BRAIN

Anantomic features

• Three major anatomical structures: cerebrum, cerebellum and brain stem

• The hindbrain - the part continuous with the spinal cord (medulla oblongata). The floor constitutes the medulla and pons, the sides - cerebellum, and the lumen of the neural tube - the cavity called the forth ventricle (metencephalon)
• The midbrain (mesencephalon) contains aggregates of nerve cells - nuclei, its lumen is reduced to a small aqueduct
• The forebrain in the caudal part (diencephalon) form thalamus and hypothalamus, its lumen - the third ventricle. In the rostral part (telencephalon) the wall form two hemispheres of cerebrum with lateral ventricles
• The gray matter contains nerve cells bodies, axons, dendrites, and glial cells and is the site of synapses
• The white matter contains axons of nerve cells, associated glial cells and blood vessels. Bundles of axons going to or coming from a specific location are called tracts

MENINGES

Function: cover the brain

Composition:

• The dura mater, the outermost layer - relatively thick sheet of dense connective tissue with venous sinuses
• The arachnoid layer - connective tissue sheet joined to the inner surface of the dura is covered by thin squamous epithelium and extends trabeculae to the pia mater. The subarachnoid space contains cerebrospinal fluid
• The pia mater - the delicate connective tissue layer that lies directly on the surface of the brain and is continuous with perivascular sheath of blood vessels of the brain. The inner surface is covered by squamous epithelium

CEREBRUM

Function: sensory information is integrated and voluntary motor responses are initiated and coordinated, complex thought processes such as learning, memorization, and acquisition and use of language take place.

• Cortex

• Molecular layer - relatively few cell bodies and numerous unmyelinated fibers which run in many directions but generally parallel with the surface
• Outer granular layer - the cell bodies of many small neurons
• Pyramidal cell layer - pyramid-shaped cell bodies of neurons
• Inner granular layer - the cell bodies of many small neurons
• Internal pyramidal layer - huge pyramidal motor neurons (Betz cells)
• Layer of polymorphic cells

• Medulla or inner core

Composition: white matter with some nuclei of gray matter

CEREBELLUM

Function: modulation and organization of the motor impulses so as to regulate and coordinate movements involving groups of muscles

• Cortex

• Molecular layer - relatively few small cell bodies and numerous unmyelinated fibers
• Purkinje cell layer - huge flask-shaped neurons.
• Granular layer - the cell bodies of many small neurons.

• Medulla or inner core

Composition: white matter with some nuclei of gray matter

BRAIN STEM

Composition: distinction between white matter and gray matter is not evident. The latter form the nuclei - the islands of cell bodies of motor neurons.