Hvad er de to dele af nervesystemet?
centralnervesystemet
Nervous system
Nervesystemet er den del af et dyr, der koordinerer dets handlinger ved at sende signaler til og fra forskellige dele af kroppen. Nervesystemet opstod først i ormelignende organismer for ca. 550-600 millioner år siden. Hos hvirveldyr består det af to hoveddele, nemlig centralnervesystemet (CNS) og det perifere nervesystem (PNS). CNS består af hjernen og rygmarven. PNS består hovedsagelig af nerver, som er lukkede bundter af lange fibre eller axoner, der forbinder CNS med alle andre dele af kroppen. Nerver, der overfører signaler fra hjernen, kaldes motoriske eller efferente nerver, mens de nerver, der overfører information fra kroppen til CNS, kaldes sensoriske eller afferente nerver. Spinalnerver har begge funktioner og kaldes blandede nerver. PNS er opdelt i tre separate undersystemer, nemlig det somatiske, det autonome og det enteriske nervesystem. Somatiske nerver formidler frivillige bevægelser. Det autonome nervesystem er yderligere underopdelt i det sympatiske og det parasympatiske nervesystem. Det sympatiske nervesystem aktiveres i nødstilfælde for at mobilisere energi, mens det parasympatiske nervesystem aktiveres, når organismen er i en afslappet tilstand. Det enteriske nervesystem fungerer til at kontrollere mave-tarmsystemet. Både det autonome og det enteriske nervesystem fungerer ufrivilligt. Nerver, der udgår fra kraniet, kaldes kranienerver, mens de nerver, der udgår fra rygmarven, kaldes rygmarvsnerver.
central nervous system
Nervous system
The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. 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 or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent. Spinal nerves serve both functions and are called mixed nerves. The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic 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. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.
Nervous system