Muscle Tissue: Focus on Skeletal Muscle
You are reading chapter 9, pages 234 - 243
(and part of page 251) for this
material in your Marieb book (stop before "Contraction
of a Skeletal Muscle Fiber"). That's only
10 pages! You will be reading similar
amounts for the next few units. However, this material is tough, and you will need
to spend a lot of time on it in order to understand it thoroughly... you will also be
using the Interactive Physiology CD that you bought with your book
to learn the concepts in this muscle unit.
This unit's material can be divided into the following major concepts:
|composition of an entire muscle|
|composition of a muscle fiber (an individual muscle cell) |
|composition of a myofibril (the contractile machinery within a muscle fiber)
|the neuromuscular junction|
|how to use the A.D.A.M. Interactive Physiology CD on the muscular system|
A few additional notes that will help you to work through this material...
- You might want to run through the CD web page and the CD program before going through
the web page. The material on the CD program you will be using this week will
include material from the composition of a muscle, composition of a muscle fiber, and
composition of a myofibril web pages.
- Muscle cells use electrical signals to tell them when to contract. The signal
originates in the nervous system and comes to the muscle cells as a nervous system
command. The cells in the nervous system also work electrically. We will spend
a lot of time going over how this electrical signalling works when we get to the nervous
system... so for now, we will only discuss it briefly.
- Muscle cells, called muscle fibers, are odd-looking cells. In
order to understand these cells you have to be able to lose your mental image of the
"typical cell" and try to re-create a new type of cellular image using the same
organelles, but in different arrangements. You will see that muscle fibers are huge
cells, filled with cytoskeleton; they have many nuclei (not just one) and have lots and
lots of sER.
- The cytoskeleton of cells can be quite complex. In muscle fibers it is very
organized and orderly. If you work to understand this order, you will find it easier
to understand how muscle fibers can contract.
- Just because something is arranged in a long tube does not mean that it is a cell or
that it is a part of a cell. You will see that muscles are made up of tubes inside
of tubes inside of tubes inside of tubes. The largest tube is the muscle itself, and
the smallest tube is the contractile machinery within individual muscle fibers.
Therefore, when you see an image of these tubes in tubes, take your time to figure out
what level the image is from... is it of muscle fibers? ...of something larger?
...of something smaller?
I hope you enjoy this change of gears from the structural bones to the dynamic muscles!