Ch. 10 Muscle and Tissue Organization Flashcards Preview

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Flashcards in Ch. 10 Muscle and Tissue Organization Deck (24)

Properties of Muscular Tissue

electrical excitability, contractility, extensibility, elasticity


Structure of Skeletal Muscle

- skeletal muscle bundle consists of a body (belly) connected by tendons to the skeleton
- tendons are nearly avascular structure, composed of a parallel arrangement of collagen fibers at the ends of the muscle
- tendon is an extension of three connective tissue layers that surrounds the different organizational levels of a skeletal muscle


Skeletal Muscle Connective Tissue Coverings

- muscle bundles are surrounded by epimysium, dense irregular tissue
- muscle fascicles (bundles) are surrounded by perimysium, transmits blood vessels
- muscle fibers are surrounded by endomysium, reticular fibers, bind muscle fibers together


Deep Fascia

- an expansive sheet of dense irregular connective tissue
- separates individual muscles
- binds together muscles with similar functions
- forms sheaths to help distribute nerves, blood vessels, and lymphatic vessels
- fill spaces between muscles


Microscopic Anatomy of a Skeletal Muscle Fiber

- muscle fibers while very small in diameter, run the length of the muscle bundle and are usually measured in inches
- muscle fibers are multinucleate, from before birth, and last a lifetime
- muscle growth after being born is due to hypertrophy (increased cell size) rather than hyperplasia (increased cell numbers)


Filaments and the Sarcomere

- myofibrils are made of thick filaments (myosin) and thin filaments (actin) which in turn are made of protein
- these filaments are arranged in special compartments called sarcomeres (the functional unit of contraction)
- the pattern of overlap of thick and thin filaments consists of zones and bands which cause the striated appearance of skeletal muscle


Muscle Proteins

- myofibrils are built from 3 kinds of proteins
Contractile Proteins: generate force during contraction by sliding past each other rather than literally shortening ex. actin and myosin
Regulatory Proteins: help switch the contraction process on and off ex. troponin and tropmyosin (covers myosin bind receptors)
Structural Proteins: keep thick and thin filaments in proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix ex. M line (hold myosin in centre) and Z-disc (actin attaches)



- major component of thick filaments
- functions as a motor protein that achieves movement by converting the chemical energy into mechanical energy



- major component of thin filaments
- also contain the regulatory proteins, tropomyosin (covers binding site for myosin) and troponin (pull tropomyosin in or out)


Microscopic Structure of Skeletal Muscle Fiber

muscle fiber cell (myofibrils)
myofilaments (thick and thin- striations)
- dark A-Band, thick and thin filaments overlapping, myosin and actin, contract and relaxation
- light I-Band, contain only thin filaments, only actin, causes only muscle movement


Nerve and Blood Supply of Skeletal

- most receive one nerve that supplies them with motor and sensory functions, other muscles receive multiple nerves
- nerves typically enter a muscle with blood vessels as a unit called a neuromuscular bundle
- these nerves carry both sensory and motor info


Somatic Motor Neurons

- individual cells (neurons) that innervate skeletal muscle fibers are called


Neuromuscular Junction (NMJ)

- is a point of near-contact between a somatic motor neuron and a skeletal muscle fiber
- each muscle fiber has one NMJ, yet the axon of a somatic motor neuron branches out and form NMJs with many different muscle fibers


Motor Unit

- one somatic motor neuron plus all the skeletal muscle fibers it stimulates is called a motor unit


Sliding Filament Mechanism Theory

- During contraction of a muscle fiber:
1. distance between Z-discs shortens (holds actin)
2. distance between A- remains the same (overlap of thick and thin, myosin doesn't move)
3. distance between I- band shortens (only actin)
4. distance between H-zone shortens (only myosin)
- distance between 2 Z-discs is sacromere


Muscle Attachment Sites: Origin and Insertion

- skeletal muscles cause movements by exerting force on tendons, which pulls on bones or other structures
- articulating bones usually do not move equally in response to contraction
- attachment of a tendon to the stationary bone is called the origin
- attachment of the muscle's other tendon to the movable bone is called the insertion
- the action of a muscle are the main movements that occur during contraction (flexion or extension)


Coordination among muscles

- movements usually result from several skeletal muscles acting as a group, most skeletal muscles are arranged in opposing pairs at joints (ex. flexors vs extensors)
Agonist: (prime mover) produces specific movement when it contracts (biceps brachii)
Antagonist: is a muscle whose action opposes that of an agonist (triceps brachii would be antagonist)
Synergist: is a muscle that assist the agonist or prime mover


Muscle Fascicle Arragement

- all muscle fibers are parallel to one another within a single fascicle
- fascicles, however, form patterns with respect to the tendons
- parallel (sternohyoid), fusiform, circular, triangular (pectoralias), pennate (uni, bi, multi)


Cardiac Muscle Cells

- striated, involuntary, branched, and uninucleate
- intercellular connections points (intercalated discs) contain structural and electrical connections, called desmosomes and gap junctions
- cardiac tissue is capable of autorhythmicity, an ability to spontaneously generate impulses that trigger contraction


Smooth Muscle Tissue

- composed of short muscle fibers that have a fusiform shape and single centrally located nucleus
- thick and thin filaments are not precisely aligned so no visible striations or sarcomeres are present
- Z discs are absent- thin filaments are attached to dense bodies by elements of the cytoskeleton
- sarcoplasmic reticulum is sparse
- transverse tubules are absent
- contraction is slow, resistant to fatigue, and usually sustained for an extended period of time
- takes longer than skeletal muscle to contract and relax
- contraction is under involuntary control


Functions of Muscular Tissue

Body movements, body stability, storing anf moving substances, heat production



plasma membrane of a skeletal muscle fiber


T Tubles

extensions of the sacrolemma that tunnel throughout the muscle fiber, are open to the outside, and filled with ISF



cytoplasm of a skeletal fiber