.
.
*********************************************************
*********************************************************
*THE PERIPHERAL NERVOUS SYSTEM*
*********************************************************
*********************************************************
.
*the nervous system is the part of an animal’s ‘body’ that |coordinates its ‘voluntary’ + ‘involuntary’ actions| / |transmits ‘signals’ to + from different parts of its ‘body’|*
.
(‘nervous tissue’ first arose in ‘worm-like organisms’ about ‘550 million’ to ‘600 million’ years ago)
.
(in ‘vertebrate species’ it consists of 2 main parts…)
‘central nervous system’
(‘CNS’)
‘peripheral nervous system’
(‘PNS’)
.
(at the ‘cellular level’, the ‘nervous system’ is defined by the presence of a special type of ‘cell’ called the ‘neuron’…)
(also known as a “nerve cell”)
.
(‘neurons’ have special structures that allow them to send ‘signals’ rapidly and precisely to other ‘cells’)
(they send these ‘signals’ in the form of ‘electrochemical waves’ traveling along ‘thin fibers’ called ‘axons’, which cause ‘chemicals’ called ‘neurotransmitters’ to be released at junctions called ‘synapses’)
(a ‘cell’ that receives a ‘synaptic signal’ from a ‘neuron’ may be ‘excited’, ‘inhibited’, or otherwise ‘modulated’)
(the connections between ‘neurons’ can form ‘neural circuits’ and also ‘neural networks’ that generate an organism’s perception of the world and determine its behavior)
(along with ‘neurons’, the ‘nervous system’ contains other ‘specialized cells’ called ‘glial cells’ (or simply ‘glia’) which provide ‘structural’ and ‘metabolic’ support)
.
(‘nervous systems’ are found in most ‘multi-cellular animals’, but vary greatly in complexity)
.
(the only ‘multicellular animals’ that have no ‘nervous system’ at all are ‘sponges’, ‘placozoans’, and ‘mesozoans’, which have very simple body plans)
(the ‘nervous systems’ of the radially symmetric organisms ‘ctenophores’ (aka ‘comb jellies’) and ‘cnidarians’ (which include ‘anemones’, ‘hydras’, ‘corals’, and ‘jellyfish’) consist of a diffuse ‘nerve net’)
(all other ‘animal species’ (with the exception of a few types of ‘worm’) have a ‘nervous system’ containing a ‘brain’, a ‘central cord’ (or 2 cords running in parallel) and ‘nerves’ radiating from the ‘brain’ and ‘central cord’)
(the size of the ‘nervous system’ ranges from ‘a few hundred cells’ in the simplest worms, to around ‘300 billion cells’ in ‘african elephants’)
(the ‘central nervous system’ functions to send ‘signals’ from one ‘cell’ to others, or from one ‘part of the body’ to others and to receive ‘feedback’)
(malfunction of the ‘nervous system’ can occur as a result of ‘genetic defects’, ‘physical damage’ due to ‘trauma’ or ‘toxicity’, ‘infection’, or simply of ‘aging’)
(the medical specialty of ‘neurology’ studies ‘disorders’ of the ‘nervous system’ and looks for ‘interventions’ that can ‘prevent’ or ‘treat’ them)
(in the ‘peripheral nervous system’, the most common problem is the failure of ‘nerve conduction’, which can be due to different causes including ‘diabetic neuropathy’ and ‘demyelinating disorders’ such as multiple sclerosis and ‘amyotrophic lateral sclerosis’)
(‘neuroscience’ is the field of science that focuses on the study of the ‘nervous system’)
.
“limbal system” –>
(latin for “border / edge”)
(although it is clearly in the center)
(so it is obviously obsolete)
.
.
.
.
👈👈👈☜*“LIST OF ‘HUMAN BODY SYSTEMS”* ☞ 👉👉👉
.
.
💕💝💖💓🖤💙🖤💙🖤💙🖤❤️💚💛🧡❣️💞💔💘❣️🧡💛💚❤️🖤💜🖤💙🖤💙🖤💗💖💝💘
.
.
*🌈✨ *TABLE OF CONTENTS* ✨🌷*
.
.
🔥🔥🔥🔥🔥🔥*we won the war* 🔥🔥🔥🔥🔥🔥