6.1The Structure of the Human Brain
Figure 6-1 shows the structure of the human brain, which is broadly divided into seven regions: the spinal cord, medulla oblongata, pons, cerebellum, midbrain, diencephalon, and cerebrum. The spinal cord passes through the vertebral column, transmits stimulation from the body to the brain, and translates commands from the brain into actions (motion) of the body. The medulla oblongata, pons, and midbrain, collectively called the brain stem, connect the spinal cord to the cerebrum and cerebellum. The medulla oblongata is the nerve center for breathing, heart rate, and blood pressure. The pons contains a mass of nerves—the locus coeruleus and raphe nucleus—that contains transmitters noradrenaline and serotonin. The midbrain contains the substantia nigra and the ventral tegmentum, both of which are bundles of nerves that use dopamine as a transmitter. Axons (described below) from the substantia nigra and the ventral tegmentum project into the basal ganglion and prefrontal cortex, respectively. These areas are involved in movement and addiction. A lack of neurons in the substantia nigra causes Parkinson's disease. The midbrain contains the thalamus, which interrupts sensory information in the cortex, and the hypothalamus, which secretes hormones. The area surrounding the thalamus contains the basal ganglion (the putamen, globus pallidus, and caudate nucleus) and the limbic system (the hippocampus and amygdala). The cerebellum controls precise movements.