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Subject - medicine, cell biology
The central nervous system (CNS) of vertebrates includes the spinal cord and the brain. There, all signals coming from the body are bundled and passed on or processed.
The spinal cord runs through the spinal column. In cross-section, it is a butterfly-shaped gray substance (substantia grisea), which contains the nerve cells and their branches (cell bodies and interneurons). This gray substance is surrounded by a white substance (substantia alba), which mainly consists of myelinated nerve fibres (axons). Between the vertebrae are the spinal nerves, which branch off to the left and right to reach all peripheral areas of the body. The reflexes, such as the knee tendon reflex, have their origin in the spinal cord; these make it possible for the body to have fast reactions that do not involve the brain. The spinal cord is thus an independent central nervous organ. The second important function of the spinal cord is to connect the higher parts of the CNS (brain, medulla oblongata) with the peripheral nervous system. Sensory nerve fibres that come from sensory organs enter the spinal cord through the dorsal root, while the motor neurons that go from the CNS to the muscles exit through the ventral root.
The brain (encephalon) is, like the spinal cord, wrapped in three membrane layers (the hard dura mater, the arachnoid mater, and the pia mater) and is anatomically divided into several regions. The cerebrum lies under the 2-3 mm thick cerebral cortex and is divided into deeply grooved halves (hemispheres) that are bound to each other through the corpus callosum. This part of the brain is responsible for our thinking and cognition. The cerebellum, which also has two hemispheres, is primarily relevant to balance, movement and coordination; however it is possibly also involved in subconscious learning and acquisition of language. Between the cerebrum and cerebellum lies the diencephalon (interbrain), which steers the vegetative nervous system, including functions like heat and energy management. The brain stem is the oldest part of the brain. Here sensory input is processed; in addition, this part of the brain is also responsible for reflexive mechanisms. The hindbrain, which merges into the spinal cord, regulates heartbeat, breathing, and metabolic processes and processes various reflexes (blinking, swallowing, coughing).