sympathetic nervous system (SNS)

(noun)

One of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response; it is also constantly active at a basal level to maintain homeostasis.

Related Terms

Examples of sympathetic nervous system (SNS) in the following topics:

  • Divisions of the Autonomic Nervous System

    • The autonomic nervous system (ANS) contains two subdivisions: the parasympathetic (PSNS) and sympathetic (SNS) nervous systems.
    • The autonomic nervous system (ANS) is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS).
    • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
    • In the autonomic nervous system, preganglionic neurons connect the CNS to the ganglion.
    • Distinguish between the parasympathetic and sympathetic subsystems of the autonomic nervous system

  • Comparing the Somatic and Autonomic Nervous Systems

    • The peripheral nervous system (PNS) is divided into the somatic nervous system and the autonomic nervous system.
    • The somatic nervous system (SoNS) is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles.
    • The somatic nervous system consists of three parts:
    • The ANS is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS).
    • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

  • Control of Autonomic Nervous System Function

    • The medulla oblongata, in the lower half of the brainstem, is the control center of the autonomic nervous system.
    • The autonomic nervous system (ANS) is the part of the peripheral nervous system that controls involuntary functions that are critical for survival.
    • The sympathetic division of the ANS is often referred to as the sympathetic nervous system (SNS).
    • The SNS provides noradrenergic drive to the ANS.
    • The medulla is a subregion of the brainstem and is a major control center for the autonomic nervous system.

  • Autonomic Nervous System (ANS)

    • The autonomic nervous system (ANS or visceral nervous system or involuntary nervous system) is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness and controls visceral functions .
    • It is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS).
    • The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.
    • It receives extensive innervation from both the SNS and the PSNS.
    • Stimulation of the enteric nerves by the sympathetic system inhibits GI activity.

  • Preganglionic Neurons

    • In the autonomic nervous system (ANS), nerve fibers that connect the central nervous system to ganglia are known as preganglionic fibers.
    • In the autonomic nervous system (ANS), fibers from the central nervous system to the ganglion are known as preganglionic fibers.
    • All preganglionic fibers, whether they are in the sympathetic nervous system (SNS) or in the parasympathetic nervous system (PSNS), are cholinergic—that is, these fibers use acetylcholine as their neurotransmitter—and are myelinated.
    • Properties of the SNS and PSNS preganglionic neurons also differ with respect to the spinal cord exit points.
    • The site of synapse formation and this divergence for both the sympathetic and parasympathetic preganglionic neurons does, however, occur within ganglia situated within the peripheral nervous system.

  • Autonomic Reflexes

    • The autonomic nervous system (ANS, visceral nervous system, or involuntary nervous system) is the part of the peripheral nervous system that acts as a control system.
    • The ANS is classically divided into two subsystems: the parasympathetic nervous system (PSNS) and sympathetic nervous system (SNS) that operate independently in some functions and interact co-operatively in others.
    • An older simplification of the sympathetic and parasympathetic nervous systems as excitatory and inhibitory was overturned due to the many exceptions found.
    • A more modern characterization is that the sympathetic nervous system is a quick- response, mobilizing system and the parasympathetic is a more slowly activated, dampening system—but there are exceptions, such as in sexual arousal and orgasm where both play a role.
    • The enteric nervous system is also sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

  • The Stress Response

    • The body's stress response is mediated by the sympathetic nervous system and the hypothalmic-pituitary-adrenal (HPA) axis.
    • The body's stress response is mediated by the interplay between the sympathetic nervous system (SNS) and the hypothalmic-pituitary-adrenal (HPA) axis.
    • This response acts primarily on the cardiovascular system and is mediated directly via impulses transmitted through the sympathetic nervous system and indirectly via catecholamines, such as the adrenaline secreted from the adrenal medulla.
    • A feedback loop exists among the components of the HPA axis and the SNS.
    • Distinguish between the nervous system and endrocrine system responses to stress

  • Autonomic Nervous System

    • The autonomic nervous system, the relay between the CNS and internal organs, is divided into the sympathetic and parasympathetic systems.
    • There are two divisions of the autonomic nervous system that often have opposing effects: the sympathetic nervous system and the parasympathetic nervous system .
    • Most preganglionic neurons in the sympathetic nervous system originate in the spinal cord.
    • While the sympathetic nervous system is activated in stressful situations, the parasympathetic nervous system allows an animal to "rest and digest."
    • The sympathetic and parasympathetic nervous systems often have opposing effects on target organs.

  • Sympathetic Responses

    • The sympathetic division of the autonomic nervous system maintains internal organ homeostasis and initiates the stress response.
    • Alongside the other two components of the autonomic nervous system, the sympathetic nervous system aids in the control of most of the body's internal organs.
    • The sympathetic nervous system is responsible for regulating many homeostatic mechanisms in living organisms.
    • Some evolutionary theorists suggest that the sympathetic nervous system operated in early organisms to maintain survival since the sympathetic nervous system is responsible for priming the body for action.
    • His theory states that animals react to threats with a general discharge of the sympathetic nervous system, priming the animal for fighting or fleeing.

  • Autonomic Interactions

    • The sympathetic and parasympathetic autonomic nervous systems cooperatively modulate internal physiology to maintain homeostasis.
    • Some typical actions of the sympathetic and parasympathetic systems are listed below.
    • The SNS promotes a fight-or-flight response, corresponds with arousal and energy generation, and performs the following functions:
    • In the autonomic nervous system, preganglionic neurons connect the CNS to the ganglion.
    • Describe the interactions between the sympathetic and parasympathetic divisions of the autonomic nervous system