13. The brain and the nervous system
Contents of the chapter
13.1 The nervous system
The central nervous system
The central nervous system consists of the brain and the spinal cord. The spinal cord runs along the spine in the spinal canal, protected by the vertebrae. In a human, 31 pairs of spinal nerves, one on each side of the vertebral column, branch around the body and form the peripheral nervous system.The peripheral nervous system
The peripheral nervous system carries messages towards the central nervous system from various sensory cells, such as the surfaces of internal organs, joints, tendons and skin.
The peripheral nervous system also includes the motor nerves that carry information from the brain and spinal cord to muscle fibers throughout the body. These motor neurons allow us to take physical action in response to stimuli in the environment.
The involuntary autonomic nervous system in the peripheral nervous system controls functions that we cannot consciously influence at all. For example, digestion and heart rate function completely without conscious control or the ability to influence it. The autonomic nervous system also regulates, for example, the body's temperature.
Part of the autonomic nervous system works when we are at rest and the other half when the person is active. For example, when you rest, your heart rate drops, but your digestion becomes more efficient. When you run, your heartbeat picks up again, but digestion stops.
The nervous system.13.2 The brain
The brain controls both our conscious and unconscious actions.
The cerebrum of the human brain is particularly wrinkled compared to those of other closely related species. The surface of the cerebral cortex contains folds, ridges and furrows, which increase the surface area of the cerebrum. This allows more nerve cells to inhabit a small space and thus increases the brain's functional capacity. Indeed, our brains consume about 20 percent of our daily energy needs.
The cerebrum processes information from different senses and makes it conscious. The cerebrum is also able to remember, learn and combine old information, as well as to produce speech. Areas of vision, hearing, smell, and speech have been separated from the cerebrum. For example, when you fall and hit the back of your head hard, the visual area of the brain is activated and you may perceive flashes in your eyes.
The cerebellum is the area at the back and bottom of the brain, behind the brainstem. The cerebellum is also very wrinkled. For example, the fine-tuning of muscle movements, such as finger movements, occurs in the cerebellum. Complex sets of movements, such as cycling, also happen with the help of the cerebellum. Alcohol has a strong effect on the cerebellum, which means that under its effects the fine-tuning of movement no longer functions properly.
The Medulla oblongata is the lowest part of the brain, positioned at the top of the spinal cord. The medulla oblongata controls activities such as heartbeat, blood pressure and breathing.
The Unfixed Brain | University of Utah Neuroscience Initiative 
13.3 Parts of the brain
- Cerebral cortex: production of sensations and voluntary movements
- Cerebrum: the source of thought, memory and emotion
- Cerebellum: the regulation of movement and balance
- Internal parts of the brain: midbrain, corpus callosum, pons
- Pituitary gland (see Chapter 11)
- Medulla oblongata: The regulation of respiration and cardiac function
13.4 Muscle control and movement
The command that makes your muscles contract can come either in the form of a conscious command from the brain or in the form of a reflex. For example, you can order your biceps to contract, causing your arm to flex.
Information travels from the cerebellum to the spinal cord and along the peripheral nervous system to the biceps muscle cells (see the drawing below).
Reflexes are quick reactions, because they are not guided by the commands of the brain. For example, information about a finger hitting a hot plate is quickly transmitted to the spinal cord. From there, the message travels to the hand muscles, which contract and lift the finger from the hot surface. In other words, the information does not pass through the brain at all.
13.5 Memory and learning
Memory is necessary for data processing, recalling things and making decisions. Without it, we would not be able to cope with everyday tasks. Remembering is one of the important functions of the brain (the hippocampus of the temporal lobe). Often, memory refers to the storing of information in the long-term memory.
Memory can be divided into many functional types: sensory memory is divided into iconic memory (visual), echoic memory (auditory) and haptic memory (touch) according to the area of the cerebral cortex in which the sensory information is stored. With the help of sensory memory, things heard and seen can be kept in mind.
Short term (working) memory only keeps things in mind momentarily for a few seconds, just like sensory memory. The working memory can be used to remember a password or a code when we write it, for example. Long-term memory, on the other hand, is where data, memories and events are stored for a lifetime. Without long-term memory, we would have no identity of our own and no life history. Procedural memory, which is a part of the long-term memory is responsible for knowing how to do things, such as accomplish movements.
Learning refers to the process of moving things into long-term memory. Sleep, memory and learning are all interrelated. Dream is known to have a learning-enhancing effect, because during sleep the so-called memory traces are strengthened. Memory traces are created when information is memorized during the learning process. In this way, permanent new routes and connections to the neural network are created, as the communication between neurons changes permanently.
