1 Nervous System Topography Flashcards
What are the basic components of the CNS and the PNS (3 each)
Grey and white matter can be found in the central nervous system.
- Distinguish between the composition of grey matter and white matter.
- Why is white matter white?
- Grey matter is composed of cell bodies and dendrites (highly vascular)
- White matter is composed of axons (+ supporting cells)
- Oligodendrocytes- many axons for one cells*
- Schwann cells- one axon for one cell*
In the peripheral nervous system, identify the equivalent structures of the following:
- Grey matter
- White matter
- The PNS equivalent of grey matter is a ganglion
- The PNS equivalent of white matter is a peripheral nerve
- Beware ‘basal ganglia’ in CNS (only ganglia in CNS)*
How many segments does the spinal cord consist of?
The spinal cord is composed of 31 segments
Describe the structure of a spinal cord segment
- Central core of grey matter
- Outer shell of white matter
Each segment connects with a mixed spinal nerve through dorsal sensory roots and ventral motor roots
Identify three components of white matter
- Funiculus
- Tract
- Fasciculus
What is a funiculus?
- A funiculus is a segment of white matter containing multiple distinct tracts
- Impulses travel in multiple directions
What is a tract?
- A tract is an anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter
- Impulses travel in one direction (unidirectional)
What is a fasciculus?
A fasciculus is a subdivision of a tract supplying a distinct region of the body
Identify the three different regions of grey matter
What is a nucleus?
A nucleus is a collection of functionally related cell bodies (grey matter)
(motor neurones supplying a given muscle arise from multiple segments and form a distinct population of neurones- a nucleus)
What is a cortex?
A cortex is a folded sheet of cell bodies found on the surface of a brain structure (grey matter) (1-5mm thick)
What is a fibre?
A fibre is an axon in association with its supporting cells e.g. oligodendrocytes (synonymous with axon)
What are the three types of fibres found in the nervous system and what do they connect?
- Association fibres
- Connect cortical regions within same hemisphere
- Association fibres
- Commissural fibres
- Connect left and right hemipheres/cord halves
- Commissural fibres
- Projection fibres
- Connect cerebral hemipheres with cord/brainstem and vice versa
- Projection fibres
What are the three components of the brainstem?
What is the function of the:
- midbrain (mesencephalon)?
- pons?
- medulla?
Which cortices are found in the following locations:
- Precentral gyrus
- Postcentral gyrus
Identify them on the following image:
- Precentral gyrus: contains primary motor cortex
- Postcentral gyrus: contains primary sensory cortex
(remember we motor forwards –>)
What is the optic chiasm?
The optic chiasm is a site where fibres in the visual system cross over
What is the uncus?
- The uncus is a part of the temporal lobe that can herniate, compressing the midbrain
- It has an important olfactory role
What are the medullary pyramids?
The medullary pyramids are a location of descending motor fibres
What is the role of the parahippocampal gyrus?
The parahippocampal gyrus is a key cortical region for memory encoding
Identify the following coloured sturctures in the diagram and state their role/functions:
Having developed from a hollow tube, the brain is itself hollow.
What are the cavities in the brain called?
The cavities in the brain are called ventricles
Describe the layout of the ventricular system
What is found inside the brain ventricles?
The ventricles each contain choroid plexus, which makes a total of 600-700ml of cerebrospinal fluid per day
What functions does CSF have?
CSF has both metabolic and mechanical functions
Describe the circulation of cerebrospinal fluid
CSF circulates through the ventricular system and subarachnoid space before being reabsorbed at the arachnoid granulations in the superior sagittal sinus (and some other sites)
FIll in the missing labels:
Identify the structures shown by the coloured lines on the image:
What are arachnoid granulations?
Describe the flow of CSF from the lateral ventricles to the venous blood.
