Sliding Filament Theory

Do Now:

1. What is the difference between actin and myosin?

2. Explain how a muscle feels when it contracts. Then draw a picture of what you believe a muscle looks like before and after contraction.

How A Muscle Contracts:

A True Story…

Today’s Objective: SWBAT explain the process of a muscle cell contraction including sliding filament theory.

4 Steps of a Muscle Contraction

1.Nerve Impulse Crosses the Neuromuscular Junction

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2.Acetylcholine Attaches to the Sarcolemma

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3.Action Potential Causes Muscle Contraction

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4.Muscle Returns to Normal

5.Nerve Impulse Crosses the Neuromuscular Junction

All skeletal muscle contractions begin with the nervous system.

A nerve impulse (or message) is sent from the nervous system to the muscle via a neuron (nerve cell).

1.Nerve Impulse Crosses the Neuromuscular Junction

The nerve impulse reaches the end of the neuron called the axon terminal.

The axon terminal forms a junction with the sarcolemma of a muscle cell called the Neuromuscular Junction

The axon terminal & the sarcolemma NEVER  TOUCH!

The gap between them is a synapse called the synaptic cleft.

Neuromuscular Junction = Axon Terminal, Synapse, and Sarcolemma.

The axon terminals release a neurotransmitter across the synaptic cleft.

A neurotransmitter is a chemical that carries the message of the impulse.

The neurotransmitter that stimulates skeletal muscle contraction is Acetylcholine (ACh)

Turn To Your Partner

Partner A – Describe the following new vocabulary terms: AXON TERMINAL, NEUROMUSCULAR JUNCTION, SYNAPTIC CLEFT, NEUROTRANSMITTER.

Partner B – Describe the first step in muscle contraction.

STEP 2:

Acetylcholine Attaches to the Sarcolemma

2.  Acetylcholine Attaches to the Sarcolemma

Acetylcholine crosses the synaptic cleft & attaches to receptors on the sarcolemma.

Acetylcholine makes the sarcolemma more permeable to sodium ions.

Sodium ions rush into the cell.

The increase of sodium ions in the cell causes the cell’s charge to change from a negative (-) charge to a positive (+) charge.

This change causes a surge of electrical current called an Action Potential.

TURN TO YOUR PARTNER

Partner A – Discuss what is acetylcholine and what does it cause within the muscle cell?

Partner B – Discuss what happens to the sodium ions around the cell and why is that important for muscle contraction?

Step 3:.

Action Potential Causes Muscle Contraction

3.  Action Potential Causes Muscle Contraction

ACh causes the sarcoplasmic reticulum to release Calcium ions into the sarcoplasm.

The calcium ions bind to the regulatory proteins on the thin filaments which allows the myosin to attach to the actin.

Myosin attaches to actin and pulls the actin closer to the center of the sarcomere.

ATP is used by the myosin to pull the actin closer.

Turn To Your Partner

Partner A – Discuss what the role of calcium ions is in the muscle cell contraction and why they are important?

Partner B – Discuss how the myosin and actin work together to create a contraction.

Sliding Filament Theory

Process by which myosin heads pull actin towards the center of the sarcomere

All-Or-None Principle

If a stimulus is strong enough to cause a contraction, the whole muscle fiber will respond or not all.

TURN TO YOUR PARTNER

Partner A – Explain the All-OR-None Principle

Partner B – Explain the Sliding Filament Theory (SFT)

Step 4:

Muscle Returns to Normal

4. Muscle returns to normal

While the action potential occurs:

 acetylcholine is broken down

Calcium ions are reabsorbed

The electrical charge in the cell returns to negative

Tell Your Partner

Alternate starting with Partner B the three things that happen to return the muscle cell back to its normal non-contracted state.

Animation Review

http://www.youtube.com/watch?v=pcayZjTKsm8&feature=related

http://www.youtube.com/watch?v=CepeYFvqmk4

FOLDABLE SUMMARY SHEET

Independent Practice

Questions in your notes

Cartoon of Muscle Contraction- Use Textbook pgs. 160-163 as reference

Using at least 8 frames you will create a cartoon that depicts the process of a muscle contraction.

Within your cartoon you need to explain the following:

The 4 Steps of the Muscle Contraction

Neuromuscular Junction

Acetylcholine and its effects

Action Potential and its effects

Sliding Filament Theory

You will also need to use the following vocabulary at least once each in your cartoon:

Axon Terminal, Neurotransmitter, Sodium Ions, Calcium Ions, Regulatory Proteins, Permeable

Number each Frame in the top left corner

Exit Ticket

Microscopic Anatomy

—Microscopic Anatomy of the
Skeletal Muscle

—DO NOW:

—Use the terms below to explain what each connective tissue of a muscle covers?

—Perimysium

—Epimysium

—Endomysium

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—Hmm…Striations

—What are striations and what gives striations their patterns?

—Today’s Objective

—We are diving into the anatomy of a single muscle fiber!

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—I can define and identify the MICROSCOPIC structure of skeletal muscle

—Structure of a Muscle Fiber

—A muscle fiber is a single, long, cylindrical muscle cell.

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—Skeletal Muscle Fibers are Multinucleate.

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—Sarcolemma =

Cell Membrane of Muscle Fiber

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—What is a cell membrane?

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—Nuclei are pushed aside by long, ribbon-like organelles called myofibrils.

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—Multiple myofibrils fill the cytoplasm of the muscle fiber.

—What is the cytoplasm?

—Sarcoplasm = Cytoplasm of Muscle Fiber

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—MYOFIBRILS & SARCOMERES

—Myofibrils are divided into chains of tiny contractile units called sarcomeres.

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—Within the sarcomeres, myofilaments (contractile proteins) give the appearance of striations.

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—Quick Quiz

—What is the name of the cell membrane of a muscle fiber?

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1.Fascicle

2.Myofibril

3.Sarcoplasm

4.Sarcolemma

—Quick Quiz

—What is the name of the cytoplasm of a muscle fiber?

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1.Fascicle

2.Myofibril

3.Sarcoplasm

4.Sarcolemma

—Quick Quiz

—What are the ribbon-like organelles that fill the cytoplasm of the muscle fiber?

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1.Fascicle

2.Myofibril

3.Sarcoplasm

4.Sarcolemma

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—FILAMENTS

—Thick Filaments = Dark Bands = Made primarily of a protein called Myosin.

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—Thin Filaments,  = Light Bands =  Made primarily of a protein called Actin.

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—A – BANDS & I - BANDS

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—A-Bands = Dark

¡Composed of Myosin

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—I-Bands = Light

¡Composed of Actin

—Turn To Your Partner

—Partner A = Explain Light Bands

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—Partner B = Explain Dark Bands

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1.What type of filaments compose that band?

2.What is the name for that band (A- or I- Band)?

—Quick Quiz

—What are the tiny contractile units that make up the myofibrils?

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1.Myosin

2.Actin

3.Sarcomere

4.Myofibril

—Quick Quiz

—What gives muscle striations the lighter appearance?

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1.Myosin

2.Actin

3.Sarcomere

4.Myofibril

—Quick Quiz

—What are thick filaments mostly composed of?

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1.Myosin

2.Actin

3.Sarcomere

4.Myofibril

—Z-Lines

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—H - Zones

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—Turn To Your Partner

—Partner A – What is important to know about the Z-Line?

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—Partner B – What is important to know about the H-Zone?

—Quick Quiz

—Which filaments are found within the H-Zone?

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1.Myosin

2.Actin

3.Z – Line

4.H – Zone

—Quick Quiz

—The length of a sarcomere is from one ______ to the next ____.

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1.Myosin

2.Actin

3.Z – Line

4.H – Zone

—Quick Quiz

—Which filament is associated with the Z-Line?

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1.Myosin

2.Actin

3.Z – Line

4.H – Zone

—Diagram Together The Muscle Fiber Structure

—Individual Activity

—You will work in your groups to create your model --- HOWEVER --- you will turn in your own individual work.

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—Don’t write on the worksheets

—You Will Need

—Toothpicks 3-5

—Straws

—Colored Pencils/Markers

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—1. First, we will use our straws. In class you learned that every muscle is made up of single muscle fibers. Your straw will represent your muscle fiber in this activity.

—2. We will use our toothpicks to demonstrate the myofibrils. We learned in class that a myofibril is a ribbon-like organelle that contains contractile units called sarcomeres. Take about 3 to 5 toothpicks and insert them into your straw.

—3. We will identify the contractile units, myofilaments and other distinguishing structures on our myofibrils. Remove the myofibrils from your straw piece.

—4.  Using different color markers or colored pencils, you will accurately draw on the myofibrils the following structures: A-Bands, I-Bands, Z-Lines, H-Zones. USE YOUR NOTES AND DIAGRAM FOR REFERENCE!

—5.  Once you have completed your labeling on the myofibrils raise your hand patiently and have it checked off by Miss Gallina.

—6. Finally, once you have been checked off (or while you are waiting) you may complete the following questions and the fill in the blank assignment on the bottom and back of this sheet.

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—Exit Ticket

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1.What are thick filaments made of?

2.Are A-Bands the light or dark appearing stripes in the muscle?

3.Z-Lines are most commonly associated with which myofilament:

Actin or Myosin?

4.Myofibrils are composed of small contractile units that extend from Z-Line to Z-Line called _______.

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Macroscopic Muscle Anatomy

Macroscopic Anatomy Notes 

—Structure of the Muscle Tissue

—Do Now: Why don’t muscles tear apart completely every time we workout strenuously?

—Today’s Objective

—SWBAT define and explain the role of the macroscopic anatomical features of the skeletal muscle:

¡Endomysium

¡Perimysium

¡Fascicle

¡Epimysium

¡Tendon

¡Aponeurosis

—Copy This Diagram Into Your Notes

—Structure of the Muscle Tissue

—Muscle Fibers are the cells of muscle tissue.

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—1000’s of these fibers are bundled together by connective tissue make a muscle

—Connective Tissue Sheaths

—Connective Tissues that wrap the muscle fibers provide strength and support to the muscle as a whole

—Turn To Your Partner

—Partner A – Discuss what are muscle fibers and what makes up a muscle.

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—Partner B – Discuss what purpose the connective sheaths in the muscle serves.

—Endomysium

—Endomysium is a connective tissue layer that covers each individual muscle fiber.

—FASCICLE

—A bundle of multiple muscle fibers is called a FASCICLE

—Perimysium

—Perimysium are the connective tissue layers that surround a fascicle.

—Epimysium

—Multiple fascicles are surrounded by the connective tissue layer called the epimysium.

—Raise The Number of Fingers for the Correct Answer for The Question

—Connective tissue that surrounds each individual muscle fiber?

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1.Endomysium

2.Perimysium

3.Epimysium

4.Fascicle

—Raise The Number of Fingers for the Correct Answer for The Question

—A bundle of multiple of muscle fibers?

1.Endomysium

2.Perimysium

3.Epimysium

4.Fascicle

—Raise The Number of Fingers for the Correct Answer for The Question

—Connective tissue that surrounds each individual Fascicle?

1.Endomysium

2.Perimysium

3.Epimysium

4.Fascicle

—Raise The Number of Fingers for the Correct Answer for The Question

—Connective tissue that surrounds bundles of fascicles?

1.Endomysium

2.Perimysium

3.Epimysium

4.Fascicle

—Tendons & Aponeuroses

—Epimysium blend together to form the tendons or aponeuroses

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—Tendons & Aponeuroses

—Tendons connect muscle to bone

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—Aponeuroses connect muscle to another muscle or connective tissue.

—Turn To Your Partner

—Partner A – Explain what a tendon is?

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—Partner B – Explain what an aponeurosis is?

—Individual Activity

—You may work with your partner – HOWEVER – each individual will complete their own work and turn in their own copy of the assignment.

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—DO NOT WRITE ON THE WORKSHEET…YOU WILL ANSWER ON YOUR OWN PAPER

—After completing the model, answer the questions on the back of the sheet.

—In Your Groups of 4 Each Person will get enough materials for their entire group:

¡Person 1 –Take One Box/Cup/Jar of Toothpicks

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¡Person 2 –Take One Box of Straws

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¡Person 3 –Take one Film Canister for each person in your group

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¡Person 4 –Take one instruction sheet for each person in your group.

—Discussion of the Activity

1.How does the activity demonstrate the structure of the muscle?

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2.What does each separate material represent?

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