MUSCLE CONTRACTION GUIDED NOTES

Name: _______________________________________ Class: _______

Do Now:

1) The connective tissue covering that encloses the sarcolemma of an individual muscle fiber is called the

a) Epimysiumb) Perimysium

c) Endomysiumd) periosteum

2) A fascicle is a) A muscleb) A bundle of muscle fibers

c) A bundle of myofibrilsd) A group of myofilaments

3) Muscle tissue that is involuntarya) cardiac muscle onlyb) Smooth muscle onlyc) Skeletal muscle only

d) Cardiac and smooth musclee) Cardiac and skeletal muscle

4) The muscle tissue that consists of single, very long, cylindrical, multinucleate cells with very obvious striations is:

a) cardiac muscle onlyb) Smooth muscle onlyc) Skeletal muscle only

d) Cardiac and smooth musclee) Cardiac and skeletal muscle

5) Which of the following is NOT a function of the muscular systema) Producing movementb) Maintaining posturec) Stabilizing joints

d) Generating heate) hematopoiesis

Muscle Structure

Muscle __________________________ (bundle of fibers) _______________________ (single cell) ____________________________ __________________________ (unit of contraction)

Microscope Anatomy of Skeletal Muscle

Use the picture to come up with a definition of the following:

I band

• Each myofibril can be divided into contractile units called ___________________________.

• Sarcomeres consist of overlapping protein filaments of ____________ and _________________.

• Regular arrangement of dark and light bands. Dark bands occur where myosin is present.

• The ______________ is where the myosin attaches

• __________________(a membrane) mark the edge of each sarcomere; serve as attachment site for actin

•

A band

H zone

Turn and Talk

First match the words …

actin cell

myofibril group of cells

sarcomere cell membrane

fascicle protein

muscle fiber organelle

sarcolemma contractile unit

Then, write a paragraph that uses all the words in both columns above and explains that structure of the muscle

Contraction Overview

Contraction Details

1. A motor neuron stimulates the muscle cell by releasing the ____________________________________ into the synaptic cleft between the neuron and muscle cell.

Note: A __________________________ is a single motor neuron and all the muscle fibers it activates

• Globular heads of myosin filaments attach to actin filaments.

• Myosin pulls ________________________ : “Sliding filament theory”

• Causes _____________________ to shorten, particularly the ______________________

Which one is contracted?

How can you tell?

2. ACh causes an electric current called an _____________________________ to move through the muscle cell.

3. The action potential causes the ________________________________________________________________.

4. ______________________________________________________________ on actin filaments.

5. Myosin heads (& ADP) attach to actin binding sites, ____________________________________.

6. Myosin heads release ADP, move the actin filament in “___________________________________”

7. ATP binds to myosin head. The crosslink between actin and myosin breaks.

8. ATP becomes ADP + P, readying the myosin head to reattach to actin.

• If Ca2+ is still present, cycle will repeat, with myosin heads reattaching and contracting the muscle even more.

• Once the action potential is over, the Ca2+ is reabsorbed into the sarcoplasmic reticulum. Without

Ca2+, myosin cannot attach to actin.

NOTE: ATP is required to breakcross-links, not to form them.

Explains rigor mortis

Why then do muscles needATP?