Brain Topography Flashcards
1
Q
Compare grey and white matter
A
- Grey matter is composed of cell bodies, synapses and dendrites and is highly vascularised
- Highly vascularised to provide energy for computations
- Contains axons, allowing it to communicate with white matter
- Grey as fewer myelin and fat, and highly vascular
- White matter is composed of axons with their supporting cells
- White due to presence of fatty myelin
2
Q
Describe the structure of the spinal nerve within a spinal cord segment
A
- Dorsal root ganglia containing cell bodies
- Dorsal nerve root entering (sensory) entering spinal cord through dorsal horn
- Interneurone connecting dorsal and ventral roots
- Ventral nerve root exits at the ventral horn (motor) and joining with dorsal root to form spinal nerve (mixed)
3
Q
Define funiculus
A
- A segment of white matter containing multiple distinct tracts
- Impulses travel in multiple directions (axons travel up and down)
- Dorsal, ventral and lateral funiculus
4
Q
Define tract
A
- An anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter
- Impulses travel in one direction
5
Q
Define fasciculus
A
A subdivision of a tract supplying a distinct region of the body
6
Q
How is grey matter organised
A
- Grey matter organised into cell columns called Rexed’s laminae which have different functions
- The motor neurones supplying a given muscle arise from multiple segments and form a distinct population of neurones in the CNS (a nucleus)
7
Q
Describe the layers of white and grey matter in the brain
A
- Nucleus (grey matter) - collection of functionally related cell bodies
- Cortex (grey matter) - folded sheet of cell bodies found in the surface of a brain structure
- Fibre (white matter) - an axon in association with its supporting cells (eg oligodendrocytes)
8
Q
Describe the types of fibres in the brain
A
- Association fibres connect cortical regions within the same hemisphere
- Commissural fibres are fibres connecting the two hemispheres
- Projection fibres connect the cerebral hemispheres with the cord/brainstem and vice versa
9
Q
Describe the actions of the brainstem components
A
- Midbrain (mesencephalon) - eye movements and reflex responses to sound and vision
- Pons - feeding, sleep
- Medulla - cardiovascular and respiratory centres
- Contains a major motor pathway - medullary pyramids
10
Q
Describe the main gyri and sulci in the brain
A
- Central sulcus - separates frontal and parietal lobes
- Precentral gyrus - contains primary motor cortex
- Postcentral gyrus - contains primary sensory cortex
- Lateral fissure - separates temporal from frontal/parietal lobes
- Parieto-occipital sulcus - separates parietal from occipital lobe
- Calcarine sulcus - primary visual cortex surrounds this
11
Q
Describe the important structures in the inferior aspect of the brain
A
- Optic chiasm - where fibres in the visual system cross over
- Uncus - part of temporal lobe that can herniate, compressing the midbrain (green)
- Where primary olfactory cortex is located
- Medullary pyramids - location of descending motor fibres
- Where decussation occurs (crossing over of fibres from one side to the other)
- Parahippocampal gyrus - key cortical region for memory encoding (yellow)
12
Q
Describe the important structures forming the midline of the brain
A
- Corpus callosum - fibres connecting the two cerebral hemispheres
- Thalamus - sensory relay station projecting to sensory cortex (green)
- Cingulate gyrus - cortical area important for emotion and memory (purple)
- Hypothalamus
- Fornix - major output pathway from hippocampus (yellow)
- Tectum - dorsal part of the midbrain involved in involuntary responses to auditory and visual stimuli (brown)
- Cerebellar tonsil - part of cerebellum that can herniate and compress the medulla due to increased intracranial pressure
13
Q
Where is CSF synthesized
A
Ventricles contain choroid plexus, which synthesizes CSF
14
Q
Describe the drainage of CSF in the brain
A
- CSF within the lateral ventricles (I and II) drain through the intraventricular foramen in 3rd ventricle
- Thalamus presses 3rd ventricle, so it looks flat
- CSF drains through the cerebral aqueduct to the 4th ventricle
- 4th ventricle contains 2 lateral aperture which drains CSF into subarachnoid space
- Median aperture drains CSF dorsally into subarachnoid space
- Children can have stenosis of cerebral aqueduct, leading to build up of CSF
- Arachnoid granulations drain CSF into dural venous sinus
15
Q
State the advantages of using CT over MRI when viewing the brain
A
- CT has low resolution - difficult to see anatomical structures
- Good at seeing bone
- Bone appears white, CSF appears black
- Done quickly, and results received faster - good for suspected intracranial haemorrhage
