Nervous system is divided into central and peripheral nervous systems. Central nervous system consists of brain and spinal cord. Brain consists of cerebrum, cerebellum, midbrain, pons, medulla oblongata. Neurons are supported by connective tissue called neuroglia. Peripheral nervous system is made up of peripheral nerves—12 pairs of cranial nerves attached to brain (olfactory, optic, oculomotor, trochlear, trigeminal, abducent, facial, vestibulocochlear, glossopharyngeal, vagus, accessory and hypoglossal) and spinal nerves attached to spinal cord, and associated ganglia. Nerves are myelinated or non-myelinated. Brain and spinal cord are covered by meninges—dura, arachnoid and pia mater. Meningeal layer of dura mater forms folds called falx cerebri, falx cerebelli, tentorium cerebelli, diaphragma sellae. Interior of brain has cavities called ventricles— two laterals, third and fourth. Ventricles contain cerebrospinal fluid. Autonomic nervous system consists of sympathetic and parasympathetic nerves.