The Five Major Divisions of the Brain

ForebrainTelencephalon

Diencephalon

MidbrainMesencephalon

HindbrainMetencephalon

Myelencephalon

Myelencephalon

(Or the medulla)Composed largely of tracts carrying signalsbetween 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 thehypothalamus 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 Documents1. Build a Brain

Tasks: Useful Links – Investigate!1. The Brain Resource2. Neuroscience (the resource for the “Brain Bee”)

3. Brain Tutorial4. Brain Atlas (scroll down)