uscles moving bones is a big part of what volleyball is all about! It is the impact with the moving bones that transfers momentum to the ball, causing it to move. When a muscle cell receives an electrical impulse from the nervous system, it uses energy harvested by its mitochondria to contract. Thus, just to lift one’s arm into position to try to hit the volleyball is a very complex motion. All the bones in the arm must be moved into position, each requiring at least one, perhaps several muscles to move it. The cells in each of those muscles must receive a “message” from the brain to contract. Another area of the brain must coordinate all the separate electrical messages so that all the muscles work together. Since muscles can only contract and pull, and cannot push, if the bones need to be slightly repositioned, that requires a whole group of “antagonistic” muscles to move the bones in the opposite direction.
Bone tissue is made up of repeated “circular” units like this one, all packed
next to each other. Each of these units is called an Haversian system. The
concentric layers that make up an Haversian system are made of collagen protein
(the same as is in many of our other tissues, and vitamin C is needed to make
it), with the difference that in bone tissue, there is a bunch of calcium
phosphate embedded in the collagen to make the bone hard. That’s why we need
so much calcium for strong bones, and that’s also why drinking too many soft
drinks containing phosphoric acid (phosphate) can actually leach calcium out
of a person’s bones. The somewhat crescent-shaped black “spots” in this photo
contain the actual bone cells, called
osteocytes.
All the bones, together, make up our skeleton. The skeleton provides strength
and shape/structure to the body, serves as attachment places for the muscles
so we can move, and helps to protect delicate internal organs (consider the
differences among the levels of protection the skeleton gives to the brain,
the heart and lungs, and the digestive tract). By the way, contrary to a
widely-circulated “urban legend,” all humans, both male and female, have 12
pairs of ribs. Many people are required to learn the names of the bones in
junior or senior high school biology classes. If you don’t know all the
names or need a review, the Biol. 105 Web page mentioned below has a diagram
and a list of bones — learn them.
The muscles that move our bones are sometimes referred to as “skeletal muscles.”
They are also referred to as “striated muscles” because of the way they look
when viewed under a microscope. Muscle cells, also called muscle fibers,
contain many mitochondria to harvest the energy they need to function. They
also contain large amounts of two special proteins: actin and myosin, and it
is the actin and myosin sliding past each other in a muscle cell that causes
that cell to contract. In skeletal muscles, the actin molecules and the
myosin molecules are very neatly organized and lined up making the areas with
and without myosin readily distinguishable from each other. Thus the muscle cell appears
“banded” with alternating “light” and “dark” bands or striations.
In Dr. Fankhauser’s photograph, the “stripe” running across the middle of the
picture is a portion of a skeletal muscle cell. Within that cell, the dark
vertical bands are the areas where the myosin fibers are lined up, and the
whitish vertical bands are the spaces between the ends of the
myosin.
We have two other types of muscle tissue in our bodies. These are known as
smooth and cardiac muscle. Smooth muscle is found in association with our
internal organs; for example, the muscles that move the food along the digestive
tract (and are also the source of the “rumbling” of an empty stomach when
someone is hungry). Smooth muscle does not have the visible striations that
skeletal muscle does; it appears to be “smooth” when viewed under a microscope.
Cardiac muscle is only found one place in the body – in the heart, and it
shares some characteristics of both striated and smooth muscles. Cardiac
muscle does have some striations, but not as many as skeletal muscle
tissue.
On Thanksgiving, when people sit down to eat the cooked muscles of a turkey,
one of the first questions that is often asked is, “Do you want light meat
or dark meat?” Biologically, we would rephrase this question as, “Do you
want red muscle tissue or white muscle tissue?” The muscles being eaten
are all skeletal muscles, but depending on the function of a muscle, it may
or may not contain an oxygen-storage chemical called myoglobin. Muscles which
contain myoglobin are typically those that are used continuously for long
periods of time (such as muscles used in maintaining posture), thus need to
have more oxygen available for their use, and
due to the presence of the myoglobin, these muscles appear more reddish in
color. Muscles which lack myoglobin are typically those that are used less
frequently and for only short periods of time, thus don’t usually need to
have a supply of “extra” oxygen stored up, and these appear more whitish in
color. The presence or absence of myoglobin in a muscle is under genetic
control, so a muscle cannot just switch from one to the other. For example,
since turkeys and chickens don’t fly very much, their flight muscles are
white, but pheasants, which fly a lot, have red flight muscles. In turkeys
and chickens, the frequently-used leg muscles contain myoglobin and are red.
Humans also contain some red and some white muscle
tissue.
As mentioned above, muscles can only contract, only pull; muscles cannot
push. They’re either contracted and pulling or else they’re relaxed. Thus,
our skeletal muscles come in sets called “antagonistic pairs” which typically
have opposite functions. The example of this with which must people are
probably the most familiar are the muscles in the upper arm. The biceps
(officially, biceps brachii) on the “top” side pull on the lower arm bones
and bend the elbow joint, while the triceps, on the “bottom” side of the upper
arm, pulls the lower arm bones the opposite direction to straighten out the
elbow joint. Notice, by the way, the proper way to refer to what’s going
on here: muscles, themselves, do not “bend,” but rather, muscles bend a
joint. Muscles such as the biceps brachii, which decrease the angle
of a joint, are called flexors, while muscles such as the triceps, which
increase the angle of (straighten) a joint, are called
extensors.
The Biology 105 Web page listed below lists the names and locations for many
of the “more significant” muscles. You should learn those muscle names and
locations.
Links to Related Information on Our Web Server
The following Web pages contain information related to
the skeletal and muscular systems.
There will be only one, combined assignment for this week’s topics (skeletal, immune, and excretory systems). Thus even though this will appear on each of those three pages to remind you, you only need to do it once. Pick a disease or disorder that affects humans, and do library and/or Web research to find out more about that disease (see below). Suggestion: get in touch with your classmates via e-mail (addresses available from the Check Grades (and Class E-Mail List) Web page) to find out what each other are doing so everybody doesn't do the same thing. As a suggestion, it seems like AIDS is almost “overdone,” these days – it might be more interesting to pick something a bit more “unusual.” If you’re looking for ideas for “different” sorts of things, a few things that come to mind include Hansen’s disease, androgen insensitivity syndrome, scurvy, kuru, beriberi, hemophilia, malaria, sickle-cell anemia, syphilus, bubonic plague, mononucleosis, human papilloma virus, etc., etc. Malaria has recently become a “hot topic.” A couple of Web sites which may be of use include The Merck Manual Online and OMIM Home Page (OMIM deals specifically with genetic conditions). The grading criteria for this assignment are given below, and you should also refer to those as you work on the assignment. A total of 30 points is possible.
1. Cause of Disease/Disorder: | ||
---|---|---|
2 | — | The cause of the disease/disorder was thoroughly researched and accurately and clearly presented |
1 | — | The cause of the disease/disorder was adequately researched and presented |
0 | — | Information on the cause of the disease/disorder was sketchy and/or mostly incorrect |
2 | — | Thorough discussion of pre-existing conditions that increase chances of getting or exacerbate the condition was also included |
1 | — | At least some mention was made of pre-existing conditions that increase chances of getting or aggravate the condition |
0 | — | Either no or incorrect information on effects of pre-existing conditions was included |
2. Discovery of Disease/Disorder: | ||
2 | — | The history of the discovery/description of this condition was thoroughly researched and accurately and clearly presented |
1 | — | The history of the discovery/description of this condition was adequately researched and presented |
0 | — | Information on the discovery of this condition was sketchy and/or mostly incorrect |
2 | — | This information was presented in a manner that was entertaining and fun to read |
1 | — | This information was adequately presented |
0 | — | Presentation of this information was monotonous and lacked interest |
3. Signs, Symptoms, etc.: | ||
2 | — | The signs, symptoms, and effects on the body systems were thoroughly researched and accurately and clearly presented |
1 | — | The signs, symptoms, and effects on the body systems were adequately researched and presented |
0 | — | Information on the effects of this disease/disorder was sketchy and/or mostly incorrect |
2 | — | The student clearly demonstrated that (s)he knows the difference between “signs” and “symptoms” |
1 | — | The delineation between “signs” and “symptoms” was included and was at least partially correct |
0 | — | “Signs” and “symptoms” were not delineated or were incorrectly distinguished from each other or most manifestations of the condition were assigned to the wrong category |
4. Diagnosis & Treatment: | ||
2 | — | The diagnosis and treatment of this condition were thoroughly researched and accurately and clearly presented |
1 | — | The diagnosis and treatment of this condition were adequately researched and presented |
0 | — | Information on the diagnosis and treatment of this condition was sketchy and/or mostly incorrect |
2 | — | Thorough discussion of role and usefulness of diet and/or “alternative” therapies was also included |
1 | — | Effectiveness of diet and/or “alternative” therapies was at least mentioned and partially discussed |
0 | — | No mention made of effects/influence of diet and/or “alternative” therapies |
5. Spread & Distribution: | ||
2 | — | The prevalence, distribution, and means of acquisition were thoroughly researched and accurately and clearly presented |
1 | — | The prevalence, distribution, and means of acquisition were adequately researched and presented |
0 | — | Information on the prevalence, distribution, and means of acquisition was sketchy and/or mostly incorrect |
2 | — | Discussion of likelihood of contracting and means of prevention was thoroughly presented |
1 | — | Likelihood of getting and means of prevention were at least mentioned |
0 | — | No mention made of how to keep from getting this disease/disorder or information presented was incorrect |
6. Misconceptions & Role in History: | ||
2 | — | Information on misconceptions associated with this condition and its role in history was thoroughly researched and accurately and clearly presented |
1 | — | Information on misconceptions associated with this condition and its role in history was adequately researched and presented |
0 | — | Information on misconceptions and/or the role in history was sketchy and/or mostly incorrect |
2 | — | This information was presented in a manner that was entertaining and fun to read |
1 | — | This information was adequately presented |
0 | — | Presentation of this information was monotonous and lacked interest |
7. Overall: | ||
2 | — | The grammar, English usage, punctuation, and spelling were very good |
1 | — | The grammar, etc. were OK |
0 | — | The grammar, etc. were poor |
2 | — | The student, obviously, went beyond the minimum requirements of the assignment |
1 | — | The student adequately completed the assignment |
0 | — | The student completed considerably less of the assignment than what was required |
2 | — | It is evident that the student used much insight, thoughtfulness, and critical thinking when completing this assignment |
1 | — | The student adequately thought about the assignment – there was, perhaps, a bit of “fuzzy thinking” in a couple places |
0 | — | The assignment gives the appearance of being “slapped together” just to get it done, with little evidence of thoughtfulness |
Total Possible: | ||
30 | — | total points |