Outline of the human nervous system

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The following diagram is provided as an overview of and topical guide to the human nervous system:

Contents

Human nervous system Nervous system diagram-en.svg
Human nervous system

Human nervous system the part of the human body that coordinates a person's voluntary and involuntary actions and transmits signals between different parts of the body. The human nervous system consists of two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain and spinal cord. The PNS consists mainly of nerves, which are long fibers that connect the CNS to every other part of the body. The PNS includes motor neurons, mediating voluntary movement; the autonomic nervous system, comprising the sympathetic nervous system and the parasympathetic nervous system and regulating involuntary functions; and the enteric nervous system, a semi-independent part of the nervous system whose function is to control the gastrointestinal system.

Evolution of the human nervous system

Some branches of science that study the human nervous system

Central nervous system

The central nervous system (CNS) is the largest part of the nervous system and includes the brain and spinal cord.

Brain

Brain center of the nervous system.

Principal regions of the vertebrate brain:

Vertebrate-brain-regions.png Brain Forebrain Telencephalon Rhinencephalon, Amygdala, Hippocampus, Neocortex, Lateral ventricles, Basal ganglia
Diencephalon Epithalamus, Thalamus, Hypothalamus, Subthalamus, Pituitary gland, Pineal gland
Midbrain Tectum, Cerebral peduncle, Pretectum, Mesencephalic duct
Hindbrain Metencephalon Pons, Cerebellum,
Myelencephalon Medulla oblongata

Peripheral nervous system

Peripheral nervous system (PNS) nervous system structures that do not lie within the CNS.

Peripheral
nervous
system
by direction afferent system
efferent system
By function Somatic
Autonomic Sympathetic
Parasympathetic
Enteric

Sensory system

A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception.

Components of the nervous system

Glial cells

Glial cells, commonly called neuroglia or glia, are supportive cells that maintain homeostasis, form myelin, and provide support and protection for the brain's neurons.

Neuron

A neuron (also known as a neurone or nerve cell) is an excitable cell in the nervous system that processes and transmits information by electrochemical signaling. Neurons are the core components of the brain, spinal cord, and peripheral nerves.

Action potential

An action potential (or nerve impulse) is a transient alteration of the transmembrane voltage (or membrane potential) across the membrane in an excitable cell generated by the activity of voltage-gated ion channels embedded in the membrane. The best known action potentials are pulse-like waves that travel along the axons of neurons.

Synapse

Synapses are specialized junctions through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands.

Neurotransmitter

Neurotransmitter endogenous chemical that relays, amplifies, and modulates signals between neurons and other cells to which they are synaptically connected.

Neurotransmitter receptor

Neurotransmitter receptor membrane receptor that can be activated by a neurotransmitter. Interactions between neurotransmitters and neurotransmitter receptors can evoke a wide range of differing responses from the cell receiving the signal, including excitation, inhibition, and various types of modulation.

Biological neural network

Biological neural network population of physically interconnected neurons that act cooperatively to form a functional circuit. Computer scientists and engineers also study artificial neural networks formed by simplified mathematical abstractions of the signaling properties of biological neurons.

Neural development

Neural development comprises the processes that generate, shape, and reshape the nervous system, from the earliest stages of embryogenesis to the final years of life.

Prenatal development of the nervous system

Neurogenesis

Eye development

Eye development

Auditory development

Motor control

Motor control comprises the activities carried out by the nervous system that organize the musculoskeletal system to create coordinated movements and skilled actions.

Learning and memory

Memory organism's ability to store, retain, and recall information. "Learning" means acquiring new knowledge, behaviors, skills, values, preferences or understanding, and may involve synthesizing different types of information.

Cognition

Cognition activities involved in processing information, applying knowledge, and changing preferences. Cognition, or cognitive processes, can be natural or artificial, conscious or unconscious.

Arousal

Arousal physiological and psychological state of being awake or reactive to stimuli.

Anatomical structures of the human nervous system by subsystem

Central nervous system

Central nervous system

Peripheral nervous system

Peripheral nervous system

See also

Related Research Articles

<span class="mw-page-title-main">Central nervous system</span> Brain and spinal cord

The central nervous system (CNS) is the part of the nervous system consisting of the brain and spinal cord, the retina and optic nerve, and the olfactory nerve and epithelia. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all parts of the bodies of bilaterally symmetric and triploblastic animals—that is, all multicellular animals except sponges and diploblasts. It is a structure composed of nervous tissue positioned along the rostral to caudal axis of the body and may have an enlarged section at the rostral end which is a brain. Only arthropods, cephalopods and vertebrates have a true brain, though precursor structures exist in onychophorans, gastropods and lancelets.

<span class="mw-page-title-main">Neuron</span> Electrically excitable cell found in the nervous system of animals

Within a nervous system, a neuron, neurone, or nerve cell is an electrically excitable cell that fires electric signals called action potentials across a neural network. Neurons communicate with other cells via synapses, which are specialized connections that commonly use minute amounts of chemical neurotransmitters to pass the electric signal from the presynaptic neuron to the target cell through the synaptic gap.

<span class="mw-page-title-main">Nervous system</span> Part of an animal that coordinates actions and senses

In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates, it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers, or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor nerves (efferent), while those nerves that transmit information from the body to the CNS are called sensory nerves (afferent). The PNS is divided into two separate subsystems, the somatic and autonomic, nervous systems. The autonomic nervous system is further subdivided into the sympathetic, parasympathetic and enteric nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Nerves that exit from the brain are called cranial nerves while those exiting from the spinal cord are called spinal nerves.

<span class="mw-page-title-main">Peripheral nervous system</span> Part of the nervous system excluding the brain and spinal cord

The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain and the spinal cord. The main function of the PNS is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body. Unlike the CNS, the PNS is not protected by the vertebral column and skull, or by the blood–brain barrier, which leaves it exposed to toxins.

<span class="mw-page-title-main">Motor neuron</span> Nerve cell sending impulse to muscle

A motor neuron is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. There are two types of motor neuron – upper motor neurons and lower motor neurons. Axons from upper motor neurons synapse onto interneurons in the spinal cord and occasionally directly onto lower motor neurons. The axons from the lower motor neurons are efferent nerve fibers that carry signals from the spinal cord to the effectors. Types of lower motor neurons are alpha motor neurons, beta motor neurons, and gamma motor neurons.

<span class="mw-page-title-main">Autonomic nervous system</span> Division of the nervous system supplying internal organs, smooth muscle and glands

The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the nervous system that operates internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its force of contraction, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response.

<span class="mw-page-title-main">Parasympathetic nervous system</span> Division of the autonomic nervous system

The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

<span class="mw-page-title-main">Sympathetic nervous system</span> Part of the autonomic nervous system which stimulates fight-or-flight responses

The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

<span class="mw-page-title-main">Nervous tissue</span> Main component of the nervous system

Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain and spinal cord, and the peripheral nervous system (PNS) comprising the branching peripheral nerves. It is composed of neurons, also known as nerve cells, which receive and transmit impulses, and neuroglia, also known as glial cells or glia, which assist the propagation of the nerve impulse as well as provide nutrients to the neurons.

In neuroanatomy, a nucleus is a cluster of neurons in the central nervous system, located deep within the cerebral hemispheres and brainstem. The neurons in one nucleus usually have roughly similar connections and functions. Nuclei are connected to other nuclei by tracts, the bundles (fascicles) of axons extending from the cell bodies. A nucleus is one of the two most common forms of nerve cell organization, the other being layered structures such as the cerebral cortex or cerebellar cortex. In anatomical sections, a nucleus shows up as a region of gray matter, often bordered by white matter. The vertebrate brain contains hundreds of distinguishable nuclei, varying widely in shape and size. A nucleus may itself have a complex internal structure, with multiple types of neurons arranged in clumps (subnuclei) or layers.

<span class="mw-page-title-main">Afferent nerve fiber</span> Axonal projections that arrive at a particular brain region

Afferent nerve fibers are axons of sensory neurons that carry sensory information from sensory receptors to the central nervous system. Many afferent projections arrive at a particular brain region.

<span class="mw-page-title-main">Myenteric plexus</span> Part of the enteric nervous system

The myenteric plexus provides motor innervation to both layers of the muscular layer of the gut, having both parasympathetic and sympathetic input, whereas the submucous plexus provides secretomotor innervation to the mucosa nearest the lumen of the gut.

<span class="mw-page-title-main">Dorsal root ganglion</span> Cluster of neurons in a dorsal root of a spinal nerve

A dorsal root ganglion is a cluster of neurons in a dorsal root of a spinal nerve. The cell bodies of sensory neurons known as first-order neurons are located in the dorsal root ganglia.

<span class="mw-page-title-main">Superior cervical ganglion</span> Largest of the cervical ganglia

The superior cervical ganglion (SCG) is the upper-most and largest of the cervical sympathetic ganglia of the sympathetic trunk. It probably formed by the union of four sympathetic ganglia of the cervical spinal nerves C1–C4. It is the only ganglion of the sympathetic nervous system that innervates the head and neck. The SCG innervates numerous structures of the head and neck.

<span class="mw-page-title-main">Sympathetic ganglia</span> Ganglia of the sympathetic nervous system

The sympathetic ganglia, or paravertebral ganglia, are autonomic ganglia of the sympathetic nervous system. Ganglia are 20,000 to 30,000 afferent and efferent nerve cell bodies that run along on either side of the spinal cord. Afferent nerve cell bodies bring information from the body to the brain and spinal cord, while efferent nerve cell bodies bring information from the brain and spinal cord to the rest of the body. The cell bodies create long sympathetic chains that are on either side of the spinal cord. They also form para- or pre-vertebral ganglia of gross anatomy.

<span class="mw-page-title-main">Lateral grey column</span>

The lateral grey column is one of the three grey columns of the spinal cord ; the others being the anterior and posterior grey columns. The lateral grey column is primarily involved with activity in the sympathetic division of the autonomic motor system. It projects to the side as a triangular field in the thoracic and upper lumbar regions of the postero-lateral part of the anterior grey column.

<span class="mw-page-title-main">Satellite glial cell</span> SINGLE CELL SOMATA

Satellite glial cells, formerly called amphicytes, are glial cells that cover the surface of neuron cell bodies in ganglia of the peripheral nervous system. Thus, they are found in sensory, sympathetic, and parasympathetic ganglia. Both satellite glial cells (SGCs) and Schwann cells are derived from the neural crest of the embryo during development. SGCs have been found to play a variety of roles, including control over the microenvironment of sympathetic ganglia. They are thought to have a similar role to astrocytes in the central nervous system (CNS). They supply nutrients to the surrounding neurons and also have some structural function. Satellite cells also act as protective, cushioning cells. Additionally, they express a variety of receptors that allow for a range of interactions with neuroactive chemicals. Many of these receptors and other ion channels have recently been implicated in health issues including chronic pain and herpes simplex. There is much more to be learned about these cells, and research surrounding additional properties and roles of the SGCs is ongoing.

Cutaneous innervation refers to an area of the skin which is supplied by a specific cutaneous nerve.

<span class="mw-page-title-main">Spinal cord</span> Long, tubular central nervous system structure in the vertebral column

The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal cord is hollow and contains a structure called the central canal, which contains cerebrospinal fluid. The spinal cord is also covered by meninges and enclosed by the neural arches. Together, the brain and spinal cord make up the central nervous system.