Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture.

Slides:



Advertisements
Similar presentations
Topic Nerves.
Advertisements

Fundamentals of the Nervous System and Nervous Tissue: Part B
This week’s plan 2 days talking about how nerve impulse Wednesday – Brain regions Thursday Dissect Sheep Brain Friday Assess regions and neuron firing.
Nervous coordination 2 The nerve impulse.
The Electrical Nature of Nerves
General Electrophysiology with emphasis on nerve action
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology SIXTH EDITION Chapter 12, part 2 Neural.
Nerve Cells and Electrical Signaling
PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 11 Fundamentals of the.
Figure 48.1 Overview of a vertebrate nervous system.
 Nerve fibers are classified according to:  Diameter  Degree of myelination  Speed of conduction Nerve Fiber Classification.
The Action Potential.
Chapter Eleven Exam Four Material Chapters 11, 12, &13.
Nervous System The master controlling and communicating system of the body Functions Sensory input – monitoring stimuli Integration – interpretation of.
11 Fundamentals of the Nervous System and Nervous Tissue: Part B.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell.
Nervous System All animals must respond to environmental stimuli
HOW MESSAGES ARE SENT.  It is a message travelling down a neuron  The message comes from:  Another neuron or  A sensory receptor  A nerve impulse.
7 December 2014 CHANNELS OF THE NEURON: ACTING ON IMPULSE.
Nervous System Neurophysiology.
Action Potentials and Conduction. Neuron F8-2 Axons carry information from the cell body to the axon terminals. Axon terminals communicate with their.
Fundamentals of the Nervous System and Nervous Tissue
AP Biology Nervous Systems Part 2. Important concepts from previous units: Energy can be associated with charged particles, called ions. Established concentration.
Copyright © 2010 Pearson Education, Inc. Neuron Function Neurons are highly irritable Respond to adequate stimulus by generating an action potential (nerve.
Chapter 48 Neurons, Synapses, and Signaling. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Lines of Communication.
Nerve Impulse. A nerve impulse is an impulse from another nerve or a stimulus from a nerve receptor. A nerve impulse causes:  The permeability of the.
Nerve Impulse. A nerve impulse is an impulse from another nerve or a stimulus from a nerve receptor. A nerve impulse causes:  The permeability of the.
Neuron organization and structure reflect function in information transfer The squid possesses extremely large nerve cells and is a good model for studying.
P. Ch 48 – Nervous System pt 1.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint.
Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated.
Quick Review What’s another name for neurons? Can you name the parts of a neuron?
Copyright © 2009 Pearson Education, Inc. Neurons and Neurological Cells: The Cells of the Nervous System  The nervous system  Integrates and coordinates.
Nervous System.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture.
Fundamentals of the Nervous System and Nervous Tissue: Part B.
Electricity Definitions Voltage (V) – measure of potential energy generated by separated charge Voltage (V) – measure of potential energy generated by.
1 Membrane Potentials (Polarity) Information found in 2 places: –Chapter 3 - pp –Chapter 9 - pp /22/12 MDufilho.
The Nerve Impulse.. The Neuron at Rest The plasma membrane of neurons contains many active Na-K-ATPase pumps. These pumps shuttle Na+ out of the neuron.
Electrical Current and the Body  Reflects the flow of ions rather than electrons  There is a potential on either side of membranes when: The number of.
11-2. LIGAND OR CHEMICAL GATE Voltage-Gated Channel Example: Na + channel Figure 11.6b.
Action Potential: Resting State Leakage accounts for small movements of Na + and K + Each Na + channel has two voltage-regulated gates.
8.2 Structures and Processes of the Nervous System
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ch 48 – Neurons, Synapses, and Signaling Neurons transfer information.
Copyright © 2010 Pearson Education, Inc. Chapter 11 Fundamentals Of The Nervous System And Nervous Tissue Part B Shilla Chakrabarty, Ph.D.
Structures and Processes of the Nervous System – Part 2
Neurons, Synapses, and Signaling
The Neuron: Pumps, Channels, and Membrane Potentials
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture.
Nerve Impulses.
Structure of a nerve Nerves and Nerve impulses “Nerve impulse: a self-propagating wave of electrical disturbance which travels along the surface of a.
Electrical Signaling. Lecture Outline Using ions as messengers Potentials in electrical signaling –Action –Graded Other electrical signaling –Gap junctions.
Human Anatomy & Physiology Ninth Edition PowerPoint ® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community College C H A P T E R © 2013 Pearson.
Quick Membrane Review 1. 2 Interfere with the neurons ability to transfer electrical impulses Over loads nervous system volts Taser Tasers.
Nerve Impulses. Neuron Physiology Action Potentials- nerve impulses which are sent by a change in electrical charge in the cell membrane. Depends on ions.
Human Anatomy & Physiology Ninth Edition PowerPoint ® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community College C H A P T E R © 2013 Pearson.
Warm-Up What is an electrochemical gradient? In what organelles do we find these in a cell?
Nerve Action potential L 21
Electrical Properties of the Nervous System Lundy-Ekman, Chapter 2 D. Allen, Ph.D.
11 Fundamentals of the Nervous System and Nervous Tissue: Part B.
6.5 Neurons and synapses Essential idea: Neurons transmit the message, synapses modulate the message. Nature of science: Cooperation and collaboration.
TEXTBOOK OF MEDICAL PHYSIOLOGY GUYTON & HALL 13TH EDITION
Neurophysiology.
Neuron Function Neurons are highly irritable
Action Potentials and Conduction
Fundamentals of the Nervous System and Nervous Tissue
Electrical Current and the Body
11 Fundamentals of the Nervous System and Nervous Tissue: Part B.
12-5 Action Potential Action Potentials
Chapter 11 The Nervous System (Part B)
Presentation transcript:

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture Slides prepared by Vince Austin, University of Kentucky 11 Fundamentals of the Nervous System and Nervous Tissue Part B

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Voltage (V) – measure of potential energy generated by separated charge  Potential difference – voltage measured between two points  Current (I) – the flow of electrical charge between two points  Resistance (R) – hindrance to charge flow  Insulator – substance with high electrical resistance  Conductor – substance with low electrical resistance Electricity Definitions

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Reflects the flow of ions rather than electrons  There is a potential on either side of membranes when:  The number of ions is different across the membrane  The membrane provides a resistance to ion flow Electrical Current and the Body

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Types of plasma membrane ion channels:  Passive, or leakage, channels – always open  Chemically gated channels – open with binding of a specific neurotransmitter  Voltage-gated channels – open and close in response to membrane potential  Mechanically gated channels – open and close in response to physical deformation of receptors Role of Ion Channels InterActive Physiology ® : Nervous System I: Ion Channels PLAY

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Example: Na + -K + gated channel  Closed when a neurotransmitter is not bound to the extracellular receptor  Na + cannot enter the cell and K + cannot exit the cell  Open when a neurotransmitter is attached to the receptor  Na + enters the cell and K + exits the cell Operation of a Gated Channel

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Operation of a Gated Channel Figure 11.6a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Example: Na + channel  Closed when the intracellular environment is negative  Na + cannot enter the cell  Open when the intracellular environment is positive  Na + can enter the cell Operation of a Voltage-Gated Channel

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Operation of a Voltage-Gated Channel Figure 11.6b

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  When gated channels are open:  Ions move quickly across the membrane  Movement is along their electrochemical gradients  An electrical current is created  Voltage changes across the membrane Gated Channels

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Ions flow along their chemical gradient when they move from an area of high concentration to an area of low concentration  Ions flow along their electrical gradient when they move toward an area of opposite charge  Electrochemical gradient – the electrical and chemical gradients taken together Electrochemical Gradient

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The potential difference (–70 mV) across the membrane of a resting neuron  It is generated by different concentrations of Na +, K +, Cl , and protein anions (A  )  Ionic differences are the consequence of:  Differential permeability of the neurilemma to Na + and K +  Operation of the sodium-potassium pump Resting Membrane Potential (V r ) InterActive Physiology ® : Nervous System I: Membrane Potential PLAY

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Resting Membrane Potential (V r ) Figure 11.8

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Used to integrate, send, and receive information  Membrane potential changes are produced by:  Changes in membrane permeability to ions  Alterations of ion concentrations across the membrane  Types of signals – graded potentials and action potentials Membrane Potentials: Signals

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Changes are caused by three events  Depolarization – the inside of the membrane becomes less negative  Repolarization – the membrane returns to its resting membrane potential  Hyperpolarization – the inside of the membrane becomes more negative than the resting potential Changes in Membrane Potential

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Changes in Membrane Potential Figure 11.9

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Short-lived, local changes in membrane potential  Decrease in intensity with distance  Their magnitude varies directly with the strength of the stimulus  Sufficiently strong graded potentials can initiate action potentials Graded Potentials

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Graded Potentials Figure 11.10

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Graded Potentials  Voltage changes in graded potentials are decremental  Current is quickly dissipated due to the leaky plasma membrane  Can only travel over short distances

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Graded Potentials Figure 11.11

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  A brief reversal of membrane potential with a total amplitude of 100 mV  Action potentials are only generated by muscle cells and neurons  They do not decrease in strength over distance  They are the principal means of neural communication  An action potential in the axon of a neuron is a nerve impulse Action Potentials (APs)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Na + and K + channels are closed  Leakage accounts for small movements of Na + and K +  Each Na + channel has two voltage-regulated gates  Activation gates – closed in the resting state  Inactivation gates – open in the resting state Action Potential: Resting State Figure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Na + permeability increases; membrane potential reverses  Na + gates are opened; K + gates are closed  Threshold – a critical level of depolarization (-55 to -50 mV)  At threshold, depolarization becomes self-generating Action Potential: Depolarization Phase Figure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Sodium inactivation gates close  Membrane permeability to Na + declines to resting levels  As sodium gates close, voltage-sensitive K + gates open  K + exits the cell and internal negativity of the resting neuron is restored Action Potential: Repolarization Phase Figure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Action Potential: Hyperpolarization  Potassium gates remain open, causing an excessive efflux of K +  This efflux causes hyperpolarization of the membrane (undershoot)  The neuron is insensitive to stimulus and depolarization during this time Figure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Repolarization  Restores the resting electrical conditions of the neuron  Does not restore the resting ionic conditions  Ionic redistribution back to resting conditions is restored by the sodium-potassium pump Action Potential: Role of the Sodium-Potassium Pump

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Phases of the Action Potential  1 – resting state  2 – depolarization phase  3 – repolarization phase  4 – hyperpolarization

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Na + influx causes a patch of the axonal membrane to depolarize  Positive ions in the axoplasm move toward the polarized (negative) portion of the membrane  Sodium gates are shown as closing, open, or closed Propagation of an Action Potential (Time = 0ms)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Propagation of an Action Potential (Time = 0ms) Figure 11.13a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Ions of the extracellular fluid move toward the area of greatest negative charge  A current is created that depolarizes the adjacent membrane in a forward direction  The impulse propagates away from its point of origin Propagation of an Action Potential (Time = 1ms)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Propagation of an Action Potential (Time = 1ms) Figure 11.13b

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The action potential moves away from the stimulus  Where sodium gates are closing, potassium gates are open and create a current flow Propagation of an Action Potential (Time = 2ms)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Propagation of an Action Potential (Time = 2ms) Figure 11.13c

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Threshold – membrane is depolarized by 15 to 20 mV  Established by the total amount of current flowing through the membrane  Weak (subthreshold) stimuli are not relayed into action potentials  Strong (threshold) stimuli are relayed into action potentials  All-or-none phenomenon – action potentials either happen completely, or not at all Threshold and Action Potentials

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  All action potentials are alike and are independent of stimulus intensity  Strong stimuli can generate an action potential more often than weaker stimuli  The CNS determines stimulus intensity by the frequency of impulse transmission Coding for Stimulus Intensity

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Coding for Stimulus Intensity  Upward arrows – stimulus applied  Downward arrows – stimulus stopped Figure 11.14

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Coding for Stimulus Intensity  Length of arrows – strength of stimulus  Action potentials – vertical lines Figure 11.14

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Time from the opening of the Na + activation gates until the closing of inactivation gates  The absolute refractory period:  Prevents the neuron from generating an action potential  Ensures that each action potential is separate  Enforces one-way transmission of nerve impulses Absolute Refractory Period

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Absolute Refractory Period Figure 11.15

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The interval following the absolute refractory period when:  Sodium gates are closed  Potassium gates are open  Repolarization is occurring  The threshold level is elevated, allowing strong stimuli to increase the frequency of action potential events Relative Refractory Period

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Conduction velocities vary widely among neurons  Rate of impulse propagation is determined by:  Axon diameter – the larger the diameter, the faster the impulse  Presence of a myelin sheath – myelination dramatically increases impulse speed Conduction Velocities of Axons InterActive Physiology ® : Nervous System I: Action Potential PLAY

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Current passes through a myelinated axon only at the nodes of Ranvier  Voltage-gated Na + channels are concentrated at these nodes  Action potentials are triggered only at the nodes and jump from one node to the next  Much faster than conduction along unmyelinated axons Saltatory Conduction

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Saltatory Conduction Figure 11.16

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  An autoimmune disease that mainly affects young adults  Symptoms include visual disturbances, weakness, loss of muscular control, and urinary incontinence  Nerve fibers are severed and myelin sheaths in the CNS become nonfunctional scleroses  Shunting and short-circuiting of nerve impulses occurs Multiple Sclerosis (MS)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The advent of disease-modifying drugs including interferon beta-1a and -1b, Avonex, Betaseran, and Copazone:  Hold symptoms at bay  Reduce complications  Reduce disability Multiple Sclerosis: Treatment