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Unformatted text preview: Chapter 10 Autonomic nervous System BME 501(pages 137-148) T. K. Hsiai, MD, PhD, FACC Neural Control of the Heart Autonomic Nervous System Parasympathetic pathways Sympathetic Pathways B r a i n Baroreceptor reflex: Pressure Sensors Bainbridge Reflex Chemoreceptor: pH Sensors Introduction Involuntary control of viscera and tissues Parasympathetic vs sympathetic systems Efferent and afferent fibers Neurotransmitters: norepinephrine vs achetycholine Autonomic Nerves Arrows indicate the anatomic structures that regulate heart rates.-1. The primary site in the brain for regulating sympathetic and parasympathetic (vagal) outflow to the heart and blood vessels.-2. It also receives sensory input from different systemic and central receptors (e.g., baroreceptors and chemoreceptors ). -3. The medulla also receives information from other brain regions (e.g., hypothalamus). The hypothalamus and higher centers modify the activity of the medullary centers and are particularly important in stimulating cardiovascular responses to emotion and stress (e.g., exercise, thermal stress). The Autonomic Nervous System The autonomic nervous system consists of sensory neurons and motor neurons that run between the central nervous system (especially the hypothalamus and medulla oblongata ) and various internal organs such as the: heart lungs viscera glands (both exocrine and endocrine ) It is responsible for monitoring conditions in the internal environment and bringing about appropriate changes in them. The contraction of both smooth muscle and cardiac muscle is controlled by motor neurons of the autonomic system. The actions of the autonomic nervous system are largely involuntary (in contrast to those of the sensory-somatic system). It also differs from the sensory-somatic system is using two groups of motor neurons to stimulate the effectors instead of one. The first, the preganglionic neurons , arise in the CNS and run to a ganglion in the body. Here they synapse with postganglionic neurons , which run to the effector organ (cardiac muscle, smooth muscle, or a gland). The autonomic nervous system has two subdivisions, the sympathetic nervous system and the parasympathetic nervous system . The Autonomic Nervous System The autonomic nervous system regulate activity of smooth muscle, cardiac muscle & certain glands Structures involved general visceral afferent neurons general visceral efferent neurons integration center within the brain Receives input from limbic system and other regions of the cerebrum. Somatic nervous system consciously perceived sensations excitation of skeletal muscle one neuron connects CNS to organ Autonomic nervous system unconsciously perceived visceral sensations involuntary inhibition or excitation of smooth muscle, cardiac muscle or glandular secretion two neurons needed to connect CNS to organ Cranial nerves S2-S4 T1-L2/L3 The Parasympathetic Nervous System...
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This note was uploaded on 02/27/2008 for the course BME 501 taught by Professor Yamashiro,hsiai during the Fall '07 term at USC.

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