Download Anatomy of Skeletal Muscle ppt 1 - Liberty Union High School District

Anatomy of skeletal muscle
ppt #1 Unit 4 Muscles
Pgs. 322-323, Chapter 11.1
Muscular System
Chapter 11
Muscle Intro
• Functions of muscles
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•
•
•
Movement: respiration, circulation, defecation
Stability: resists gravity and provides tension to tendons
Communication
Heat Production: muscle provides 85% of body heat
• https://www.youtube.com/watch?v=Ktv-CaOt6UQ
Types of Muscle
●Skeletal – striated & voluntary
●Smooth – involuntary
●Cardiac - heart
The word “striated”
means striped.
Skeletal muscle
appears striped
under a microscope.
Connective Tissues of Muscle
• Skeletal muscles are composed of muscular AND connective tissues.
• A skeletal muscle can be about 100um in diameter BUT up to 30cm in
length!!
Muscle Cell=Muscle Fiber
Muscle fiber is surrounded by connective tissue, Endomysium
(allows for nerves and blood capillaries to to reach each fiber)
Muscle fibers are bundled into Fascicles
(can be seen by naked eye, looks like strands)
Muscles and Muscle Fiber Structure
Muscles are composed of many FIBERS that
are arranged in bundles
called FASCICLES
--Each Fascicle is separated (wrapped) from other fascicles by a connective tissue
sheath, Perimysium
--The entire muscle as a whole is surrounded by another connective tissue layer,
Epimysium
--The Epimysium gradually becomes connective tissue sheaths called Fascia
Fascia thickens and becomes Deep
Fascia
(no fat) between adjacent muscles.
--This becomes even thicker and becomes Superficial fascia between muscles
and skin. Some places like buttocks and abdomen is very adipose.(fat)
EPIMYSIUM = outermost layer, surrounds entire
muscle.
PERIMYSIUM = separates and surrounds fascicles
(bundles of muscle fibers)
ENDOMYSIUM =
surrounds each
individual muscle
fiber(cell)
This model of the muscles
uses straws to represent
fibers.
Green = endomysium
Epimysium
Perimysium
Endomysium
Muscle Layers
Muscle Fiber
Endomysium
Perimysium
Epimysium
Individual muscles are separated by FASCIA,
which also forms tendons
• https://www.youtube.com/watch?v=XoP1diaXVCI
How are muscle cells created?
• In embryonic development, STEM CELLS called Myoblasts fuse to produce
each muscle fiber.
Muscle Cell Organization:
Each muscle fiber, (1 muscle cell) has: many myofibrils (protein bundles)
Each muscle fiber has: many flattened or sausage shaped nuclei pushed
against the plasma membrane
Each muscle fiber (cell) has: plasma membrane= Sarcolemma
Each muscle fiber (cell) has: cytoploasm = Sarcoplasm
Each muscle fiber (cell) has: many Mitochondria
Nucleus
Sarcolemma
Mitochondrion
Sarcoplasm
Myofibril
• The Sarcoplasm also contains lots of Glycogen (stored carb)
which provides energy and the red pigment Myoglobin
which stores Oxygen.
• Other organelles are packed into the spaces between the
myofibrils like:
• Sarcoplastic Reticulum: has channels to release FLOOD of
Ca+ Forms a network around each myofibril .
• T Tubules= Transverse tubules which signal the SR to release
Ca+
Mitochondria: Produces ATP from O2 and glucose (cellular
respiration)
Structure of a Skeletal Muscle Fiber
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Muscle
fiber
Nucleus
A band
I band
Z disc
Openings into
transverse tubules
Mitochondria
Sarcoplasmic
reticulum
T riad:
Terminal cisternae
Transverse tubule
Sarcolemma
Myofibrils
Sarcoplasm
Myofilaments
11-16
Figure 11.2
Structure of Myofibrils
• Myofibrils are the long protein cords that fill most of the muscle
cell
• Each Myofibril is a bundle of parallel protein microfilaments
called:Myofilaments
• 3 kinds of Myofilaments:
1. Thick Filaments: hundreds of strands of proteins called :
MYOSIN looks like golf clubs
THICK FILAMENTS
Single myosin
•Hundreds
•of myosin
2. Thin Filaments: 2 intertwined strands of protein called:
Fibrous ACTIN
Fibrous Actin (F actin) with “globs” of Globular Actin (G actin)
* each G-Actin (globular Actin)has an active site that binds to the
head of myosin
• Thin Filaments also have 40-60 protein strands of Tropomyosin
• When muscle is relaxed, the tropomyosin blocks the G actins and prevents myosin from
binding.
• Thin filaments also have Troponin: a Ca+ binding protein
• Tropomyosin and Troponin are Regulatory proteins
• Myosin and Actin are Contractile Proteins
Thin
Myofilaments
G act
(c) Thin filament
11-21
Figure 11.3c
3. Elastic Filaments:
Titan, this helps
made of huge springy proteins called
stabilize the thick filaments and helps prevent overstretching.
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•
•
•
flank each thick filament and anchor it to the Z disc
helps stabilize the thick filament
center it between the thin filaments
prevents over stretching
• Accessory Proteins include(more than 20 dif proteins) Dystrophin)
• 1. Links actin in outermost myofilaments and
• 2. transfers forces of muscle contraction to
•
connective tissue around muscle cell
• Genetic defects in dystrophin produce the
• disease muscular dystrophy.
Myofibrils are made of
1. MYOSIN = thick filaments
2. ACTIN = thin filaments
3. Elastic filaments
Filament organization
Actin and Myosin are in all cells and control
motility .
In muscle cells they areContractile proteins (act to
shorten muscle fibers)
Actin and Myosin are organized in a precise array
which then is seen as striations in the muscle.
Striated muscle has DARK A bands
alternating with light I bands
Myofilaments ACTIN (thin) and MYOSIN (thick)
-- form dark and light bands
 A band = dArk • thick (myosin)
 I band = lIght • thIn (actin)
Overlap of Thick and Thin Filaments
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Thick filament
Thin filament
Bare zone
(d) Portion of a sarcomere showing the overlap
of thick and thin filaments
Figure 11.3d
11-27
Bands in muscle myofibrils:
A bands= thick filaments lying side by side
- very dark where thick and thin overlap
H bands= lighter region with no overlap of
thick and thin…just thick
I Bands = is region with only thin filaments and is
anchored to Z disc by elastic filaments
Z disc = Protein disc to which thin and elastic filaments
are anchored
Sarcomere= segment of myofibril from one Z disc to the
next Z disc
A muscle shortens because
individual sarcomeres
shorten and pull the z discs
closer to each other.
As discs are pulled closer
they pull on the
sarcolemma to achieve
shortening of the cell.
Striations and Sarcomeres
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Nucleus
M line
4
Z disc
A band
I band
1
I band
2
3
H band
Individual myofibrils
5
Sarcomere
(a)
Visuals Unlimited
Figure 11.5a
• sarcomere – functional contractile unit of the muscle fiber
• muscle shortens because individual sarcomeres shorten
• pulls z discs closer to each other
11-31
It is important to remember the hierarchy
fasicles
myofibrils
myofilaments
actin
myosin