Lesson 6 (Bio) 4-7

Do Now
• Quick experiment:
• In one jar is an egg covered by water and in the other
jar an egg covered with vinegar.
• Briefly do the following:
• 1. What is the purpose?
• 2. What are the materials used?
• 3. What do you think will happen and why? This is the
• What do we know about vinegar? Where does it sit on
the PH Scale?
Homework due today
• Homework
1. Read pages 930 – 934.
a. Be prepared to discuss the article on page 934 (Steroids)
2. Given the length of the quiz and the fact that so many
did not finish the Pre-Lab Write up.
a. Pre-lab report?
b. Steroids article
• Homework - Re-read / summarize if necessary
1. Read pages 930 – 934.
a. Be ready show your notes from the reading assignment
b. Be prepared to discuss the article on page 934 (Steroids)
2. For Tuesday – Each of you will have a topic to begin
to research and present (written and presentation
form). Use the attached sheet to begin to develop your
Are we ready for the lab?
• Are we ready? If so, then follow instructions
and begin to do the lab.
• Put on an apron, goggles and gloves.
• Re-read your instructions and then begin.
• If we are not ready then class-time.
Muscular System
• Muscles allow movement, but they also
allow basic functions to occur.
• There are three types of muscle:
• 1. Cardiac – the muscle of the heart is very
special. Never rests.
• 2. Smooth Muscle (aka involuntary muscle) –
such as muscles around the rib cage.
• 3. Skeletal Muscle (aka voluntary muscle) –
muscles that you decide to move or control.
Muscular System
• Skeletal muscles – eventually attach to
• Skeletal muscle under a microscope will
show striation caused by white and dark
• Why do chicken legs have dark meat?
• Darker generally means more blood travels
through. More in the legs because the
muscle is thicker and used for walking
versus the breast which is more white meat.
Muscular System
• Smooth Muscle – little or no striation. Under
the microscope the muscle appears smooth
(hence the term).
• They are called involuntary because you do
not have control over these muscles. Other
muscles that are smooth – digestive
• Question – if you are paralyzed will these
muscles still function?
• Depends where the cut to the spinal cord is.
Sometimes the impulse will allow the muscle
to still function. Skeletal will not
Muscular System
• Cardiac muscle – is somewhat a
combination of smooth & skeletal.
• Smooth because the person has no control
over them.
• Like skeletal because it is very strong and
fibrous (striation).
• The heart can never stop beating or tire.
• It has its own impulse to beat known as a
pacemaker. Some people have an external
pace because their heart does not beat on
its own.
Muscular Contraction
• What is a muscle contraction?
• It occurs in the body when movement is
necessary. It is when muscle is shortened.
• Skeletal muscles are filled with bundles of
filaments called myofibrils.
• Myo means muscle
• Each myofibril contains a layer of
protein called myosin (thick layered)
and a thin layer of protein called actin
Muscular Contraction
• These thick & thin layered fibers are weaved
together or overlaid which produced what
looks like stripes.
• The thin actin filaments are arranged in Zlines.
• Two Z-lines and the filament between them
form a sacromere
Muscular Contraction
• During a contraction, myosin filaments form
a cross-bridge with the actin filaments.
• These cross bridges change shape and pull
the actin filaments to the center of the
• Then it detaches and then it repeats. As they
slide the muscle shortens or contracts.
• The process is known as the sliding filament