Neuro1 - CNS Topography

Question 1

4 features of grey matter

Composition x3
Nucleus
Cortex
PNS Equivalent

Answer 1

1. ) Composition - cell bodies and dendrites
   - highly vascularised due to computational role
   - also contains axons to communicate w/ white matter

2.) Nucleus - collection of functionally related cell bodies

3. ) Cortex - folded sheet of cell bodies on brain surface
   - folded to increase volume/SA

4.) PNS Equivalent - ganglion (collection of neuronal cell bodies)

Question 2

4 features of white matter

Composition x2
Types of Fibres x3
Spinal Cord Segments x3
PNS Equivalent

Answer 2

1. ) Composition - fibres (axons w/ their supporting cells e.g. oligodendrocytes)
   - contains lots of fatty myelin making it appear white
2. ) Types of Fibres
   - association fibres: connect cortical regions within the same hemisphere
   - commisural fibres: connect contralateral hemispheres
   - projection fibres: connect cerebral hemispheres w/ the brainstem/spinal cord (can ascend or descend)
3. ) Spinal Cord Segments
   - funiculus: segment containing multiple distinct tracts with impulses travelling in multiple directions (ascending and descending)
   - tract: connects 2 distinct regions of grey matter with impulses travelling in one direction
   - fasciculus: subdivision of a tract supplying a distinct region of the body

4.) PNS Equivalent - the peripheral nerve

Question 3

3 parts of the brainstem and their functions

Midbrain x5
Pons x2
Medulla x2

Answer 3

1. ) Midbrain - eye movements and reflex responses to sound and vision
   - cerebral peduncles (crus cerebri) connects midbrain to cerebrum
   - colliculi sit on dorsal aspect, dealing with reflex actions to visual stimuli
   - lies at the level of the tentorium cerebelli ‘tentorial notch’
2. ) Pons - responsible for feeding and sleep
   - CNV and CN VII emerges laterally from ponto-medullary junction
   - CNVI emerges ventrally from the ponto-medullary junction
3. ) Medulla - cardiovascular and respiratory centres
   - Ondine’s curse is breathing manually

Question 4

What are sulci, gyri, and fissures?

Sulci x3
Gyri x2
Fissure x2

Answer 4

1. ) Sulcus - groove separating adjacent gyri
   - central: separates frontal and parietal lobes
   - parieto-occipital: separates parietal and temporal lobe
   - calcarine: surrounded by the primary visual cortex
2. ) Gyrus - fold in the brain
   - pre-central: primary motor cortex
   - post-central: primary somatosensory cortex
3. ) Fissure - large split between adjacent large areas
   - longitudinal: separates the 2 cerebral hemispheres
   - lateral: separates temporal from frontal/parietal lobes

Question 5

4 key structures on the inferior aspect of the cerebrum

Optic Chiasm
Uncus
Parahippocampal Gyrus
Medullary Pyramids

Answer 5

1.) Optic Chiasm - where fibres in the visual system cross

2. ) Uncus - medial part of temporal (olfactory cortex)
   - can herniate, compressing the midbrain
3. ) Parahippocampal Gyrus - memory encoding
   - point of convergence of sensory information

4.) Medullary Pyramids - location of descending motor fibres (1 million axons each)

Question 6

6 structures in the midline (saggital plane) of the cerebrum

Corpus Callosum
Thalamus
Hypothalamus
Fornix
Tectum
Cerebellar Tonsil

Answer 6

1. ) Corpus Callosum - fibres (dense white matter) connecting the 2 cerebral hemispheres
2. ) Thalamus - sensory relay station projecting to sensory cortex
3. ) Hypothalamus - centre for homeostasis
4. ) Fornix - major output pathway connecting the hippocampus to the cerebral cortex
5. ) Tectum - dorsal part of the midbrain involved in involuntary responses to auditory and visual stimuli
6. ) Cerebellar Tonsil - part of the cerebellum
   - can herniate and compress the medulla

Question 7

3 features of cerebrospinal fluid (CSF)

Functions x3
Production
Re-absorption

Answer 7

1. ) Functions - metabolic and mechanical functions
   - renders the brain weightless, holding it in place
2. ) Production - by choroid plexus in ventricles
   - produces 600-700ml of CSF per day
3. ) Re-absorption - occurs at the arachnoid granulations
   - evaginations of arachnoid into dural venous sinuses

Question 8

Structure of the ventricular system

Lateral Ventricles
Third Ventricle
Cerebral Aqueduct
Fourth Ventricle

Answer 8

1. ) Lateral Ventricles - ventricle 1 and 2
   - septum pellucidum separates the 2 lateral ventricles
   - communicate via the interventricular foramen
2. ) Third Ventricle - below the lateral ventricles
   - squashed between the left and right thalamus
   - interthalamic adhesion connects the thalami
3. ) Cerebral Aqueduct - drains into the 4th ventricle
   - very narrow so can be occulded leading dilation of the ventricles above
4. ) Fourth Ventricle - CSF enters subarachnoid space via:
   - median aperture (foramen of magendie)
   - lateral aperture (foramen of luschka) x2

Question 9

Order of the flow of CSF from the brain to the heart and lungs

6 structures

Answer 9

1. ) Lateral Ventricles
   - flow through interventricular foramina
2. ) 3rd Ventricle
   - flow through cerebral aqueduct
3. ) 4th Ventricle
   - flow through lateral and median apertures
4. ) Subarachnoid Sapce
5. ) Arachnoid Villi of DVS
   - flow through venous blood
6. ) Heart and Lungs

Question 10

What is the difference between a T1 and T2 MRI scan

Why is gadolinium contrast added to MRI scans?

Answer 10

T1 - tissues are bright

T2 - water/CSF is bright

Gadolinium Contrast - doesn’t pass the BBB
- useful in detecting disruption of the BBB by neoplasm, infection, trauma