Week 6: Hogg Style

What is the function of the conjunctiva of the eye?

• barrier that prevents objects from getting into the eye and then the brain

The _______ functions to close the eye and is operated by CN ____

• orbicularis oculi

• CN VII: facial nerve

The _______ functions to lift the upper eyelid and is innervated by CN _______

• levator palpebra

• CN III: oculomotor

What is the function of the superior tarsal muscle? What type of muscle/innervation does it receive? What happens if there are issues with it?

• function: keeps eyelid taut/lifted

  • helps open your eyes wider

• smooth muscle; innervation: GVE from sympathetic CN nerves

• dysfunction: causes eyelid to be a little droopy

Which cranial nerve is responsible for CLOSING the eyelids?

closing: CN VII; facial nerve

Which cranial nerve is responsible for OPENING the eyelids?

opening: CN III; oculomotor

Which nerve innervates the sphincter pupillae and what is the resulting function?

• CN III: oculomotor

• constricts pupil: GVE; parasympathetic; lens contracts

• dilates pupil: GVE; sympathetic

Which structures are contained within the anterior and posterior segments of the eye?

• anterior

  • aqueous humor: liquid

• posterior

  • vitreous humor: jelly-like

What is the flow of tears produced from the lacrimal gland?

1. lacrimal gland produces tears

2. washes lateral to medial of eye

3. enters lacrimal puntum

4. goes into lacrimal canaliculi

5. lacrimal sac

6. nasolacrimal duct

7. inferior meatus of nasal cavity

The outer or _____ layer of the eye is known as the _____ or _______

• fibrous

• sclera

• dura mater of eye: protection

What are characteristics of the cornea?

• transparent

• lots of collagen fibers

• lots of nerve endings

• avascular

• bends light entering

Which structures are contained within the vascular layer of the eye?

• choroid

• ciliary muscle

• iris: colored part of the eye

What is the function of the ciliary muscle and iris?

• ciliary muscle

  • lens accommodation

    • convex: objects that are close

    • flat: objects that are far

• iris

  • dilator and sphincter of the pupil

Which structures are contained within the sensory layer of the eye?

• retina (pigmented layer)

• photoreceptors (neural layer)

Compared to cones, rods are _______, _________, _________

• more numerous

• can be active in low light

• grayscale/fuzzy image

Compared to rods, cones are _______, ________, ________

• less numerous

• require a high light level

• color: green, red, blue

I wake up in the morning and its still dark out, which photoreceptor cells am I using to see?

• rods

Why can’t I see clear colors/pictures in the dark?

• because cones are required to see color

• in order to be active, cones require a high light level

The _______ has the highest concentration of ________ but no _________

• fovea centralis

• cone cells

• no rods

What is the significance of the fovea centralis?

• light falling on this spot gives the best resolution image

What happens to vision with macular degeneration?

• cone cells get damaged

• lose high resolution vision

• hard to read/differentiate faces

• peripheral view remains fine

Where the _________ attaches to the eye there is a ________ because ________

• optic nerve

• blind spot

• no photoreceptors are in this spot

When the _______ contracts, this causes the lens to ________ in order to see objects that are _______

• ciliary muscle

• be curved

• near

When the _______ relaxes, this causes the lens to ________ in order to see objects that are _______

• ciliary muscle

• flatten

• far

What is the advantage of having two eyes close together? What happens when one eye is not funcitoning?

• allows for 3D vision

• allows for depth perception/distance

• 3D vision requires object to be in view of both eyes

• with one eye a person loses depth perception

Which muscles of the eye are NOT innervated by CN III? Which nerves innervate them?

• superior oblique: CN IV; trochlear

• lateral rectus: CN VI; abducens

Which muscles of the eye are innervated by cranial nerve III?

• superior rectus

• inferior rectus

• medial rectus

• inferior oblique

When performing an H test with a patient which motion of the eye tests which muscle/CN?

1. eye goes medially: medial rectus; CN III (oculomotor)

2. eye goes medial/down: superior oblique; CN IV (trochlear)

3. eye goes medial/up: inferior oblique; CN III (oculomotor)

4. eye goes lateral: lateral rectus; CN VI (abducens)

5. eye goes inferior: inferior rectus; CN III (oculomotor)

6. eye goes superior: superior rectus; CN III (oculomotor)

What is the general pathway for vision?

1. optic nerve

2. optic chiasm

3. optic tract

4. synapses in different areas

   1. thalamus

   2. hypothalamus

   3. tectum of midbrain

Axons from the optic nerve synapse in the hypothalamus for:

• regulation of sleep/wake cycles

• circadian clock

Axons from the optic nerve synapse in the tectum of midbrain for:

• visual reflexes

• in superior colliculus

• ex: turning your head to follow a dog that is running by

Axons from the optic nerve synapse in the thalamus for:

• being relayed to visual cortex in occipital lobe

Each hemisphere of the brain processes visual information from _____. Why is this?

• BOTH EYES

• L hemisphere

  • R field from both eyes

• R hemisphere

  • L field from both eyes

The left visual field from the left eye gets processed in the______ hemisphere which means it _______

• right hemisphere

• crosses over the optic chiasm

The left visual field from the right eye gets processed in the ______ hemisphere, which means it _______

• right hemisphere

• does not cross over on the optic chiasm to get to its tract

_____ field of view from both eyes get processed in the R brain

LEFT

______ field of view from both eyes gets processed in the L brain

RIGHT

Optic nerve lesion damage of the R eye will cause…

damage to BOTH visual fields

• like wearing an eye patch

A lesion of the optic chiasm will cause…

damage to the R field of view of the R eye (can’t get to L brain)

damage to the L field of view of the L eye (can’t get to R brain)

• tunnel vision

A lesion of the R optic tract will cause…

• damage to the L field of view of BOTH eyes

What is the function of the external ear?

• to capture and amplify sound

What is the function of the middle ear? Where does it connect to? What issues does this cause?

• function: funnel sound waves into inner ear through oval window

• connects to pharynx via the pharygotympanic tube

• otitis media: throat bacteria gets into ears and causes ear infection

What is the function of the inner ear (specifically: cochlea, vestibule, semicircular canals)

• process sound and balance

• cochlea: hearing

• vestibule: equilibrium; static/linear acceleration

• semicircular canals: equilibrium; rotational/angular acceleration

The ear ossicles (malleus, incus, stapes) _______ while the tensor tympani _______

ear ossicles: amplify vibrations

tensor tympani: limits vibrations during loud sounds

What is the general process of hearing?

1. sound waves hit tympanic membrane

2. vibration of stapes causes fluid in inner ear to start moving

3. hair cells in cochlea bend + release neurotransmitters

4. vestibulocochlear nerve stimulated to take sensory information to the brain

What is the function of the round window?

• releases energy so there is no echo

In the cochlear duct, basilar cells sense ______ pitch and travel _____; while apical cells sense _____ pitch and travel _______

• basilar cells: sense high pitch and travel close (not far)

• apical cells: sense low pitch and travel far

What is the auditory pathway?

1. cochlear branch of CN VIII

2. superior olivary nuclei

3. inferior colliculi —> auditory reflex

4. thalamus

5. auditory cortex

What happens to hair cells in vestibule during linear acceleration?

• crystals and hair cells lag behind and sense a change in motion sending signal to the brain

What happens to hair cells in vestibule during linear deceleration?

• crystals and hair cells continue moving forward even though body is stopped and fire action potentials to communicate to brain new position of head

When you rotate your head to the right, your head moves but ______ stays still. The ______ is pushed through still fluid and while it bends, ______ bend. So brain detects change in head position

• fluid: stays still

• cupula

• hair cells

After you stop spinnnig, why does your body naturally keep rotating?

• the fluid is still moving and cupula is still moving

• brain gets signal that you’re moving even though you’re not

• you subconsciously continue to rotate

Vestibular nuclei located in the ____ and ______ carry signals to which areas?

• pons & medulla

• areas:

  • superior colliculi

  • cerebral cortex

  • spinal cord

  • cerebellum