4. The 3 Muscle Types
• The job of all muscles is to contract
• They are all fibrous because cells are
elongated
• The 3 Muscle Types Are:
–Skeletal Muscle
–Cardiac Muscle
–Smooth Muscle
Overview
Of
Muscle
5.
6. Skeletal Muscle
• Cigar Shaped
• Multinucleated
• Striated
• Voluntary
• Can Be Involuntary When Reflexes Are
Involved
• Very Strong and Fast But Need Rest
• Most Attached to Bone
• Do not undergo mitosis. Once dead, dead.
10. How are Muscles Structured?
• Muscle Cells have a plasma
membrane called a Sarcolemma.
• The muscle fiber is enclosed in
Endomysieum. (Endo= , Mys= )
• Many Muscle fibers bound together
make a Fascicle.
• The Fascicle is wrapped in a
membrane called the Perimysieum
(Peri= ). Pg. 174 Tortora
11. Muscle Structure Continued
• Many fascicles are wrapped together
by an Epimysium. (Epi= )
• Epimysia attach to tendons or
Aponeuroses. (pg. 192: Tortora)
• Tendons: Strong, Thin, and made up
of collagen (dense connective tissue).
Aponeuroses are sheet-like tendons.
13. What is the major Organelle of the
Muscle Cell? Pg. 176
• Myofibril(s)=Working unit of the
muscle cell. Made of Subunits called
sarcomeres.
–Give muscles the striped or striated
appearance
–The light band is the I-band
–The dark band is the A-band
–Between the I-bands is the Z-line
–Between the A-bands is the H-zone
Match the
Terms
14. Mechanism of muscle contraction
• The above micrographs show that the
sarcomere gets shorter when the muscle
contracts
• The light (I) bands become shorter
• The dark bands (A) bands stay the same length
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15. Take a long deep breath, its not
that bad.
• And remember a bicycle cannot stand
alone, because it is two tired.
• Now lets go on.
• But lets first watch this short video clip.
Overview of the
Job of the Bands
16. So how do these bands work?
• The myofibrils are surrounded by the
sarcoplasmic reticulum, a specialized
form of smooth endoplasmic reticulum that
releases calcium.
• They are made of bands of
– Actin (the thin filaments) that make up the I-
bands
– Myosin (the thick filaments) that make up the
A-bands
17. So what is the Molecular Basis of
Muscle Contraction? (pg. 176)
• 1) Nerve sends out Acetylcholine or ACh
• 2) Motor Unit= All muscles triggered by
nerve. (1 nerveTriggers 100’s of cells)
• 3) The Sarcolema becomes permeable to
Na+
• 4) Na+ causes an action potential
because it disturbs the electrical
conditions of the sarcolema (pg.178)
18. How does ACh stimulate the
muscle?
• ACh causes the sarcolema to release
Calcium (Ca+)
• Ca+ binds to the actin causing it to
change shape.
• Myosine finds actin’s new shape
attractive and grabs hold.
19. What happens after the Myosin
grabs hold? (pg. 179)
• Myosin’s head snaps towards the H-band
of the sarcomere.
• ATP releases and re-cocks the myosin
• Only some myosin heads move at one
time.
• Over all: Pg. 181
Description of
Muscle movement
20. How does the muscle relax?
• When the action potential ends:
–Sarcomere absorb Ca+
–ATP releases myosin heads
–Actin takes on its former and less
attractive shape.
–Muscle Cells can relax Best Movie on
Muscle Contraction
Revisited
Best Movie review
of the muscle
21. Write one paragraph explaining
how a muscle works.
Do this from memory.
This will help you learn.
Paul Anderson
Review
22. So, What is this Action Potential?
• Action Potential
– Electrical Current or Charge
– In order to return the cell to its original
condition, K+ is pumped into the cell by the
sodium potassium pump.
Sodium/
Potassium
Pump
23. How do muscles work together?
• Prime Mover: Major muscle doing the bulk
of the work contracting.
• Synergist: Group of muscles working
together to contract.
• Antagonist: Muscle that works against the
prime mover and or synergists.
How do Muscles work Together?
24. Summation and Tetanus
• Twitch: a single action potential causing
the muscle to contract for a millisecond
and then relax.
Latent...Contraction...Relaxation period
• Summation effect: a second action
potential arrives before the first is over.
The contraction is larger. Wave summation
• Tetanus: multiple summation effects
causing a smooth sustained contraction.
• Fatigue will set in and forces relaxation.
25. What is Recruitment?
• Motor unit recruitment: various motor
neurons in a whole muscle do not fire at
the same time. Some are relaxed some
are contracted.
• Why?
– Creates smooth muscle units not jerky
movements.
– Put your hand out and hold it still…..
26. Types of Skeletal Muscle Fibers
• Slow…Slow Oxidative Fibers (SO)
– Red, Make ATP Aerobiclatly, Fatigue
resistant. Marathon runners getting out of a
chair when old.
• Fast
– Fast oxidative –glycolytic Fibers (FOG).
• Red, ATP by anaerobic Medium fast
– Fast glycolytic Fibers (FG)
• White. Anaerobic. Short, Fast, circuit trainers
27. Why can you crack your joints?
Click here to find out!
49. Interesting Aspects:
• Some of us may have a spare muscle: the
Plantaris muscle 1 in 10 don’t.
• Want to see it? Click the link.
• Groin pull? Here is the problem:
Groin Pull
Or strain.
Plantaris
In
Action
Editor's Notes
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Each muscle fibers contains: an array of myofibrils that are stacked lengthwise and run the entire length of the fiber.
mitochondria
an extensive endoplasmic reticulum
many nuclei.
The multiple nuclei arise from the fact that each muscle fiber develops from the fusion of many cells (called myoblasts). Because a muscle fiber is not a single cell, its parts are often given special names such as sarcolemma for plasma membrane
sarcoplasmic reticulum for endoplasmic reticulum
sarcosome for mitochondrion
sarcoplasm for cytoplasm
although this tends to obscure the essential similarity in structure and function of these structures and those found in other cells. The
nuclei and mitochondria are located just beneath the plasma membrane
the endoplasmic reticulum extends between the myofibrils.
The striated appearance of the muscle fiber is created by a pattern of alternating dark A bands and
light I bands.
The A bands are bisected by the H zone
The I bands are bisected by the Z line.
Each myofibril is made up of arrays of parallel filaments. The thick filaments have a diameter of about 15 nm. They are composed of the protein myosin.
The thin filaments have a diameter of about 5 nm. They are composed chiefly of the protein actin along with smaller amounts of two other proteins:
troponin and
tropomyosin.
Pronation: Ceasar Thumbs down you will die
Supination: turn hand up “What’s sup?”
