2
Q

Ventromedial Pathway

Controls posture

A
  1. Vestibulospinal
  2. Tectospinal
  3. Pontine Reticulospinal
  4. Medullary reticulospinal

all 4 input on VENTRAL horn of spinal cord.

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3
Q

Vestibulospinal and Tectospinal Tracts

A

Functions: Keep head balanced when body in motion.
1. Vestibulospinal:
Sensory input from vestibular labyrinth (inner ear).
Tracts originate from vestibular nuclei in medulla.
2. Tectospinal:
Sensory input from retina.
Tracts originate from superior colliculus.
Directs head and eyes to particular location.

vestibulospinal also maintains upright posture via extensor motor neurons of leg.

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4
Q

Pontine and Medullary Reticulospinal Tracts

A
  1. Pontine Reticulospinal:
    Enhances antigravity reflexes of spinal cord.
    Faciliate extension of lower limbs and maintains standing posture against gravity.
  2. Medullary Reticulospinal:
    Liberates antigravity musles (opposite of pontine).

Arise from reticular formation.
Controlled by Cerebellum and Cortex.

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5
Q

Outer Ear

Anatomy and Function

A

Pinna (Auricle).
External Auitory Meatus (Ear canal).
Tympanum (Eardrum).

Function: Converts acoustic energy into kinetic energy.

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6
Q

Pinna/Auricle

Visible part of Ear

Function

A

Funnels sound into ear canal.
Aids in vertical localisation of sounds (filters only sounds capable of being heard(20-20000hz))

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7
Q

External Auditory Meatus

Anatomy and Function

A

Sigmoid canal.
7mm Width, 25mm length.
Runs until Tympanum.
Proximal 2/3 surrounded by bone vs cartilage.
Hair/sebaceous/ceruminous glands in cartilaginous 1/3.

Cerumen = ear wax

Function: Focuses sound on eardrum. Amplifies sound corresponding to human speech (10-15dB).

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8
Q

Tympanic Membrane

Eardrum

A

Collagenous membrane.
Separates outer and middle ear.
Made up of 4 parts:
1. Umbo (most depressed part of concavity).
2. Malleus (attached to medial tympanic surface).
3. Pars flaccida.
4. Pars tensa

Function: Vibrates in response to sound pressure waves thus, trnsmits sound energy to middle ear.

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9
Q

Middle Ear

A

Air filled chamber.
3 smallest bones in body (OSSICLES) connect eardrum to oval window.

Function: Convert kinetic energy to hydraulic energy in inner ear.

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10
Q

Ossicles

A

Malleus.
Incus.
Stapes (foot part sits in oval window).

Function: Ampify/leverage sound, 20x.

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11
Q

Eustachain Tube

A

Connection between middle ear and nasopharynx.
Typically closed, can be opened by lowering and protruding the mandible (yawning/chewing).

function: equalizes pressure between middle ear and external ear. Prevents damage to tympanic membrane.

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12
Q

Middle Ear Muscles

A
  1. Tensor Tympani: Attaches to malleus.
  2. Stapedius: Attaches to stapes.

Contraction results in decreased mobility of ossicles therefore dampens hearing.
Muscles are contracted in response to high intensity sound or during vocalisation (Acousitc Reflex).
1. (O = Auditory tube)(Sup. Tympanic Artery)(Medial pterygoid nerve of mandibular)
2. (O=pyramidal eminence)(Stapedial branch of posterior auricle)(Facial nerve)

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13
Q

Inner Ear

A

Labyrinth made up of Vestibular system (balance) and Cochlea (hearing).
Converts kinetic energy of ossicles into hydraulic energy of fluid in inner ear and then into electrochemical signals in CN8.
Cochlea uses movement of fluid to sense external pressure changes (sound).

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14
Q

Inner Ear Anatomy

A

Bony Labyrinth: Surrounds petrous part of temporal bone.
Membranous labyrinth: System of tubes and chambers filled with ENDOLYMPH (fluid w/ high K+ conc). Sits within Bony labyrinth.

Between bony and membranous labyrinth, there is PERILYMPH (high Na+ conc).

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15
Q

Cochlea

A

2.75 turns around bony column (modiolus).
3 components:
1. Scala Media (Cochlar duct); filled with endolymph.
2. Scala Vestibuli (above media); filled with perilymph.
3. Scala Tympani (beflow media); filled with perilymph.

Reissner membrane separates scala vestibuli and media.
Basilar membrane separates scala media and tympni.
Organ of Corti: converts fluid movement into nerve signals is found within basilar membrane.

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16
Q

Organ of Corti

A

Located in Cochlear duct (Scala Media, filled w/ endolymph).
Contains 20,000 auditory receptors each with its own hair cell.
Displacement of Basilar membrane causes shear of hair cells, opening non-selective ion channels, leading to depolarization.

17
Q

Cochlear Hair Cells

A

Displacement of STEREOCILIA towards KINOCILIUM stimulates hair cell.
Displacement away from Kinocilium inhibits hair cell.
Inner hair cells sends signal to brain via spiral ganglion and CN8.

Loud noise can cause irreversible damage to hair cell.

18
Q

Auditory Pathway

A

Information from CN8 travels via SLIM:
- Superior Olivary Complex
- Lateral Lemniscus
- Inferior Colliculus
- Medial geniculate Nucleus (in thalamus)

Before going to auditory cortex.
Decussaation occurs b/t cochlear nuclei and superior olivary complex and at inferior colliculi.

19
Q

Auditory Cortex

A

Located on TEMPORAL LOBE.
Brodmann areas 41/42.

20
Q

Sound localization

A

Medial SON (Sup. Olivary Nuclei) detects difference in timing.
Lateral SON detects differences in intensity.

High Fz (>1600 Hz) occurs by LSON.
Low Fz ( <800 Hz) occurs by MSON.

21
Q

Hearing Loss

2 types

A

Conductive: problem conducting sound waves through outer ear, eardrum, or middle ear.

Sensorineural: problem in the cochlea, organ of corti, CN8.

22
Q

Anatomy of the Eye

3 Layers

A
  1. Fibrous Layer
    - Cornea
    - Sclera
  2. Vascular Layer
    - Iris
    - Ciliary Body
    - Choroid
  3. Neural Layer

Fovea: region of highest resolution.
Centre of retina = Macula.

Cornea: Front part of te eye
Sclera: White of the eye, site of muscle attachment

Iris: cirular structure w/ pupil in the middle.
Ciliary body: ciliary muscle + ciliary processes. Muscles attach to the eye (changing lens shape), processes produce aqueous humor.
Choroid: layer of connective tissue + vessels.

23
Q

Structure of Eye ball

Chambers + Fluid

A

Vitreous humour fills the space between lens and retina.
Aqueous humour is between Cornea and lens (ant. chamber) and iris and ciliary process (post. chamber).

Aqueous humour is drained via trabecular meshwork, at base of cornea.

24
Q

Blood Supply of the Eye

A

Ophthalmic Artery.

Sup. & Inf. Ophthalmic veins.

Internal carotid > Ophtalmic Art.
Veins drain into cavernous sinus.

25
Q

Innervation of the Eye

A

Sight = Optic Nerve.
Miosis (pupil constrction) + lens = Short Ciliary Nerve.
Mydriasis (dilation) = Long Ciliary Nerve.
CN 3,4,6 = Eye movements.
CN5 V1= eyeball, upper eyelid, nose ridge sensation.

LR6, SO4

Ophthalmic N > Nasociliary N > Long ciliary N. (sympathetic)
Edinger westphal nucleus > CN3 > Ciliary ganglion > Short ciliary N. (paraSympathetic)

26
Q

Accommodation Reflex

A

Purpose: to focus on nearby objects.
Near vision = Thick lens.
Parasympathetic control.

3 Components:
Pupil constricton.
Lens accommodation.
Convergence.

27
Q

Pathophysiology of Cataracts

A

Lens is composed of specialized proteins called CRYSTALLINS, which are dependent on 3D structure and hydration. Membrane channel proteins maintain osomotic and ionic balance across the lens. Protein-bound Sulfhydryl (SH) groups of crystallins are protected against oxidation and cross-linking by high concentrations of reduced GLUTATHIONE (mother of all anti oxidants). Aging leads to increased oxidative stress, leads to breakdown and aggregation of protein.

Tx: Surgery; replace cloudy lens with artifical lens.

Risk factors:
Age
Trauma
UVB light
Genetics

28
Q

Pathophysiology of Glaucoma

A

Raised intra ocular pressure (Nr=12-22mm Hg).

Increased resistance to aqueous humour outflor through the trabecular meshwork. Typically via obstruction.

Tx: beta blockers, A2 agonist, carbonic anhydrase, prostagladins

29
Q

6 Retinal Cell types

A
  1. Optic Nerve fibres
  2. Ganglion cells
  3. Amarine cells
  4. Bipolar cells
  5. Horizontal cells
  6. Photo receptors (Rods + cones)

Pigment epithelium.

30
Q

Lateral Geniculate nucleus

A

Thalamic visual relay station.
3 layers from each eye.

Parvocellular: small cell, tyop 4 layers. Receive input from B ganglion cells (Midget). 90% color component.

Magnocellular: large cell, bottom 2 layers. Receive input from A ganglion cells (Parasol). Light/dark, greysale.

31
Q

Difference between Nicotinic and Muscarinic cholinergic receptors

A

Nicotinic = somatic nervous system
Muscarinic = Autonomic nervous system

32
Q

3 types of Cone cells

A

L - Long wavelength (red)
M - Middle wavelength (green)
S - Short wavelength (blue)

Dichromat (only 2 cone types).

Protanopia - lack L cones.
Deuteranopia - lack M cones.
Trianopia - lack S cones.

33
Q

Foveal vision processing

Foveal vision = sharp central vision

A

Foveal vision processed in posterior aspect of primary visual cortex.
Peripheral vision processed in anterior aspect.

V4 area; responsible for color (lesion=Achromatopsia).
V5; specialized for motion (lesion=Akinetopsia).

34
Q

Higher level visual areas

A

Fusiform Face Area = Faces
Parahippocampal = Scenes/Places
Lateral Occipital Cortex: Objects

35
Q

Information Processing from LGN

A

Retina > LGN >

Path 1: Magnocellular > Primary VC > Dorsal Stream > Posterior parietal cortex
Path 2: Parvocellular > Primary VC > Ventral stream > Infero-temporal cortex

VC = visual cortex

Path 1 aka “Where pathway”. Lesion = optic ataxia (Balint’s syndrome).
Path 2 aka “What pathway”. Lesion = Visual agnosia.

36
Q

Horner Syndrome

A

Triad.
Ptosis, miosis, anhidrosis.

miosis = constricted pupil

Lesion to sympathetic pathway.

Block 12 (8 decks)

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