For example, the sympathetic system will release NE at both alpha and beta receptors. However, the specific response of the effector organ is dependent on the types of receptors present. In general, the parasympathetic system is responsible for promoting ‘rest & digest’ functions, and the sympathetic system is responsible for promoting ‘fight or flight’ functions. In the adrenergic synapse, released norepinephrine is either reabsorbed into the preganglionic neuron or degraded by catechol-o-methyl transferase (COMT) enzyme. In the cholinergic synapse, released acetylcholine is degraded down by the enzyme acetylcholinesterase, or reabsorbed into the preganglionic neuron. Most sympathetic postganglionic neurons are adrenergic (meaning they release norepinephrine (NE)), but a few are cholinergic- such as the ones to sweat glands and to smooth muscles of certain blood vessels. However in the sympathetic system, postganglionic are not all the same. In the parasympathetic system, postganglionic neurons are also cholinergic. The exception to this is the adrenal medulla which is connected directly to the preganglionic neuron.īoth sympathetic and parasympathetic preganglionic neurons are cholinergic, meaning they release acetylcholine (Ach) at the synapse in the ganglion. These neurons synapse together in the autonomic ganglia. The first neuron is called the preganglionic neuron, and the second is the postganglionic neuron. In general, there are 2 neurons that combine to link each effector organ with its respective sympathetic or parasympathetic system. The parasympathetic system originates from craniosacral regions (brainstem nuclei CN III, VII, IX, and X as well as sacral levels S2-S4). The sympathetic system originates from the thoracolumbar regions (T1-L2) of the spinal cord.
This chapter also discusses age-related changes in the nervous system and age-related nervous system disorders.The autonomic nervous system is made up of 2 subdivisions: sympathetic and parasympathetic systems. The integrating parts of the nervous system are composed of the central nervous system (CNS), including the brain and spinal cord, and the peripheral nervous system (PNS), which includes both the somatic nervous system and the autonomic nervous system (ANS). Adaptive behavior requires: complex and highly specialized sensory receptors receiving information from both the external and internal environments processing and interpreting such information appropriately in the nervous system, a process called integration and effectors that enable people to act on new information in an adaptive and life-sustaining manner. The nervous system allows people to adapt their behavior according to the stimuli they receive. Along with the endocrine system, it regulates and maintains homeostasis. The nervous system, one of the most complex systems in the body, controls, coordinates, and integrates all body activities. Appendix A: Practical Hints for the Safety of Older Adults.Chapter 23: Death and Grief in the Later Years.
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