CNS Basics And Embryology

Question 1

What is grey matter composed of?

Answer 1

Cell bodies and dendrites with a large vascular supply.

Question 2

What is white matter composed of?

Answer 2

Axons and their supporting cells, along with myelin giving its white colour.

Question 3

What is a nucleus?

Answer 3

A collection of functionally related cell bodies within the CNS

Question 4

What is the cortex?

Answer 4

A folded sheet of cell bodies found on the surface of a brain structure, typically 1-5mm thick.

Question 5

What are the three types of fibre?

What do they connect?

Answer 5

Association fibres - cortical regions within the same hemisphere.
Commisural fibres - left and right hemispheres.
Projection fibres - cerebral hemispheres and the brainstem/cord.

Question 6

Why are the spinal nerves of the cauda equina drawn out further than those of the cervical spine?

Answer 6

Rapid growth of the vertebral column occurs faster than the spinal nerves.

Question 7

What is a funiculus?

Answer 7

A segment of white matter containing distinct tracts in which impulses travel in multiple directions.

Question 8

What is a tract?

Answer 8

A white matter pathway connecting two distinct regions of grey matter. Impulses travel in one direction.

Question 9

What is a fasciculus?

Answer 9

A subdivision of a tract supplying a distant region of the body

Question 10

Which fasiculus supplies the upper half of the body?

What about the lower half?

Answer 10

Fasiculus cuneatus.

Fasiculus gracilis.

Question 11

What are Rexed’s laminae?

Answer 11

Organised grey matter columns supplying a certain area of the body.

Question 12

What is the midbrain responsible for?

Answer 12

Eye movements and visual/auditory reflexes

Question 13

What is the pons responsible for?

Answer 13

Feeding and sleep regulation

Question 14

What is the medulla responsible for?

Answer 14

Cardiovascular and respiratory control,

Major motor pathways (medullary pyramids).

Question 15

Which fissure separates the temporal and frontal/parietal lobes?

Answer 15

Lateral (sylvian) fissure.

Question 16

Which sulcus separates the parietal and occipital lobes?

Answer 16

Parieto-occipital sulcus.

Question 17

What is the significance of the calcarine sulcus?

Answer 17

Primary visual cortex surrounds it. Found in the occipital lobe.

Question 18

What is the function of the parahippocampal gyrus?

Answer 18

Region for memory encoding.

Question 19

What is the clinical relevance of the uncus?

Answer 19

Part of the temporal lobe that may herniate and compress the midbrain. Also has an important olfactory role.

Question 20

What is the role of the corpus callosum?

Answer 20

Contains fibres connecting the two cerebral hemispheres

Question 21

What is the function of the thalamus?

Answer 21

Sensory relay station to sensory cortex

Question 22

What is the importance of the cingulate gyrus?

Answer 22

Cortical area involved in emotion and memory

Question 23

What is the role of the fornix?

Answer 23

Major output pathway from the hippocampus. Damage to it leads to amnesia.

Question 24

What is the role of the tectum?

Answer 24

Dorsal midbrain involved in involuntary responses to auditory and visual stimuli via inferior and superior colliculi respectively

Question 25

What is the clinical importance of the cerebellar tonsil?

Answer 25

Inferior portion of the cerebellum that may herniate and compress the medulla.

Question 26

Where is choroid plexus found? | How much CSF does is secrete per day?

Answer 26

I’m the ventricles of the brain, | 600-700ml.

Question 27

State the pathway through each of the ventricles for CSF drainage

Answer 27

Lateral ventricles - interventricular foramen - third ventricle - cerebral aqueduct of midbrain - fourth ventricle - lateral and median apertures - arachnoid granulations.

Question 28

What is craniorachischisis?

Answer 28

Failure of the entire neural tube to close, not viable with life

Question 29

What is anencephaly?

Answer 29

Failure of the neural tube to close cranially, resulting in failed development of the diencephalon. Not viable for life

Question 30

Which part of the neural tube fails to develop in most defects?

Answer 30

Dorsal scleratome.

Question 31

What is Myelocoele? (Rachischisis)

Answer 31

Failure of spinal cord to close caudally leaving it exposed. Results in severe lower limb neurological defects

Question 32

What is meningomyelocoele?

Answer 32

Herniated cyst containing spinal cord material, closed off by dura and arachnoid mater. Results in less severe lower limb defect. Caused by failed fusion of the neural arches.

Question 33

What is meningocoele?

Answer 33

Herniation of subarachnoid space containing CSF. Often neurologically stable but at increased risk of meningitis. Caused by failed fusion of the neural arches.

Question 34

What is spina bifida occulta?

Answer 34

Neural tube development defect resulting in a lack of dorsal arches but no symptoms. Usually benign.

Question 35

What cells does the neural crest help give rise to?

Answer 35

``` Sensory neurones, Enteric neurones, Schwann cells, Adrenal medulla, Melanocytes, Arachnoid and pia mater, Thymus tissue, Spiral septum of heart. ```

Question 36

What is DiGeorge syndrome?

Answer 36

22q11 deletion leading to neural crest cell defects such as an absent or dysfunctional thymus, cleft palate, congenital heart disease, learning disability and motor problems.

Question 37

What is Hirschsprung’s disease?

Answer 37

Congenital neural crest cell defect resulting in abscence of some enteric neurones and therefore chronic constipation.

Question 38

How might Spina Bifida cause hydrocephaly?

Answer 38

Adhesions may form between neurones and the spinal cord that pull the neurones down during the cords rapid growth. This compresses the foramen magnum that aids drainage of CSF and results in hydroencephaly.