3. Central Nervous System

NERVOUS SYSTEM

There are two types of nervous system.

1. Central Nervous System (CNS)

2. Peripheral Nervous System (PNS)

3.1 CENTRAL NERVOUS SYSTEM (CNS)

The CNS consists of the brain and the spinal cord.

Above - The brain and the spinal cord are inter-connected.

THE BRAIN

The brain is covered by an outermost protective layer known as the meninges. The meninges protects the brain from infections.

The brain consists of the forebrain, midbrain and the hindbrain.

Above - Different parts of the brain.

3.1.1 Forebrain

• Main components – cerebrum, hypothalamus & pituitary gland

1. Cerebrum: Intelligence, memory, learning and overall control of all voluntary actions.

2. Hypothalamus: Regulation of body temperature, blood osmotic pressure, appetite, sleep.

3. Pituitary gland: Serves as a master gland that produces many important hormones, eg. Anti-diuretic hormone (ADH).

3.1.2 Mid-brain

· Consists of the optic lobes which are responsible for visual reflexes (eg movement of eyeballs).

3.1.3 Hind-brain

· Consists of cerebellum and medulla oblongata.

· Cerebellum: Control muscular coordination & maintain body balance.

· Medulla oblongata: Controls involuntary action, eg. Heartbeat, peristalsis, rate of respiratory movements, contraction and dilation of blood vessels.

THE SPINAL CORD

Transverse section of the spinal cord when viewed under the light microscope, 40x magnification.

· The spinal cord extends from the medulla oblongata to the end of the vertebral column.

· Vertebral column serves to protect the spinal cord.

The cerebrospinal fluid provides nutrients for the spinal cord.

· Grey matter mainly consists of cell bodies of neurones. Grey matter makes up the inner region of the spinal cord and the outer region of the brain respectively.

· White matter mainly consists of nerve fibres. White matter makes up the outer region of the spinal cord and the inner region of the brain respectively.