BHS 150.2 – Biochemistry II
Notetaker: Elisabeth Anderson
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Date: 11/12/2012, 1st hour
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Ciliary Body, Aqueous Humor, and Trabecular Meshwork
o Ciliary Process
 Important for making the aqueous
o Aqueous flows from posterior chamber through the pupil into the anterior chamber
 Flow is important for maintaining pressure
 Exits through trabecular meshwork
o Aqueous humor
 Provides nutrients to the cornea
 Glucose
o Endothelial cells need glucose for energy
 Vitamin C
o Collagen production for cornea and lens
o Antioxidant
o Aqueous
 Made up of an ultrafiltrate of plasma
 Can compare make up of plasma to aqueous
o Electrolytes
 Sodium and potassium have similar concentrations in plasma and aqueous
 There is less calcium in the aqueous than the plasma
 Calcium is not allowed to enter in
 All the others are pretty similar
o Organic Solutes
 Lactate
 Higher in the aqueous than plasma which indicates:
o There is low oxygen and anaerobic glycolysis is occurring with the H
and M subunits so pyruvate is converted to lactate
 Ascorbate
 Higher in aqueous
 Acts as a sink
 Glutathione
 About half as much in aqueous than plasma
 Antioxidant
o Need NADPH to recycle it
 Total protein
 Low protein in aqueous
o Reduce cloudiness
o Clear
o Don’t want to prevent outflow
 Free amino acids provide nutrients for cornea and lens
 Hyaluronic acid pulls water in
Aqueous Production
o Produced by ciliary processes
 Have certain anatomical arrangement
 Pumps and channels
 Move potassium, chloride, sodium and ascorbate from blood to aqueous
 Need to maintain pH
o Ciliary Body stroma has fenestrated capillary
 Pigmented epithelium closest to capillary
 Unpigmented cells closer to chamber
 Lots of gap junctions in between these
 Tight junctions on the outside to control things that can go through cells
o Inside ciliary body stroma and epithelial cells
 Carbonic anhydrase converting bicarb to co2 and water and vise versa
o Pumps and channels
 Sodium potassium ATPase on both pigmented and unpigmented cells
BHS 150.2 – Biochemistry II
Notetaker: Elisabeth Anderson
Date: 11/12/2012, 1st hour
Page2
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Sodium potassium symporter brings sodium in the cells
Sodium ascorbate symporter brings sodium into the cells
 Ascorbate then moves down its concentration gradient out of cell probably
o Not 100% positive on mechanism of this
 Water is following all the ions out into the aqueous
o Important pumps for maintaining pH and bicarb
 Take advantage of metabolism occurring in the cells
 Have a balance of charges with the pumps
 As bicarb concentration is building in the cell an antiport system puts bicarb out into the
aqueous and brings chloride back in
 This will cause a pH change
 Hydrogen ions will then move out of the cell with the passive transport sodium
hydrogen antiporter which balances the pH perfectly
o Sodium concentration is slowly going up inside the cell and then the pumps are pushing it out of
the cell and the water will follow
Regulation of Aqueous Production
o Two receptor types on ciliary body
 α2 adrenergic receptor
 Dephosphorylates phosphate from the sodium potassium ATPase
o Deactivation (slows down) ATPase
 Less sodium and water head out to the posterior chamber
 Β2 adrenergic receptor
 Metabatrobic receptor (G protein) that activates adenylate cyclase which makes
CAMP and activates protein kinase to add phosphate group to sodium
potassium ATPase to make it work
 Pulls sodium and water out into posterior chamber
 Creating a bigger concentration gradient difference to bring in more ascorbate,
potassium, and chloride to the aqueous
 More ions are dumped into the aqueous because of this driving force
 Both bind norepinephrine
Trabecular Meshwork
o Intraocular pressure is maintained by trabecular meshwork
o Type 1 collagen beams are the framework
o Cells line these beams
 Actin inside that is contractile
 Calcium independent, regulated by α2 adrenergic receptors
 When actin is stimulated, the cells relax and changes the arrangement of the
beams which increases the size of the holes in the meshwork
o Actin is contracted when not activated
 Pulls on collagen beams and decreases the size of the holes
 Changes outflow of aqueous
 Bigger holes = more outflow
 Smaller holes = less outflow
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Fibronectin links the cell to the collagen beamwork
Clicker Question:
o Q: The presence of lactate in the aqueous indicates:
o A: Anaerobic glycolysis