The Muscular System - Welcome to Miss Loulousis' Cell Structure ... Gluteus maximus v gluteus minimus ... covers muscle fiber Maintains chemical environment of contracting cells

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    Human Physiology Chapter 6 DOERFLER

  • Overview

    Movement would be impossible without muscle tissue

    Contractile cell allows muscles to do job Have specialized cell membrane and cytoskeleton that

    permit them to change their shape Can shorten along one or more planes

    Muscle cells are laid out as sheets of muscle tissue that produce coordinated contractions

    Over of bodys mass is composed of muscle tissue Over 90% of muscle tissue is involved in skeletal


  • Overview, cont.

    Contractile cells have HIGH energy needs

    Associated with ample blood supply (lots)

    Blood provides glucose and oxygen while removing metabolic wastes

    Electrolytes transported by blood essential components of muscle cell contractions

    Along with nervous tissue, muscle consumes almost 70% of food energy

  • Body Mass Index

    BMI indirect measure of body density

    Muscle makes up large component of BMI

    People with a lean body have higher amounts of muscle mass compared with body fat composition

    Leanness is known to reduce heart disease and metabolic disorders

  • Muscle Categorization

    Categorized several ways

    1st - Evaluates microscopic appearance

    Nonstriated have random pattern of contractile proteins

    Provide weaker contractions than striated

    Contractile protein cytoskeleton proteins involved in contraction

    Striated striped appearance results from uniform arrangement of cytoskeleton

    Cardiac & skeletal

  • Muscle Categorization, cont. 2nd Control

    Voluntary people have large degree of control Some function involuntary muscles needed for

    breathing, but you can control when needed

    Involuntary contract without conscious control Carry out jobs that must be done automatically

    3rd Location Cardiac - The muscle of the heart


    Skeletal - Muscle attached to bone; produces body movement Voluntary

    Smooth - Found in the linings of blood vessels and tubular organs Involuntary provide the body with weak contractions that can last for

    long periods of time

  • Types of Muscle Tissue

    End 6.1

  • 6.2 Types of Muscle Tissue

    All muscle tissue develops from mesoderm in process called myogenesis

    Begins when stem cells in mesoderm form into myoblasts

    Myoblasts (stem cells) help develop the 3 muscle types

  • Cardiac Muscle


    Involuntary, striated

    Provides strong contractions

    Cells have 2 nuclei

    Communicate at special junctions called intercalated disks

    Intrinsic beat a natural contraction cycle

  • Smooth Muscle

    Found in many organ systems


    Produce weak involuntary contractions

    Peristalsis weak, pulsating contractions that move food and wastes through the digestive system

  • Skeletal Muscle

    Focus of this chapter..

    Provides movement of the bones and joints

    Voluntary, striated

    Powerful contractile capabilities

    Muscle fiber several myoblasts fused together, a muscle tissue cell

    Motor nerve cells contract skeletal muscle fibers

  • Muscle Cell Structure

    Skeletal muscles are long, cylindrical cells covered by excitable membrane filled with specialized cytoskeleton Respond to signals from others cells + environment

    Sarcolemma = membrane (covering) of muscle cells

    Cytoskeleton composed of band of proteins called myofilaments Thick composed of protein called myosin

    Thin 3 proteins actin, tropomyosis, and troponin

    Titin - elastic

  • Muscle Cell Structure, cont.

    Sarcomere contractile unit of muscle cell Many thousands run length of muscle cell

    Chains of sarcomeres form myofibrils Each muscle fiber is made of many bundled myofibrils

    Thick and thin myofilaments arrange to form overlapping pattern Overlapping is what carries out the muscle cells contraction,

    and what gives it a striated pattern

    Z line marks the boundaries between each sarcomere Movement of Z line changes length of muscle

    Sarcoplasmic reticulum surrounds each sarcomere System of tubes that stores and transports calcium

    needed for muscle contraction,d.aWM&psig=AFQjCNH28uL5rRwYtUD50kyYyfMQL78-fg&ust=1383846533746442


  • Muscle Cell Structure

  • Its important to remember the heirarchy muscles

    Composed of

    Muscle fibers


    Composed of

    Light and Thin Dark & thicker



    Composed of



    Individual types Myosin Actin


    Fasicles Muscles

    Myofilaments Myosin

    Myofibrils Muscle fibers



  • Muscle Cell Function

    Contraction is achieved by simultaneous shortenings of all sarcomeres in a cell

    Process of contraction

    *Each on individual slide

    Neural stimulation (1st)

    Muscle cell contraction (2nd)

    Muscle cell relaxation (3rd)

  • Neural Stimulation (1st) Takes place at neuromuscular junction

    Where nerve cells communicate with muscles

    Contraction initiated when end of nerve cell releases neurotransmitter Chemicals used for cell-to-cell communication

    Acetylcholine neurotransmitter that communicates with muscle cells Binds to acetylcholine receptors, located on sarcolemma

    Sodium-potassium pump controls the ionic distribution of Na and K inside and outside of cell In resting cell, Na+ is higher outside cell, K+ higher

    inside Pumps maintains this unequal ion concentrations

    When stimulated, it loses its ability to maintain the imbalance Imbalance opens ions channels causing free flow of ions,

    initiating the muscle contraction phase.



  • Muscle Cell Contraction (2nd)

    Begins when calcium released by sarcoplasmic reticulum binds to troponin on thin myofibrils

    Results in temporary rigid tension that keeps filaments in place

    ATP provides energy

    Swivel motion brings the two Z-lines together, shortening sarcomere

    Takes another neural stimulation to continue another cycle

    1 muscle contraction requires several cycles of neural stimulation

  • Sliding Filament Model,d.aWM&psig=AFQjCNH_jeKwCkhfW0bWPq1Yq3TTQ6mqgA&ust=1383918119967094

  • Muscle Cell Relaxation (3rd)

    When no more neural stimulations are exciting the sarcolemma

    Calcium leakage out of the sarcoplasmic reticulum into the sarcomere is common after death Rigor mortis muscle stiffness

    Eventually, this stops

    Creatine phosphate stores energy in cells Collects ATP from cells, can store for long periods of


    Glycogen stored form of glucose Myoglobin stores oxygen for muscle cells

  • 6.3 Musculature

    Muscle morphology shape of muscle

    Determined by arrangement of muscle fibers

    Most muscles attach to two or more bones

    Origin stable, immovable attachment point

    Insertion connects a muscle to the body part it moves

  • Muscle Terminology

    Muscle PATTERNS

    Parallel Sheets of muscle cells that run in the same direction

    Provide contractions for moving light loads over a long distance

    Latissimus dorsi (back)

    Pinnate feather-patterned



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