chap 9 ppt 1 gm anat - blair school...

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MUSCLES A tale of movement & stability

What do you already know?

What we’re going to learn…

Muscle Contraction Process: Molecular Mechanism 3-D (4:24)

Some Muscle Terminology

Muscle Cell

Myo- / Mys-

= Muscle Fiber

= Muscle

Sarco- = Flesh

More Muscle Terminology

Muscle Cell Plasma Membrane

Muscle Cell Cytoplasm

= Sarcolemma

= Sarcoplasm

Three types of muscle tissue

Striation

Voluntary

Locations

Special Details

Drawing

Smooth Skeletal Cardiac

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Skeletal � 640 in the human body � Striated � Voluntary � Attach to and cover bony skeleton � Contract rapidly, tire easily � Responsible for body movement � Extremely adaptable � Contractions are variable, not all or none

�  Can exert forces from a fraction of an ounce to > 70 lbs

Smooth �  Involuntary � NO striations � Locations include

� Digestive tract � Respiratory passages � Walls of hollow visceral organs

� stomach, urinary bladder, etc.

� Blood vessels

Cardiac � Striated � Involuntary � Only in the heart � Contracts at a steady rate set by

heart’s pacemaker � Neural control allows the heart to

change to body’s needs


Skeletal Smooth Cardiac

� Skeletal � Striated � Voluntary � Movement

� Visceral � No striated � Involuntary � Organs

� Cardiac � Striated � Involuntary � Heart

Muscle Tissue: Special Functional Properties

Excitability •  Ability to receive and respond to a stimulus Contractility •  Ability to shorten when stimulated Extensibility •  Ability to be stretched/extended Elasticity •  Ability to recoil and resume resting length

Muscle Functions

Ø  Movement Ø  Maintain Body Posture & Position

Ø  Stabilize Joints

Ø  Generate Heat

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Skeletal Smooth Cardiac

� Skeletal � Striated � Voluntary � Movement

� Visceral � Not striated � Involuntary � Organs

� Cardiac � Striated � Involuntary � Heart

Skeletal Muscle Gross Anatomy •  Composition •  Nerve & Blood Supply •  Connective Tissue Sheaths •  Muscle Attachments

Skeletal Muscle

GROSS ANATOMY •  Each skeletal muscle is a discrete organ •  Composed of

•  Muscle tissue •  Blood vessels •  Nerve Fibers •  Connective Tissue

Nerve & Blood Supply Each muscle has

•  One nerve •  Each muscle is supplied with a nerve ending

that controls contraction

•  One artery •  Each contraction requires continuous delivery

of oxygen and nutrients via arteries

•  One or more veins •  Waste removal occurs via veins (lots of

metabolic waste!)

Skeletal Muscle Gross Anatomy

Connective Tissue Sheaths

•  Endomysium “Within the muscle”

•  Areolar & reticular CT •  Surrounds individual muscle fibers



•  Perimysium “Around the muscle”

•  Fibrous CT •  Surrounds fascicles


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•  Epimysium “Upon the muscle” •  Dense irregular CT •  Surrounds whole muscle


Connective Tissue Sheaths They are??

•  Endomysium •  Perimysium

•  Epimysium

Ø  All are continuous with each other and the tendons that join muscles to bones.


Muscle Attachments Ø  Skeletal muscles span joints and are

attached to bone in at least two places


1. Insertion •  Attachment to

moveable bone

2. Origin

•  Attachment to immovable/less moveable bone


Muscle Attachments, cont. Ø  Both insertion and origin can attach

•  Directly

•  Indirectly


•  Direct Attachments

•  Epimysium of muscle fused to periosteum of bone

•  Indirect Attachments

•  Connective tissue wrappings extend beyond the muscle as a ropelike tendon or sheet like aponeurosis


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Skeletal Muscle Gross & Microscopic Anatomy

Myofibrils Muscle

Fibers (cell) Muscle Organ

Fascicle

Endomysium Perimysium Epimysium

Sarcomere 1 unit of muscle

Myofilaments •  Actin •  Myosin

See also: Table 9.1, page 282

Muscle Fibers (cell)

Muscle Organ

Fascicle


Skeletal Muscle Gross Anatomy p. 283

Skeletal Muscle

Microscopic Anatomy

Muscle Fiber Muscle cell •  Long, cylindrical cells

•  Diameter = 10 -100 micrometers (HUGE) •  Length = up to 30 cm long (phenomenal)

Muscle Fiber Cell Structure (like other cells) Ø  Sarcolemma

•  Plasma Membrane

Ø  Sarcoplasm •  Cytoplasm

Ø  Nuclei •  Multiple nuclei just beneath sarcolemma

Ø  Mitochondria •  LOTS of them… WHY???

•  Mitochondria make what??? •  ATP! ATP is what??? •  Cellular Energy!

Skeletal Muscle Micro Anatomy

Muscle Fiber Cell Structure, cont. Ø  Sarcoplasmic reticulum

•  Endoplasmic reticulum

Ø  Other organelles Ø  all the usual eukaryotic organelles


Unique to Muscle Fibers (Muscle cells) •  Glycosomes •  Myoglobin •  Myofibrils •  Myofilaments •  T-Tubules


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Glycosomes •  In the sarcoplasm •  Glucose storage unit •  Cellular respiration breaks down glucose

to produce ATP •  Food Energy à Chemical Energy

•  Muscles •  Chemical Energy à Mechanical Energy


Glyco = Some =

Glucose Body Myoglobin

•  In the sarcoplasm •  Oxygen-binding protein •  Stores oxygen in muscles •  Oxygen is needed for aerobic respiration

•  Aerobic respiration produces 32-36 ATP •  No oxygen = anaerobic = fermentation =

4 ATP (also lactic acid build-up and sore muscles)

Skeletal Muscle Micro Anatomy Myo=

Globin = Muscle Containing Protein think hemoglobin

Glucose… Oxygen… ATP…

Need a review? Unique to Muscle Fibers (Muscle cells) •  Glycosomes •  Myoglobin •  Myofibrils •  Myofilaments •  T-Tubules



Myofibrils •  Densely packed, rod-like contractile elements

•  Densely packed •  80% of cellular volume in muscles •  Mitochondria and other organelles are squeezed in

between them

p. 285 Skeletal Muscle Micro Anatomy


•  Rod-like •  1-2 micrometers in width

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•  Contractile •  Contain myofilaments that cause/allow

contraction


Myofibrils •  Arrangement of myofibrils in a muscle fiber

gives a perfectly aligned, visible, repeating series of dark A bands and light I bands


But to talk about myofilaments, first we have to talk about…

Skeletal Muscle Micro Anatomy Skeletal Muscle Micro Anatomy

Sarcomeres •  The smallest contractile unit of a muscle •  The area of a myofibril between two

successive Z discs

p. 285


Sarcomeres •  Composed of myofilaments

•  Myofilaments are contractile proteins •  Thick (myosin) •  Thin (actin)


Myofilament Banding •  Thick (Myosin) Filaments

•  Extend the entire length of the dark A Band

•  Thin (Actin) Filaments •  Extend across the light I Band and partway into

the dark A Band

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•  Z Disc •  Coin-shaped sheet of connectin proteins •  Anchors thin actin filaments •  Connects myofibrils to each other


Myofilament Banding •  Why is the I band light? •  What is contained in it? •  Why is the A band dark? •  What is contained in it?


Myofilament banding gives skeletal and cardiac muscle a striped… striated… appearance

Myofilaments

In your own words, based on these illustrations: •  Describe the structure of the thin actin filament (blue). •  Describe the structure of the thick myosin filament (red).

p. 286

Now make your own illustrations: •  One of the thin actin filament •  Two of the thick myosin filament: individual and group •  One of the thin and thick filaments together.

Myofilaments Skeletal Muscle Micro Anatomy

Thick Filaments Composed of the protein myosin •  Myosin = rod-like tail + globular heads •  Tail: Two interwoven polypeptide chains •  Heads: two smaller polypeptide chains

•  Heads link thick and thin filaments together via cross bridges

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Thick Filaments Composed of the protein myosin •  Myosin = rod-like tail + globular heads •  Tail: Two interwoven polypeptide chains •  Heads: two smaller polypeptide chains •  NOTE: Heads have Actin binding sites and

ATPase Enzymes (split ATP)


Thin Filaments Composed mostly of the protein actin •  Active sites: for myosin heads to attach •  Tropomyosin: two strands spiral actin units •  Troponin: unit of three polypeptides Note: There are additional filaments being discovered!


Add to your notes: Troponin: unit of three polypeptides 1.  TnI – binds to actin 2.  TnT – binds to Tropomyosin 3.  TnC – binds to Calcium


But to talk about T-Tubules, first we have to talk about…


Sarcoplasmic Reticulum •  Elaborate, smooth endoplasmic reticulum that

runs longitudinally and surrounds each myofibril •  Regulates intracellular calcium levels

Skeletal Muscle Micro Anatomy p. 288

Sarcoplasmic Reticulum •  SR penetrates the cell at A band / I band junctions •  This forms cross channels called terminal cisternae

•  terminal = end cisternae = sac


•  Terminal cisternae always occur in pairs

•  T-Tubules run between the paired terminal cisternae

•  Forms a triad

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WHY??? •  Muscles move by electrical impulses that come from nerves •  Those impulses travel along the sarcolemma •  T-Tubules pass those impulses to every sarcomere in every

myofibril in every muscle fiber in every muscle organ

Skeletal Muscle

Myofibrils Muscle

Fibers (cell) Muscle Organ

Fascicle


Sarcomere 1 unit of muscle

Myofilaments •  Actin •  Myosin

Now that we know all the parts… How do muscles actually move??

It’s an old-fashioned LOVE story

chap 9 ppt 1 gm anat - blair school...

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