Life Sciences Term 2

Structure of the central nervous system

The Central Nervous System (CNS):

• The brain and the spinal cord together form the central nervous system (CNS)
• The whole CNS is surrounded by a system of membranes called the meninges, which protect it
• The brain is housed in the cranium and the spinal cord in the vertebral column

Structure and function of the parts of the brain

• The brain consists of three main external parts:
• The large cerebrum
• The smaller spherical cerebellum
• The brainstem which has the medulla oblongata and the pons
• The cerebrum and cerebellum are divided into two hemispheres
• The two hemispheres of the cerebrum are joined by the corpus callosum.

The spinal cord

• The spinal cord is inside the vertebral canal and is an extension of the brain
• Protection:  vertebrae, meninges and cerebrospinal fluid
• From each side of the cord 31 pairs of spinal nerves arise from ventral and dorsal roots
• Function:
• The spinal cord is the pathway for all impulses conducted to and from the brain
• The grey matter lies on the inside in the shape of an ‘H’
• The white matter lies on the outside (opposite to the cerebrum)
• The spinal cord processes all reflex actions
• The spinal cord functions automatically and is not controlled by the will
• Sympathetic and parasympathetic nerve impulses are conducted along the spinal cord to all organs