Physiology Flashcards
Where is CSF produced?
Secretory epithelium of the choroid plexus
What are the 3 major functions of CSF?
- Mechanical protection - shock absorption to protect brain tissue
- Homeostatic function - pH affects pulmonary ventilation and cerebral blood flow, hormone transport
- Circulation - medium for minor exchange of nutrients and waste products between blood and brain tissue
Where do the ventricles derive from embryologically?
Neural Canal
What is the choroid plexus?
Network of capillaries in the walls of ventricles.
Secretion of CSF from choroid plexus is dependent on what ion transport?
Na+ –> Cl- follow –> water follows by osmosis
CSF has higher Na+ and Cl- thn blood plasma, and has lower K+, glucose and protein
What lies between the lateral and third ventricles?
Intraventricular Foramen of Monroe
What is between the third and fourth ventricle?
Cerebral Aqueduct of Sylvius
What two structures are between the fourth ventricle and the subarachnoid space?
Foramina of Magendie (medial)
Foramina of Luschka (lateral)
Where does CSF join the venous blood circulation?
through arachnoid granulations into the superior sagittal sinus
What is the function of the BBB?
Protection of brain from bacterial infection and toxins, and prevent paracellular movement of molecules
What cells make up the BBB?
Basal endothelial cells and perivascular astrocytes in brain capillaries
What is the common site of colloid cysts?
Interventricular foramen
3 types of ventricular haemorrhage
Epidural (between skull + dura)
Subdural (dura + arachnoid)
Subarachnoid
What is hydrocephalus?
Accumulation of CSF in the ventricular system or around the brain due to obstruction or overproduction, causing ventricular enlargement and pressure
Symptoms of Idiopathic Intracranial HTN?
headache + visual disturbances (due to papilloedema)
What is the function of Aqueous Humor?
Provides oxygen and metabolites
Contains bicarbonate to buffer H+ produced in cornea and lens
Ascorbate = antioxidant
Where is aqueous humor produced?
epithelial layer of ciliary body, into the posterior chamber of the eye (energy dependent)
Describe the drainage of aqueous humor
Posterior chamber
Anterior chamber
Scleral venous sinus through trabecular network and the canal of Schlemm
NB small amount through vitreous, absorbed across retinal pigment epithelium
What enzyme is responsible for the hydration of CO2 into HCO3 and H+ in the epithelial cells?
Carbonic Anhydrase
What ions are HCO3 and H+ exchanged for across the basolateral membrane in PE cells?
Cl- and Na+ (respectively)
How is the ionic movement of Cl- and Na+ into PE cells opposed?
Via Na+K+2Cl- cotransporter at NPE cells (pumps into aqeuous humor)
How does aqueous humor secretion relate to Glaucoma?
Raised IOP occurs due to imbalance in the rates of secretion and removal of aqueous humor
What type of drugs can be used to help reduce IOP in Glaucoma?
Carbonic Anhydrase inhibitors e.g. Dorzolamide (eye drops) or Acetazolomide (oral - wary of systemic SEs e.g. acidosis)
Describe the direct vertical pathway for signal transmission in the retina.
Photoreceptors
Bipolar Cells
Ganglion Cells
