The Five Major Divisions of the Brain
Forebrain Telencephalon Diencephalon Midbrain Mesencephalon Hindbrain Metencephalon Myelencephalon
(Or the medulla) Composed largely of tracts carrying signals between the rest of the brain and the body. A major component is the reticular formation – a complex network of about 100 tiny nuclei that occupies the central core of the brain stem. Q. What is the function of the reticular formation? A.
Metencephalon Like the myelencephalon, the metencephalon houses many ascending and descending tracts and part of the reticular formation. These structures create a bulge, called the pons – the other major division is called the cerebellum (little brain) Q. What is the function of the pons and cerebellum? A.
Mesencephalon Like the metencephalon, the mesencephalon has two major divisions: tectum and tegmentum. The tectum is composed of two bumps, the colliculi (“little hills”) The tegmentum is ventral to the tectum. Q. What is the function of the tectum and tegmentum? A.
Diencephalon The diencephalon is also composed of two major structures: the thalamus and hypothalamus. The thalamus is the large, two-lobed structure that constitutes the top of the brain stem. The two lobes are joined by the massa intermedia. The hypothalamus is located below (hypo means “below”) the anterior thalamus. Q. What is the function of the thalamus and hypothalamus? What is the relationship between the hypothalamus and the pituitary gland? A.
Telencephalon The largest division of the brain and it mediates its most complex functions. Cerebral Cortex: a layer of tissue, deeply convoluted. The large furrows are called fissures, the small ones are sulci. The ridges between are called gyri.
Landmarks The two major landmarks on the lateral surface of each hemisphere are the central fissure and lateral fissure. These fissures partially divide each hemisphere into four lobes: frontal, parietal, temporal, and occipital. Q. Complete the colouring handout.
Neocortex About 90% of the cerebral cortex is neocortex (new cortex); six-layered cortex of relatively new evolution. Q.Who is Korbinian Brodmann? What is his contribution to the world of neuroscience? Provide a brief biography.
Telencephalon con’t. The hippocampus is one important area of cortex that is not neocortex – it only has three layers. It folds back on itself in the medial temporal lobe. This folding produces a shape that is, in cross-section, somewhat reminiscent of a sea horse (hippocampus means “sea horse”). Q. What is the function of the hippocampus? A.
Telencephalon con’t The limbic system and the basal ganglia motor system are structures of the subcortex. The limbic system is a circuit of midline structures that circle the thalamus (limbic means “ring”). The limbic system is involved in the regulation of motivated behaviours – including the four F’s: fleeing, feeding, fighting, and sexual behaviour.
Major structures of the limbic system include the following: amygdala, hippocampus, fornix, cingulate cortex, septum, and mammillary bodies. The three major structures of the basal ganglia: amygdala (found in both systems), striatum, (caudate + putamen) and globus pallidus. Q. The basal ganglia play a major role in the performance of voluntary motor responses. How is Parkinson’s Disease associated with this system? A.
Limbic System
ClassNet Tasks: Class Documents 1.Build a Brain Tasks: Useful Links – Investigate! 1.The Brain Resource 2.Neuroscience (the resource for the “Brain Bee”) 3.Brain Tutorial 4.Brain Atlas (scroll down)