Physiology Flashcards
Hydrocephalus
Obstruction of CSF flow/increased production
Enlarged ventricles
Headache, N+V, visual disturbance, coma
CSF production involves transport of what ions?
Na, Cl, HCO3-
CSF compared with plasma
Lower K, gluose, bicarb and protein
Higher, Na and Cl
BBB consists of
Endothelium
Basal membrane
Perivascular astrocytes
Tumours associatd with the venricles
Colloid cyst (glioma at IV foramen)
Pinealoma (pineal gland in midbrain)
Ependymoma (glioma of ependymal cells of ventricles, kids)
Choroid plexus tumours (kids)
Epidural haematoma
Between skull and dura
Subdural haematoma
Between dura and arachnoid
Normal pressure hydrocephalus
Incontinence, dementia, gait disturbance
Idiopathic Intracranial HT
Obese females, childbearing age
Headache, visual disturbance, papilloedema, NO imaging features
Tx: weight loss, meds, shunt
Papilloedema
Optic disc swelling due to raised ICP
Blind spot, blurring, loss of vision
Bulging optic disc, flame haemorrhage
Bilateral
2 layers of ciliary body epithelium
Inner pigmented epithelium
Outer non-pigmented epithelium
How is aqueous formed?
Net movement of NaCl from IF to aqueous = water follows
Which is replaced faster, posterior or anterior chamber?
Posterior
CA inhibitors
Reduce production of aqueous = treats glaucoma (blocks NaCl and water)
Dorzolamide - local
Acetazolamide - systemic effect on kidney = acidosis
Transduction
Light to electrical energy
Layers light has to cross
Ganglion cells
Bipolar cells
Photoreceptors
Horizontal cells
Receive from photoreceptors
Transmit to photoreceptors and bipolar cells
Amacrine cells
Receive from bipolar cells
Transmit to bipolar cells and ganglion cells
Constant/Dark current
More active in dark (more depolarisation = more glutamate released), Na channel open (positive charge enters = depol)
Resting membrane potential
-20mV
What happens with light exposure?
Hyperpolarisation (more negative)
Na channel closes
In the dark which is greater Pna or Pk?
Pna = Pk
In the light which is greater Pna or Pk?
Pk is greater than Pna
Rhodopsin
Visual pigment molecules
Allows reactions to different amounts of light
Light converts 11-cis-retinal to:
all-trans-retinal (activated form of rhodopsin)
What does all-trans-retinal do?
Decreases cGMP = closes Na channel = hyperpol
More or less glutamate in the dark?
More glutamate in dark
Less glutamate in light
Define visual acuity
Ability to distinguish between 2 points (determined by photoreceptor spacing)
Rods activated in:
dim light
Cones activated in:
bright light (less sensitive than rods)
Acuity of rods and cones
Cones: high acuity
Rods: low acuity
Convergence of rods and cones
Cones: low convergence
Rods: high convergence
3 types of cone
Blue: short wave
Green: middle wave
Red: long wave
Features of rods
Achromatic Peripheral retina High convergence Low acuity Sensitive
Features of cones
Chromatic Central retina Low convergence High acuity Not very sensitive
Define receptive field
Part of retina that needs to be stimulated to elicit AP from a ganglion cell
What layer of the striate cortex are inputs segregated?
Layer 4 = monocular info
In most of visual cortex inputs are segrgated into:
Ocular dominance columns (each column dominated by one eye)
Amblyopia
Cortical blindness
One eye has better vision than the other
Cause of amblyopia
Strabysmus = surgery or patch
