1) Nervous System and Topography Flashcards
What are the Basic Components of the Central Nervous System ?
CNS:
> Cerebral Hemispheres
> Brain Stem and Cerebellum
> Spinal Cord
PNS:
> Dorsal and Ventral Roots => Cauda Equina and CNs
> Spinal Nerves
> Peripheral Nerves
White Matter Vs Grey Matter
White Matter:
> Myelinated axons with no cell bodies
> Connect areas of grey matters
> In the PNS it is referred as peripheral nerves
Grey Matter:
> Composed of Cell Bodies and dendrites
> Highly Vascularised
> In the PNS it is referred as Ganglion
What would a sensory deficit in a dermatomal pattern suggest ?
This would suggest that the lesion is at the level of dorsal roots or spinal nerves
What would a sensory deficit across multiple segments suggest ?
This would suggest a spinal cord lesion
What would a sensory deficit in a homuncular pattern suggest ?
This would suggest a lesion above the Thalamus
What are the 3 parts that make up White Matter
Funniculus:
> An area of white matter which contains multiple distinct tracts. Impulses run in multiple direction.
[] Dorsal => Contains Dorsal Column Tract (Ascending)
[] Lateral => Contains Lateral Corticospinal Tract (Descending) and Spinothalamic Tract (Ascending)
[] Ventral => Ventral Corticospinal Tract (Descending)
Tract:
> Anatomically and Functionally Defined white matter pathway connecting two distinct regions of grey matter. Impulses only travel one direction
Fasciculus:
> A Subdivision of a tract that supplies distinct body regions
e.g.
Gracile Fasciculus => Subdivision of dorsal column tract supplying lower half of body
Cuneate Fasciculus =>
Subdivision of DCT supplying upper half of body excluding head.
Describe the Anatomy of the CNS.
Nucleus => Collection of functionally Cell bodies
Cortex => The outer shell of grey matter found on the cerebral hemispheres and cerebellum
Fibre => An Axon in association with supporting Glial Cells.
> Association: Connection between cortical regions within a hemisphere
> Commissural Fibres: Connect the 2 Hemispheres together e.g. Corpus Callosum
> Projection Fibres: Connect Cerebral Hemispheres with the cord or brainstem (Crosses Mid line)
Outline a Basic Spinal Reflex
1) Receptor senses stretch
2) Afferent Sensory Neuron carries sensation to dorsal horn
3) Synapses at ventral horn
4) Efferent motor Neuron carries signal to muscles
What is a seizure ?
A medical emergency caused by uncontrolled electrical activity in the brain.
If the seizure is caused by a lesion in the cerebral cortex, activity can propagate
How can you visualise the brain ?
T1 or T2 weighted MRI
T1 vs T2 > CSF > White Matter > Cortex > Fat > Inflammation
> Dark : Bright > Light : Dark Gray > Gray : Light Gray > Bright : Light > Dark : Bright
T2 Shows Water
Why does Gadolinium (Gd) Enhance lesions ?
It can pass through the blood brain barrier, when there is inflammation the blood vessels are more leaky and so the contrast can get to the lesion
Where is CSF produced ?
The brain contains cavities, known as “Brain Ventricles”
These Ventricles contain Choroid Plexus, which is highly vascular and makes around 600 - 700 ml of CSF per day
What are the functions of CSF ?
Both Metabolic and Mechanical functions
> Contains Glucose and maybe even hormones
> Shock absorbs for the brain
> Renders the brain effectively weightless
Describe the Flow of CSF through the brain ventricles
1) All ventricles make CSF but a majority of CSF is produced large lateral ventricles
-> They sit deep in the hemispheres
2) CSF circulates through the inter ventricular foramen into 3rd Ventricle
-> Squashed flat in the mid line by the Thalamus on each side
3) CSF drains via Cerebral Aqueduct (in the mid brain) into the 4th Ventricle
-> Sits beneath the Cerebellum, within the brain stem
4) CSF can then drain 1 of 2 ways
o Lateral (Foramen of Luschka)
o Median (Foramen of Magendie)
These are direct holes in the brain, draining CSF from ventricular system into the Sub Arachnoid Space
5) Once in SAS CSF move around the surfaces of the brain and spinal cord before being reabsorbed in Granulations
