chap 9 ppt 1 web - blair school district · special functional properties ... cardiac muscles a...

1/3/16

1

MUSCLES A tale of movement & stability

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

Skeletal Smooth Cardiac

Skeletal � 640 in the human body � Striated � Voluntary � Attached to and cover bony skeleton � Contact rapidly, tire easily � Responsible for body motility � Extremely adaptable � 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) � Blood vessels

1/3/16

2

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 � Striated � Voluntary

� Visceral � Nonstriated � Involuntary

� Cardiac � Striated � Involuntary

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



� Skeletal � Striated � Voluntary

� Visceral � Nonstriated � Involuntary

� Cardiac � Striated � Involuntary

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

Skeletal Muscle Micro Anatomy

1/3/16

3

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 fiber (cell) 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

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 fasicles



•  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.


1/3/16

4

Muscle Attachments Ø  Skeletal muscles span joints and are

attached to bone in at least two places


Insertion

•  Attachment to moveable bone

Origin

•  Attachment to immovable/less moveable bone


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

•  Directly

•  Epimysium of muscle fused to periosteum of bone

•  Indirectly

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

Skeletal Muscle Gross Anatomy Skeletal Muscle Gross Anatomy

Skeletal Muscle Gross & Microscopic Anatomy

Myofibrils Muscle

Fibers (cell) Muscle Organ

Fascile

Endomysium Perimysium Epimysium

Sarcomere 1 unit of muscle

Myofilaments •  Actin •  Myosin

Muscle Fibers (cell)

Muscle Organ

Fascile


Skeletal Muscle Gross Anatomy p. 283

1/3/16

5

Skeletal Muscle

Microscopic Anatomy

Muscle cell = muscle fiber •  Long, cylindrical cells

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

Muscle Fiber Cell Structure 1.  Plasma Membrane = Sarcolemma 2.  Cytoplasm = Sarcoplasm 3.  Nuclei… multiple nuclei just beneath

sarcolemma 4.  Mitochondria… LOTS of them

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


Muscle Fiber Cell Structure, cont. 5.  Endoplasmic reticulum =

Sarcoplasmic reticulum 6.  And all the usual eukaryotic

organelles


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


Glycosomes •  In the sarcoplasm •  Storage unit for glucose •  Cellular respiration breaks down glucose

to produce ATP •  Food Energy à Chemical Energy

•  Muscles •  Chemical Energy à Mechanical Energy


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)


1/3/16

6

Glucose… Oxygen… ATP…

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



Myofibrils •  Densely packed, rodlike 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


•  Rodlike •  1-2 micrometers in width



•  Contractile •  Contains the 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

1/3/16

7


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 made up of contractile proteins

•  Two types of myofilaments •  Thick •  Thin


Myofilament Banding •  Thick Filaments

•  Extend the entire length of the dark A Band •  Myosin

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

the dark A Band •  Actin


Myofilament Banding •  Z Disc

•  Coin-shaped sheet of connectin proteins •  Anchors the 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?

1/3/16

8


Myofilament banding is what gives skeletal and cardiac muscles 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


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

1/3/16

9


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


Sacroplasmic Reticulum •  Elaborate, smooth endoplasmic reticulum that

runs longitudinally and surrounds each myofibril •  Regulates intracellular calcium levels

Skeletal Muscle Micro Anatomy p. 288

Sacroplasmic Reticulum •  Some of the SR penetrates the cell interior at each

A band / I band junction •  This forms cross channels called terminal cisternae


terminal = end cisternae = sac

•  Terminal cisternae always occur in pairs

T-Tubules •  Sarcolemma is what? •  At each A band / I band junction the

sarcolemma penetrates the cell interior •  This forms a transverse tube…. T Tubule


•  T-Tubules run between the paired terminal cisternae

•  Forms a triad


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

Fascile


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

1/3/16

10

Movement

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

It’s an old-fashioned LOVE story

Old-fashioned

Actual dating…. And wooing…

And meeting the parents… Including fathers who may be armed.

Our Love Story

Bobby Myosin Susie Actin

And they LIKE each other

But Susie has an overprotective dad. The kind that will meet a boy at the door with a shotgun.

Mr. Tropomyosin But Mrs. Troponin is Susie’s very sweet mother. And, she knows Bobby is a good guy. She sees him wooing Susie and bringing her flowers.

Our Love Story Those flowers are Calcium…. And they soften up Mrs. Troponin And she takes Mr. Tropomyosin’s arm and leads him into the house

Our Love Story

And Susie and Bobby can go on their date

Our Muscle Story

Myosin Actin

And they are attracted to each other

But Actin’s binding sites are blocked by Tropomyosin Remember Troponin? Unit of three polypeptides

1.  TnI – binds to actin

2.  TnT – binds to tropomyosin

3.  TnC – binds to Calcium

Our Love Story

1/3/16

11

Calcium binds to TnC which changes the shape of the troponin protein

Since troponin is also bound to tropomyosin, the shape change of troponin moves the tropomyosin away from the Actin binding sites.

Our Love Story

And the myosin head can attach to the actin (forming a cross bridge)

Our Love Story

This uses ATP which changes the shape of myosin again, retracting it. And the whole process starts over again.

Our Love Story

This continuing process slides the myosin and actin filaments past each other, causing a muscle contraction

It is called the Sliding Filament Theory of Contraction

Sliding Filament Theory

ß Relaxed

ß Contracted

ß In-Between

chap 9 ppt 1 web - blair school district · special functional properties ... cardiac muscles a...

Documents