Brain and Behavior, Week 3 Flashcards
What’s the difference between the way nerves are myelinated in the periphery vs the central nervous system?
Periphery: Schwann cells (each one myelinates one segment of the nerve)
CNS: Oligodentrites myelinate multiple nerve fibers
Where are neuronal cell bodies for cranial nerves located? What’s the exception?
- Brain stem
- Olfactory nerve: goes directly to cortex
What anatomical feature of the skull is important for olfaction?
Cribiform plate
Why do people with Klinefelter syndrome tend to have anosmia?
GnRH releasing nerves are created in the nose during development and then migrate to the hypothalamus. The mutation(s) that causes KF syndrome is actually a defect in the olfactory system. GnRH neurons never make it to the hypothalamus.
How do unconscious saccadic movements work to maintain visual perception?
By constantly shifting focus, these movements ensure that the same image does not stay on the fovea for very long, thus preventing retinal desensitization.
Light causes _____ of the rods and cones and a _____ in their electrical potential:
- hyperpolarization
- decrease
What is the difference between rods/cones and bipolar cells on the one hand, and EPSP/IPSP cells on the other, in regard to action potentials.
- rods/cones/bipolar cells lack voltage gated sodium channels and therefore only have a graded response
- EPSP/IPSP cells have voltage gated sodium channels and therefore have action potentials
Compare and contrast rods vs cones:
Rods:
- Require only low levels of light
- Night vision
- Respond to one wavelength only
Cones:
- Require more light to activate
- Concentrated in the fovea
- Day vision
- 3 forms, which respond differently to different wavelengths
Which ligaments are important for maintaining the vibratory axis of the malleus, incus and stapes?
- malleal ligament
- incudal ligament
Outline the basic process by which hair cells trigger action potentials:
Hair cells in the organ of Corti are pressed up against the tectorial membrane during vibration, which stimulates action potentials in the vestibulocochlear nerve.
What neurotransmitter is released by gustatory afferent neurons?
Serotonin
Which cranial nerves convey information about taste?
- Facial (CN VII)
- Glossopharyngeal (CN IX)
- Vagus (CN X)
Which cranial nerves have a purely motor function?
- Accessory
- Hypoglossal
Which cranial nerves have a purely sensory function?
- Optic
- Olfactory
- Vestibulocochlear
Why are smell and emotion so closely linked?
A lot of the smell pathways are interlaced with limbic system pathways
What is the function of the pinhole device in an eye exam?
Helps screen for refractive errors
A patient presents with left superior quadrantopia. Where is the lesion?
Right temporal lobe
Tracts that carry information from the superior visual field pass through what part of the brain?
Temporal lobe
Tracts that carry information from the inferior visual field pass through what part of the brain?
Parietal lobe
In the swinging flashlight test, a paradoxical dilation indicates what?
Afferent pupillary defect
A patient reports seeing black dots that move in a swarm, as well as flashes of light resembling lightning. What’s the most likely diagnosis?
Retinal detachment
DDx:
- posterior vitreous detachment
- retinal tear
- aura of migraine
Risk factors for retinal detachment:
- Age (middle age, can be younger if myopic)
- Myopic
- Family Hx
- Trauma
- Intraocular surgery
Wet age-related macular degeneration (AMD):
- Blood vessel growth under macula, leading to scarring
- Driven by VEGF
- Treated with anti-VEGF therapy (monthly injections into eye: Avastin, Lucentis, or Eylea)
Advanced dry AMD:
- Caused by geographic atrophy
- Slowly progressive vision loss
- No way to prevent or treat
Most common cause of retinal detachment:
Posterior vitreous detachment
After cataracts and glaucoma, what is the most common cause of vision loss?
- Age related macular degeneration
- Diabetic retinopathy the most common cause among working-age people
What is the definition of “lazy eye” (amblyopia)?
- When one eye cannot be corrected to match the acuity of the other eye.
- Because the brain can’t focus eyes independently, it neglects the eye that requires more correction.
Most common etiology of viral conjunctivitis:
Adenovirus
Treatment for bacterial conjunctivitis:
Moxifloxacin (Vigamox) QID x 7d
Common etiologies for scleritis:
What other condition are these things a risk factor for?
- Does not occur in healthy people
- Rheumatologic associations: RA, Wegener’s
- Infectious associations: syphilis, sarcoid, TB
- Also risk factor for anterior uveitis (iritis)
Treatment for scleritis:
Systemic steroids (won’t respond to topical)
How do you distinguish between scleritis and episcleritis?
- Scleritis: extremely painful, violaceous hue, non-blanching deep vessels
- Episcleritis: mildy painful, no violaceous hue
True or false: treatment for corneal abrasion includes both prophylactic abx (erythromycin) and topical anesthetics
False: do NOT use topical anethetics
SSx of anterior uveitis (iritis):
- Photophobia
- Pain
- Redness
- Decreased vision
- Hypopyon (leukocytic infiltrate that settles at the bottom of the iris- “snowstorm”)
A patient with a history of diabetes and sinus infection presents with decreased vision, eye pain, and severe orbital swelling that includes the conjunctiva. The most likely diagnosis is?
Orbital cellulitis
Definition of “eye rupture”
Full thickness (open globe) wound from a blunt object. Injury occurs from the inside out due to increased intraocular pressure.
How do you diagnose a corneal abrasion?
Fluorescein stain with cobalt light source
Definition of “chemosis”
Swelling of the conjunctiva
In addition to possible surgery, what treatment should be considered for patients with orbital laceration?
- Systemic abx with Augmentin
- Tetanus prophylaxis
What should you use to treat hyphema and microhyphema, and why?
- IOP reducing agents + ocular steroids
- Bleeding into AC can elevate IOP
A patient presents with chemosis and a “peaked” pupil due to intraorbital foreign body. What does the peaked pupil suggest?
Rupture
Describe the pathophysiology of amblyopia:
Due to differences in visual inputs between eyes (possibly due to strabismus, anisometropia, ptosis, cataract), the brain starts to favor the good eye, leading to anatomical changes in the brain that make the defect uncorrectable, with poor vision in the affected eye.
How does atropine work to treat amblyopia?
Atropine drops inhibit the eye’s ability to change its lens’ shape, leading to decreased vision in the good eye. This causes the amblyopic eye to try and compensate. Over time this helps the amblyopic eye to develop the needed neural pathways.
What options are there for restoring vision in a person with vision loss due to proliferative diabetic retinopathy?
- Anti-VEGF medications (Avastin, Lucentis, Eylea) can help patients with macular edema
- Vitrectomy can help with proliferative retinopathy
What other conditions is blepharitis related to?
- Seborrhea
- Rosacea
Treatment options for blepharitis:
- Warm compresses, lid scrubs
- Topical steroids
- Abx ointment
- Oral doxycycline for underlying rosacea
- Flax, omega 3
Medical term for stye:
Hordeolum
What is the treatment for hordeolum/chalzion?
Basically the same as for blepharitis:
- Abx ointment
- Topical steroids
- Warm compresses/lid scrubs
A patient who spends a lot of time in the sun presents with a new, painless bump on his eyeball. What is it? What could it become? How do you treat it?
- Pinguecula
- Pterygium
- Artificial tears, or steroids if inflamed
When should you refer a patient who has viral conjunctivitis?
- If they have decreased vision.
- May indicate corneal involvement and need steroid treatment
Treatment for episcleritis
Topical or systemic NSAIDS
Corneal ulcer:
- Associated with trauma, contact lens use
- White corneal infiltrate with staining
- Mostly bacterial, but also viral/fungal etiology
- Treat with Vigamox, or Vancomycin/Tobramycin if severe
Treatment for HSV keratitis:
- Topical trifluridine (Viroptic), gancyclovir or acyclovir
- Oral acyclovir
- May require topical steroids
- Urgent ophthalmology referral due to risk of inflammatory glaucoma, retinal necrosis, corneal stromal dz
How do HSV keratitis and VZV keratitis present differently under a lamp?
Corneal dendrites lack a terminal bulb with VSV
How are HSV and VZV keratitis treated differently?
Viroptic (trifluridine) not used for VZV. Also, treat VZV with prophylactic abx
Management of anterior uveitis:
- Topical steroids
- Rheumatology workup
- Cycloplegics for pain and synechiae prevention
Easy to miss signs of orbital cellulitis:
- Afferent pupillary defect
- Increased IOP
- Optic disk edema
Cycloplegic agents:
- Atropine
- Scopolamine
- Cyclopentolate
Treatment for burns:
- Abx (erythromycin)
- IOP agents
- Cycloplegics
Signs of orbital blowout fx:
- V2 paresthesias
- Binocular diplopia
- Crepitus after nose blowing
- Well tolerated intraorbital foreign bodies:
- Fairly well tolerated:
- Poorly tolerated:
- Glass, stone, plastic, inert metal
- Copper alloys
- Non-inert metals, organic material
How should you treat a ruptured globe and penetrating ocular injury? How do you locate the rupture site?
- Eye shield, NPO, bed rest, antiemetic and pain control
- CT or B scan
By what age is binocular vision well developed in children?
6 months
Other side effects of lumigan:
URI, bacterial keratitis, HA
Describe timolol (Timoptic):
- Beta blocker
- Reduces aqueous humor production
- Don’t use in pts with Hx of asthma, COPD, heart problems
- Fatigue, dyspnea, impotence are side effects
General side effects of glaucoma drops:
- Corneal irritation
- Follicular conjunctivitis
- Contact dermatitis
- Iris and eyelash changes
Brimonidine:
- Alpha adrenergic agonist for glaucoma
- Side effects are CNS depression, drowsiness
- Decreases both production and outflow of aqueous humor
Common topical NSAID:
Ketorolac
Common topical antihistamines:
- Chromolyn
- Olopatadine (Patamol, Pataday)
Name the cycloplegics:
- Atropine (Isopto)
- Cyclopentolate (Cyclogel)
- Phenylephrine (AK dilate)
- Tropicamide (Mydriacyl)
What is an afferent pupillary defect also known as?
Marcus Gunn sign
Tonic (Adie) pupil:
- Reactive to accommodation but not light
- Pilocarpine drops
Risk factors for non-arteritic optic neuropathy:
DM, HTN, small cup to disk ratio, NOT smoking
SSx of optic neuritis:
Pain, swelling, APD, monocular vision loss, color desaturation, progression to MS
