Topography Of Central Nervous System Flashcards
Basic components of central nervous system
Cerebral hemispheres
Brainstem + cerebellum
Spinal cord
What is grey matter composed of?
Cell bodies
Dendrites
Highly vascular
(Some axons)
What is white matter composed of?
Axons
+ supporting cells
Why is white matter white?
Presence of fatty myelin
Define nucleus in terms of CNS
A collection of functionally related cell bodies
Grey matter
Define cortex in terms of CNS
Folded sheet of cell bodies found on surface of brain structure
Grey matter
Describe fibre in terms of CNS
A term relating to an axon in association with its supporting cells e.g. oligodendrocytes
White matter
Types of fibres in the CNS
What do they connect?
- Association fibres: cortical regions with same hemisphere
- Commissural fibres: left and right hemispheres
- Projection fibres: cerebral hemispheres with brainstem
What are grey and white matter termed in the peripheral nervous system
grey - ganglion
white - nerve
How many segments is the spinal cord made up of?
~31
Describe the composition of matter in the spinal cord
Central grey matter
Outer shell of white matter
What do association fibres connect?
Cortical regions within same hemisphere
What do commissural fibres connect?
Left and right hemispheres
What do projection fibres connect?
Cerebral hemispheres with brainstem
What do these suggest?
- sensory deficit in dermatomal pattern
- sensory deficit across multiple segments
- sensory deficiency in homuncular pattern
- dermatomal pattern: lesion at level of doral root or spinal nerve
- multiple segments: cord lesion
- homuncular pattern: lesion above thalamus
What does a sensory deficit in dermatomal patter suggest?
Lesion at level of dorsal roots or spinal nerves
What does a sensory deficiency across multiple segments suggest?
Cord lesion
What does a sensory deficit in a homuncular pattern suggest?
Lesion above thalamus
Define funiculus
- A segment of white matter containing multiple distinct tracts
- Impulses travel in multiple directions
Define tract
- Anatomically + functionally defined white matter pathway connecting two distinct regions of grey matter
- Impulses travel in one direction
Define fasciculus
A subdivision of a tract supplying a distinct region of the body
Location of dorsal and ventral roots of spinal cord
Is it sensory or motor?
dorsal - back | sensory
ventral - front |motor
What is the midbrain responsible for?
Eye movements
Reflex responses to sound + vision
What is the pons responsible for?
Feeding
Sleep
What is the medulla responsible for?
CVS + resp centres
Major motor pathway
Subdivisions of white matter
Funiculus
Tracts
Fasciculus
Types of tracts in white matter
ascending: sensory
descending: motor
What does the central sulcus separate?
Frontal and parietal lobes
What does the pre central gyrus contain?
Primary motor cortex
What does the post central gyrus contain?
Primary sensory cortex
What does the lateral fissure separate?
Temporal lobe from the frontal + parietal lobes
What does the parieto-occipital sulus separate?
Parietal from occipital lobe
What are the medullary pyramids the location of?
Descending motors fibres
Role of the parahippocampal gyrus
Key cortical region for memory encoding
Function of corpus callosum
Fibres connecting the two cerebral hemispheres
What is the cingulate gyrus?
Cortical area important for emotion + memory
What are the fornix of the brain?
Major output pathway from hippocampus
What is the tectum?
Dorsal part of midbrain involved in involuntary responses to auditory + visual stimuli
What are the brain ventricles?
Hollow cavities in the brain containing CSF
What produces cerebral spinal fluid?
Choroid plexus in the brain ventricles
Where is most CSF made?
Lateral ventricles
Describe the flow of CSF
- made by choroid plexus
- from lateral ventricles, CSF circulates through interventricular foramen into 3rd ventricle
- 3rd ventricle into 4th ventricle via cerebral aqueduct
- drains via lateral + median apertures into subarachnoid space
- reabsorbed at arachnoid granulation in superior Sagittal sinus
What will a blockage in the ventricular system cause?
Upstream dilatation + possible damage to surrounding structures
What is the most common site of blockages in the ventricular system?
Cerebral aqueduct
Identify three different regions of grey matter
Dorsal horn
Lateral horn
Ventral horn
What types of functions does CSF have?
Metabolic
Mechanical
Why does grey matter contain axons?
To make connections with white matter
What is the limbic system circuit?
- hippocampus + amygdala connect to fornix in midline
- output to mammillary bodies
- projects to thalamus (memory) + hypothalamus (stress)
Why can damage to the fornix cause damage to memory consolidation?
Output of hippocampus to mammillary bodies
Function of the midbrain colliculus
Involved in processing optical stimuli, orienting attention, coordinating eye + head movements
