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Nervous System

Beyond Human‐Artificial intelligence not so far away! Beyond Human‐Artificial intelligence not so far away! The real challenge of Artificial intelligence (AI) is to understand how natural intelligence works. We do know that the brain contains billions and billions of neurons, and that we think and learn by establishing electrical connections between different neurons. But we don't know exactly‐how all of these connections add up to higher reasoning, or even low‐level operations. The complex circuitry seems incomprehensible. Because of this, AI scientists hypothesize on how and why we learn and think, and they experiment with their ideas using robots. Let's start understanding the organization of human nervous system which forms the base for such type of advances.

Learning Objectives

After completing the topic, the student will be able to:

  • Describe the basic structure of neuron and list different types of neurons.
  • Discuss the changes in ion concentrations inside and outside of a neuron that result in an action potential.
  • Define the term ″synapse″ and distinguish between direct synaptic and indirect synaptic transmission.
  • Summarize the role of various neurotransmitters in propagating nerve impulses.
  • Compare and contrast Central nervous system and Peripheral nervous system.
  • Describe the anatomy and function of spinal cord and spinal nerves.
  • List out the major regions of human brain and describe some of the major functions of each.
  • Understand and explore the mechanism of reflex action and arcs.
  • Explore the causes and types of symptoms seen in some common neurological disorders.
Human nervous system Human nervous system Illustration of the nervous system within a human male figure. The brain (at top) and spinal cord constitute the central nervous system (CNS). The CNS integrates all nervous activities. There are 31 pairs of nerves that branch off the spinal cord into a network; they carry nerve impulses from the CNS to various structures of the body (skin, skeletal muscle, internal organs, glands) and back from these structures to the CNS. Nerves outside of the CNS are part of the peripheral nervous system. This nerve anatomy allows the human body to respond to outside stimuli, to move, feel, and to make intelligent choices.
Nervous system and Brain

Nervous System

The nervous system is a highly specialized network, which regulates activities that are under conscious control such as receiving external stimuli and coordinating the body's movements. The nervous system responds to external stimuli such as viewing a football match and responds through physiological changes such as increase of adrenaline in the system and increase of one's heartbeat along with the sense of excitement.

The nervous system works even when a person is resting by controlling and coordinating activities such as slowing the heart beat, dilation of blood vessels and the stimulation of the digestive and genitourinary systems. The nervous system also manages every aspect of digestion.

The human nervous can be connected into many systems that can function together and the two systems, which the neural pathways cross through are central nervous system (CNS) and the peripheral nervous system (PNS). The peripheral nervous system (PNS) consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system (CNS) to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood‐brain barrier, leaving it exposed to toxins and mechanical injuries. The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

Peripheral nervous system connections with various organs and structures of the body are established through cranial nerves and spinal nerves. There are 12 pairs of cranial nerves in the brain that establish connections in the head and upper body, while 31 pairs of spinal nerves do the same for the rest of the body. While some cranial nerves contain only sensory neurons, most cranial nerves and all spinal nerves contain both motor and sensory neurons.

Central nervous system Central nervous system Artwork showing the brain, facial nerves and the top portion of the spinal cord. Above the spinal cord is the brainstem, which controls automatic functions, sleep and arousal and relays messages from the brain to the spinal cord. The striped structure to the right of the brainstem is the cerebellum, which controls muscle coordination and balance.
Central nervous system

The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. Brain is covered by protective layer of membranes and the skull, while the spinal cord is also protected by the vertebrae. The PNS consists of the large majority of what are commonly called nerves and are actually axonal processes of nerve cells.

The nervous system is made up of neurons which are interconnected to each other in complex arrangements and have the property of conducting, using electrochemical signals, a great variety of stimuli both within the nervous tissue as well as from and towards most of the other tissues.

Neurons are sensors that send electric messages to the Central Nervous System, which send the electric messages back to the neurons telling them how to react and the messages are finally sent back to the brain. Thus, neurons coordinate multiple functions in organisms by sending messages that travel at a usual pace of 100 meters per second. Glia cells provide support and protection for neurons and are thus known as the "glue" of the nervous system.

The four main functions of glia cells are to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy pathogens and remove dead neurons. Glia cells also maintain homeostasis, form myelin and participate in signal transmission in the nervous system.

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