Date: Mon, 12 Dec 1994 13:11:45 -0800 From: Deborah Stiles Subject: Nervous System Anatomy To: Multiple recipients of list SOREHAND > > Yes, tingling is generally believed to be because of dilation of the > > blood vessels, increasing circulation, and warming. This is due to a > > decrease in the sympathetic nervous system response conducive to a > > relaxed state. There may also be "tingling" sensations occurring because > > Oh, so I guess that means excited sympathetic nerves contract blood vessels. The sympathetic nervous system (SNS) constricts the blood vessels of the skin and many organs; however, it dilates the vessels of the heart, lungs, brain, and the skeletal muscles needed for fighting off "danger". The tingling is from a decrease in the SNS thereby allowing the vessles of the skin to dilate and warm up. The Parasympathetic Nervous System (PSNS) generally works opposite of the SNS; however in this case, the PSNS does not usually innervate or change the vessels of the skin. > > > you are simply more aware of a particular body part and the associated > > sensations are more "loud". This may be where specific nerves are more > > heightened to slight sensations which send these signals to the brain > > (afferent sensory nerves). It is amazing all the things you can feel > > Afferent sensory nerves? I've heard bits and pieces about the > anatomy of the nervous system but I'm still pretty fuzzy. > I know there are sympathetic nerves that have to do with > autonomic functions, i.e. nominally aren't under conscious control? > And there are parasympathetic nerves which do what -- control > conscious muscle actions? And where do afferent nerves fit in -- > are they part of the sympathetic or parasympathetic systems or > another category altogether? Nervous System Anatomy I: The Central Nervous System (CNS) is made up of the brain and the spinal cord. The Peripheral Nervous System (PNS) consists of the various nerve processes that connect the brain and spinal cord to receptors, muscles, and glands. The spinal and cranial nerves are part of the PNS. The PNS is comprised of Afferent and Efferent systems which refer to the direction of communication between the CNS and the body's muscles and glands. The Afferent system conveys sensory information from receptors TO the CNS such as sensations of touch, pressure, heat, cold, and pain. The Efferent system conveys information AWAY FROM the CNS to receptors (e.g. telling your arm muscle to contract). The Efferent system consists of the Somatic Nervous System which conveys information from the CNS to skeletal muscles such as telling your leg to move. The Efferent system also consists of the Autonomic Nervous System (ANS) which conveys information from the CNS to smooth muscle, cardiac muscle, and glands (e.g. digesting food). The ANS means "automatic" or "self-governing" because it was thought that these functions were always involuntary and independent from the CNS; however, the name "ANS" has not kept up with recent advances in health sciences. Usually and thankfully the ANS is under involuntary control so we do not have to remember to breath or pump our blood. But as we have learned, the ANS can be regulated with some voluntary control. The ANS is made up of the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System (PSNS). Most organs receive impulses from both the SNS and the PSNS. They generally work opposite each other, for example, the SNS increases heart rate and the PSNS decreases heart rate. The SNS is associated with the stress response, or the "fight or flight" response. The SNS prepares your body and mind for perceived "danger". The SNS is generally concerned with the expenditure of energy from reserves that are stored in the body (e.g inhibits digestion, increases secretion of epinephrine, norepinephrine, and glucocorticoids, dilates bronchial tubes of lungs, dilates heart vessels, breaks down glycogen from the liver, inhibits insulin, tenses muscles). The PSNS is associated with relaxation and is often concerned with activites which increase the body's supply of stored energy (salivation, gastric motility, digestion, changes glucose to glycogen to be stored in the liver). Research has shown that various relaxation exercises (Yoga, biofeedback, meditation, etc.) alter physiologic processes which were once thought to be uncontrollable. Relaxation enhances the PSNS and/or inhibits the SNS and affects every system/organ of the body, even things like brain wave patterns, pupil dilation, immunity, and fertility. Eastern systems have been practicing these concepts for centuries but finally Western medicine is finding proof--and there is still so much that we still do not know. I believe in the future that we will learn to control much more. So, the mind and body are linked much more than we ever thought. The way to wellness is through both the body and the mind working together for a common cause. Added note: A common misconception is that when people feel that they are somehow supposed to control their physiology and all their illnesses (self-management), it implies fault. There is no fault in getting a disorder. Too many other factors, often unknown factors, are interacting together (environment, ergonomics, lifestyle, physiology, genetics). The mind is just one factor, but an important one, and one that can be an extremely powerful healer with practice. Happy Holidays, Debbie Stiles, MN, RN Management of Stress Response Clinic University of Washington