Advance Preparation—ATP Muscle Kit
1. Order the ATP muscle kits (Carolina) to be delivered no more than seven days before the lab. One kit provides generously for eight students. Extra vials of the chemical solutions can be ordered separately (Carolina) and will reduce waiting time. Just before the lab begins, cut the muscle bundles into 2-centimeter lengths and place in a petri dish in the accompanying glycerol.
R E V I E W
S H E E T
LAB TIME/DATE _______________________
and Organization of
Skeletal Muscle Cells and Their Packaging into Muscles
From the inside out, name the three types of connective tissue wrappings of a skeletal muscle. a.
Why are the connective tissue wrappings of skeletal muscle important? (Give at least three reasons.) They support and bind muscle fibers, strengthen the muscle as a whole, and provide a route for the entry and exit of nerves and blood vessels that serve the muscle fibers.
Why are there more indirect—that is, tendinous—muscle attachments than direct muscle attachments? (Your text may help you answer this.)
Tendons provide durability and conserve space. They are tough collagen fibers so they can cross rough, bony projections that would tear delicate muscle tissues. Because of their small size, more tendons can pass over a joint.
On the following figure, label endomysium, perimysium, epimysium, and fascicle. Muscle
The diagram illustrates a small portion of a muscle myofibril in a highly simplified way. Using terms from the key, correctly identify each structure indicated by a leader line or a bracket. Below the diagram make a sketch of how this segment of the myofibril would look if contracted.
The Neuromuscular Junction
For skeletal muscle cells to contract, they must be excited by motor neurons. However, the electrical impulse cannot pass directly from a nerve cell to the skeletal muscle cells to excite them. Just what does pass from the neuron to the muscle cells, and what effect does it produce?
A neurotransmitter chemical called acetylcholine diffuses from the axon into the synaptic cleft and combines with the receptors on the muscle cells. The permeability of the muscle cells change, allowing more sodium ions to diffuse into the muscle fiber, resulting in the generation of an action potential.
Why is it that the electrical impulse cannot pass from neuron to muscle cell? The neuron and muscle fiber membranes, close as they are, do not actually touch. They are separated by a small fluid-filled gap called the synaptic cleft.
Review Sheet 11
Classification of Skeletal Muscles
Several criteria were given for the naming of muscles. Match the muscle names (column B) to the criteria (column A). Note that more than one muscle may fit the criterion in some cases. Column A
flexor digitorum superficialis
1. action of the muscle
• biceps brachii
• pectoralis major
2. shape of the muscle
flexor digitorum superficialis
3. location of the origin and/or insertion of
4. number of origins
• erector spinae • abdominis transversus • pectoralis major • external intercostals
5. location of the muscle relative to a bone or
• rectus abdominis
• abdominis transversus
6. direction in which the muscle fibers run relative
to some imaginary line
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