Lab 7 The Muscular System BIO201L
Student Name: Gloria Arajulu
Access Code (located on the lid of your lab kit): AC-OF2X1AP
Pre-Lab Questions
”1.
1. How do banding patterns change when a muscle contracts?”
During muscle contraction, the banding patterns change due to the thick
filaments being pulled towards the center of the sarcomere. The actin slides past the myosin
which changes the appearance of band thickness without changing the size of the
myofilaments.
”2.
2. What is the difference between a muscle organ, a muscle fiber, myofibril and a
myofilament? ”
- Muscle Organ: A muscle organ refers to a whole muscle made up of multiple bundles of
muscle fibers, blood vessels,, nerves, and connective tissue
- Muscle Fiber: A muscle fiber is a single muscle cell, also known as a muscle cell, responsible for
muscle contraction.
- Myofibril: Myofibrils are long, thread
thread-like
like structures within muscle fibers that consist of
protein filaments (myofilaments) and are responsible for muscle contraction.
- Myofilament: Myofilaments are the smallest protein filaments within myofibrils, consisting of
actin and myosin, which slide past each other during muscle contraction.
”3.
3. Outline the molecular mechanism for skeletal muscle contraction. At what point is ATP used
and why? ”
Ca2+ is released from storage in the sarcoplasmic reticulum -> > Intracellular Ca2+
binds with troponin ->> Tropomyosin changes positions and exposes the myosin binding sites on
the actin->> myosin heads bound to ADP and P attach to actin and forms cross cross-bridges
bridges -> ADP
and P are released, which alter the shap
shape e of the myosin head and cause a sliding motion
moving actin towards the center of the sarcomere -> ATP binds to myosin -> > Myosin ATP
hydrolze ATP into ADP and P, which provide energy to return the myosin head to it’s original
position -> ADP and Premain bound ound to the myosin head -> > Ca is pumped back into the
sarcoplasmic reticulum.ATP is used as chemical energy that is converted into mechanical energy
”4.
4. Explain why rigor mortis occurs. ”
Rigor mortis occurs after death due tto o the depletion of ATP (adenosine triphosphate),
which is the energy source required for muscle relaxation. Without ATP, the myosin heads in
the muscle cells remain bound to actin filaments, causing the muscles to become stiff and rigid.
This stiffness typically
ically starts to develop a few hours after death, peaks around 12-24
12 hours, and
gradually dissipates over the next 11-2 2 days as the muscle tissues begin to decompose. Rigor
mortis is a natural post-mortem
mortem process and helps forensic investigators determine the t time of
death in certain cases.
.
Experiment 1: Tendons and Ligaments
Post-Lab Questions
”1.
1. Label the arrows in the slide images below based on your observations from the
experiment. ”
, Lab 7 The Muscular System BIO201L
A- Chondrocytes
B- collagen
C- nucleus
D- skeletal muscle fibers
E- nuclei
F- collagen fibers
Student Name: Gloria Arajulu
Access Code (located on the lid of your lab kit): AC-OF2X1AP
Pre-Lab Questions
”1.
1. How do banding patterns change when a muscle contracts?”
During muscle contraction, the banding patterns change due to the thick
filaments being pulled towards the center of the sarcomere. The actin slides past the myosin
which changes the appearance of band thickness without changing the size of the
myofilaments.
”2.
2. What is the difference between a muscle organ, a muscle fiber, myofibril and a
myofilament? ”
- Muscle Organ: A muscle organ refers to a whole muscle made up of multiple bundles of
muscle fibers, blood vessels,, nerves, and connective tissue
- Muscle Fiber: A muscle fiber is a single muscle cell, also known as a muscle cell, responsible for
muscle contraction.
- Myofibril: Myofibrils are long, thread
thread-like
like structures within muscle fibers that consist of
protein filaments (myofilaments) and are responsible for muscle contraction.
- Myofilament: Myofilaments are the smallest protein filaments within myofibrils, consisting of
actin and myosin, which slide past each other during muscle contraction.
”3.
3. Outline the molecular mechanism for skeletal muscle contraction. At what point is ATP used
and why? ”
Ca2+ is released from storage in the sarcoplasmic reticulum -> > Intracellular Ca2+
binds with troponin ->> Tropomyosin changes positions and exposes the myosin binding sites on
the actin->> myosin heads bound to ADP and P attach to actin and forms cross cross-bridges
bridges -> ADP
and P are released, which alter the shap
shape e of the myosin head and cause a sliding motion
moving actin towards the center of the sarcomere -> ATP binds to myosin -> > Myosin ATP
hydrolze ATP into ADP and P, which provide energy to return the myosin head to it’s original
position -> ADP and Premain bound ound to the myosin head -> > Ca is pumped back into the
sarcoplasmic reticulum.ATP is used as chemical energy that is converted into mechanical energy
”4.
4. Explain why rigor mortis occurs. ”
Rigor mortis occurs after death due tto o the depletion of ATP (adenosine triphosphate),
which is the energy source required for muscle relaxation. Without ATP, the myosin heads in
the muscle cells remain bound to actin filaments, causing the muscles to become stiff and rigid.
This stiffness typically
ically starts to develop a few hours after death, peaks around 12-24
12 hours, and
gradually dissipates over the next 11-2 2 days as the muscle tissues begin to decompose. Rigor
mortis is a natural post-mortem
mortem process and helps forensic investigators determine the t time of
death in certain cases.
.
Experiment 1: Tendons and Ligaments
Post-Lab Questions
”1.
1. Label the arrows in the slide images below based on your observations from the
experiment. ”
, Lab 7 The Muscular System BIO201L
A- Chondrocytes
B- collagen
C- nucleus
D- skeletal muscle fibers
E- nuclei
F- collagen fibers
