Central Nervous System >The Human Brain

1. The cerebellum is located at the base of the brain beneath the cerebrum.
2. It has an outer gray matter cortex and inner white matter, with a tree-like appearance in section.
3. It lacks convolutions but has numerous furrows.
4. Its main function is to maintain balance and coordinate muscular movements.
5. It does not initiate movement, but ensures timing and coordination of muscle actions; alcohol affects its function, causing unsteady movements.

The brain is protected by 3 membranous coverings called meninges (meninx: membrane) which continue backwards on the spinal cord.

The cerebrum is divided into two halves called the right and left cerebral hemispheres.

1. It is the lowest part of the brain, connecting the brain to the spinal cord.
2. It controls involuntary activities such as heartbeat, breathing, and peristalsis.
3. Damage to the medulla is usually fatal due to its role in vital functions.

The outer portion (cortex) of the cerebrum contains cell bodies of the neurons and, being grayish in colour, is called the gray matter.

Inflammation of the meninges is called meningitis.

White matter is the inner region of the cerebrum that consists mainly of myelinated axons (nerve fibres).

• Brain weighs ~1.35 kg (2% body weight, 80% water), protected in cranium, uses over 25% of body oxygen.
• Meninges & CSF — Three membranes: Dura mater → Arachnoid → Pia mater. CSF between them cushions the brain and fills the ventricles and the spinal canal.
• Forebrain — Cerebrum (85% brain mass; 2 hemispheres; 4 lobes — frontal, parietal, temporal, occipital); Diencephalon (contains thalamus and hypothalamus — regulates homeostasis).
• Midbrain — Has corpora quadrigemina (superior colliculi = visual; inferior colliculi = auditory reflexes) and red nucleus (controls posture and motor coordination).
• Hindbrain — Pons (connects brain parts); Cerebellum (balance, posture, muscle tone); Medulla Oblongata (controls heartbeat, respiration, and reflex actions like coughing, sneezing).

Gyri are the raised folds or ridges on the surface of the cerebrum.

Sulci are the grooves or depressions between the gyri on the surface of the cerebrum.

The corpus callosum is a thick band of nerve fibres that connects the two cerebral hemispheres and allows communication between them.

The subconscious or unconscious mind is a part of the cerebrum where past experiences are stored and may be recalled during dreams or hypnosis.

1. The cerebrum is the largest part of the brain and is divided into right and left hemispheres.
2. Its surface is highly convoluted with gyri (ridges) and sulci (grooves), increasing the surface area for more nerve cells.
3. The outer cortex consists of gray matter (cell bodies of neurons), while the inner portion contains white matter (nerve fibres).
4. The corpus callosum connects the two cerebral hemispheres and transfers information between them.
5. The cerebrum is the seat of intelligence, reasoning, memory, consciousness, and voluntary actions, and also stores subconscious experiences.