Autonomic nervous system


The autonomic nervous system is responsible for maintaining and controlling the involuntary effectors of the human body. This means that smooth muscles and involuntary actions, such as the heart, are regulated by the part of the nervous system that requires no conscious thought, but still receives directive from the brain. The human brain need not think about the heart beat, it happens because there is a specified section of the brain known as the autonomic nervous system.

Every portion of the body, whether controlled by conscious thought or hormonal release, is technically controlled by brain function. In the case of autonomic nervous system elements, variables and adjustments are made via the brain’s response to stimuli. The brain sends a signal to the heart during strenuous exercise, explaining that it requires the heart to beat faster with more force in order to sustain the body’s health during this level of activity.


The autonomic nervous system is not entirely independent of the central nervous system or the peripheral nervous system even though it does function without intentional decision or thought by the brain. The involuntary effectors which are dependant upon the autonomic nervous system include the cardiac muscle, visceral smooth muscle tissue, and glandular epithelium which is cell which secrete substances such as sweat, mucous, milk, wax, and saliva. This can mean that the variances of the diverse effectors might be part of visceral organs, blood vessels, or specialized functions that are adherent to other organs. In some cases, only part of an organ is controlled via the autonomic nervous system.
Autonomic nervous system
Image: Autonomic Nervous System


The autonomic nervous system uses somatic motor innervation to maintain the involuntary control and effects associated with involuntary action. This is in stark contrast to the entire system the voluntary skeletal muscles are controlled. The majority of somatic motor control is typically conducted along a single axiom, the necessary information passing along the spinal cord to be intercepted by the neuromuscular junction. However, the autonomic motor system in this instance relies on two neurons which follows a predetermined pathway and adheres to the motor transmission of impulses. One cell of the motor neuron begins in the brain’s gray matter or in the top of the spinal cord. The first motor neuron joins a second motor neuron and exchanges information within the bounds of an autonomic ganglion. The ganglion is defined as a cluster of cells which linger just outside the central nervous system.


To illustrate this further, the first cell is referred to either as preganglionic or presynaptic. The postganglionic cell then follows its own axon to the effector organ to help the process of carrying out the brain’s commands.

The origination point of the preganglionic neuron begins in either the mid or hindbrain as well as the spinal cord stemming from the fourth sacral portions. It does not begin however, between the area or the spinal cord known as areas L3 and S1. The clusters of cells known as autonomic ganglia are located in the abdomen as well as the head and neck. Long links of the autonomic ganglia run alongside both sides of the spinal cord, parallel to its path.


Skeletal muscles can not function without the assistance of the appropriate motor nerves and in fact will become flaccid and paralyzed if communication with the motor nerves is lost. In contrast, involuntary effects can remain in a state of chronic motion for en extended period of time despite a lack of communication with the autonomic motor nerves. While the involuntary effects can not adjust to stimuli without the motor nerves, the ability to maintain a reasonable rate of motion is present. Smooth muscles have the ability to retain a level of tension despite a lack of nerve stimulus. In the event the nerve itself becomes damaged, the involuntary effects can often become more sensitive to stimulation. The built in muscle tone helps these muscles achieve this ability. Not excluding other muscles, the cardiac muscle is able to retain a natural rhythm. The nerves are also able to obtain and retain a reasonable resting rate, despite lack of communication for a period of time.

The autonomic nervous system is a built in, never ending, battery power for those muscles and organs that require constant action or activity without demanding the conscious brain endure the constant reminding of these effectors to maintain themselves.
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human anatomy Organs included in Autonomic nervous system

Adrenal glandsAdrenergic stimulationCardiac muscle
Cholinergic stimulationDual innervationHypothalamus
NeurotransmittersParasympathetic divisionPeripheral ganglia
Smooth muscleSympathetic divisionVisceral effector organs