Physiology

Question 1

what are the role of CSF

Answer 1

medium for exhange of nutrients (amino acids, ions and water) and waste products/ metabolites between blood and brain tissue

pH of CSF affects pulmonary ventilation and cerebral blood flow

transports hormones

shock absorping medium, suspends the brain inside the cranial cavity

Question 2

where is CSF made and what is its path

Answer 2

produced by secretory epithelium of the choroid plexus in the ventricles
flows into third ventricle through two narrow openings (interventricular foramina)
floes through cerebral aqueduct in the midbrain

circulates in the subarachnoid space (gets into it via apetures in the roof of the fourth ventricle)

circulates in the central canal of spinal chord
absorped into the venous circulation

Question 3

what makes CSF

Answer 3

secretory epithelium of the choroid plexus

Question 4

how is CSF obtained for clinical analysis

Answer 4

lumbar punsture

Question 5

what does normal CSF look like

Answer 5

clear and colourless

Question 6

describe the embryological development of the brain

Answer 6

3 weeks neural canal - its cavity makes ventricles and central canal (spinal chord)
choroid plexus develops from cells in the wall of the ventricles

Question 7

what usually causes hydrocephalus

Answer 7

obstruction of CSF flow causing enlargement of ventricular space upstream to the blockage

Question 8

how is the choroid plexus formed

Answer 8

arteries invaginate the roof of the ventricle to form the choroid fissure
the involuted ependymal cells + vssels enlarge into villiand form the choroid plexus

Question 9

where is the choroid plexus found in adults

Answer 9

3rd, 4th and lateral ventricles

Question 10

what is a choroid plexus

Answer 10

networks of capillaries in walls of ventricles

Question 11

what cells line the capillaries in the choroid plexus

Answer 11

ependymal cells - make CSF

Question 12

how do ependymal cells make CSF

Answer 12

absorb plasma from circulation, modify it, secreted from apical membrane of cells

Question 13

what does CSF secretion involve

Answer 13

transport of ions Na+, CL- and HCO3- across the epithelium from blood to CSF
(HCO3- out, Na and Cl in)

water secretion along with these ions

Question 14

what does secretion of CSF depend on

Answer 14

Na+ transport across the cells into the CSF- electrical gradient brings along Cl-
both ions drag water

Question 15

how does CSF ions compare to blood

Answer 15

lower K+, glucose, protein

Question 16

what is the ventricular system of the braim

Answer 16

set of four interconnected cavities (ventricles) in thebrain, where the cerebrospinal fluid (CSF) is produced

Question 17

how are the ventricles connected

Answer 17

Intraventricular Foramina (of Monroe): Lateral Ventricles to Third Ventricle
Cerebral Aqueduct (of Sylvius): Third Ventricle to Fourth
Foramen of Magendie: Median aperture – Fourth ventricle to subarachnoid space
Foramina of Luschka: Lateral apertures – Fourth ventricle to subarachnoid space

Question 18

where is CSF formed

Answer 18

in choroid plexus of each lateral ventricle

some made in subarachnoid membrane and cicumventricular organs structures in the brain that are characterized by their extensive vasculature and lack of a normal blood brain barrier)

Question 19

how much CSF is produced and absorbed each day

Answer 19

500 ml

Question 20

how does CSF return to the venous circulation

Answer 20

through arachnoid granulations into superior sagittal sinus

Question 21

where is the blood brain barrier

Answer 21

endothelial cells in brain capillaries

Question 22

what makes up the BBB

Answer 22

capillary endothelium, basal membrane, perivascular astrocytes

Question 23

what parts of the brain dont have a blood brain barrier

Answer 23

circumventricular organs

the pineal gland

Question 24

what tumours can you get in the ventricles or choroid

Answer 24

colloid cyst (intraventricular foramen)
ependtmomas (arise from ependymal cells)
choroid plexus tumours

Question 25

what are the types of ventricular haemorrhage

Answer 25

Epidural hematoma, arterial bleed between skull and dura Subdural hematoma, venous bleed between dura and arachnoid Subarachnoid hemorrhage

Question 26

what is hydrocephalus and what causes it

Answer 26

accumulation of CSF in the ventricular system/ around brain subsequent enlargement of one or more ventricles and increase in CSF pressure too much generation of CSF or obstruction

Question 27

what is idiopathic intracranial hypertension/ pseudotumor cerebri

Answer 27

increased CSF pressure | head ache and visual disturbances due to papilloaedema

Question 28

what is papilloedema

Answer 28

optic disc swelling due to increased intracranial pressure transmitted to the subarachnoid space surrounding the optic nerve

Question 29

what are the visual symptoms of papilloedema

Answer 29

enlarged blind spot, blurring of vision, visual obscurations and loss of vision

Question 30

what is aqueous humor

Answer 30

fluid that bathe the structures within the eye

Question 31

what are the roles of aqueous humor

Answer 31

provides oxygen, metabolites and bicarbonate (buffers the H+ produced in the cornea and lens)

Question 32

where is aqueous humor produced- what is its path

Answer 32

epithelial layer in ciliary body- into posterior chamber, then anterior chamber, then drains to the scleral venous sinus though the canal od schlemm

Question 33

where is the angle of schlemm

Answer 33

angle between the iris and cornea - iridocorneal epithelium

Question 34

describe the epithelium of the ciliary body and posterior surface or iris

Answer 34

covered by two layers one a continuation of pigment epithelium of the retina (PE) this is covered by an inner non pigmented epithelial layer (NPE) pigment cells under non pigment

Question 35

describe the ionic composition of aqueous humour and how it happens

Answer 35

HCO3- and H+ go across basolateral membranes of pigmented epithelium into interstitial fluid in exchange Cl- and Na+ go in via gap junctions out of non pigemented epithelium into aqueous humour (Na+/K+/2Cl- transporter) water goes with ions via aquaporins

Question 36

how can you control aqueous humour production

Answer 36

block it with carbonic anhydrase (enzyme that makes HCO3- and H+) inhibitors

Question 37

what causes glaucoma

Answer 37

raised intra ocular pressure caused by an imbalance in rates of secretion and removal of aqueous humour

Question 38

what is the treatment for glaucoma

Answer 38

Carbonic anhydrase inhibitors Dorzolamide - is administered as eye drops- avoiding systemic side effects Acetazolomide - oral administration-also targets kidney-acidosis.

Question 39

what is the pathway of signal transduction in the eye

Answer 39

photoreceptors, bipolar cells, ganglion cells, optic nerve | opposite to the path light takes

Question 40

what lateral connections affect signal processing in the eye

Answer 40

horizontal and amacrine cells (project info to photoreceptors)

Question 41

what are the main regions of a photorecptor

Answer 41

outer and inner segment, cell body, synaptic terminal

Question 42

what neurotransmitter is released from photoreceptors

Answer 42

glutamate

Question 43

describe phototransduction

Answer 43

photoreceptors have depolarised resting membrane potential | with light exposure less glutamate is released hyperpolarising the cell generating a graded potential

Question 44

why is photoreceptors resting membrane potential positive

Answer 44

because of 'dark current' still making potentials when no light

Question 45

influx of what ion causes dark current

Answer 45

Na

Question 46

more glutamate is released by photoreceptors in thr dark or light

Answer 46

dark

Question 47

why is tlight signal graded and local

Answer 47

to allow visual acuity

Question 48

what is rhodposin

Answer 48

visual pigment molecules (for rods) made from retinal + opsin that photoconverts molecules by activating transducin

Question 49

what does rhodposin convert with light

Answer 49

11-cis-Retinal to all-trans-Retinal (activated form)

Question 50

what does all trans retinal do

Answer 50

activates transducin which causes a molecular cascade GMP= closure of cGMP gated Na+ channel, this lowers Na entry= hyperpolarisation

Question 51

is the dark current channel open or closed in the dark

Answer 51

open in the dark (cGMP gated and lots of cGMP in dark)

Question 52

what is visual acuity

Answer 52

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

Question 53

what do rods do

Answer 53

see in dim light

Question 54

what do cones do

Answer 54

see in normal daytime light

Question 55

is there more convergence in rods or cones

Answer 55

rod (more photoreceptors going to each ganglion meaning less acuity)

Question 56

what is the fovea

Answer 56

where con of cones is highest

Question 57

what allows colour vision

Answer 57

different opsins for discrete wavelengths of light

Question 58

where in retina are rods and cones

Answer 58

reds peripheral retinal | cones central retina

Question 59

what photoreceptors see colour

Answer 59

cones

Question 60

do rods or cones have high light sensitivity

Answer 60

rods have high sensitivity, cones low

Question 61

does our vision detect local differences in light intensity or the absolute amounts on light

Answer 61

local differences

Question 62

what are the monocular and binocular visual fields

Answer 62

monocular is area seen by only one eye +/- 45 degrees binocular seen by both eyes +/- 45 degrees

Question 63

where in primary cisual cortec are specific eye inputs segregate

Answer 63

layer 4 - segregated by ocular dominance columns (each coloumn dominated by input from one eye) outside this layer receive input from both eyes

Question 64

how does congenital cataracts presents

Answer 64

impaired vision from birth

Question 65

what is amblyopia/ cortical blindness

Answer 65

when one eye has better vision than the other but no problems with eye

Question 66

what can cause amblyopia

Answer 66

wandering eye (strabisumus)

Question 67

how do you treat wandering eye

Answer 67

surgically, covering good eye for a few hours until then

Question 68

why is binocular vision important

Answer 68

for development of both eyes deprived eye will have less branches of LGN axons