Nerve Impulses

10 Key excerpts on "Nerve Impulses"

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  The Computer and the Brain

  • John von Neumann, Ray Kurzweil(Authors)
  • 2012(Publication Date)
  • Yale University Press

    (Publisher)

  However, on the near-molecule level of the nerve membrane, all these aspects tend to merge. It is, there-fore, not surprising that the nerve impulse turns out to be a phenomenon which can be viewed under any one of them. The Process of Stimulation As I mentioned before, the fully developed Nerve Impulses are comparable, no matter how induced. Because their character is not an unambiguously defined one (it may be viewed electrically as well as chemically, cf. above), its in-duction, too, can be alternatively attributed to electrical or to chemical causes. Within the nervous system, however, it is mostly due to one or more other Nerve Impulses. Under the nature of the nerve impulse 43 such conditions, the process of its induction—the stimulation of a nerve impulse—may or may not succeed. If it fails, a passing disturbance arises at first, but after a few millisec-onds, this dies out. Then no disturbances propagate along the axon. If it succeeds, the disturbance very soon assumes a (nearly) standard form, and in this form it spreads along the axon. That is to say, as mentioned above, a standard nerve impulse will then move along the axon, and its ap-pearance will be reasonably independent of the details of the process that induced it. The stimulation of the nerve impulse occurs normally in or near the body of the nerve cell. Its propagation, as dis-cussed above, occurs along the axon. The Mechanism of Stimulating Pulses by Pulses; Its Digital Character I can now return to the digital character of this mechanism. The nervous pulses can clearly be viewed as (two-valued) markers, in the sense discussed previously: the absence of a pulse then represents one value (say, the binary digit 0), and the presence of one represents the other (say, the binary digit 1). This must, of course, be interpreted as an occur-rence on a specific axon (or, rather, on all the axons of a specific neuron), and possibly in a specific time relation to other events.

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  General Biophysics

  • M Volkenstein(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  C H A P T E R 4 Nerve Impulses 4.1. Axons and Nerve Impulses The generation and propagation of the nerve impulse and the excitation of nerve and muscle cells are among the most important membrane phenomena in animals. The membrane theory of excitation was formulated by Bernstein in 1902 [1]. According to the theory, excitation is determined by electro-chemical processes localized in the membranes of nerve and muscle cells. These processes correspond essentially to the movement of small ions. A monograph by Lazarev on the ionic nature of nerve excitation was later published [2]. The research done by Hodgkin, Katz, Huxley, Tasaki, and other scientists [3-6] has brought to light the fundamental mechanisms of the generation and propagation of Nerve Impulses (see also [7-9]). Nerve excitation is transmitted throughout the nerve fibers (axons). The nervous systems of higher organisms are traditionally subdivided into the central and the peripheral. The peripheral system contains axons used to transmit messages as well as the ganglia of the vegetative nervous system. Axons serve as communicators of afferent messages from the sense organs to the central system and of efferent messages from the central system to the muscles. Axons represent appendages of the centrally located cells. The nervous system of invertebrates has a different structure but also contains communication axons. 162 4.1. AXONS A N D Nerve Impulses 163 The study of the generation of the nerve impulse and its propagation in the axon is an old, traditional problem faced by biophysics. Helmholtz measured the velocity of propagation of nerve excitation. Today, important physical problems relating to the function of the axon have been solved; but the present-day science makes it possible to model only formally the func-tioning of the central nervous system, and we are far from understanding the physical nature of its supreme functions, memory and thinking.

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  Excitable Cells

  Monographs in Modern Biology for Upper School and University Courses

  • F. A. Miles(Author)
  • 2013(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  CHAPTER 3 The Nerve Impulse The nerve impulse is a wave of electrical activity which pro-pagates along the axon without decrement. Fig. 27 shows an intracellular recording from a squid giant axon and illustrates the reversal of membrane potential, from its resting level of —60 mV, to a peak of +45 mV during the impulse. The main spike has a FIG. 27. A nerve impulse recorded with an internal electrode from the isolated axon of squid. The membrane potential is about — 60mV during rest and reverses during the action potential, almost reaching + 50mV. (Hodgkin, 1958.) 38 The Nerve Impulse 39 duration of about 1 millisecond and is followed by a prolonged hyperpolarization* lasting several milliseconds. Experimentally, the most convenient way of generating such impulses in the axon is by passing a brief electric current across the membrane. However, not all currents lead to the generation of Nerve Impulses, and in part, the form of the recording depends upon the position of the pick-up electrodes relative to the site of stimulation. It can be seen from Fig. 28 that Nerve Impulses are only initiated by depolarizing currents, and then, only when E m is > -I current pce/ses —WJ |_j J_J-m V = o Ξ. H membrane potential threshold it XL A mV . o^-IH membrane potent/a/ I I I 1 t I f ■6/'me,m l seQ. FIG. 28. The effect of passing current pulses across the nerve membrane (trace I) on the membrane potential of the nerve axon recorded locally (trace II) and at a distance (trace III). It can be seen that such stimu-lation always gives rise to local electrotonic potentials, but propagating action potentials only arise after depolarization of the membrane beyond a certain threshold. The local responses are of a kind that can be recorded from any transmission cable, but the self-reinforcing action potentials are unique to nerve and muscle and derive from special features in the membrane.

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  Essential Biological Psychology

  • Jim Barnes(Author)
  • 2013(Publication Date)
  • SAGE Publications Ltd

    (Publisher)

  NEURONS, NEUROTRANSMISSION AND COMMUNICATION

  CHAPTER OUTLINE How the nervous system is organised Cells of the nervous system The neuron Neuroglial cells Information exchange in the nervous system The resting membrane potential The action potential and nerve impulse Summation effects Synaptic transmission The synaptic vesicle Modulation of synaptic transmission Non-synaptic chemical communication Postsynaptic receptors and receptor types Neurotransmitters The amino acids Monoamines Acetylcholine Neuropeptides and neuromodulators Soluble gases Summary Further reading Key questions

  The purpose of biological psychology is to elucidate the biological mechanisms involved in behaviour and mental activity. Biological psychologists (sometimes referred to as neuropsychologists) attempt to understand how the neural circuits and connections are formed and put together during the development of the brain, allowing the individual to perceive and interact with the world around them. We cannot answer all of the questions that we would like to, nor do we believe that we have access to the best possible tools for studying the brain, but the questions do stir up curiosity and a better understanding of the biological processes that play a role in behaviour. It can be hard to remember the complicated names of nerve cells and brain areas. However, to develop theories of behaviour regarding the brain, a psychologist must know something about brain structure. This chapter will focus on the nervous system : its organisation, its cell composition, and the type of chemical signals that make it possible for us to process an incredible amount of information on a daily basis.

  HOW THE NERVOUS SYSTEM IS ORGANISED

  In vertebrates , the nervous system has two divisions: the peripheral nervous system and the central nervous system (Figure 1.1 ). The central nervous system (CNS), which consists of the brain and spinal cord, is surrounded by another nervous system called the peripheral nervous system (PNS). The PNS gathers information from our surroundings and environment and relays it to the CNS; it then acts on the signals or decisions that the CNS returns. The peripheral nervous system itself consists of two parts: the somatic nervous system and the autonomic nervous system . The autonomic nervous system is divided into two subsystems: the parasympathetic nervous system and the sympathetic nervous system . The parasympathetic system is responsible for slowing the heart rate, increasing the intestinal and gland activity and undertaking actions when the body is at rest. Its action can be described as opposite to the sympathetic nervous system, which is responsible for controlling actions associated with the fight-or-flight response. The somatic system contains the sensory receptors and motor nerves

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  Essentials of Psychology

  Concepts and Applications

  • Jeffrey Nevid(Author)
  • 2021(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  sensory neurons Neurons that transmit information from sensory organs, muscles, and inner organs to the spinal cord and brain. motor neurons Neurons that convey Nerve Impulses from the central nervous system to muscles and glands. glands Body organs or structures that produce secretions called hormones. hormones Secretions from endocrine glands that help regulate bodily processes. interneurons Nerve cells within the central nervous system that process information. nerve A bundle of axons from different neurons that transmit Nerve Impulses. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 44 CHAPTER 2 BIOLOGICAL FOUNDATIONS OF BEHAVIOR individual axons are microscopic, a nerve may be visible to the naked eye. The cell bodies of the neurons that contain the axons are not part of the nerve itself. Neurons are not the only cells in the nervous system. Far more numerous are smaller cells that play supportive roles, called glial cells (named from the Greek word meaning “glue”). Although they do not transmit neural signals or messages, they have various roles to play in keeping the nervous system functioning, includ- ing removing waste products, providing insulation between neurons, and assist- ing neurons in communicating with one another (Fields, 2013; Unhavaithaya & Orr-Weaver, 2012). Glial cells serve yet another important function: They form the myelin sheath, a fatty layer of cells that—like the insulation that wraps around electrical wires—acts as a protective shield on many axons.

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  Principles of Anatomy and Physiology, 3rd Asia-Pacific Edition

  • Gerard J. Tortora, Bryan H. Derrickson, Brendan Burkett, Gregory Peoples, Danielle Dye, Julie Cooke, Tara Diversi, Mark McKean, Simon Summers, Flavia Di Pietro, Alex Engel, Michael Macartney, Hayley Green(Authors)
  • 2021(Publication Date)
  • Wiley

    (Publisher)

  CHECKPOINT 9. Define the terms resting membrane potential, depolarisation, repolarisation, nerve impulse, and refractory period and identify the factors responsible for each. 10. How is saltatory conduction different from continuous conduction? 11. What effect does myelination have on the speed of propagation of an action potential? 12. How can you tell the difference between a stroke on the cheek and a slap across the face? CHAPTER 12 Nervous tissue 541 12.4 Signal transmission at synapses LEARNING OBJECTIVE 12.4 Describe signal transmission at a chemical synapse, summation, and excitatory and inhibitory neurotransmitters. Recall from chapter 10 that a synapse (SIN-aps) is a region where communication occurs between two neurons or between a neuron and an effector cell (muscle cell or glandular cell). The term presynaptic neuron (pre- = before) refers to a nerve cell that carries a nerve impulse towards a synapse. It is the cell that sends a signal. A postsynaptic cell is the cell that receives a signal. It may be a nerve cell called a postsynaptic neuron (post- = after) that carries a nerve impulse away from a synapse or an effector cell that responds to the impulse at the synapse. Most synapses between neurons are axodendritic (ak ′ -so-den-DRIT-ik = from axon to dendrite), while others are axosomatic (ak ′ -sō-sō-MAT-ik = from axon to cell body) or axoaxonic (ak ′ -so-ak-SON-ik = from axon to axon) (figure 12.22). In addition, synapses may be electrical or chemical and they differ both structurally and functionally. FIGURE 12.22 Examples of synapses between neurons. Arrows indicate the direction of information flow: presynaptic neuron → postsynaptic neuron. Presynaptic neurons usually synapse on the axon (axoaxonic: red), a dendrite (axodendritic; blue), or the cell body (axosomatic; green). Neurons communicate with other neurons at synapses, which are junctions between one neuron and a second neuron or an effector cell.

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  Pesticides and Neurological Diseases

  • Donald J. Ecobichon, Robert M. Joy(Authors)
  • 1993(Publication Date)
  • CRC Press

    (Publisher)

  The peripheral nerves contain sensory, motor, and autonomic fibers in varying numbers. Additional autonomic fibers, whose cells of origin are located in the brain, reach their destination by traveling in one of the cranial nerves. IV. ELECTROCHEMICAL PROPERTIES OF NEURONS A. THE NEURON AS AN INFORMATION PROCESSING DEVICE The neuron is a cell specially designed to receive, evaluate, and transmit in-formation. It is helpful to think of the neuron as differentially specialized to perform these various functions (Figure 5). It possesses an information receiving section consisting of the cell soma and dendrites. These regions act as chemical to electrical transducers and convert afferent input into changes in electrical potential. The axon hillock and the initial segment of the axon can be viewed as a threshold detecting section. These regions monitor the net change in electrical potential occurring on the somatic and dendritic surfaces and, if appropriate, initiate an action potential. The axon is the transmitting section of the neuron and is designed to rapidly and faithfully convey the action potential to the nerve terminal. The terminal converts the electrical signal of the action potential back into a chemical signal by releasing a neurotransmitter into the synaptic cleft. The chemical diffuses to the post-synaptic cell's soma and dendrites to start the process anew. The Nervous System 41 This view of the neuron emphasizes that function depends on a combination of chemical and electrical activities. Intercellular communication is predominately chemical in nature. B. BACKGROUND CONCEPTS l. Unicellular Measurements Neuronal cell bodies are typically 10 to 50 tA. in diameter. Their axons can be of any length up to 1 to 2 m. Most of the bulk of a neuron is in the dendrites and the long axonal process. Neurons weigh only nanograms (ng). Membrane potentials can range from +45 mV to -90 mV (inside referenced to outside).

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  Essential Psychology

  • Philip Banyard, Christine Norman, Gayle Dillon, Belinda Winder, Philip Banyard, Christine Norman, Gayle Dillon, Belinda Winder(Authors)
  • 2019(Publication Date)
  • SAGE Publications Ltd

    (Publisher)

  COMMUNICATION WITHIN THE BRAIN Lead authors: Lucy Webster and Christine Norman 11 CHAPTER OUTLINE 11.1 INTRODUCTION 260 11.2 CELLS IN THE NERVOUS SYSTEM 260 11.2.1 Neurones 260 11.2.2 Glial cells 261 11.3 COMMUNICATION WITHIN THE NEURONE 263 11.3.1 Neurone membrane structure 263 11.3.2 Resting membrane potentials 264 11.3.3 Action potentials 265 11.3.4 Post-synaptic potentials 267 11.4 COMMUNICATION BETWEEN NEURONES 267 11.4.1 The chemical synapse and pre-synaptic events 268 11.4.2 Receptor activation and post-synaptic events 268 11.4.3 Termination of the signal 269 11.5 NEUROTRANSMITTERS AND DRUGS 270 11.5.1 Neurotransmitters 270 11.5.2 Drugs and the brain 273 11.5.3 How do we measure neurotransmitter function in the brain? 276 11.6 CHAPTER SUMMARY 280 DISCUSSION QUESTIONS 281 SUGGESTIONS FOR FURTHER READING 281 260 BIOLOGICAL PSYCHOLOGY 11.1 INTRODUCTION When you are awake, your brain generates 25 watts of power – which is enough to power a light bulb. That energy comes from all the activity of sending and receiving messages between the 100 billion cells that make up your brain and there are at least 10 trillion connections between those cells (this is starting to sound like a show presented by Brian Cox!). If you started to count them at one every second it would take you over 300,000 years to get them all. In the previous chapter we took a brief tour of the main structures of the nervous system. Now it is time to examine how information is transported around those systems in order to achieve the various functions. At its most basic, the brain’s purpose is to monitor and respond to the environment. It receives information from its surroundings, processes it and signals the body to respond, but how does the nervous system communicate this information? In this chapter we will find out by examining the processes of communication of information within and between neurones (brain cells).

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  Anatomy and Physiology of Farm Animals

  • Anna Dee Fails, Christianne Magee(Authors)
  • 2018(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  Chapter 11 Physiology of the Nervous System

  • Functional Regions of the Neuron
  • Physiology of the Nerve Impulse
    • Conduction Velocity and Myelination
  • Synaptic Transmission
  • Neurotransmitters
  • Neural Control of Skeletal Muscle
    • Reflexes Involving Skeletal Muscle Contraction
    • Voluntary Movement
  • Physiology of the Autonomic Nervous System
    • Regulation of Autonomic Nervous System Activity
    • Autonomic Neurotransmitters and Their Receptors
  • Regeneration and Repair in the Nervous System

  Learning Objectives

  • Define and be able to explain the significance of the bold italic terms in this chapter.
  • Be able to detail the events associated with action potential generation and propagation. Be able to sketch the action potential graphically and explain what events produce each part of the graph.
  • Explain the anatomy and role of myelination in action potential propagation.
  • Describe the anatomy of the synapse, and explain the events that lead to synaptic transmission.
  • Identify by name the most common neurotransmitters; describe where they are found and what their primary effects are.
  • Be able to draw and explain the parts of a typical reflex arc.
  • Be able to explain the nature of the myotatic reflex arc and point out how it is different than most reflexes.
  • Explain how a conscious desire to move travels to muscle.
  • Describe the role of the cerebellum in voluntary movement.
  • Describe and be able to illustrate the visceral motor system and predict the effects of parasympathetic and sympathetic input on the organs they target.
  • Identify the neurotransmitters and receptors found at the autonomic ganglion synapse, between sympathetic neurons and their targets, and between parasympathetic neurons and their targets.
  • Explain how axonal regeneration in the PNS differs from that in the CNS.

  Functional Regions of the Neuron

  Recall from Figures 10‐2 and 10‐3 that neurons have cell bodies with processes extending from them. Of these cellular extensions, one is an axon, and all others are considered dendrites. With the exception of the pseudounipolar neurons in the peripheral nervous system (PNS), the dendrites and cell body represent the receptive zone of the neuron, where it receives information from other neurons. The axon is the conducting zone of the neuron, where the specialized ion channels in the axon’s membrane permit the rapid conduction of a wave of depolarization (the action potential) down to the telodendrion where it initiates the steps leading to synaptic transmission of information to target cells (Fig. 11‐1

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  Tortora's Principles of Anatomy and Physiology

  • Gerard J. Tortora, Bryan H. Derrickson(Authors)
  • 2017(Publication Date)
  • Wiley

    (Publisher)

  The value of synchronized action potentials in the heart or in visceral smooth muscle is coordinated contraction of these fibers to produce a heartbeat or move food through the gastrointestinal tract. Chemical Synapses Although the plasma membranes of presynaptic and postsynaptic neu- rons in a chemical synapse are close, they do not touch. They are sepa- rated by the synaptic cleft, a space of 20–50 nm* that is filled with interstitial fluid. Nerve Impulses cannot conduct across the synaptic cleft, so an alternative, indirect form of communication occurs. In res- ponse to a nerve impulse, the presynaptic neuron releases a neurotrans- mitter that diffuses through the fluid in the synaptic cleft and binds to (ak′-sō-sō-MAT-ik = from axon to cell body) or axoaxonic (ak′-so-ak- SON-ik = from axon to axon) (Figure 12.22). In addition, synapses may be electrical or chemical, and they differ both structurally and functionally. In Chapter 10 we described the events occurring at one type of synapse, the neuromuscular junction. Our focus in this chapter is on synaptic communication among the billions of neurons in the nervous system. Synapses are essential for homeostasis because they allow in- formation to be filtered and integrated. During learning, the structure and function of particular synapses change. The changes may allow some signals to be transmitted while others are blocked. For example, the changes in your synapses from studying will determine how well you do on your anatomy and physiology tests! Synapses are also im- portant because some diseases and neurological disorders result from disruptions of synaptic communication, and many therapeutic and addictive chemicals affect the body at these junctions. Electrical Synapses At an electrical synapse, action potentials (impulses) conduct directly between the plasma membranes of adjacent neurons through struc- tures called gap junctions.

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