Chapter 10 - Muscle Tissue

Total Page:16

File Type:pdf, Size:1020Kb

Chapter 10 - Muscle Tissue Chapter 10 - Muscle Tissue 1. Describe the functions and characteristics of muscle tissue. 2. Describe and compare the 3 types of muscle tissue based on location, histological structure, innervation (somatic/voluntary or autonomic/involuntary), and function. Draw a cell of each type including major features like nuclei, striations, etc. 3. Describe the gross structure of a skeletal muscle, including the different tissue components. 4. Describe the following parts of a skeletal muscle including location and tissue composition if applicable: a. epimysium b. perimysium c. endomysium d. fascicle 5. Draw and label a longitudinal section through a skeletal muscle showing connective tissue elements and fascicles. Draw and label a cross section through the belly of a skeletal muscle. 6. Define a. tendon b. insertion c. origin d. aponeurosis e. biarticular muscle 7. Define and compare direct and indirect attachment of muscles. 8. In the muscles of the limbs, the origin is (proximal or distal?) __________ to the insertion. In the limbs, muscles that move a bone are usually located (proximal or distal?)____________ to the bone being moved. 9. Describe the structure and function of these components of skeletal muscle tissue: Strong/Fall 2008 page 1 a. sarcolemma b. t-tubules c. sarcoplasmic reticulum (SR) and terminal cisternae d. motor end plate 10. Draw and label a longitudinal section of part of a skeletal muscle cell showing the sarcolemma, t-tubules, sarcoplasmic reticulum, terminal cisternae and myofibrils. 11. Define and state the function of: a. myofibril b. myofilament c. sarcomere d. actin e. myosin f. titin g. Z disc h. M line 12. Describe the relationships between: a. actin, troponin, and tropomyosin b. myosin and thick filaments c. sarcomeres and myofibrils d. myofibrils and muscle cells e. muscle cells and fasciculi f. fasciculi and whole muscles g. thick filaments and thin filaments Strong/Fall 2008 page 2 13. Draw and label a sarcomere, including: Z-lines (discs), thick and thin filaments, titin, A and I bands, H zone, and M line. Describe the molecular basis for the A and I bands and the H zone. 14. Briefly describe the process of muscle contraction and extension. 15. Describe and compare the three main types of skeletal muscle fiber based on size, color, and physiological characteristics. 16. Describe the location and function of myoglobin. 17. Define, discuss and compare atrophy, hypertrophy and hyperplasia. 18. Describe the basic structure and function of cardiac muscle tissue. 19. Describe the basic structure and function of smooth muscle tissue. 20. Compare the embryonic development of skeletal, cardiac and smooth muscle cells. 21. Explain how skeletal muscles grow during childhood. Draw and label a diagram comparing embryonic myoblast arrangement and a mature skeletal muscle cell. 22. Compare regeneration (following injury) in skeletal, cardiac and smooth muscle. Strong/Fall 2008 page 3 .
Recommended publications
  • Microanatomy of Muscles
    Microanatomy of Muscles Anatomy & Physiology Class Three Main Muscle Types Objectives: By the end of this presentation you will have the information to: 1. Describe the 3 main types of muscles. 2. Detail the functions of the muscle system. 3. Correctly label the parts of a myocyte (muscle cell) 4. Identify the levels of organization in a skeletal muscle from organ to myosin. 5. Explain how a muscle contracts utilizing the correct terminology of the sliding filament theory. 6. Contrast and compare cardiac and smooth muscle with skeletal muscle. Major Functions: Muscle System 1. Moving the skeletal system and posture. 2. Passing food through the digestive system & constriction of other internal organs. 3. Production of body heat. 4. Pumping the blood throughout the body. 5. Communication - writing and verbal Specialized Cells (Myocytes) ~ Contractile Cells Can shorten along one or more planes because of specialized cell membrane (sarcolemma) and specialized cytoskeleton. Specialized Structures found in Myocytes Sarcolemma: The cell membrane of a muscle cell Transverse tubule: a tubular invagination of the sarcolemma of skeletal or cardiac muscle fibers that surrounds myofibrils; involved in transmitting the action potential from the sarcolemma to the interior of the myofibril. Sarcoplasmic Reticulum: The special type of smooth endoplasmic Myofibrils: reticulum found in smooth and a contractile fibril of skeletal muscle, composed striated muscle fibers whose function mainly of actin and myosin is to store and release calcium ions. Multiple Nuclei (skeletal) & many mitochondria Skeletal Muscle - Microscopic Anatomy A whole skeletal muscle (such as the biceps brachii) is considered an organ of the muscular system. Each organ consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue.
    [Show full text]
  • Characterization of Cecal Smooth Muscle Contraction in Laying Hens
    veterinary sciences Communication Characterization of Cecal Smooth Muscle Contraction in Laying Hens Katrin Röhm 1, Martin Diener 2 , Korinna Huber 1 and Jana Seifert 1,* 1 Institute of Animal Science, University of Hohenheim, 70593 Stuttgart, Germany; [email protected] (K.R.); [email protected] (K.H.) 2 Institute of Veterinary Physiology and Biochemistry, Justus-Liebig University, 35392 Gießen, Germany; [email protected] * Correspondence: [email protected] Abstract: The ceca play an important role in the physiology of the gastrointestinal tract in chickens. Nevertheless, there is a gap of knowledge regarding the functionality of the ceca in poultry, especially with respect to physiological cecal smooth muscle contraction. The aim of the current study is the ex vivo characterization of cecal smooth muscle contraction in laying hens. Muscle strips of circular cecal smooth muscle from eleven hens are prepared to investigate their contraction ex vivo. Contraction is detected using an isometric force transducer, determining its frequency, height and intensity. Spontaneous contraction of the chicken cecal smooth muscle and the influence of buffers (calcium-free buffer and potassium-enriched buffer) and drugs (carbachol, nitroprusside, isoprenaline and Verapamil) affecting smooth muscle contraction at different levels are characterized. A decrease in smooth muscle contraction is observed when a calcium-free buffer is used. Carbachol causes an increase in smooth muscle contraction, whereas atropine inhibits contraction. Nitroprusside, isoprenaline and Verapamil result in a depression of smooth muscle contraction. In conclusion, the present results confirm a similar contraction behavior of cecal smooth muscles in laying hens as Citation: Röhm, K.; Diener, M.; shown previously in other species.
    [Show full text]
  • Back-To-Basics: the Intricacies of Muscle Contraction
    Back-to- MIOTA Basics: The CONFERENCE OCTOBER 11, Intricacies 2019 CHERI RAMIREZ, MS, of Muscle OTRL Contraction OBJECTIVES: 1.Review the anatomical structure of a skeletal muscle. 2.Review and understand the process and relationship between skeletal muscle contraction with the vital components of the nervous system, endocrine system, and skeletal system. 3.Review the basic similarities and differences between skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. 4.Review the names, locations, origins, and insertions of the skeletal muscles found in the human body. 5.Apply the information learned to enhance clinical practice and understanding of the intricacies and complexity of the skeletal muscle system. 6.Apply the information learned to further educate clients on the importance of skeletal muscle movement, posture, and coordination in the process of rehabilitation, healing, and functional return. 1. Epithelial Four Basic Tissue Categories 2. Muscle 3. Nervous 4. Connective A. Loose Connective B. Bone C. Cartilage D. Blood Introduction There are 3 types of muscle tissue in the muscular system: . Skeletal muscle: Attached to bones of skeleton. Voluntary. Striated. Tubular shape. Cardiac muscle: Makes up most of the wall of the heart. Involuntary. Striated with intercalated discs. Branched shape. Smooth muscle: Found in walls of internal organs and walls of vascular system. Involuntary. Non-striated. Spindle shape. 4 Structure of a Skeletal Muscle Skeletal Muscles: Skeletal muscles are composed of: • Skeletal muscle tissue • Nervous tissue • Blood • Connective tissues 5 Connective Tissue Coverings Connective tissue coverings over skeletal muscles: .Fascia .Tendons .Aponeuroses 6 Fascia: Definition: Layers of dense connective tissue that separates muscle from adjacent muscles, by surrounding each muscle belly.
    [Show full text]
  • Muscle Physiology Dr
    Muscle Physiology Dr. Ebneshahidi Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Figure 9.2 (a) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the muscular system . 1. Locomotion . 2. Vasoconstriction and vasodilatation- constriction and dilation of blood vessel Walls are the results of smooth muscle contraction. 3. Peristalsis – wavelike motion along the digestive tract is produced by the Smooth muscle. 4. Cardiac motion . 5. Posture maintenance- contraction of skeletal muscles maintains body posture and muscle tone. 6. Heat generation – about 75% of ATP energy used in muscle contraction is released as heat. Copyright. © 2004 Pearson Education, Inc., publishing as Benjamin Cummings . Striation: only present in skeletal and cardiac muscles. Absent in smooth muscle. Nucleus: smooth and cardiac muscles are uninculcated (one nucleus per cell), skeletal muscle is multinucleated (several nuclei per cell ). Transverse tubule ( T tubule ): well developed in skeletal and cardiac muscles to transport calcium. Absent in smooth muscle. Intercalated disk: specialized intercellular junction that only occurs in cardiac muscle. Control: skeletal muscle is always under voluntary control‚ with some exceptions ( the tongue and pili arrector muscles in the dermis). smooth and cardiac muscles are under involuntary control. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Innervation: motor unit . a) a motor nerve and a myofibril from a neuromuscular junction where gap (called synapse) occurs between the two structures. at the end of motor nerve‚ neurotransmitter (i.e. acetylcholine) is stored in synaptic vesicles which will release the neurotransmitter using exocytosis upon the stimulation of a nerve impulse. Across the synapse the surface the of myofibril contains receptors that can bind with the neurotransmitter.
    [Show full text]
  • Massive Alterations of Sarcoplasmic Reticulum Free Calcium in Skeletal Muscle Fibers Lacking Calsequestrin Revealed by a Genetic
    Massive alterations of sarcoplasmic reticulum free calcium in skeletal muscle fibers lacking calsequestrin revealed by a genetically encoded probe M. Canatoa,1, M. Scorzetoa,1, M. Giacomellob, F. Protasic,d, C. Reggiania,d, and G. J. M. Stienene,2 Departments of aHuman Anatomy and Physiology and bExperimental Veterinary Sciences, University of Padua, 35121 Padua, Italy; cCeSI, Department of Basic and Applied Medical Sciences, University G. d’Annunzio, I-66013 Chieti, Italy; dIIM-Interuniversity Institute of Myology and eLaboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, 1081BT, Amsterdam, The Netherlands Edited* by Clara Franzini-Armstrong, University of Pennsylvania Medical Center, Philadelphia, PA, and approved November 12, 2010 (received for review June 30, 2010) The cytosolic free Ca2+ transients elicited by muscle fiber excitation tion essential to maintain a low metabolic rate in quiescent ex- are well characterized, but little is known about the free [Ca2+] citable cells. In addition, CSQ has been shown to modulate RyR- dynamics within the sarcoplasmic reticulum (SR). A targetable mediated Ca2+ release from the SR (6). To understand the pivotal ratiometric FRET-based calcium indicator (D1ER Cameleon) allowed role of CSQ in SR function, it is critical to determine free SR us to investigate SR Ca2+ dynamics and analyze the impact of cal- Ca2+ concentration, and this has been made possible by the ad- sequestrin (CSQ) on SR [Ca2+] in enzymatically dissociated flexor vent of a targetable ratiometric FRET-based indicator, such as digitorum brevis muscle fibers from WT and CSQ-KO mice lacking D1ER Cameleon (7). Seminal studies using this technique have isoform 1 (CSQ-KO) or both isoforms [CSQ-double KO (DKO)].
    [Show full text]
  • Single-Cell Analysis Uncovers Fibroblast Heterogeneity
    ARTICLE https://doi.org/10.1038/s41467-020-17740-1 OPEN Single-cell analysis uncovers fibroblast heterogeneity and criteria for fibroblast and mural cell identification and discrimination ✉ Lars Muhl 1,2 , Guillem Genové 1,2, Stefanos Leptidis 1,2, Jianping Liu 1,2, Liqun He3,4, Giuseppe Mocci1,2, Ying Sun4, Sonja Gustafsson1,2, Byambajav Buyandelger1,2, Indira V. Chivukula1,2, Åsa Segerstolpe1,2,5, Elisabeth Raschperger1,2, Emil M. Hansson1,2, Johan L. M. Björkegren 1,2,6, Xiao-Rong Peng7, ✉ Michael Vanlandewijck1,2,4, Urban Lendahl1,8 & Christer Betsholtz 1,2,4 1234567890():,; Many important cell types in adult vertebrates have a mesenchymal origin, including fibro- blasts and vascular mural cells. Although their biological importance is undisputed, the level of mesenchymal cell heterogeneity within and between organs, while appreciated, has not been analyzed in detail. Here, we compare single-cell transcriptional profiles of fibroblasts and vascular mural cells across four murine muscular organs: heart, skeletal muscle, intestine and bladder. We reveal gene expression signatures that demarcate fibroblasts from mural cells and provide molecular signatures for cell subtype identification. We observe striking inter- and intra-organ heterogeneity amongst the fibroblasts, primarily reflecting differences in the expression of extracellular matrix components. Fibroblast subtypes localize to discrete anatomical positions offering novel predictions about physiological function(s) and regulatory signaling circuits. Our data shed new light on the diversity of poorly defined classes of cells and provide a foundation for improved understanding of their roles in physiological and pathological processes. 1 Karolinska Institutet/AstraZeneca Integrated Cardio Metabolic Centre, Blickagången 6, SE-14157 Huddinge, Sweden.
    [Show full text]
  • Localization of Ca2l Release Channels with Ryanodine in Junctional
    Proc. NatI. Acad. Sci. USA Vol. 82, pp. 7256-7259, November 1985 Biochemistry Localization of Ca2l release channels with ryanodine in junctional terminal cisternae of sarcoplasmic reticulum of fast skeletal muscle (muscle contraction/excitation-contraction coupling/ruthenium red/longitudinal cisternae/gated channels) SIDNEY FLEISCHER, EUNICE M. OGUNBUNMI, MARK C. DIXON, AND EDUARD A. M. FLEER Department of Molecular Biology, Vanderbilt University, Nashville, TN 37235 Communicated by William J. Darby, July 8, 198S ABSTRACT The mechanism of Ca2' release from tional terminal cisternae consist of two types of membranes, sarcoplasmic reticulum, which triggers contraction in skeletal the Ca2l pump membrane (80-85%) and the junctional face muscle, remains the key unresolved problem in excita- membrane (15-20%) (16). A unique characteristic of junc- tion-contraction coupling. Recently, we have described the tional terminal cisternae is that they have a poor Ca2+ loading isolation of purified fractions referable to terminal and longi- rate, which can be enhanced 5-fold or more by addition of tudinal cisternae of sarcoplasmic reticulum. Junctional termi- ruthenium red (RR) (ref. 17; unpublished data). This study nal cisternae are distinct in that they have a low net energized describes the drug action of ryanodine on the junctional Ca2+ loading, which can be enhanced 5-fold or more by terminal cisternae in blocking the action of RR. It provides addition of ruthenium red. The loading rate, normalized for evidence that the action of ryanodine is on the Ca2' release calcium pump protein content, then approaches that of longi- mechanism and supports the view that Ca2' release is tudinal cisternae of sarcoplasmic reticulum.
    [Show full text]
  • Nomina Histologica Veterinaria, First Edition
    NOMINA HISTOLOGICA VETERINARIA Submitted by the International Committee on Veterinary Histological Nomenclature (ICVHN) to the World Association of Veterinary Anatomists Published on the website of the World Association of Veterinary Anatomists www.wava-amav.org 2017 CONTENTS Introduction i Principles of term construction in N.H.V. iii Cytologia – Cytology 1 Textus epithelialis – Epithelial tissue 10 Textus connectivus – Connective tissue 13 Sanguis et Lympha – Blood and Lymph 17 Textus muscularis – Muscle tissue 19 Textus nervosus – Nerve tissue 20 Splanchnologia – Viscera 23 Systema digestorium – Digestive system 24 Systema respiratorium – Respiratory system 32 Systema urinarium – Urinary system 35 Organa genitalia masculina – Male genital system 38 Organa genitalia feminina – Female genital system 42 Systema endocrinum – Endocrine system 45 Systema cardiovasculare et lymphaticum [Angiologia] – Cardiovascular and lymphatic system 47 Systema nervosum – Nervous system 52 Receptores sensorii et Organa sensuum – Sensory receptors and Sense organs 58 Integumentum – Integument 64 INTRODUCTION The preparations leading to the publication of the present first edition of the Nomina Histologica Veterinaria has a long history spanning more than 50 years. Under the auspices of the World Association of Veterinary Anatomists (W.A.V.A.), the International Committee on Veterinary Anatomical Nomenclature (I.C.V.A.N.) appointed in Giessen, 1965, a Subcommittee on Histology and Embryology which started a working relation with the Subcommittee on Histology of the former International Anatomical Nomenclature Committee. In Mexico City, 1971, this Subcommittee presented a document entitled Nomina Histologica Veterinaria: A Working Draft as a basis for the continued work of the newly-appointed Subcommittee on Histological Nomenclature. This resulted in the editing of the Nomina Histologica Veterinaria: A Working Draft II (Toulouse, 1974), followed by preparations for publication of a Nomina Histologica Veterinaria.
    [Show full text]
  • MODULE 1: HISTOLOGY I an Introduction to Histology; Begin Epithelial Tissue and Connective Tissue
    MODULE 1: HISTOLOGY I An Introduction to Histology; Begin Epithelial Tissue and Connective Tissue Histology is the study of the microscopic anatomy of the cells and extracellular matrix that make up the tissues of the body. Using the physical appearance of cells and the matrix that surrounds them, the 10-100 trillion cells of the human body can be grouped into just four major tissue types: epithelial, connective, muscle and nervous tissues. In the Histology Modules of this course, you will learn to identify each of these tissue types as well as their subclasses and important structures. Chemical fixatives are used to preserve tissues when they are harvested. These fixatives are important to preserve the tissue from degradation. These chemicals also destroy the biological function of the cells, so all of the cells in any micrograph images that you see are dead. Biological tissue has little inherent color. In fact, in reality, the tissues that you study would look transparent or have various shades of gray for the most part. However, scientists use staining techniques to help highlight particular features of a tissue. As a student of histology, you should avoid the temptation to memorize tissues based on color. Since it is possible to stain the same tissue with a variety of different colors, you could be easily fooled if you trained yourself to recognize color as the major feature of tissues that you study. The wiser approach would be to carefully learn the shapes and physical characteristics other than color when studying histology. Students who memorize color as the main characteristic to trigger their memory will be disappointed when the exam does not maintain color schemes.
    [Show full text]
  • Ultra-High Resolution Scanning Electron Microscopic Studies on the Sarcoplasmic Reticulum and Mitochondria in Various Muscles: a Review
    Scanning Microscopy Volume 7 Number 1 Article 16 12-29-1992 Ultra-High Resolution Scanning Electron Microscopic Studies on the Sarcoplasmic Reticulum and Mitochondria in Various Muscles: A Review Takuro Ogata Kochi Medical School Yuichi Yamasaki Kochi Medical School Follow this and additional works at: https://digitalcommons.usu.edu/microscopy Part of the Biology Commons Recommended Citation Ogata, Takuro and Yamasaki, Yuichi (1992) "Ultra-High Resolution Scanning Electron Microscopic Studies on the Sarcoplasmic Reticulum and Mitochondria in Various Muscles: A Review," Scanning Microscopy: Vol. 7 : No. 1 , Article 16. Available at: https://digitalcommons.usu.edu/microscopy/vol7/iss1/16 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Scanning Microscopy by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Scanning Microscopy, Vol. 7, No. 1, 1993 (Pages 145-156) 0891-7035/93$5 .00+ .00 Scanning Microscopy International, Chicago (AMF O'Hare), IL 60666 USA ULTRA-HIGH RESOLUTION SCANNING ELECTRON MICROSCOPIC STUDIES ON THE SARCOPLASMIC RETICULUM AND MITOCHONDRIA IN VARIOUS MUSCLES: A REVIEW Takuro Ogata* and Yuichi Yamasaki Department of Surgery, Kochi Medical School Nankoku, Kochi, 783 Japan (Received for publication March 23, 1992, and in revised form December 29, 1992) Abstract Introduction The three-dimensional structure of the sarco­ The three-dimensional models of the membrane plasm.ic
    [Show full text]
  • MUSCLE TISSUE Larry Johnson Texas A&M University
    MUSCLE TISSUE Larry Johnson Texas A&M University Objectives • Histologically identify and functionally characterize each of the 3 types of muscle tissues. • Describe the organization of the sarcomere as seen in light and electron microscopy. • Identify the endomysium, perimysium, and epimysium CT sleeves in muscle. • Relate the functional differences of the three muscle cell types. From: Douglas P. Dohrman and TAMHSC Faculty 2012 Structure and Function of Human Organ Systems, Histology Laboratory Manual MUSCLE FUNCTION: • GENERATION OF CONTRACTILE FORCE DISTINGUISHING FEATURES: • HIGH CONCENTRATION OF CONTRACTILE PROTEINS ACTIN AND MYOSIN ARRANGED EITHER DIFFUSELY IN THE CYTOPLASM (SMOOTH MUSCLE) OR IN REGULAR REPEATING UNITS CALLED SARCOMERES (STRIATED MUSCLES, e.g., CARDIAC AND SKELETAL MUSCLES) MUSCLE • DISTRIBUTION: SKELETAL – STRIATED MUSCLES MOSTLY ASSOCIATED WITH THE SKELETON MUSCLE • DISTRIBUTION: SKELETAL – STRIATED MUSCLES MOSTLY ASSOCIATED WITH THE SKELETON CARDIAC – STRIATED MUSCLES ASSOCIATEWD WITH THE HEART MUSCLE • DISTRIBUTION: SKELETAL – STRIATED MUSCLES MOSTLY ASSOCIATED WITH THE SKELETON CARDIAC – STRIATED MUSCLES ASSOCIATEWD WITH THE HEART SMOOTH – FUSIFORM CELLS ASSOCIATED WITH THE VISCERA, RESPIRATORY TRACT, BLOOD VESSELS, UTERUS, ETC. MUSCLE • HISTOLOGICAL INDENTIFICATION: SKELETAL MUSCLE – VERY LONG CYLINDRICAL STRIATED MUSCLE CELLS WITH MULTIPLE PERIPHERAL NUCLEI MUSCLE • HISTOLOGICAL INDENTIFICATION: SKELETAL MUSCLE – VERY LONG CYLINDRICAL STRIATED MUSCLE CELLS WITH MULTIPLE PERIPHERAL NUCLEI CARDIAC MUSCLE –
    [Show full text]
  • Spinal Reflexes
    Spinal Reflexes Lu Chen, Ph.D. MCB, UC Berkeley 1 Simple reflexes such as stretch reflex require coordinated contraction and relaxation of different muscle groups Categories of Muscle Based on Direction of Motion Flexors Æ reduce the angle of joints Extensors Æ increase the angle of joints Categories of Muscle Based on Movement Agonist Æmuscle that serves to move the joint in the same direction as the studied muscle Antagonist Æ muscle that moves the joint in the opposite direction 2 1 Muscle Spindles •Small encapsulated sensory receptors that have a Intrafusal muscle spindle-like shape and are located within the fibers fleshy part of the muscle •In parallel with the muscle fibers capsule •Does not contribute to the overall contractile Sensory force endings •Mechanoreceptors are activated by stretch of the central region Afferent axons •Due to stretch of the whole muscle Efferent axons (including intrafusal f.) •Due to contraction of the polar regions of Gamma motor the intrafusal fibers endings 3 Muscle Spindles Organization 2 kinds of intrafusal muscle fibers •Nuclear bag fibers (2-3) •Dynamic •Static •Nuclear chain fibers (~5) •Static 2 types of sensory fibers •Ia (primary) - central region of all intrafusal fibers •II (secondary) - adjacent to the central region of static nuclear bag fibers and nuclear chain fibers Intrafusal fibers stretched Sensory ending stretched, (loading the spindle) increase firing Muscle fibers lengthens Sensory ending stretched, (stretched) increase firing Spindle unloaded, Muscle fiber shortens decrease firing 4 2 Muscle Spindles Organization Gamma motor neurons innervate the intrafusal muscle fibers. Activation of Shortening of the polar regions gamma neurons of the intrafusal fibers Stretches the noncontractile Increase firing of the center regions sensory endings Therefore, the gamma motor neurons provide a mechanism for adjusting the sensitivity of the muscle spindles.
    [Show full text]