Our adult brain weighs in at about 3 pounds.
It is divided into three major regions; The Cerebrum, the Brain Stem, and the Cerebellum.
The Cerebrum- makes up about 80% of our brains and consists of two hemispheres that are mirror images of each-other.
Each Cerebral hemisphere is divided into four lobes:
1.) Frontal lobe- located behind the forehead. This lobe is responsible for intellect, planning, problem solving, and the voluntary motor control of muscles.
2.) Parietal lobe- Located posterior to the frontal lobe. This lobe receives and interprets sensory information, like spoken words.
3.) Temporal lobe- Located below the frontal and parietal lobes. This lobe interprets sensory experiences.
4.) Occipital lobe- Forms the posterior part of the hemisphere. This lobe interprets visual images and written words.
Brain Stem- Relays sensory impulses from peripheral nerves to higher brain centers. The brain stem also controls vital cardiovascular and respiratory activities.
Cerebellum- The most posterior area of the brain. The cerebellum coordinates skeletal muscle activity to maintain the body's posture and balance.
The Spinal Cord
Our spinal cord lies within, and is protected by, the vertebral canal of the spinal column.
It consists of 31 segments, each of which gives rise to a single pair of spinal nerves. These segments are the major link between the brain and the peripheral nervous system, and are the pathway for sensory and motor impulses.
The Spinal cord is divided into four regions:
1.) Cervical region- Contains the motor neurons that supply the neck, shoulders, and upper limbs through 8 pairs of cervical spine nerves (C1- C8).
2.) Thoracic region- Contains the motor neurons that supply the thoracic cage, rib movement, vertebral column movement, and postural back muscles through 12 pairs of thoracic spinal nerves (T1 - T12).
3.) Lumbar region- Supplies the hips and the front of the lower limbs through 5 pairs of lumbar nerves (L1- L5).
4.) Sacral region- Supplies the buttocks, genitalia, and backs of the lower limbs through 5 sacral nerves (S1- S5) and 1 coccygeal nerve, relative to the small bone at the base of the spine.
Our brain and spinal cord are protected by the cranium and the vertebrae, cushioned by the cerebral spinal fluid (CSF), and covered by the meninges.
The Meninges have three layers:
1.) Dura Mater- The outermost layer of tough connective tissue attached to the cranium's inner surface, but it is separated from the vertebral canal by the epidural space, into which epidural injections are introduced.
2.) Arachnoid Mater- A thin web over the brain and spinal cord. The CSF is contained in the subarachnoid space, between the arachnoid and pia mater.
3.) Pia Mater- The innermost layer of the meninges, attached to the surface of the brain and spinal cord. It supplies nerves and blood vessels that nourish the outer cells of the brain and spinal cord.