L1 - intro Flashcards
Components of the CNS
- spinal cord
- brainstem
- cerebellum
- cerebral hemisphere
PNS
- spinal nerves
- cranial nerves
- ANS
- peripheral nerves
- dorsal and ventral roots
- cauda equina
Difference between the CNS and PNS
CNS:
- can’t regenerate
- myelinated by oligodendrocytes
- grey matter
- white matter
PNS:
- regenerates well
- myelinated by Schwann cells
- ganglion
- peripheral nerves = white matter equivalent
Grey matter
- Collection of cell bodies with dendrites in the CNS
- Also contains axons but less than the white matter
- highly vascular
White matter
- mainly axons in the CNS
- contains myelin which makes it white
Difference between the brain and spinal cord
The brain has an extra layer of grey matter surrounding the white matter caller the cerebral cortex
The spine has central grey matter and outer white matter. Spinal nerves are connected to a segment of the spinal cord by ventral and dorsal roots
Where does the spinal cord terminate
L2
Continues as the cauda equina
Parts of white matter
- funiculus
- tracts
- fasciculus
Funiculus
A segment of white matter containing multiple distinct tracts travelling in different directions
- dorsal, lateral and ventral funiculi
Tracts
Anatomically and functionally distinct pathways of white matter connecting two regions of grey matter travelling in one direction only.
Therefore either motor or sensory
Fasciculus
An aspect of a tract supplying a distinct region of the body
Organisation of grey matter
Organised in cell columns - rexed laminae
Nucleus
A collection of cell bodies that are functionally related
Surrounded by white matter
Tracts connect nuclei
Cortex
Folded sheet of cell bodies found on the surface of the brain
(1 - 5 mm thick)
Fibre
Axon with its supporting cells e.g. oligodendrocytes
Types of fibre
Association
Projection
Commissural
Association fibres
Connect adjacent gyri in the same hemisphere
Projection fibres
Connects the cerebral hemisphere in the brain with the spinal cord or brainstem and vice versa
Commissural fibres
Connect the left and right hemispheres
Purpose of the midbrain
Eye movements
Reflex responses to sound and vision
Role of pons
Feeding
Sleeping
Role of the medulla
Cardiovascular and respiratory centres
Contain major motor pathways in the medullary pyramids
Precentral gyrus
Contains the primary motor cortex
Postcentral gyrus
Contains the primary sensory cortex
Lateral (Sylvian) fissure
Separates the temporal lobe from the frontal and parietal lobe
Parieto- occipital sulcus
Separates the occipital lobe and parietal lobe
Calcarine sulcus
The primary visual cortex surrounds this
Optic chiasm
Site where the optic fibres cross over
Uncus
- Part of the temporal lobe that can herniate, compressing the midbrain and occulomotor nerve
- olfactory role
Medullary pyramids
Location of descending motor fibres (corticospinal tracts)
Parahippocampal gyrus
Memory encoding
Corpus callosum
Fibres connecting the 2 cerebral hemispheres
Thalamus
Sensory relay station projecting to the sensory cortex
Conscious awareness
Inferior to fornix
Cingulate gyrus
Surround the corpus callosum
Emotion and memory
Hypothalamus
Inferior to the thalamus
Homeostasis
Fornix
Inferior to the corpus callosum
Output pathway of the hippocampus
Tectum
Dorsal part of the midbrain
Responsible for involuntary responses to auditory and visual stimuli
Superior colliculus - visual
Inferior colliculus - auditory
Cerebellar tonsil
Part of the cerebellum that can herniate and compress the medulla if intracranial pressure is raised - coning
Ventricles
Cavities in the brain filled with CSF
Contain choroid plexus which produce CSF
How much CSF is produced per day
600-700ml
Ventricular system
- 1st and 2nd ventricle - lateral ventricles
- Connected by the intervertebral foramen
- 3rd ventricle compressed by the thalamus either side
- Cerebral aqueduct
- 4th ventricle which is diamond shaped
Cerebral aqueduct
Connects the third and fourth ventricle
Very narrow therefore most susceptible to occlusion
CSF leaving the ventricular system
Leaves the 4th ventricle via
- central canal (minimal)
- foramen of Luschka laterally
- foramen of magendie medially
Drains into the subarachnoid space where it is reabsorbed by arachnoid granulations
CSF
Metabolic function
Contains immune cells
Acts as buoyancy mechanism for brain
Lateral ventricles
Where most CSF made
Biggest ventricles
