Anatomy and Physiology

If it's OK, I would like to use this writing opportunity to both complain and to study my Anatomy and Physiology. I do like this class very much, I find it interesting, however, it is difficult and there is a lot of material to go over. Not only do we study each bone and muscle, etc. We look at what makes everything work all the way down to what each cell is doing to accomplish every move our bodies make.
Right now we are studying skeletal muscles. Since we do not have the facilities to support a human cadaver, we are dissecting cats. Cats have many of the same muscles, but of those that are the same, some look different, and some have different names. In addition to taking this poor cat apart muscle by muscle, we are required to find time to identify muscles on a plastic human model. There are 200 muscles and we have to identify muscles on the cat and on the human...I'm not going to veterinarian school! As if 200 muscles isn't enough, at home on our own time we have to study 4 different chapters over muscle fibers, the muscular system, parts of the endocrine system and the autonomic nervous system. The lecture test is this coming Thursday (the parts I need to learn from lectures on the computer and in the book).
So here we go, a small taste of some skeletal muscle tissue. A skeletal muscle is surrounded by epimyseum, which is made of collagen fibers,and seperates the muscle from surrounding tissues. Inside the epimyseum there are several fasicles, which are bundles of muscle fibers. Each of these fasicles are surrounded by a coat of perimyseum. The perimyseum also contains collagen, but also includes elastic fibers, blood vessels and nerves; this maintains blood flow and innervates the muscle fibers. Each muscle fiber inside the fasicle is surrounded by endomysium, which interconnects muscle fibers, and contains cappilary networks that supply blood to the fibers. Endomysium also contains myosatellite cells which are stem cells that can help repair damaged muscle tissue. Nerve fibers are also located in the endomysium layer which communicate through neuromuscular junctions (which is a whole other monster). At each end of a muscle, collagen fibers from the endomysium, perimysium, and epimysium come together to form either a bundle known as a tendon or a sheet known as an aponeurosis. These connect the muscle to the bone.
A muscle fiber is surrounded by a coat called the sarcolemma; in a normal cell it would be called the plasma membrane. The fluid inside a normal cell would be called the cytoplasm-but someone decided to be smart and make us remember that muscle cell fluid is called sarcoplasm.A muscle fiber is filled with rods called myofibrils. Each myofibril is made up of thick fibers called myosin and thin fibers called actin (we also have to break down what these are made of in order to understand how muscle contractions work, but I will leave that out). These rods have sarcoplasmic reticulum (Same as smooth endoplasmic reticulum in other cells), t-tubules. which help spread signals through the muscle faster, terminal cisternae, which releases calcium to communicate muscle contractions, and sarcomeres. Sarcomeres are made up of bands of those thick and thin filaments which create a pattern of an I-band, z line, A band, H band, and M line.
When a muscle is told to contract, it of course has to go through a process. First, nero stimulation causes excitation-contraction coupling, the cisternae releases the calcium which triggers interactions of the thick and thin filaments, which consumes ATP (energy) and causes tension. Blah blah blah...The neurons send information from the brain or spinal cord, telling the muscle to contract. The thick and thin filaments slide together, shortening, or contracting the muscle.

I sure hope you enjoyed today's A&P lesson, have a great weekend!