Week 6 Work Sheet 14

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           

 

 

 

       1. Use the items in the key to correctly identify the structures described below.    



 

Key:

1.

connective tissue ensheathing a bundle of muscle cells

a.

endomysium

2.

bundle of muscle cells

b.

epimysium

3.

contractile unit of muscle

c.

fascicle

d.

fiber

e.

myofibril

4.

a muscle cell

5.

thin reticular connective tissue surrounding each muscle cell

f.

myofilament

6.

plasma membrane of the muscle fiber

g.

perimysium

7.

a long filamentous organelle with a banded appearance found within muscle cells

h.

sarcolemma

i.

sarcomere

8.

actin- or myosin-containing structure

j.

sarcoplasm

9.

cord of collagen fibers that attaches a muscle to a bone

k.

tendon

2. List three reasons why the connective tissue wrappings of skeletal muscle are important.

3. Why are there more indirect—that is, tendinous—muscle attachments to bone than there are direct attachments?

4. How does an aponeurosis differ from a tendon structurally?

How is an aponeurosis functionally similar to a tendon?

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5. The diagram illustrates a small portion of several myofibrils. Using letters from the key, correctly identify each structure indicated by a leader line or a bracket. Key: a. b. c.

A band actin filament I band

d. e. f.

myosin filament T tubule terminal cisterna

g. triad h. sarcomere i. Z disc



6. On the following figure, label a blood vessel, endomysium, epimysium, a fascicle, a muscle cell, perimysium, and the tendon.

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

 7. Complete the following statements: The junction between a motor neuron’s axon and the muscle cell membrane is called a neuromuscular junction or a __1__ junction. A motor neuron and all of the skeletal muscle cells it stimulates is called a __2__. The actual gap between the axon terminal and the muscle cell is called a __3__. Within the axon terminal are many small vesicles containing a neurotransmitter substance called__4__. When the __5__ reaches the ends of the axon, the neurotransmitter is released and diffuses to the muscle cell membrane to combine with receptors there. The combining of the neurotransmitter with the muscle membrane receptors causes the membrane to become permeable to both sodium and potassium. The greater influx of sodium ions results in __6__ of the membrane. Then contraction of the muscle cell occurs.

1.

________________________

2.

________________________

3.

________________________

4.

________________________

5.

________________________

6.

________________________

8. The events that occur at a neuromuscular junction are depicted below. Identify by labeling every structure provided with a leader line. Key:

Action potential

Nucleus

(a)

a.

axon terminal

b.

mitochondrion

c.

muscle fiber

d.

myelinated axon

e.

sarcolemma

f.

synaptic cleft

g.

synaptic vesicle

h.

T tubule

Junctional folds of the sarcolemma

Part of a myofibril

(b)



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