SN2016 Anatomy and Physiology Lecture 5 PDF

SN2016 Anatomy and Physiology Lecture 5 Nervous system Part 1 Somatic Nervous System Automatic Nervous System  Learning Outcomes At the end of this session, students should be able to – Specify the components of the afferent...

SN2016 Anatomy and Physiology Lecture 5 Nervous system Part 1 Somatic Nervous System Automatic Nervous System  Learning Outcomes At the end of this session, students should be able to – Specify the components of the afferent and efferent divisions of the nervous system. – Compare the organization of the autonomic nervous system with that of the somatic nervous system. – Describe the structures and functions of the sympathetic division of the autonomic nervous system. – Describe the structures and functions of the parasympathetic division of the autonomic nervous system. Figure 12-1 A Functional Overview of the Nervous System. Organization of the Nervous System Central Nervous System (CNS) Integrate, process, and coordinate sensory (brain and spinal cord) data and motor commands Sensory information Motor commands within within afferent division efferent division Peripheral Nervous System (PNS) (neural includes tissue outside the CNS) Somatic nervous Autonomic system (SNS) nervous system (ANS) Parasympathetic Sympathetic division division Receptors Effectors Smooth muscle Special sensory Visceral sensory Somatic sensory Cardiac receptors receptors receptors muscle monitor smell, taste, vision, monitor internal organs monitor skeletal Glands balance, and hearing muscles, joints, and Skeletal Adipose tissue skin surface muscle © 2015 Pearson Education, Inc. © 2018 Pearson Education, Inc.  SNS vs ANS Somatic Nervous System (SNS) – Operates under conscious control – Seldom affects long‐term survival – SNS controls skeletal muscles Autonomic Nervous System (ANS) – Operates without conscious instruction – ANS controls visceral effectors – Coordinates functions of cardiovascular, respiratory, digestive, urinary, reproductive system Figure 16-1a The Organization of the Somatic and Autonomic Nervous Systems. Upper motor neurons in primary motor cortex Brain Somatic motor nuclei of brain stem Skeletal Lower Spinal cord muscle motor neurons Somatic motor nuclei of spinal cord Skeletal muscle a Somatic nervous system © 2015 Pearson Education, Inc. Figure 16-1b The Organization of the Somatic and Autonomic Nervous Systems. Visceral motor nuclei in hypothalamus Brain Preganglionic neuron Visceral Effectors Smooth muscle Autonomic Glands Autonomic nuclei in ganglia brain stem Cardiac Ganglionic Spinal cord muscle neurons Adipocytes Autonomic nuclei in spinal cord Preganglionic neuron b Autonomic nervous system © 2015 Pearson Education, Inc. Figure 16-10 A Comparison of Somatic and Autonomic Function. Central Nervous Cerebral cortex System Limbic system Thalamus Hypothalamus Somatic sensory Visceral sensory Relay and processing centers in brain stem Somatic Long reflexes reflexes Lower motor Preganglionic Peripheral neuron neuron Nervous Sensory System pathways SNS ANS Short reflexes Ganglionic neuron Skeletal Sensory Visceral muscles receptors effectors © 2015 Pearson Education, Inc. Table 16-5 A Comparison of the ANS and SNS. © 2015 Pearson Education, Inc.  Divisions of the ANS – Operates largely outside our awareness – Has two divisions 1. Sympathetic division – Kicks in only during exertion, stress, or emergency – “Fight or flight” – Increases alertness, metabolic rate, and muscular abilities 2. Parasympathetic division – Controls during resting conditions – “Rest and digest” – Reduces metabolic rate and promotes digestion Sympathetic and parasympathetic division 1. Most often, these two divisions have opposing effects. If the sympathetic division causes excitation, the parasympathetic causes inhibition 2. The two divisions may work together, with each controlling one stage of a complex process 3. The two divisions may also work independently, and only one division innervates some structures  Sympathetic division – Preganglionic fibers are short (near spinal cord) – Postganglionic fibers are long – Prepares body for crisis, producing a “fight or flight” response Stimulates tissue metabolism Increases alertness  Responses to increased sympathetic activity 1. Heightened mental alertness 2. Increased metabolic rate 3. Reduced digestive and urinary functions 4. Energy reserves activated 5. Increased respiratory rate and respiratory passageways dilate 6. Increased heart rate and blood pressure 7. Sweat glands activated  Parasympathetic division – Synapse in ganglia is close to (or within) target organs – Preganglionic fibers are long – Postganglionic fibers are short – Parasympathetic division stimulates visceral activity – Conserves energy and promotes sedentary activities  Responses to increased parasympathetic activity 1. Decreased metabolic rate 2. Decreased heart rate and blood pressure 3. Increased secretion by salivary and digestive glands 4. Increased motility and blood flow in digestive tract 5. Urination and defecation stimulation  Dual innervation Sympathetic Division has a widespread impact by reaching organs and tissues throughout body Parasympathetic division innervates only specific visceral structures Most vital organs receive instructions from both sympathetic and parasympathetic divisions Two divisions commonly have opposing effects Figure 16-7 Summary: The Anatomical Differences between the Sympathetic and Parasympathetic Divisions. Sympathetic Parasympathetic CNS Preganglionic neuron PNS Preganglionic KEY Sympathetic fiber Neurotransmitters ganglion Acetylcholine Norepinephrine or Epinephrine Ganglionic neurons Bloodstream Postganglionic Parasympathetic fiber ganglion TARGET © 2015 Pearson Education, Inc. Figure 16-2 Overview of the Autonomic Nervous System (Part 1 of 2). Sympathetic Division (Thoracolumbar) Preganglionic Neurons Preganglionic neurons are located in the lateral T –L. gray horns 1 2 of spinal segments Ganglia Ganglia are located near the spinal cord. Preganglionic fibers release acetylcholine (Ach), stimulating ganglionic neurons. Target Organs Most postganglionic fibers release norepinephrine (NE) at neuroeffector junctions. Sympathetic activation “Fight or flight” response KEY Preganglionic fibers Postganglionic fibers © 2015 Pearson Education, Inc. Figure 16-2 Overview of the Autonomic Nervous System (Part 2 of 2). Parasympathetic Division (Craniosacral) Preganglionic Neurons Preganglionic neurons in brain stem and in lateral portion of anterior gray horns of S2–S4. Ganglia Ganglia are in or near the target organ. Preganglionic fibers release acetylcholine (Ach), stimulating ganglionic neurons. Target Organs All postganglionic fibers release Ach at neuroeffector junctions. Parasympathetic stimulation “Rest and digest” response KEY Preganglionic fibers Postganglionic fibers © 2015 Pearson Education, Inc. © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Integration of SNS and ANS activities – Many parallels in organization and function – Integration at brain stem – Both systems under control of higher centers  Summary Vocabulary: SNS, ANS Structure and function difference of sympathetic and parasympathetic divisions