1. Neuroanatomy

Question 1

how is the composition of CNS grey matter and white matter different

Answer 1

grey matter:

• cell bodies + dendrites + axon terminals/synapses
• highly vascular due to ‘processing’ role with many metabolic processes

white matter:

• axons + supporting glial cells (oligodendrocytes) = fibre
• white due to presence of fatty myelin

Question 2

name the PNS equivalents of grey and white matter

Answer 2

grey matter = ganglion

white matter = peripheral nerve

Question 3

name the 3 CNS regions where grey matter is found

Answer 3

1. cerebral CORTEX (outer layer of cerebral hemispheres)
2. 100s of discrete bilateral NUCLEI deep in cerebral hemispheres
3. ventral and dorsal HORNS of spinal cord (columns of GM) - organised into REXED’S LAMINAE

Question 4

name and describe the 3 types of WM fibres

Answer 4

1. ASSOCIATION fibres
   - connecting cortical regions within same hemispheres (e.g. U fibres)
2. COMMISSURAL fibres
   - connect left and right hemispheres or cord halves (e.g. corpus callosum)
3. PROJECTION fibres
   - connect the cerebral hemispheres with the cord/brainstem and vice versa (run longitudinally)

Question 5

describe the organisation of the WM in the spinal cord

Answer 5

1. FUNICULI:
   - segments of WM containing multiple tracts with ascending and descending axons (i.e. motor and sensory)
   - dorsal, lateral and ventral
2. TRACTS:
   - discrete pathways connecting 2 distinct regions of GM, with fibres having a similar function and being all either ascending or descending
3. FASCICULI:
   - subdivisions of tracts supplying a distinct region of the body
   - e.g. gracile and cuneate fasciculi within dorsal column tract

Question 6

which cells produce CSF

Answer 6

choroid plexus cells located in each of the brain ventricles (total of 600-700mL/day)

Question 7

describe the circulation of CSF in the cranium

Answer 7

i. lateral ventricles are the largest ventricles with largest choroid plexus so synthesise the most CSF…
ii. flows into 3rd ventricle via small interventricular foramen (which also connects 2 lateral ventricles)…
iii. flows into cerebral aqueduct (midbrain level) which drains CSF into 4th ventricle (pons and medullary level)…
iv. CSF leaves 4th ventricle via:
- central canal of spinal cord (very narrow so only small amount)
- median aperture of 4th ventricle
- 2 lateral apertures
v. flows into subarachnoid space via apertures before being reabsorbed at arachnoid granulations into venous plexus

Question 8

which structure causes the flattened shape of the 3rd ventricle

Answer 8

thalamus and hypothalamus

Question 9

which type of MRI would be used to visualise CSF

Answer 9

T2 = bright water, intermediate signal from fat

T1 = bright fat, dark fluid

Question 10

why do tumours often appear hyperdense in T1 + Gd MRI

Answer 10

tumours, eg meningiomas, often highly vascularised and may affect blood-brain barrier so absorb more contrast (gadolinium) than other parts of brain - exhibit homogenenous enhancement

Question 11

label the parts of the ventricular system

Answer 11

Question 12

label this mri

Answer 12

Question 13

label these MRIs

Answer 13

Question 14

describe the patellar reflex

Answer 14

i. reflex hammer strikes pattelar tendon, stimulating quadriceps stretch Rs…
ii. afferent sensory neurones synapse with efferent motor neurones in L3/4 ventral horn of spinal cord…
iii. impulses along efferent motor neurones stimulate quadriceps femoris contraction