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?