While it is clear that such a response would be critical for survival for our ancestors, who lived in a world full of real physical threats, many of the high-arousal situations we face in the modern world are more psychological in nature. For example, think about how you feel when you have to stand up and give a presentation in front of a roomful of people, or right before taking a big test.
You are in no real physical danger in those situations, and yet you have evolved to respond to any perceived threat with the fight or flight response. This kind of response is not nearly as adaptive in the modern world; in fact, we suffer negative health consequences when faced constantly with psychological threats that we can neither fight nor flee.
Once the threat has been resolved, the parasympathetic nervous system takes over and returns bodily functions to a relaxed state. These processes are associated with activation of the parasympathetic nervous system. The brain and spinal cord make up the central nervous system. The peripheral nervous system is comprised of the somatic and autonomic nervous systems. The somatic nervous system transmits sensory and motor signals to and from the central nervous system.
The autonomic nervous system controls the function of our organs and glands, and can be divided into the sympathetic and parasympathetic divisions. Sympathetic activation prepares us for fight or flight, while parasympathetic activation is associated with normal functioning under relaxed conditions. What are the implications of compromised immune function as a result of exposure to chronic stress?
Hopefully, you do not face real physical threats from potential predators on a daily basis. However, you probably have your fair share of stress. What situations are your most common sources of stress? The peripheral nervous system includes both a voluntary, somatic branch and an involuntary branch that regulates visceral functions.
Examples of body processes controlled by the ANS include heart rate, digestion, respiratory rate, salivation, perspiration, pupillary dilation, urination, and sexual arousal. 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 SoNS consists of efferent nerves responsible for stimulating muscle contraction, including all the non-sensory neurons connected with skeletal muscles and skin.
The somatic nervous system controls all voluntary muscular systems within the body, and also mediates involuntary reflex arcs. The somatic nervous system consists of three parts:. Your five basic senses — touch, small, taste, vision and hearing — are rooted in your nervous system.
There are many ways to divide the nervous system up for purposes of study; for example, "afferent nerves of the right lower limb" would refer specifically to the afferent sensory nerves of your right thigh, calf and shin, and exclude the efferent motor nerves of those regions. The nervous system can be divided into portions on the basis of anatomy, on the basis of function or using a combination of both. Most schemes begin by distinguishing between the central nervous system or CNS, which includes the brain and spinal cord, and the peripheral nervous system, which includes all other nervous-system tissue.
Finally, the ANS can be divided into the parasympathetic and sympathetic nervous systems on the basis of the type of involuntary responses generated within each. The somatic nervous system includes everything under your voluntary control as well as one involuntary function, the somatic reflex arc this is what a doctor tests for when tapping the tendon under your knee with rubber hammer.
The SNS includes both afferent sensory nerves that transmit various types of information e. The nerves of the SNS are classified on the basis of location. For example, there are 12 pairs of cranial nerves, which originate in the head and supply the muscles of the eyes, throat and other areas within the head with both motor and sensory fibers; and 31 pairs of spinal nerves, all of which service the voluntary muscles of the trunk, pelvis, arms and legs.
The neurotransmitter chemical acetylcholine is an excitatory neurotransmitter in the SNS, meaning that it tends to stimulate movements.
The autonomic nervous system vs somatic nervous system distinction is functional: While the somatic nervous system is under your conscious control, none of the autonomic nervous system is. Of course, the two systems interact, with involuntary nervous-system responses permitting more energetic purposeful movements and so on.
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