1.1 intro and basic topography

Question 1

What are the basic components of the cns?

Answer 1

Cerebral hemispheres
Brainstem and cerebellum
Spinal cord

Question 2

What are the basic components of the pns?

Answer 2

Dorsal and ventral roots
Spinal nerves
Peripheral nerves

Question 3

True or false: because the Cauda equina lies in the cranial cavity, it is in the central nervous system.

Answer 3

False

Cranial cavity doesn’t automatically mean its in the cns

Question 4

What is grey matter composed of?

Answer 4

Cell bodies and dendrites, its highly vascular
In the central nervous system

( has some axons to communicate with white matter)

In PNS = grey matter = ganglion = collection of cell bodies

Question 5

What is white matter composed of and why is it white?

Answer 5

It’s composed of axons
(Myelinated and unmylinated) It’s white because of the presence of fatty myelin

In the PNS is termed a nerve or root.

Question 6

What is the pns equivalent of grey and white matter?

Answer 6

Grey after = ganglion (connecting cell bodies) was

Whit matter = peripheral nerve

Question 7

What is the basic structure of a spinal cord segment?

Answer 7

• 31 segments each supplying a dermatome and myotonic on each side
• central grey matter and outer white matter
• connects with a spinal nerve through dorsal sensory and ventral motor roots
• if you know the dermatome/myotome, you can localise the lesions to a given cord segment

Question 8

What type of matter makes up the cerebral cortex?

Answer 8

Grey matter

Question 9

What is a funiculius?

Answer 9

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

Question 10

What is a tract of white matter?

Answer 10

An anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter. Impulses travel in one direction (either ascending or descending)

This is how white matter is arranged

Question 11

What is a fasciculus of white matter?

Answer 11

A subdivision of a tract supplying a distinct region of the body.

Question 12

How is grey matter arranged?

Answer 12

Into cell columns

Question 13

What is a nucleus of grey matter?

Answer 13

A collection of functionally related cell bodies

Question 14

What is a cortex of grey matter?

Answer 14

A folded sheet of cells bodies found on the surface of a brain structure.

Question 15

What is a fibre of white matter?

Answer 15

A term relating to an axon in association with its supporting cells. Used synonymously with axon.

• association fibres connect cortical regions with the same hemisphere e.g U fibres
• commissary fibres connect left and right hemispheres, or cord halves e.g the corpus callosum
• projection fibres connect the cerebral hemispheres with the cord/brainstem and vice versa

Question 16

What is the function of the midbrain?

Answer 16

Eye movements and reflex responses to sound and vision

Question 17

What is the function of the pons?

Answer 17

Feeding and sleeping

Question 18

What is the function of the medulla?

Answer 18

Cardiovascular and respiratory pathway and medullary pyramids

Question 19

Where is CSF made?

Answer 19

The choroid plexus

In every brain ventricle, the most being made in large lateral ventricles (sit deep in the hemispheres)

Highly vascular choroid plexus and makes 600-700ml of CSF a day.

Question 20

Why is the brain hollow?

Answer 20

It’s developed from a hollow tube, so has hollow cavities called brain ventricles. These ventricles each contain choroid plexus which makes csf.

Question 21

Where is CSF reabsorbed?

Answer 21

At arachnoid granulation mainly

(Resemble little cauliflowers, projecting into the superior Sagittal sinus. Here CSF crosses the wall of the granulation and enters venous blood)

Question 22

What are the three primary brain regions for the

• forebrain
• midbrain
• hindbrain

Answer 22

Forebrain = prosencephalon

Midbrain = mesencephalon

Hindbrain = rhombencephalon

After neural tube closure in 4th week these dilations at the cranial end become the three primary brain vesicles

Question 23

What are flexures in the CNS?

Answer 23

Growth and development at cranial neural tube exceeds availability of space linearly so it must fold up.

Cervical floured is at the spinal cord - hindbrain junction

Cephalon flexure at the midbrain region as well.

Thus the neuraxis doesnt remain straight.

Question 24

How does a ventricular system develop in the cns?

Answer 24

Tubular structures of the developing CNS persists as development proceeds

In the adult, comprised of interconnected reservoirs filled by csf produced by cells of ventricular lining

Role: to cushion brain and spinal cord within their bony cases

Question 25

What abnormalities can occur in the ventricular system?

Answer 25

Hydrocephalus Most common in newborns suffering from spina bifida (readily treatable by use of shunt) Can occur where there is any blockage of the ventricular system e.g tumour or infection

Question 26

What are the layers of the neural tube from inside out?

Answer 26

- neural epithelial layer - intermediate mantle layer with neuroblasts - marginal layer with processes Roof and flow plates regulate dorsal and ventral patterning Alar plate = sensory Basal plate = motor

Question 27

How do you get a neural crest in cns formation?

Answer 27

Cells of the lateral border of the neuralectoderm tube They become displaced and enter the mesoderm and undergo epithelial to mesenchymal transition

Question 28

Where do functions e.g eye movement, swallowing and cardiorespiratory homeostasis take place?

Answer 28

In the brainstem and cerebellum

Question 29

What are the ascending and descending pathways in the spinal cord?

Answer 29

``` Ascending = sensory Descending = motor ```

Question 30

How does CSF flow?

Answer 30

In every brain ventricle, the most being made in large lateral ventricles (sit deep in the hemispheres) and circulates to interventricular foramen into the third ventricle (squashed flat in the mid line by the thalamus on each side). Drains from third ventricle to the fourth via the cerebral aqueduct (in the midbrain) Fourth ventricle sirs beneath the cerebellum and CSF can drain from it via the lateral (of Luschka) and median (of magendie) apertures. (Holes in the beak for CSF to drain from ventricular system into subarachnoid space) Once in subarachnoid space CSF percolates around the superficial surface of the brain and spinal cord before being ewabsodbed in franhlations

Question 31

What effect can blockage of the ventricular system have?

Answer 31

Blockage of a part of the ventricular system will lead to upstream dilatation and potential damage to structures surrounding the dilated ventricles The cerebral aqueduct is a common site for such occlusions, maybe due to congenital stenosis or tumour Blockage of the aqueduct would cause dilatation of the lateral and third ventricles but with a normal fourth ventricle (downstream)