Physiology Flashcards
what is CSF
clear, colourless liquid composed mostly of water
produced by the choroid plexus
Supplies water, amino acids, ions
Removes metabolites
what are the 3 major functions of CSF
Mechanical protection: shock-absorbing medium that protects brain tissue
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
in embryonic development, what gives rise to adult brain’s ventricules and the spinal cord’s central canal
cavity of the neural canal
where does the choroid plexus develop from
from cells in the walls of the ventricules
what ions are important in CSF production
Na+, Cl¯ and HCO3¯
what tumours can affect the ventricles, choroid plexus and CSF
- Colloid cyst (often found at the interventricular foramen)
- Ependymomas (arising from the ependymal cells lining the ventricles)
- Choroid plexus tumours
what can cause a ventricular haemorrhage
Epidural hematoma, arterial bleed between skull and dura
Subdural hematoma, venous bleed between dura and arachnoid
Subarachnoid haemorrhage
what is hydrocephalus
accumulation of CSF in the ventricular system or around the brain
what are symptoms of idiopathic intracranial hypertension
Headache and visual disturbances due to papilloaedema
what is papilloedema
optic disc swelling due to increased intracranial pressure
Sx of papilloedema
enlarged blind spot
blurring of vision
visual obscurations
loss of vision
what is aqueous humor and its functions
specialised fluid that bathes the structures within the eye.
provides oxygen and metabolites and contains bicarbonate (HCO3)
what produces aqueous humor
ciliary body
where does aqueous humor drain
scleral venous sinus through a trabecular meshwork and the canal of Schlemm
where is the canal of Schlemm situated
in the angle between the iris and cornea iridocorneal angle
what needs to happen in order to see an object
- 1- the pattern of the object must fall on the vision receptors (rods and cones in the retina) accommodation
- 2- the amount of light entering the eye must be regulated
- 3- the energy from the waves of photons must be transduced into electrical signals
- 4- The brain must receive and interpret the signals
what is the direct (vertical) pathway for signal transmission in the retina
photoreceptors >> bipolar cells >> ganglion cells
what are the types of photoreceptors
rods and cones
what is the function of photoreceptors
Converts electromagnetic radiation to neural signals
what is the basis of phototransduction
1 - Vertebrate Photoreceptors have a depolarized rmp
2 - With light exposure, Vm hyperpolarizes
3 - A cGMP-gated Na+ channel that is open in the dark and closes in the light
4 - change in Na+ with light is the signal that enables the brain to perceive objects in the visual field
what vitamin is needed for sight
Vit A
when is the dark-current channel open and closed
opens in the dark
closes in the light
what opens the dark-current channel
cGMP
why is the dark-current channel important
Keeps photoreceptor Vm more positive than most neurons
→ Steady release of neurotransmitter
what is visual acuity
Ability to distinguish two nearby points. Determined largely by photoreceptor spacing and refractive power
when do rods and cones see
Rods – seeing in dim light
Cones – seeing in normal daylight and colours
what is the basis for colour vision
Cones
- Different opsins for discrete wavelengths
what are features of rods
achromatic peripheral retina high convergence high light sensitivity low visual acuity
what are features of cones
chromatic central retina (fovea) low convergence low light sensitivity high visual acuity
