Some Numbers

Our brain, the source of our reason, emotions and personality, is a slimy conglomerate of several cell types that interact in a complex manner, using electrical signal transduction and chemical messengers. It weighs about 1 to 1.5 kilograms (which corresponds with 2.2 to 3.3 pounds), and while it only occupies 2% of the body’s volume, it uses 10 times as much of the oxygen, 25% of the total energy provided and 20% of the blood flow.

Man vs. Woman?

Even though it shows similarity in many aspects, there are also some differences between the brain of a man and the brain of a woman. Most notably:

• The hypothalamus, more specifically the area preoptica medialis
• The amygdala, more specifically the corticomedial nucleus
• The size, a man’s brain is on average 10% larger than that of a woman
• The number of neurons, which is larger in women, for example in the corpus callosum that connects both brain hemispheres.

Structure Simplified

In general, two types of ‘substance’ can be discerned in the human brain, gray matter and white matter. Now, what are these types of matter?

• Gray matter: This is largely composed by the cellular bodies. It is primarily found in the cortex (the outside of the brain).
• White matter: This is constituted by the myelin shafts of the axons and neural fibers and is mostly found on the inside of the brain.

The brain has a strongly layered structure and an obviously folded surface, which is strewed with coils (or gyri), deep furrows (or fissurae) and shallow furrows (or sulci).

Brain Protection

There are four structures that serve as guards for the structural integrity of the brain.

• The skull: probably the most obvious protective structure of the brain.
• The hard cerebral membrane (or dura mater): The first (and outer) of the three layers of a membrane system that surrounds the brain (called meninges), composed of dense, fibrous tissue.
• The arachnoid mater: The second (middle) layer of the meninges, with its name due to its spiderweb-like appearance. It is composed of fibrous tissue, covered with flat cells to make it impermeable to fluids.
• The pia mater: The third (inner) layer of the meninges. This is a very delicate membrane that follows all the minor contours of the brain. It is pierced with blood vessels that travel to the brain and spinal cord, and its capillaries are responsible for nourishing the brain.

Another form of protection is the cerebrospinal fluid, found between the arachnoid mater and the pia mater and in four cerebral ventricles.