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inside the spinal cord, while the axons of the somatic motor neurons are in the spinal ganglia. The axons form synapses directly with skeletal muscle and provide only excitatory signals (acetylcholine). b. Autonomic44.16 The autonomiccomponent (also called visceral) conveys signals that regulate smooth and cardiac muscle an internal organs. In turn, the autonomic system is divided into the sympatheticand the parasympatheticdivisions. In contrast to somatic motor neurons, autonomic neurons all form synapses in ganglia outside the CNS. Most organ systems are innervated by both divisions, and they can induce both excitation and inhibition of target cells.

Sympathetic prepare for action energy consumption near spinal cord norepinephrine epinephrine thoracic, lumbar

Parasympathetic gain and conserve energy

Effects

Point of synapse Postsynaptic Transmitter CNS attachment

near target organ acetylcholine

cranial, sacral

In general, the sympathetic nervous system prepares the body for violent physical activity (fight or flight) - stimulates HR, raises BP, dilates pupils, dilates respiratory system, stimulates conversion of glycogen into glucose, and shunts blood to skeletal muscles, brain and heart. In addition, the sympathetic nervous system triggers the release of epinephrine (adrenaline) into the blood from the adrenal medulla. The main nerve of the parasympathetic sytem is the tenth cranial nerve (called the vagus nerve) that exits from the brain stem. The postsynaptic neuron releases acetylcholine to its target tissue. The parasympathetic system tends to counteract the effects of the sympathetic nervous system - slows HR, lowers BP, constricts pupils, increases blood flow to skin and internal organs, stimulates digestion. B. Central nervous system (CNS) The basic role of the CNS is to process and respond to information provided to it from the periphery. It is bilaterally symmetrical and consists of the brain