Introduction to the Central Nervous System
Brain
Concentrate on three distinct regions of the brain; cerebrum, cerebellum and brainstem.
Cerebrum is fully developed telencephalon, the forward portion of the embryonic prosencephalon. It takes the shape of two large lateral hemispheres. Cerebrum is associated with memory, reasoning ability, sensory integration and cognitive control of motor efferents. On slide 84, look for the following in the cerebrum:
- pia mater
- grey matter
- molecular layer
- succeeding layers of larger pyramidal cells
- white matter
- myelinated efferent fibres
- ependymal cells from the lateral ventricles
Cerebellum is associated with coordination, motor skills and automatic (not autonomic) use of skeletal muscles, for example, the muscles of posture. It is easily located on slide 84. Look for the following structures:
- pia mater with small blood vessels
- grey matter
- molecular layer
- Purkinje cells
- granular cell layer
- white matter
- myelinated efferent fibres
- rows of oligodendrocyte nuclei
Brainstem begins at the end of the spinal cord approximately below the cerebellum and pons. In the spinal cord grey matter is in the centre ... in the cerebrum and cerebellum grey matter is peripheral ... in the brainstem the switching of locations of grey and white matter takes place, producing a mixture of the two matters. Brainstem is also characterized by dense collections of nerve somas into regions called nuclei.
The brainstem includes the entire diencephalon and mesencephalon, the ventral portion of the metencephalon and the entire myelencephalon. It connects the cerebrum to the spinal cord and cerebellum, houses the limbic system that controls seasonal changes of reproduction and the hypothalamus where basic bodily functions such as temperature regulation occur. The neural pituitary is considered an extension of the brainstem. Look for the following features on slide 84:
- base of cerebellum
- distinct clusters of somas (nuclei)
- both central and peripheral white matter
- (possibly) some ependyma of the 4rth ventricle
- cross sections of (accessory) cranial nerve XI
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