KIN 267 - Nervous Tissue & Muscle Cells

Chapter 4 The Tissue Level of Organization This slide deck contains animations. Please disable animations if they cause issues with your device. What Is a Tissue? A tissue is a group of cells that usually have a common embryonic origin and function together to carry out specialized a...

Chapter 4 The Tissue Level of Organization This slide deck contains animations. Please disable animations if they cause issues with your device. What Is a Tissue? A tissue is a group of cells that usually have a common embryonic origin and function together to carry out specialized activities There are 4 basic types of tissues in the human body and they are categorized according to their structure and function Cell Junctions Cells can be held together in a number of ways to form tissues. These points of contact between the plasma membrane of cells are called cell junctions. Epithelial Tissues  General Features of Epithelial Tissue Cells are arranged in sheets and are densely packed (no spaces between plasma membranes) Is avascular (no blood vessels) but does have a nerve supply Function: protects, secretes, absorbs and excretes Surface epithelial: forms skin and some organs, inner lining of blood vessels, ducts, body cavities Glandular epithelial: makes up portions of glands (Chapter 18 upcoming) Many cell junctions are present Epithelial cells attach to a basement membrane  Surfaces of Epithelial Cells and the Basement Membrane Anchors epithelium to connective tissue Assist in Involved in satellite cell activity (in muscle section)  Connective Tissue Note: Bone Biology (Chapter 6) – will be reviewed in detail later in the term General Features of Connective Tissue Consists of two basic elements: 1. Cells 2. (ground substance and protein fibers) Connective tissue is highly vascularized and has a nerve supply Exceptions: Connective Tissue Cells Connective Tissue Extracellular Matrix Fibers in the extracellular matrix provide strength and support to a tissue fibers- very strong (cartilage, bone) Elastic fibers- strong and flexible (skin, lungs) Reticular fibers- structure support (blood vessels) Main Classifications of Connective Tissue Mature Cartilage Bone-Chapter 6 (upcoming) Blood-Chapter 19 (upcoming)  Cartilage Made by cells (primary role is to produce ) Cartilage consists of collagen fibers and : gel-like component of ground substance Strength comes from and resilience (ability to change shape and maintain structure) comes from chondroitin Does not have in extracellular matrix Tissue Repair Tissue repair is the process that replaces worn out, damaged, or dead cells Epithelial cells are replaced by the division of stem cells or undifferentiated cells Not all connective tissue cells have the ability to repair Muscle cells can perform limited repair Some nervous cells can perform limited repair, others cannot Fibrosis is the formation of scar tissue Muscular Tissue- Chapter 10 (upcoming) Nervous Tissue – Chapter 12 (next)  Chapter 12 Nervous System & Tissue This slide deck contains animations. Please disable animations if they cause issues with your device. 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 Neuron - Cells that possess “ excitability” - Can respond to a stimulus and generate an action potential (reliant on ) 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 contain Rough endoplasmic reticulum (thus no ) 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) 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 messages 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) 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)  Astrocytes – strong; protect neuron; maintains by maintaining health of endothelial cells; allows nutrients to flow between neurons and capillaries Oligodendrocytes – Provides structural support and forms/maintains myelin sheath around 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 cells – completely surround and form myelin shealth around axons; can help regenerate axons Satellite cells – regulate nutrient exchange between neurons and interstitial fluid Myelination (≤ 100 layers)  Multiple Sclerosis 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 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’ 27 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??) Electrical Signals in Neurons Resting Membrane Potential 32  Axon Axon Interior of muscle fiber Interior of muscle fiber At Rest Axon Na+ K+ Na+ K+ Na+ Interior of muscle fiber Passive Transport: Channel Mediated Facilitated Diffusion 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+ K+ K+ “Leaky’ K+ Channel Interior of muscle fiber  At Rest Outside is more Axon POSITIVELY charged than inside Na+ K+ Na+ K+ Na+ NA+/ K+ATP ‘pump’ K+ K+ “Leaky’ K+ Channel Interior of muscle fiber  At Rest Axon Creates “ElectroChemical” Gradient Na+ K+ (Outside is more positively charged vs. Na+ K+ inside based on Na+ and K+) Na+ Referred to as ‘Resting Membrane Potential” K+ -70mV “Leaky’ K+ Channel Interior of muscle fiber Action Potential Na+ ion channel Na+ Na+ Na+ Na+ Na+ Na+ Axon -55 mV Threshold Achieved 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 mV K+ K+ “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 ( ) Interior of muscle fiber Whatever happened to Ach in the Neuromuscular Junction? Stay tuned for the section on Skeletal Muscle! What happens post-depolarization?  Na+ Na+ Closed Na+ “Voltage-Gated” K+ Channels K+ K+ Axon Closed Na+ K+ K+ Closed Na+ K+ K+ All K+ Closed Na+ channels open 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+ Repolarization “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+ “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 continually firing Closed Na+ = “Absolute ” K+ K+ Closed -90 mV K+ “HYPERpolarization” “Leaky’ K+ Channel Interior of muscle fiber 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+ Interior of muscle fiber