Lab 7 The Muscular System BIO201L
Student Name:
Access Code (located on the lid of your lab kit): Click here to enter text.
Pre-Lab Questions
”1. How do banding patterns change when a muscle contracts?”
The actin and myosin myofilaments become smaller in length. The H and I zones also become
smaller and narrower. The A band does not change during contractions.
”2. What is the difference between a muscle organ, a muscle fiber, myofibril and a myofilament?
”
The muscular system is an organ with the main purpose of movement. There are three muscle
types which are: skeletal, cardiac and smooth muscle. Muscle fibers are the cells that make up
the muscles themselves. Myofibrils are long threadlike structures that contain actin and myosin
myofilaments. These myofilaments are arranged into units called sarcomeres, which connect to
form the myofibrils.
”3. Outline the molecular mechanism for skeletal muscle contraction. At what point is ATP used
and why? ”
ATP is essential to begin the cycle necessary for muscle contraction. ATP supplies the chemical
energy that is then converted into movement of the muscles. First, ATP binds to myosin. Then,
myosin ATPases hydrolyze ATP into ADP and Pi. These are bound to the myosin head.
Intracellular Ca2+ binds with troponin, which causes a change to the position of tropomyosin.
The tropomyosin moves and exposes myosin binding sites on the actin filaments. This allows
myosin heads to attach, which forms a cross-bridge between myosin heads and actin filaments.
After this ADP and Pi are released and this alters that shape of the myosin head. This shape
movement is a sliding motion resulting in a power stroke. The cycle ends when Ca2+ is pumped
back to the sarcoplasmic reticulum.
”4. Explain why rigor mortis occurs. ”
Rigor mortis occurs when ATP production stops and the levels begin to decrease after death.
This causes active transport of Ca2+ into the sarcoplasmic reticulum to stop, and Ca2+ leaks into
the sarcoplasm. These Ca2+ levels increase over time and cross-bridges form. Without enough
ATP to bind to the myosin molecules, the cross-bridges are unable to release and reform in a
usual cycle. This causes the muscles to become very stiff and remain in that state until the
muscle tissue begins to degenerate.
Experiment 1: Tendons and Ligaments
Post-Lab Questions
”1. Label the arrows in the slide images below based on your observations from the experiment.
”
A- Chondrocytes
B- Collagen
C- Collagen Fibers
D- Skeletal Muscle Fiber
E- Nuclei
F- Collagen Fibers
, Lab 7 The Muscular System BIO201L
Student Name:
Access Code (located on the lid of your lab kit): Click here to enter text.
Pre-Lab Questions
”1. How do banding patterns change when a muscle contracts?”
The actin and myosin myofilaments become smaller in length. The H and I zones also become
smaller and narrower. The A band does not change during contractions.
”2. What is the difference between a muscle organ, a muscle fiber, myofibril and a myofilament?
”
The muscular system is an organ with the main purpose of movement. There are three muscle
types which are: skeletal, cardiac and smooth muscle. Muscle fibers are the cells that make up
the muscles themselves. Myofibrils are long threadlike structures that contain actin and myosin
myofilaments. These myofilaments are arranged into units called sarcomeres, which connect to
form the myofibrils.
”3. Outline the molecular mechanism for skeletal muscle contraction. At what point is ATP used
and why? ”
ATP is essential to begin the cycle necessary for muscle contraction. ATP supplies the chemical
energy that is then converted into movement of the muscles. First, ATP binds to myosin. Then,
myosin ATPases hydrolyze ATP into ADP and Pi. These are bound to the myosin head.
Intracellular Ca2+ binds with troponin, which causes a change to the position of tropomyosin.
The tropomyosin moves and exposes myosin binding sites on the actin filaments. This allows
myosin heads to attach, which forms a cross-bridge between myosin heads and actin filaments.
After this ADP and Pi are released and this alters that shape of the myosin head. This shape
movement is a sliding motion resulting in a power stroke. The cycle ends when Ca2+ is pumped
back to the sarcoplasmic reticulum.
”4. Explain why rigor mortis occurs. ”
Rigor mortis occurs when ATP production stops and the levels begin to decrease after death.
This causes active transport of Ca2+ into the sarcoplasmic reticulum to stop, and Ca2+ leaks into
the sarcoplasm. These Ca2+ levels increase over time and cross-bridges form. Without enough
ATP to bind to the myosin molecules, the cross-bridges are unable to release and reform in a
usual cycle. This causes the muscles to become very stiff and remain in that state until the
muscle tissue begins to degenerate.
Experiment 1: Tendons and Ligaments
Post-Lab Questions
”1. Label the arrows in the slide images below based on your observations from the experiment.
”
A- Chondrocytes
B- Collagen
C- Collagen Fibers
D- Skeletal Muscle Fiber
E- Nuclei
F- Collagen Fibers
, Lab 7 The Muscular System BIO201L
