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Autonomic Nervous System: The enteric, parasympathetic, and sympathetic nervous systems taken together. Generally speaking, the autonomic nervous system regulates the internal environment during both peaceful activity and physical or emotional stress. Autonomic activity is controlled and integrated by the central nervous system, especially the hypothalamus and the solitary nucleus, which receive information relayed from Visceral afferents; these and related central and sensory structures are sometimes (but not here) considered to be part of the autonomic nervous system itself.

What is a Nervous System?

JoVE 10838

The nervous system is the collection of specialized cells responsible for maintaining an organism’s internal environment and coordinating the interaction of an organism with the external world—from the control of essential functions such as heart rate and breathing to the movement needed to escape danger.

The vertebrate nervous system is divided into two major parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain, spinal cord, and retina—the sensory tissue of the visual system. The PNS contains the sensory receptor cells for all of the other sensory systems—such as the touch receptors in the skin—as well as the nerves that carry information between the CNS and the rest of the body. Additionally, part of both the CNS and PNS contribute to the autonomic nervous system (also known as the visceral motor system). The autonomic nervous system controls smooth muscles, cardiac muscles, and glands that govern involuntary actions, such as digestion. The vertebrate brain is primarily divided into the cerebrum, cerebellum, and brainstem. The cerebrum is the largest, most anterior part of the brain that is divided into left and right hemispheres. Each hemisphere is further divided into four lobes: frontal, parietal, occipital, and temporal. The outermost layer of the cerebrum is called

 Core: Nervous System

The Parasympathetic Nervous System

JoVE 10839

The parasympathetic nervous system is one of the two major divisions of the autonomic nervous system. This parasympathetic system is responsible for regulating many unconscious functions, such as heart rate and digestion. It is composed of neurons located in both the brain and the peripheral nervous system that send their axons to target muscles, organs, and glands.

Activation of the parasympathetic system tends to have a relaxing effect on the body, promoting functions that replenish resources and restore homeostasis. It is therefore sometimes referred to as the “rest and digest” system. The parasympathetic system predominates during calm times when it is safe to devote resources to basic “housekeeping” functions without a threat of attack or harm. The parasympathetic nervous system can be activated by various parts of the brain, including the hypothalamus. Preganglionic neurons in the brainstem and sacral part of the spinal cord first send their axons out to ganglia—clusters of neuronal cell bodies—in the peripheral nervous system. These ganglia contain the connections between pre- and postganglionic neurons and are located near the organs or glands that they control. From here, postganglionic neurons send their axons onto target tissues—generally smooth muscle, cardiac muscle, or glands. Typic

 Core: Nervous System

The Sympathetic Nervous System

JoVE 10840

The sympathetic nervous system—one of the two major divisions of the autonomic nervous system—is activated in times of stress. It prepares the body to meet the challenges of a demanding circumstance while inhibiting essential body functions—such as digestion—that are a lower priority at the moment.

As a student, you may have had the experience of walking into class and finding a surprise exam that you were not expecting. In the moment of realization, you may sense your gut tighten, your mouth goes dry, and your heart starts to race all of a sudden. These are signs of the sympathetic system taking over in preparation to react. While you may not be in immediate danger, the system has evolved to facilitate immediate reaction to stress or threats: blood is directed away from the digestive system and skin to increase energy supplies to muscles. Furthermore, the heart rate, and blood flow increase, and pupils dilate to maximize visual perception. At the same time, the adrenal gland releases epinephrine into the circulatory system. Your body is now primed to take action, whether that means to swiftly flee from danger or fight whatever threat may be at hand. The sympathetic nervous system can be activated by various parts of the brain, with the hypothalamus playing a particularly important role. Sympathetic instructions from the central

 Core: Nervous System

Physiological Correlates of Emotion Recognition

JoVE 10297

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel—University of Southern California


The autonomic nervous system (ANS) controls the activity of the body's internal organs and regulates changes in their activity depending on the current environment. The vagus nerve, which innervates many of the internal organs, is an…

 Neuropsychology

Muscle Contraction

JoVE 10869

In skeletal muscles, acetylcholine is released by nerve terminals at the motor end plate-the point of synaptic communication between motor neurons and muscle fibers. Binding of acetylcholine to its receptors on the sarcolemma allows entry of sodium ions into the cell and triggers an action potential in the muscle cell. Thus, electrical signals from the brain are transmitted to the muscle. Subsequently, the enzyme acetylcholinesterase breaks down acetylcholine to prevent excessive muscle stimulation. Individuals with the disorder myasthenia gravis, develop antibodies against the acetylcholine receptor. This prevents transmission of electrical signals between the motor neuron and muscle fiber and impairs skeletal muscle contraction. Myasthenia gravis is treated using drugs that inhibit acetylcholinesterase (allowing more opportunities for the neurotransmitter to stimulate the remaining receptors) or suppress the immune system (preventing the formation of antibodies). Unlike skeletal muscles, smooth muscles present in the walls of internal organs are innervated by the autonomic nervous system and undergo involuntary contractions. Contraction is mediated by the interaction between two filament proteins-actin and myosin. The interaction of actin and myosin is closely linked to intracellular calcium concentration. In response to neurotransmitter or hormone sig

 Core: Musculoskeletal System

Neural Regulation

JoVE 10835

Digestion begins with a cephalic phase that prepares the digestive system to receive food. When our brain processes visual or olfactory information about food, it triggers impulses in the cranial nerves innervating the salivary glands and stomach to prepare for food.

The cephalic phase is a conditioned or learned response to familiar foods. Our appetite or desire for a particular food modifies the preparatory responses directed by the brain. Individuals may produce more saliva and stomach rumblings in anticipation of apple pie than of broccoli. Appetite and desire are products of the hypothalamus and amygdala—brain areas associated with visceral processes and emotion. After the cephalic phase, digestion is governed by the enteric nervous system (ENS) as an unconditioned reflex. Individuals do not have to learn how to digest food; it happens regardless of whether it is apple pie or broccoli. The ENS is unique in that it functions (mostly) independent of the brain. About 90% of the communication are messages sent from the ENS to the brain rather than the other way around. These messages give the brain information about satiety, nausea, or bloating. The ENS, as part of the peripheral nervous system, is also unique in that it contains both motor and sensory neurons. For example, the ENS directs smooth muscle movements that churn and propel food al

 Core: Nutrition and Digestion

Blood Pressure Measurement

JoVE 10083

Source: Meghan Fashjian, ACNP-BC, Beth Israel Deaconess Medical Center, Boston MA


The term blood pressure (BP) describes lateral pressures produced by blood upon the vessel walls. BP is a vital sign obtained routinely in hospital and outpatient settings, and is one of the most common medical assessments performed around…

 Physical Examinations I

A Cross-Disciplinary and Multi-Modal Experimental Design for Studying Near-Real-Time Authentic Examination Experiences

1Department of Engineering Education, College of Engineering, Utah State University, 2Department of Electrical and Computer Engineering, College of Engineering, Utah State University, 3Department of Educational Psychology, College of Education, University of Oregon

JoVE 60037

 Behavior

Pre-clinical Model of Cardiac Donation after Circulatory Death

1Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 2Deparment of pharmacology and physiology, Faculty of Medicine, Université de Montréal, 3Division of Cardiovascular Surgery, Toronto General Hospital, University Health Network, 4Department of surgery, Faculty of Medicine, Université de Montréal

JoVE 59789

 Medicine

Laboratory Administration of Transcutaneous Auricular Vagus Nerve Stimulation (taVNS): Technique, Targeting, and Considerations

1Department of Biomedical Engineering, City College of New York, 2U.S. Army Research Laboratory, Aberdeen Proving Ground, 3Brain Stimulation Laboratory, Department of Psychiatry, Medical University of South Carolina, 4Department of Pediatrics, Medical University of South Carolina, 5Department of Neurology, Medical University of South Carolina, 6Ralph H. Johnson VA Medical Center

JoVE 58984

 Neuroscience

Conducting Hyperscanning Experiments with Functional Near-Infrared Spectroscopy

1Child Neuropsychology Section, Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, Medical Faculty, RWTH Aachen University, 2JARA-Brain Institute II, Molecular Neuroscience and Neuroimaging, RWTH Aachen & Research Centre Juelich, 3Lehrstuhl II für Mathematik, RWTH Aachen University, 4Translational Brain Research in Psychiatry and Neurology, Department of Child and Adolescent Psychiatry, Psychosomatics, and Psychotherapy, University Hospital Aachen

JoVE 58807

 Neuroscience

Vagus Nerve Stimulation As an Adjunctive Neurostimulation Tool in Treatment-resistant Depression

1Universitätsklinik für Psychiatrie und Psychotherapie, Carl von Ossietzky Universität Oldenburg, 2Universitätsklinikum Bonn AöR, Klinik und Poliklinik für Psychiatrie, 3Universitätsklinik für Neurochirurgie am Evangelischen Krankenhaus Oldenburg, Carl von Ossietzky Universität Oldenburg, 4Klinik für Neurodegenerative Erkrankungen und Gerontopsychiatrie, Abteilung für medizinische Psychologie, Klinik für Psychiatrie und Psychotherapie, Universitätsklinikum Bonn, 5Psychiatrische und Psychotherapeutische Klinik, Universitätsklinikum Erlangen

JoVE 58264

 Medicine

Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System

1Department of Cardiology-Electrophysiology, cNEP (cardiac Neuro- and Electrophysiology research group), University Heart Center, University Hospital Hamburg-Eppendorf, 2DZHK (German Center for Cardiovascular Research), 3Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf

JoVE 57617

 Medicine

A Modified Trier Social Stress Test for Vulnerable Mexican American Adolescents

1Center for Environmental Research and Children's Health (CERCH), Berkley School of Public Health, University of California, Berkeley, 2San Francisco (UCSF) School of Nursing, University of California, San Francisco, 3Human Development and Family Studies, Iowa State University

JoVE 55393

 Developmental Biology

Autonomic Function Following Concussion in Youth Athletes: An Exploration of Heart Rate Variability Using 24-hour Recording Methodology

1Concussion Centre, Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, 2Faculty of Kinesiology and Physical Education, University of Toronto, 3Rehabilitation Sciences Institute, Faculty of Medicine, University of Toronto, 4Department of Occupational Science and Occupational Therapy, Faculty of Medicine, University of Toronto

JoVE 58203

 Medicine

Using Fiberless, Wearable fNIRS to Monitor Brain Activity in Real-world Cognitive Tasks

1Department of Medical Physics and Biomedical Engineering, Malet Place Engineering Building, University College London, 2Infrared Imaging Lab, Institute for Advanced Biomedical Technology (ITAB), Department of Neuroscience, Imaging and Clinical Sciences, University of Chieti-Pescara, 3Institute of Cognitive Neuroscience, Alexandra House, University College London

JoVE 53336

 Behavior

Dual Labeling of Neural Crest Cells and Blood Vessels Within Chicken Embryos Using ChickGFP Neural Tube Grafting and Carbocyanine Dye DiI Injection

1Birth Defects Research Centre, UCL Institute of Child Health, 2Blizard Institute, Centre for Digestive Diseases, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, 3Department of Clinical Genetics, Erasmus University Medical Center, Rotterdam

JoVE 52514

 Developmental Biology
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