Physiology Flashcards
What is cerebrospinal fluid?
- clear liquid
- composed of water
- Na+ and Cl-
- very little protein
What are the 3 functions of CSF?
- Mechanical protection
- Homeostatic function
- circulation
How do you clinically analyse the CSF?
- Lumbar puncture
- L4/5
What is the ventricles of the brain embryologically formed from?
- neural tube
What is the choroid fissure?
- developing arteries invaginate the roof of the ventricles
Where is the choroid plexus found?
- lateral ventricles (2)
- 3rd ventricle
- 4th ventricle
What is lower in CSF compared to blood?
- protein
- glucose
- potassium
What is in higher concentrations in the CSF compared to blood?
- Na+
- Cl-
What produces CSF?
- Ventricles
- ependymal cells - choroid plexus
What is the connection between the lateral ventricles and the 3rd ventricle called?
- intraventicular framing of monroe
What is the connection between the 3rd and 4th ventricle called?
- cerebral aqueduct of sylvius
Where is the final destination of CSF
- Subarachnoid space
- venous sinuses through arachnid granulations
What is the function of the blood brain barrier?
- protects the brain from common bacterial infections and toxins
Define hydrocephalus?
- accumulation of CSF in the ventricular system
- subsequent enlargement of one or more ventricles
- increase in pressure
Define papilloedema?
- optic disk swelling due to increased intracranial pressure transmitted to the subarachnoid space surrounding the optic nerve
What are the symptoms of papilloedema?
- enlarged blind spot
- blurring or less of vision
What would papilloedema appear like in the fundoscope?
- bulging of the optic disk
Where is the aqueous humour found?
- between the cornea and lens
Name a powerful antioxidant in the aqueous humour?
- ascorbate
Aqueous humour production is energy ___dependant/independant___
- dependant
Where does the aqueous humour finally drain into?
- scleral venous sinus
- iridocorneal angle
What is responsible for the production of the ions in the aqueous humour?
- carbonic anhydrase
What drug class can be used to reduce intraocular pressure as a result of a build up of aqueous humour?
- carbonic anhydrase inhibitors
What is the symptoms of open angle glaucoma?
- gradual reduction of the peripheral vision
What is the name given to the field of vision which is the overlap between the right and left visual field?
- binocular visual field
superior visual field is perceived by the _____
- left cortex
Where is the processing dominant neutrons in the cortex found?
- level 4C
What is the role of photoreceptors?
- converts electromagnetic radiation to neural signals
Where are cones found?
- fovea
Where are rods found?
- distributed along the length
At rest (dark) what is the membrane potential of the photoreceptors?
- depolarised
When activated (light) what is the membrane potential of the photoreceptors?
- hyperpolarised
- more negative
Explain why when it is dark the membrane potential is depolarised?
- Na+ channel open
- cGMP present
- depolarised
List the steps that occur when light hits the photoreceptors?
- light converts 11 cis-retinal to all trans-retinal
- signals opsin
- G protein transduction
- PDE hydrolyses cGMP
- reduced concentration of cGMP
- closes Na+ channels
- hyperpolarisation
Define visual acuity
- ability to distinguish two nearby points
- determined largely by photoreceptors spacing and refractive power
Where are rods less likely to be found?
- fovea
Where are cones most likely to be found in greatest numbers?
- fovea
Short wavelength cones see what colour?
- blue
Medium wavelength cones see what colour
- green
Long wavelength cones see what colour
- red
What returns CSF to the superior sagittal sinus?
- arachnoid granulations
What is the activated form of 11-cis retinal?
- all trans-retinal
__Rods / Cones___ have high convergence?
- rods
