BY 30 – Fall 2001
15.1.
Overview of Muscle Tissue
a. The three types of muscle tissue are _______________________________; ___________________________; and ______________________________. Of the three, _________________________ and _______________________ are striated whereas _____________________________ is not. Of the three, _______________________ is voluntary while ________________________ and __________________________ are not.
b. The five functions of muscle tissue are ______________________________; ____________________________; _________________________________; ____________________________; and ______________________________.
c. The functions of producing body movements and stabilizing body positions is largely accomplished by _________________________________ muscle. In contrast, regulation of organ volume and moving substances within the body is done by __________________________ muscle. One way that substances are controlled in terms of leaving organs is through smooth muscle structures called ___________________________. The type of muscle responsible for moving blood is called __________________________ muscle.
d. The type of muscle responsible for generating body heat is ___________________________________ muscle. Specifically when body temperature falls, contraction of this muscle, called _____________________, produces heat which raises body temperature.
e. The four properties of muscle cells are that they have ___________________ membranes; they have the ability to ____________________________; they can also be stretched (a property known as ___________________________); and they have ___________________________ meaning that their shape and length can return to normal following contraction or extension.
f. Skeletal muscle contraction can be _________________________ when there is an increase in tension but no change in length; or _____________________ when there is a change in length while maintaining constant tension.
15.2.
Structure of Skeletal Muscle
a. Each muscle in the body (e.g., biceps, triceps, etc.) is considered to be a(n) ______________________________ because it contains all four of the basic _____________________________. Of these the most important tissue type present is called _____________________________.
b. Each skeletal muscle cell is called a ________________________________.
c. Within a skeletal muscle, there are a number of connective tissue structures, which include the ______________________; _______________________; and ________________________. Of these, it is the __________________ that surrounds the entire muscle, while the ___________________________ penetrates inward to encircle groups of 10-100 skeletal muscle fibers forming bundles called __________________________. The __________________ surrounds individual skeletal muscle fibers.
d. Muscles attach to bones by _____________________________. When these structures are broad and flat, it is called a(n) __________________________.
e. Each skeletal muscle fiber contains _____________________ nuclei clustered at the ___________________________ of the cell. This situation results from their embryonic development in which each skeletal muscle fiber is formed by fusion of __________________________. Following this process the muscle fiber becomes _____________________ so that any increase in muscle mass is due to an increase in _________________, not ______________________.
f. The plasma membrane of a skeletal muscle fiber is called the __________________________; the cytoplasm is called the __________________________; and the smooth endoplasmic reticulum is called the _______________________________.
g. The sarcolemma is invaginated to form ________________________, which conduct action potentials into the cell interior.
h. The sarcoplasm contains many ____________________________ reflecting the high ATP requirements of these cells, along with a O2 binding protein called _________________________. There are also __________________ deposits which serve as glucose reservoirs.
i. The contractile units of muscle are contained within ____________________, each of which is only about 2 mm (= microns) in diameter. Disuse atrophy involves the ____________________________ of myofibrils whereas muscle hypertrophy involves the _________________________ of myofibrils.
j. Encircling each myofibril is a portion of the __________________________ that serves as a storehouse for _________________. At the junction with T tubules, the SR dilates to form structures called _______________________. The combination of two terminal cisternas and a T tubule is called a(n) ________________________.
k. The basic structural unit of the myofibril is the _________________________ defined as the region between two successive _________________________. Muscle contraction involves ______________________ shortening and is due to the interaction of _____________________ and _____________________ filaments.
l. The pattern of striations seen in skeletal muscle is due to the overlap of thick and thin filaments giving rise to: _________________________ which are the darker middle portion of the sarcomere, consisting mostly of _____________ filaments; ______________________________ which are the lighter staining region to either side of the A bands which has the ______________________ in the middle; the _______________________ zone which is the part of the A band with only thick filaments; and the ______________________ line which runs down the middle of the A band.
m. Each thick filament consists of about 300 ____________________ molecules, each with a ________________________ that lines up in parallel forming the shaft of the thick filament and ___________________ groups which stick out.
n. Each thin filament consists of ______________________ monomers joined together to form a helical molecule. Each actin monomer has a ___________ binding site which is normally covered by a __________________________ molecule. Also connected to the tropomyosin molecule is _____________________________, another regulatory protein.
o. The structural protein that extends from Z disc to M line is ______________ which serves to anchor __________________________ to Z discs. Also, the portion that attaches to the ____________________________ is very elastic, which imparts elasticity to the myofibril.
15.3.
The Neuromuscular Junction
a. Skeletal muscle fibers only contract in response to ______________________ that arise from cells known as _________________________ which reside in the __________________ of the spinal cord or _______________________.
b. Axons from a motor neurons divide as they approach a skeletal muscle, each branch goes to __________________ skeletal muscle fiber.
c. A ______________________ is defined as an a motor neuron along with all the skeletal muscle fibers that it supplies. Motor units contract as a ________________________________.
d. The size of motor units vary with muscle ____________________________. For example, muscles that control precise movements tend to have _____________________ motor units, while muscles that provide power have _____________________ motor units. ______________________ refers to the progressive activation of motor units producing a smooth increase in muscle tension.
e. The synapse between a nerve and skeletal muscle is called the __________________________, of which each skeletal muscle cell has ______________________. The region of the sarcolemma that takes part is called the _______________________________.
f. The neurotransmitter at the NMJ is _______________________, which binds to ______________________ ACh receptors on the sarcolemma. Activation of these receptors allows ____________________ to enter these cells producing a local ________________________ current. This in turn brings the sarcolemma to ________________________________ generating an _________________ which propogates down the sarcolemma. ACh activity is terminated by an enzyme called ________________________.
g. Of the various agents that can affect NMJ function, ____________________ blocks the release of synaptic vesicles while _____________________ binds to and blocks the nicotinic ACh receptors. In either case, skeletal muscles can’t contract and patients often die due to paralysis of the ______________. By contrast ___________________________ prevent ACh from being broken down and thus prolong the effects of ACh. These agents are used clinically to treat patients that have been poisoned with _________________________ or ________________________________; or who have the disease ________________________________, an autoimmune disease where antibodies block ACh receptors making the muscles weak.