Define the sympathetic nervous system, Science

Define the Sympathetic Nervous System

The sympathetic component of the autonomic nervous system is concerned with in- creasing the level of arousal and energy expenditure - primitive 'fight or flight' behaviour at times of stress. Alike the parasympathetic nervous system, the central integrating center for sympathetic activity is within the hypothalamus. This may be influenced by higher cortical centre. Efferent fibres descend from the hypothalamus within the intermediolateral columns of the spinal cord. As sympathetic fibres emerge from the central nervous system at spinal segments TI (thoracic) to L5 (lumbar), the sympathetic system is also known as the thoraco-lumbar outflow. Here 3 neurons are involved in covering impulses from the hypothalamus and medulla oblongata to effectors organs and tissues.

Neuron - 1: has its cell in the brain and its fibre extends to the spinal cord.

Neuron - 2: has its cell in lateral column of gray matter in the spinal cord.

Neuron - 3: has its cell in a ganglion (small mass of nerve tissue containing the cell bodies of the neuron) and terminates in the organ or tissue supplied.

 The preganglionic motor neurons of the sympathetic system arise in the spinal cord (lateral group column). They pass into sympathetic ganglia which are organized into two chains that run parallel to and on either side of the spinal cord. The neurotransmitter of the preganglionic sympathetic neurons is acetylcholine (ACh). It stimulates action potentials is the postganglionic neurons. The neurotransmitter released by the postganglionic neurons is noradrenaline (also called norepinephrine). The action of noradrenaline on a particular gland or muscle is excitatory in some cases, inhibitory in others.

Posted Date: 5/17/2013 4:08:10 AM | Location : United States

Related Discussions:- Define the sympathetic nervous system, Assignment Help, Ask Question on Define the sympathetic nervous system, Get Answer, Expert's Help, Define the sympathetic nervous system Discussions

Write discussion on Define the sympathetic nervous system
Your posts are moderated
Related Questions
how can change the image to array

Dental Clinic Case Study A clinic with three dentists and several dental hygienists needed a system to help administer patient records. This system keeps patient details and m

Explain the Bowman’s capsule - Structures of a Nephron Bowman’s capsule: It contains the primary filtering device of the nephron, that is, glomerulus. It is a double-walled, cu

Transport of Bulk Chemicals : Ideally only sufficient concentrated acids, flammable solvents and other hazardous chemicals should be kept in the laboratory for immediate requireme

Causes of Fire :  The potential fire risk arises from the presence of combustible solids, liquids or gases in conjunction with ignition sources. One or more class is generally fou

Mars- the  Red  Planet   After Venus, Mars  is our closest neighbour. It seems very earth-like. There are ice-caps on its poles, drifting white clouds and raging dust storms in

comparing a cell to a hospital

How to Calculate the Mass of Atoms in AMU's ? To calculate the masses of atoms we need only know the numbers of the various subatomic particles within the nucleus. For our purp

Explain the Composition and Functions of Gastric Juice In resting condition, the secretion of gastric juice is little in amount and is about 10- 15 ml. After taking each meal,

In hydraulic machines a liquid that has filled a pipe is pushed at one end of the pipe. The liquid then pushes a machine part located at other end of the pipe. Why isn''t gas used