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Introduction to the Muscular

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Introduction to the Muscular

ANSWERS TO PRE- LAB ASSIGNMENTS

[pic 1]

Pre-Lab Activity 1:

1.        a.        Muscle

b.        Fascicle

c.        Muscle fiber

d.        Endomysium

e.        Perimysium

f.        Epimysisum

2.        a.        T-tubule

b.        Sarcoplasmic reticulum

c.        Nucleus

d.        Triad

e.        Sarcolemma

f.        Terminal cisternae

g.        Myofibril

h.        Mitochondrion

Pre-Lab Activity 2:

1.        a.

2.        c.

3.        Motor neuron, muscle fiber

4.        Neurotransmitter

Pre-Lab Activity 3:

1.        a

2.        c

3.        glycerol

4.        Z-discs

5.        They slide past one another.

Pre-Lab Activity 4:

1.        b

2.        b

ANSWERS TO ACTIVITY QUESTIONS

Activity 1

Muscle Fiber Structure

Function

Connections to Things I Have Already Learned

Sarcolemma

Surrounds skeletal muscle fiber; regulates what goes in and out of cell

Another name for the plasma membrane is the plasmolemma; “sarco” means flesh and refers to skeletal muscle.

Sarcomere

Functional unit of muscle contraction

Z-disc to Z-disc

Sarcoplasm

The cytoplasm within a skeletal muscle fiber

Packed with myofibrils

Sarcoplasmic reticulum

Stores calcium

Modified endoplasmic reticulum (synthesis and transport of proteins)

Terminal cisternae

Terminal end sacs of SR; stores calcium

Cisternae = reservoir

T-tubule

Invagination of the plasma membrane that carries muscle action potential deep into the muscle fiber’s interior

T-tubule + adjacent terminal cisternae = triad

Mitochondrion

Produces ATP

Abundant in cells that have high metabolic activity: muscle fibers, liver cells, sperm

Nucleus

Contains DNA; skeletal muscle fibers are multinucleate

Hundreds of embryonic cells fuse to produce muscle fibers; therefore, muscle fibers are multinucleate.

Myofibril

Specialized organelle in skeletal muscle fibers that contains thick filaments and thin filaments

Arrangement of actin and myosin within myofibril gives muscle fiber a striated appearance

Triad

T-tubule + adjacent terminal cisternae = triad

Triad made of three structures

Thin filament

Actin, troponin, and tropomyosin

Slides past the thick filament during muscle contraction

Thick filament

Myosin

Contains “heads” with binding sites for both actin and ATP

Activity 2

1.        What causes the striations in this tissue?

the arrangement of actin and myosin in the myofibrils        

Are these cells uninucleate or multinucleate?

multinucleate        

2.        What are two functions of the connective tissue wrappings of muscles?

They separate and electrically insulate portions of the muscle.        

What is a fascicle?

a bundle of skeletal muscle fibers        

3.        What is released by the axon terminal?

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