The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and processes input from the senses, and initiates actions. (see Central Nervous System). Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria  Acoelomorpha  Orthonectida  Rhombozoa  Myxozoa  Superphylum Deuterostomia     Chordata (vertebrates, etc. ... A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... In biology, an organ (Latin organum: instrument, tool) is a group of tissues, which perform a specific function or group of functions. ... Senses are the physiological methods of perception. ... A primary concern of the theory of action in philosophy is to demarcate actions from other doings. ... The vertebrate central nervous system consists of the brain and spinal cord. ...

In animals with brains, the nervous system also generates and conducts thoughts and emotions. Thus it is the system that animates "animals" (sponges are an exception). Chemicals that target the activity of nerves generally are the most rapidly acting toxins, typically causing paralysis and/or death. In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ... This article is about the animal. ... A nerve is an enclosed, cable-like bundle of nerve fibers or axons, which includes the glia that ensheath the axons in myelin. ... A neurotoxin is a toxin that acts specifically on nerve cells, or neurons, usually by interacting with membrane proteins and ion channels. ... Paralysis is the complete loss of muscle function for one or more muscle groups. ...

Anatomy

The nervous system consists basically of two types of cells: Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ...

• Neurons are the primary cells of the nervous system
• Glia are secondary cells involved in nourishment and structural support.

Rapid signalling within the nervous system occurs by two primary mechanisms: Neurons (also spelled neurones or called nerve cells) are the primary cells of the nervous system. ... Neuroglia cells of the brain shown by Golgis method. ...

• Within neuronal nerve fibers by way of action potentials
• Between neurons by way of neurotransmitter diffusion across synapses.

An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, which conducts electrical impulses away from the neurons cell body or soma. ... Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ... Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between two neurons: the presynaptic neuron and the postsynaptic neuron. ... Diffusion is the spontaneous spreading of something such as particles, heat, or momentum. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ...

Vertebrate nervous systems

The nervous systems of vertebrate animals are often divided into a central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of all other nerves and neurons that do not lie within the CNS. The large majority of what are commonly called nerves (which are actually axonal processes of nerve cells) are considered to be PNS. The peripheral nervous system can also be roughly seen as consisting of sensory pathways and motor pathways, the latter being divided into the somatic (voluntary) nervous system and the autonomic nervous system. Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... The vertebrate central nervous system consists of the brain and spinal cord. ... The peripheral nervous system or PNS, is part of the nervous system, and consists of the nerves and neurons that reside or extend outside the central nervous system--to serve the limbs and organs, for example. ... In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... The somatic nervous system is that part of the peripheral nervous system associated with the voluntary control of body movements through the action of skeletal muscles. ... Anatomy and Physiology of the A.N.S. In contrast to the voluntary nervous system, the involuntary or autonomic nervous system is responsible for homeostasis, maintaining a relatively constant internal environment by controlling such involuntary functions as digestion, respiration, perspiration, and metabolism, and by modulating blood pressure. ...

The somatic nervous system is the voluntary part of the nervous system that coordinates a body's movements, such as maintaining a particular posture and walking. The autonomic nervous system is the involuntary part of the nervous system where all of the internal maintenance is taken care of.

The autonomic nervous system is then divided into the sympathetic division and parasympathetic division. The sympathetic nervous system responds to impending danger or stress, and is responsible for the increase of one's heartbeat and blood pressure, among other physiological changes, along with the sense of excitement he feels. The parasympathetic nervous system, on the other hand, is evident when a person is resting and feels relaxed, and is responsible for such things as the constriction of the pupil, the slowing of the heart, the dilation of the blood vessels, and the stimulation of the digestive and geniturinary systems. The sympathetic nervous system (SNS) is one half of the autonomic nervous system; the parasympathetic nervous system (PNS) is the other. ... The parasympathetic nervous system is one of two divisions of the autonomic nervous system. ...

See also

• neuroscience
• zootomy
• sensory system
• auditory system
• vision
• olfactory
• taste
• somatic sensation

Neuroscience is a field of study which deals with the structure, function, development, genetics, biochemistry, physiology, pharmacology and pathology of the nervous system. ... Zootomy is the zoological discipline that focuses on animal anatomy, in particular on the dissection of animals. ... (See also sense) A sensory system is a part of the nervous system that consists of sensory receptors, neural pathways, and those parts of the brain responsible for processing the information. ... The auditory system is the sensory system for the sense of hearing. ... Vision can refer to: Visual perception is one of the senses. ... Olfaction, the sense of smell, is the detection of chemicals dissolved in air (or, by animals that breathe water, in water). ... Taste is one of the most common and fundamental of the senses in life on Earth. ... The somatosensory system is the sensory system of somatic sensation. ...