Nervous System Chapter 12 PDF

Chapter 12 Nervous Tissue This slide deck contains animations. Please disable animations if they cause issues with your device. Copyright ©2021 John Wiley & Sons, Inc. Nervous System Nervous Tissue: Consists of neurons and ne...

Chapter 12 Nervous Tissue This slide deck contains animations. Please disable animations if they cause issues with your device. Copyright ©2021 John Wiley & Sons, Inc. Nervous System Nervous Tissue: Consists of neurons and neuroglia Nerve: bundles of axons, connective tissue and blood vessels that are located outside CNS & PNS Sensory receptors: monitor changes in the external and internal environment Copyright ©2021 John Wiley & Sons, Inc. 2 Neuron - Cells that possess “electrical excitability” - Can respond to a stimulus and generate an action potential (reliant on sodium & potassium) Copyright ©2021 John Wiley & Sons, Inc. 3 Cell body (soma)-contains nucleus and typical cell components Dendrites- receiving portion of neuron Axon - sending portion of neuron -sends signals to another neuron, muscle fiber or gland - does NOT contain Rough endoplasmic reticulum (thus no protein synthesis) Copyright ©2021 John Wiley & Sons, Inc. 4 Axon Terminal: Contains synaptic vesicles that contain neurotransmitters (relays the action potential) Synapse: Site of communication between 2 neurons or a neuron and effector cell (muscle, gland) Copyright ©2021 John Wiley & Sons, Inc. 5 Organization of the Nervous System “Effere nt” “Affere nt” Temperatur Smell e Taste Pain Vision Pressure Hearing Equilibrium Sensory Division (i.e. Afferent): Conveys messages INTO the CNS Motor Division (i.e. Efferent): Conveys Copyright ©2021 John Wiley &messages Sons, Inc. 6 FROM CNS Functions of the Nervous System- General Overview Sensory Detect changes through sensory receptors (i.e. touching hot stove) Integrative Analyze incoming sensory information, store some aspects, and make decisions regarding appropriate behaviors Motor Respond to stimuli via effectors (i.e. muscles & glands; move hand away quickly) Copyright ©2021 John Wiley & Sons, Inc. 7 Functions of the Nervous System- Detailed Overview Sensory/Afferent neurons- convey information to the CNS - Once a stimulus activates the sensory receptor (usually in dendrite), sensory neuron sends nerve impulse (action potential) through its axon and subsequently cranial and spinal nerves to CNS Interneurons/Association neurons –located in CNS between sensory and motor neurons - Process sensory information and elicit a motor response Motor/Efferent neurons- convey information through nerves to muscles/gland - Conveys action potential from the CNS Copyright ©2021 John Wiley & Sons, Inc. 8 Copyright ©2021 John Wiley & Sons, Inc. 9  Neurotransmi tter Neurotransmi tter Neurotransmi tter Copyright ©2021 John Wiley & Sons, Inc. 10  Neurotransmi tter Neurotransmi tter Neurotransmi tter Copyright ©2021 John Wiley & Sons, Inc. 11 Motor Units The motor neuron and ALL the muscle fibers that it innervates Neuroglia (glue of nervous system) - Not electrically excitable - Do not transmit action potentials - When neurons die, neuroglia fills in spaces - 6 kinds in total (4 in CNS, 2 in PNS) Copyright ©2021 John Wiley & Sons, Inc. 13  Astrocytes – strong; protect neuron; maintains blood brain barrier by maintaining health of endothelial cells; allows nutrients to flow between neurons and capillaries Oligodendrocytes – Provides structural support and forms/maintains myelin sheath around CNS axons Myelin Sheath: multi-layered lipid and protein covering around some axons that insulates them and SPEEDS up the rate of action potentials. Ependymal cells – contain microvilla and cilia; help produce and monitor cerebrospinal fluid (protects and nourishes spinal cord and brain) Microglia – function as removers of cell debris/damage Schwann cells – completely surround and form myelin shealth around axons; can help regenerate axons Satellite cells – regulate nutrient exchange between neurons and interstitial fluid Copyright ©2021 John Wiley & Sons, Inc. 14 Summary Myelinated Axon Unmyelinated Axon - Most axons in CNS -primarily found in & PNS Autonomic Nervous System Copyright ©2021 John Wiley & Sons, Inc. 15 Question What types of cells form the myelin sheath? Copyright ©2021 John Wiley & Sons, Inc. 16 Myelination (≤ 100 layers) Copyright ©2021 John Wiley & Sons, Inc. 17 Multiple Sclerosis Autoimmune disease that causes progressive destruction of myelin sheath Cause is unclear; may be genetic and/or environmental Symptoms include muscle weakness, abnormal sensations and double vision Copyright ©2021 John Wiley & Sons, Inc. 18 Myelin Sheath Gaps (Nodes of Ranvier): Contain ion channels for sodium/potassium - Allow for the exchange of ions in/out of neuron=speeds up action potential by ‘jumping’ Copyright ©2021 John Wiley & Sons, Inc. 19 19 Copyright ©2021 John Wiley & Sons, Inc. 20 Factors That Affect Propagation Speed 1. Axon diameter Larger diameter axons propagate action potential faster 2. Amount of myelination Myelin increases speed of action potential 3. Temperature Higher temperature increases speed of action potential (i.e. possibly influence in warm-up??) Copyright ©2021 John Wiley & Sons, Inc. 21 Electrical Signals in Neurons Copyright ©2021 John Wiley & Sons, Inc. 22 Resting Membrane Potential Copyright ©2021 John Wiley & Sons, Inc. 23 Copyright ©2021 John Wiley & Sons, Inc. 24 24  Axon Axon Interior of muscle fiber Interior of muscle fiber At Rest Axon Na+ K+ Na+ K+ Na+ Interior of muscle fiber At Rest Axon Na+ K+ Na+ K+ Na+ Interior of muscle fiber At Rest Axon Na+ K+ Na+ K+ Na+ NA+/ K+ATP ‘pump’ Interior of muscle fiber  At Rest Axon K+ Na+ K+ Na+ Na+ NA+/ K+ATP ‘pump’ K+ K+ “Leaky’ K+ Channel Interior of muscle fiber  At Rest Outside is Axon more POSITIVELY charged than Na+ K+ inside Na+ K+ Na+ NA+/ K+ATP ‘pump’ K+ K+ “Leaky’ K+ Channel Interior of muscle fiber  At Rest Axon Creates “ElectroChemical” Gradient K+ (Outside is more positively charged vs. Na+ K+ inside based on Na+ and K+) Na+ Na+ Referred to as ‘Resting Membrane NA+/ Potential” K+ATP ‘pump’ K+ -70mV “Leaky’ K+ Channel Interior of muscle fiber Action Potential Na+ ion channel Na+ Na+ Na+ Na+ Na+ Na+ Axon -55 mV Threshol d Achieve d K+ K+ “Leaky’ K+ Channel Interior of muscle fiber What happens once inside of cell reaches – 55mV? Action Potential Na+ Na+ “Voltage-Gated” Na+ Channels Na+ Axon Na+ Na+ K+ K+ “Leaky’ K+ Channel Interior of muscle fiber Action Potential Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ K+ K+ “Leaky’ K+ Channel Interior of muscle fiber Action Potential Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ “Leaky’ K+ Channel Interior of muscle fiber Action Potential Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ +30 K+ K+ mV “Leaky’ K+ Channel Interior of muscle fiber Action Potential Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ +30 mV Depolarization “Leaky’ K+ Channel Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Ca2+ Ca2+ Voltage-gated Ca2+ channel Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Synaptic vesicles Ca2+ Ca2+ Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Synaptic vesicles Ca2+ Ca2+ Ach: Acetylcholine Ach Ach Ach (Neurotransmitter) Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Synaptic vesicles Ca2+ Ca2+ Ach Ach Ach Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Synaptic vesicles Ca2+ Ca2+ Ach Ach Ach Neuromuscular junction (synapse) Interior of muscle fiber What happens once Ach leaves terminal axon?  Na+ Na+ Closed Na+ “Voltage-Gated” K+ Channels K+ K+ Axon Closed Na+ K+ K+ Closed Na+ K+ K+ Closed Na+ K+ K+ Closed K+ K+ “Leaky’ K+ Channel Interior of muscle fiber  Na+ Na+ Closed Na+ K+ K+ Axon Closed Na+ K+ K+ Closed Na+ K+ K+ Closed Na+ K+ K+ Closed K+ Repolarizatio “Leaky’ K+ Channel n Interior of muscle fiber  Na+ Na+ Closed Na+ K+ K+ Axon Closed Na+ K+ K+ Closed Na+ K+ K+ Closed Na+ K+ K+ Closed -90 mV K+ “Leaky’ K+ Channel Interior of muscle fiber  Na+ Na+ Closed Na+ K+ K+ Axon Closed Na+ K+ K+ Closed Na+ K+ K+ Closed Na+ K+ K+ Closed -90 mV K+ “HYPERpolarization” “Leaky’ K+ Channel Interior of muscle fiber  Na+ Na+ Closed Na+ K+ K+ Axon Closed Na+ K+ K+ Closed Na+ K+ K+ HYPERpolarization: prevents neuron from Closed Na+ continually firing = K+ K+ “Absolute Refractory Period” Closed -90 mV K+ “HYPERpolarization” “Leaky’ K+ Channel Interior of muscle fiber Copyright ©2021 John Wiley & Sons, Inc. 50 How does the neuron ‘reset’ itself for the next action potential (i.e. how does the cell cause Na+ to leave the inside of the neuron and bring K+ back inside the neuron?)  Axon K+ Na+ K+ Na+ Na+ NA+/ K+ATP ‘pump’ Interior of muscle fiber Whatever happened to Ach in the Neuromuscular Junction? Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Synaptic vesicles Ca2+ Ca2+ Ach Ach Ach Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Ca2+ Ca2+ Only has 1 millisecond to bind Ach Ach Ach Ligand/chemical gated channels Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Ca2+ Ca2+ Na+ Na+ Na+ Ach Ach Ach Na+ Na+ Na+ Interior of muscle fiber Action Potential (i.e. muscle contraction) Na+ Na+ Na+ Axon Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Ca2+ Ca2+ Na+ Na+ Na+ Ach Ach Ach Na+ Na+ Na+ “Wave of Depolarization” Interior of muscle fiber Match the components on the left with the definition on the right Axons these are exchanged across the sarcolemma during contraction acetyl choline transmit electrical signals from nerves to muscle fibers motor Nerve cells connected to neurons muscle fibers Chemical messenger between motor unit axons and muscle fibers sodium and A motor neuron and all the muscle fibers that are potassium connected to it 2-58 Put the following events during muscle contraction in proper order calcium enters the axon action potential travels down the axon acetyl choline is released from the axon acetyl choline binds to a receptor on the muscle membrane 2-59  Axon Ach Ach Ach T-Tubules Na+ Na+ Action Na+ potenti al Sarcoplasmic Reticulum Interior of muscle fiber  Axon Ach Ach Ach T-Tubules Na+ Na+ Action Na+ potential Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Interior of muscle fiber  Axon Ach Ach Ach T-Tubules Na+ Na+ Action Na+ potential Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Interior of muscle fiber Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Interior of muscle fiber  Troponin Ca2+ Tropomyosin Ca2+ Ca2+ ATPase myosin Actin  Troponin Ca2+ Tropomyosin Ca2+ Ca2+ ATPase myosin Actin Muscle Proteins Contractil Regulatory: e: Troponin Myosin Tropomyo Actin sin Copyright ©2021 John Wiley & Sons, Inc. 67 Skeletal Muscle Fiber Proteins (1 of 3) Type of Protein Description Contractile Proteins that generate force during muscle proteins contractions. Myosin Contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules of thin filament during muscle contraction. Actin Contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction. Copyright ©2021 John Wiley & Sons, Inc. 68 Skeletal Muscle Fiber Proteins (2 of 3) Type of Protein Description Regulatory Proteins that help switch muscle contraction process proteins on and off. Tropomyosin Regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from binding to actin. Troponin Regulatory protein that is a component of thin filament; when calcium ions (Ca2+) bind to troponin, it changes shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin. Copyright ©2021 John Wiley & Sons, Inc. 69 Excitation-Contraction Coupling Copyright ©2021 John Wiley & Sons, Inc. 70 The Contraction (Cross-Bridge) Cycle Copyright ©2021 John Wiley & Sons, Inc. 71 General Summary of Contraction/Relaxation in Skeletal Muscle Copyright ©2021 John Wiley & Sons, Inc. 72  Axon Ach Ach Ach Na+ Na+ Na+ NA+/ K+ATP ‘pump’ K+ K+ K+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ ATP ‘pump’ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Now that we know how a muscle contracts, what exactly is muscle?