physiology Flashcards
what is cerebrospinal fluid?
-a clear, colourless liquid composed mostly of water
what produces cerebrospinal fluid?
-secretory epithelium of the choroid plexus
what ate the major functions of cerebrospinal fluid?
- mechanical protection: shock- absorbing medium that protects brain tissue. Brain ‘floats’ inside the cranial cavity
- Homeostatic function: pH of CSF affects pulmonary ventilation and cerebral blood flow. Transports hormones
- Circulation: medium for minor exchange of nutrients and waste products between blood and brain tissue
where is CSF obtained for clinical analysis?
-obtained via a lumbar puncture
what dies clinical CSF analysis allow the diagnosis of?
-problems in the brain, meninges and spinal cord
Describe normal CSF
- clear and colourless
- contains little protein (15-45mg/dl)
- contains little immunoglobulins
- contains only 1 to 5 cells/ ml
what does the developing nervous system consist of at 3 weeks?
-a tube (neural canal)
what is the choroid plexus?
-networks of capillaries in walls of ventricles
CSF secretion involves the transport of mainly what ions across the epithelium from blood to CSF?
- sodium (na+)
- chloride (Cl-)
- bicarbonate (HCO3-)
what is the basolateral side?
-the blood side
what is the apical side?
epithelium side
what does the secretion of fluid by the choroid plexus depend on?
-the active Na+ transport across the cells into the CSF
how does CSF return to venous blood?
-through arachnoid granulations into the superior sagittal sinus (SSS)
what restricts the blood supply to the majority of the brain?
-the blood brain barrier (BBB)
what is hydrocephalus?
- the accumulation of CSF in the ventricular system or around the brain (either due to obstruction or overproduction)
- subsequent enlargement of one or more ventricles and increase in CSF pressure
