Physiology

Question 1

what is CSF

Answer 1

clear, colourless liquid composed mostly of water
produced by the choroid plexus
Supplies water, amino acids, ions
Removes metabolites

Question 2

what are the 3 major functions of CSF

Answer 2

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

Question 3

in embryonic development, what gives rise to adult brain’s ventricules and the spinal cord’s central canal

Answer 3

cavity of the neural canal

Question 4

where does the choroid plexus develop from

Answer 4

from cells in the walls of the ventricules

Question 5

what ions are important in CSF production

Answer 5

Na+, Cl¯ and HCO3¯

Question 6

what tumours can affect the ventricles, choroid plexus and CSF

Answer 6

• Colloid cyst (often found at the interventricular foramen)
• Ependymomas (arising from the ependymal cells lining the ventricles)
• Choroid plexus tumours

Question 7

what can cause a ventricular haemorrhage

Answer 7

Epidural hematoma, arterial bleed between skull and dura

Subdural hematoma, venous bleed between dura and arachnoid

Subarachnoid haemorrhage

Question 8

what is hydrocephalus

Answer 8

accumulation of CSF in the ventricular system or around the brain

Question 9

what are symptoms of idiopathic intracranial hypertension

Answer 9

Headache and visual disturbances due to papilloaedema

Question 10

what is papilloedema

Answer 10

optic disc swelling due to increased intracranial pressure

Question 11

Sx of papilloedema

Answer 11

enlarged blind spot
blurring of vision
visual obscurations
loss of vision

Question 12

what is aqueous humor and its functions

Answer 12

specialised fluid that bathes the structures within the eye.

provides oxygen and metabolites and contains bicarbonate (HCO3)

Question 13

what produces aqueous humor

Answer 13

ciliary body

Question 14

where does aqueous humor drain

Answer 14

scleral venous sinus through a trabecular meshwork and the canal of Schlemm

Question 15

where is the canal of Schlemm situated

Answer 15

in the angle between the iris and cornea iridocorneal angle

Question 16

what needs to happen in order to see an object

Answer 16

• 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

Question 17

what is the direct (vertical) pathway for signal transmission in the retina

Answer 17

photoreceptors
>>
bipolar cells
>>
ganglion cells

Question 18

what are the types of photoreceptors

Answer 18

rods and cones

Question 19

what is the function of photoreceptors

Answer 19

Converts electromagnetic radiation to neural signals

Question 20

what is the basis of phototransduction

Answer 20

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

Question 21

what vitamin is needed for sight

Answer 21

Vit A

Question 22

when is the dark-current channel open and closed

Answer 22

opens in the dark

closes in the light

Question 23

what opens the dark-current channel

Answer 23

cGMP

Question 24

why is the dark-current channel important

Answer 24

Keeps photoreceptor Vm more positive than most neurons

→ Steady release of neurotransmitter

Question 25

what is visual acuity

Answer 25

Ability to distinguish two nearby points. Determined largely by photoreceptor spacing and refractive power

Question 26

when do rods and cones see

Answer 26

Rods – seeing in dim light

Cones – seeing in normal daylight and colours

Question 27

what is the basis for colour vision

Answer 27

Cones

- Different opsins for discrete wavelengths

Question 28

what are features of rods

Answer 28

achromatic
peripheral retina
high convergence
high light sensitivity
low visual acuity

Question 29

what are features of cones

Answer 29

chromatic
central retina (fovea)
low convergence
low light sensitivity
high visual acuity