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CHI 108 > Lecture 16: The Special Senses > Flashcards

Lecture 16: The Special Senses Flashcards

1
Q

Describe the structure and function of accessory eye structures, eye layers, the lens, and humours of the eye

A

H

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2
Q

Accessory structures of the eye to protect the eye and aid eye function. Name them

A
  • eyebrow
  • eyelids (palpebrae)
  • conjunctiva
  • lacrimal apparatus
  • extrinsic eye muscles
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3
Q

Be able to label the eye.

A

Do it!

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4
Q

Give the structure and function of the following:
Eyebrows
Eyelids (upper and lower)
Eyelashes (nerve endings of follicles initiate blinking
Lubricating glands associated with the eyelids

A

Eyebrow: shading the eye and preventing perspiration from reaching the eye
Eyelids: protect the eye. Levator palpebrae-give the upper eyelid mobility
Eyelashes: nerve endings if follicles initiate reflex blinking
Lubricating glands associated with the eyelids:
-tarsal glands
-sebaceous gland associated with follicles

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5
Q

Conjunctiva

A

Transparent membrane
-palpebral conjunctiva- lines the eyelids
-bulbar conjunctiva-covers the white of the eyes
-produces a lubricating mucous secretion
Refer to slide 8 for picture

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6
Q

Lacrimal apparatus

A

Lacrimal gland and ducts that connect to nasal cavity
Lacrimal secretion (tears)
-dilute saline solution containing mucus, antibodies, and lysozyme
-blinking spreads the tears towards the medial commissure
-tears entered paired lacrimal canaliculi via the lacrimal puncta
-drain into the nasolacrimal duct
Slide 10 for picture

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7
Q

Extrinsic eye muscles

A

6 strap like extrinsic eye muscles

  • originate from the bony orbit
  • enable the eye to follow moving objects

Four rectus muscles: names indicate the movement they promote
Two oblique: muscles move the eye in the vertical plane and rotate the eyeball

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8
Q

Label the diagram of the eye muscles on side 15 and 16

A

Do it

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9
Q

Summary of muscle actions on eye and innervating cranial nerves

A

Lateral rectus muscle-moves eye laterally (abducens)
Medial rectus muscle- moves eye medially (3- oculomotor)
Superior rectus muscle- elevates eye (3)
Inferior rectus muscle - depresses eye (3)
Inferior oblique- elevates eye and turns it laterally (3)
Superior oblique- depresses eye and turns it laterally (trochlear) 4

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10
Q

Structure of the eyeball

Wall of eyeball contains 3 layers, what are they?

A

Fibrous (outer)
Vascular (middle)
Sensory (inner)
Internal cavity is filled with fluids called humors
The lens separates the internal cavity into anterior and posterior segments

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11
Q

Label diagram on slide 16

A

Do it

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12
Q

Describe the fibrous layer and what it consists of

A

Outermost dense avascular connective tissue
Two regions: sclera and cornea
Sclera: opaque (white)
-protects and shapes the eyeball
-anchors extrinsic eye muscles
Cornea: transparent
-numerous pain receptors here contribute the blinking and tearing reflexes

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13
Q

Describe the vascular layer and what it consists of

A

Middle pigmented layer (uvea)
3 regions: choroid, ciliary body and iris
1. Choroid: posterior portion of the uvea
-supplied blood to all layers of the eyeballs
-brown pigment absorbs light to prevent visual confusion
2. Ciliary body
-ring of tissue surrounding the lens
-smooth muscle bundles (ciliary muscles) controls lense shape
-ciliary zonule (Suspensory ligament) holds lens in position
3. Iris
-the coloured part of the eye
Pupil- central opening that regulates the amount of light entering the eye
-bright light-sphincter papillae (circular muscle) contracts; pupils constrict

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14
Q

Sensory layer: retina

A

Delicate 2 layered membrane

  1. Pigmented layer
    - outer layer
    - absorbs light
    - stores vitamin A
  2. Neural layer
    - photoreceptors

Ganglion cell axons
-run along the inner surface of the retina

Optic disc (blind spot)

  • site where the optic nerve leaves the eye
  • lacks photoreceptors

Two sources of blood supply

  • choroid supplies the outer third (photoreceptors)
  • central artery and vein of the retina supply the inner 2 thirds
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15
Q

Photoreceptors

What are the 2 kinds and their properties

A

Rods- more of them at peripheral region of retina, away from the macula lutes
-operate in dim light
-provide indistinct , fuzzy, non coloured peripheral vision
Cones:
-found in the macula lutea: concentrated in the fovea centralis
-operate in bright light
-provide high acuity coloured vision

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16
Q

What are the internal chambers and fluids of the eye?

A

The lens and ciliary zonule separate the anterior and posterior segments
Posterior segments contains vitreous humor that:
-transmits light
-supports posterior surface of the lens
-holds the neural retina firmly against the pigmented layer
-contributes to the intra ocular pressure

Anterior segments is composed of 2 chambers

  • anterior chamber- between the cornea and the iris
  • posterior chamber- between the iris and the lens
17
Q

Internal chambers and fluids

A

Anterior segments contain aqueous humor

  • plasma like fluid
  • drains via the scleral venous sinus (canal of schlemm) at the sclera- cornea junction
  • supplies nutrient and oxygen mainly to the lens and cornea but also the retina, and removes wastes
18
Q

Lens

A

Biconvex, transparent, flexible, elastic and avascular

  • allows precise focusing of light on the retina
  • lens becomes denser, more convex, and less elastic with age
19
Q

Focusing light on the retina

A

Pathway of light entering the eye: cornea- aqueous humor- lens- vitreous humor- neural layer of retina- photoreceptors
Light is refracted
-at the cornea
-entering the lens
-leaving the lens
Change in lens curvature allows for fine focusing of an image

20
Q

Focusing for close vision

A

Close vision requires:
Accommodation- changing the lens shape by ciliary muscles to increase refractory power
-near point of vision is determined by the maximum bulge the lens can achieve

Constriction- the accommodation of the pupillary reflex constricts the pupils to prevents the most divergent light rays from entering eye

Controlled by oculomotor, parasympathetic fibres

21
Q

Visual pathway to the brain

A
  • Axons of retinal ganglion cells form the optic nerve
  • medial fibres of the optic nerve decussate at the optic chiasm
  • most fibres of the optic tracts continue to the superior colliculi
  • the optic radiation fibres connect to the primary visual cortex in the occipital lobes
22
Q

Sense of smell

A

Taste and smell (olfaction)

  • their chemoreceptors respond to chemicals in aqueous solution
  • olfactory epithelium in the roof of the nasal cavity
  • bundles of axons of olfactory receptor cells form the filaments of the olfactory nerve (CN 1)
23
Q

Sense of taste

A

Receptor organs are taste buds
-found on the tongue: CN 7 and 9
-found on the epiglottis: CN 10
Taste is 80% smell
-thermoreceptors, mechanoreceptors and nociceptors in the mouth also influence taste
-Cranial nerves 7, 9 and 10 carry impulses from the taste buds to the gustory cortex in the insula

24
Q

What are the 5 taste sensations

A
  1. Sweet
  2. Bitter
  3. Umami
  4. Sour
  5. Salty
25
Q

The ear: hearing and balance

What are the 3 parts of the ear?

A
  1. External
  2. Middle
  3. Internal

External ear and middle ear are involved with hearing
Internal ear (labyrinth) functions in both hearing and equilibrium
Receptors for hearing and balance: CN 8

26
Q

Label diagram on slide 34

A

Do it

27
Q

List the parts of the external ear

A

The auricle (pinna)
External acoustic meats (auditory canal)
Tympanic membrane
-boundary between external ear and middle ears
-connective tissue membrane that vibrates in response to sound
-transfers sound energy to bones of the middle ear

28
Q

List the parts of the middle ear

A

A small cavity in the temporal bone
Pharyngotympanic (auditory tube) -connects the middle ear to the nasopharynx
-equalizes pressure in the middle ear cavity with the external air pressure
Ear ossicles: 3 small bones in tympanic cavity: the malleus, incus and stapes
-suspended by ligaments and are synovial joints
-transmit vibratory motion of the eardrum to the oval window

29
Q

List the parts of the internal ear

A

Bony labyrinth
-three parts: vestibule, semicircular canals, and cochlea
Vestibule:
-central egg-shaped cavity of the bony labyrinth
-contains 2 membranous sacs
Semicircular canals:
-3 canals (anterior, lateral, and posterior) that each define 2/3 of a circle
Cochlea:
-a spiral, conical, bonds chamber
-the cochlear branch of nerve 8 runs from the spiral organs of corti to the brain

30
Q

Transmission of sound to the internal ear

A

Sound waves vibrate the tympanic membrane
Ossicles vibrate and amplify the pressure at the oval window
-pressure waves move through the perilymph

31
Q

Equilibrium and orientation

A

Vestibular apparatus consists of the equilibrium receptors in the semicircular canals and vestibule

32
Q

How are the receptors activated?

What is the equilibrium pathway to the brain?

A

Bending in the opposite direction
-hyperpolarizes vestibular nerve fibres
-reduces the rate if impulse generation
Thus the brain is informed of the changing position of the head

Equilibrium pathway to the brain

  • impulses travel to the vestibular nuclei in the brain stem or the cerebellum, both if which receive input
  • 3 modes of input for balance and orientation
    • vestibular receptors
    • visual receptors
    • somatic receptors

CHI 108 (24 decks)

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