S1) Topography of the Nervous System Flashcards
What are the four basic components of the central nervous system?
- Cerebral hemispheres
- Brainstem
- Cerebellum
- Spinal cord
What are the four basic components of the peripheral nervous system?
- Dorsal and ventral roots
- Spinal nerves
- Peripheral nerves
- Ganglia
Distinguish between the composition of grey matter and white matter
- Grey matter is composed of cell bodies and dendrites (highly vascular)
- White matter is composed of axons with no cell bodies(+ supporting cells) connects ares of grey matter
Why does grey matter contain axon terminals?
Grey matter contains axons to allow communication with white matter
Why is white matter white?
White matter is white due to the presence of fatty myelin
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
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, up and down
- dorsal funiciulus contains dorsal column tract (ascending)
- lateral funiciulus contains contains lateral corticospinal trac t (descending)
- spinothalamic tract (ascending)
- ventral funiculus contains ventral corticospinal tract (descending)
What is a tract?
- found within each funiculus
- A tract is an anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter
- Impulses travel in one direction, either up or down (sensory or motor)
- eg spinothalamic tract (connects spinal cord dorsal horn to thalamus)
What is a fasciculus?
A fasciculus is a subdivision of a tract supplying a distinct region of the body
- eg gracile fasciculus supplying lower half of body, cuneate fasciculus supplying upper half
Identify the three different regions of grey matter
What is a nucleus?
A nucleus is a collection of functionally related cell bodies (grey matter)
eg thalamus
What is a cortex?
A cortex is a folded sheet of cell bodies found on the surface of a brain structure (grey matter)
outer shell of grey mater found on cerebral hemispheres and the cerebellum
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?
- Association fibres
- Commissural fibres
- Projection fibres
What do association fibres do?
Association fibres connect cortical regions within the same hemisphere
What do commisural fibres do?
Commissural fibres connect left and right hemispheres or cord halves
What do projection fibres do?
Projection fibres connect the cerebral hemispheres with the cord/brainstem and vice versa
What are the three components of the brainstem?
What is the function of the midbrain (mesencephalon)?
The midbrain regulates eye movements and reflex responses to sound and vision
Which processes are regulated by the pons?
- Feeding
- Sleep
Which key centres are found in the medulla?
- Cardiovascular and respiratory centres
- Major motor pathway (medullary pyramids)