The Hindbrain
The hindbrain is composed of the medulla oblongata, pons and cerebellum (See Diagram 2). The hindbrain collectively controls the involuntary/autonomic nervous system, sensory perception, coordination and movement.
The medulla oblongata is found in the lowest most part of the brainstem. It relays nerves signals between the brain and the spinal cord and controls and regulates the autonomic functions of respiration, blood pressure and heart rate, as well as swallowing, vomiting, defecation, and urination. Interestingly, death by hanging is a result of cervical vertebra piercing the medulla oblongata by the force of the rope, which stops breathing and the heart.
The pons resides above the medulla oblongata. The pons acts to transmit sensory information between the cerebellum and the forebrain/cerebrum, plays a role in sleep and arousal, and also acts to regulate the autonomic nervous system.
The cerebellum (See Diagram 1) contains approximately 50% of the neurons of the brain or 50 billion of the 100 billion neurons in the whole brain. Surprisingly, this is only 10% of the total volume of the whole brain, because the cerebellum is primarily composed of tiny granule cells.
The cerebellum is involved in sensory perception, coordination, and movement. The cerebellum contains many neural pathways connecting it with the cerebral motor cortex and the spinocerebellar tract. Cerebral motor cortex is a region in the forebrain that relays information to muscles. Spinocerebellar tract is a tract of nerve fibers originating in the spinal cord providing feedback on limb and joint position in space. By integrating these two pathways, the cerebellum defines movements based on constant feedback from the spinocerebellar tract.
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