Intro | Forebrain | Midbrain | Hindbrain
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
The Hindbrain is the most primitive of CNS regions and is located both posterior (toward the back) and inferior (below) relative to the other CNS regions. The cerebellum and lower brain stem structures, the medulla and pons, are located in this division. The medulla and pons are essential for maintaining life, such as cardiac function and the sleep-wake cycle. The cerebellum is essential for maintaining the integrity of motor movement.
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The hindbrain is also referred to by the Greek name, rhombencephalon; which literally means paralleogram-brain. The medulla oblongata lies just inside the skull and above the spinal cord. The medulla controls the vital reflexes underlying heart rate, respiration, vomiting, salivation, sneezing, and coughing via the cranial nerves that have nuclei (clusters of neuronal cell bodies) in this region. The 12 cranial nerves connect the skin and muscles of the head and the internal organs to the brain. Cranial nerves V through XII have nuclei located in the medulla and pons of the hindbrain. Whereas cranial nerves I through IV are located in the midbrain and forebrain. Most of the cranial nerves have both sensory and motor components. Damage to the medulla is often fatal.
Drugs such as the opiates and cocaine have profound effects on the medulla nuclei when taken at high doses; which is why these substances may result in "overdose" and death. The pons (meaning bridge) lies above the medulla, and is so named because many axons cross sides within this region of the hindbrain. Both the medulla and pons contain the reticular formation and raphe system. These nuclei contain high levels of the neurotransmitters, norepinephrine and serotonin, respectively. The projections of each nucleus are widely distributed throughout the forebrain, and these projections in concert control the overall state of physiological and behavioral/psychological arousal. Norepinephrine increases arousal to external events, whereas serotonin increases arousal to internal events.