PHGY 215 - module 4 Exam Questions and Answers Fully Solved Latest Update 2025-2026
3 components of the structure of skeletal muscle - Answers Muscle, muscle fibre, myofibrils
innervation of skeletal muscle - Answers somatic nervous system (voluntary movement)
Muscle - Answers - made of od individual muscle fibres
- the muscle fibres run the entire length of the muscle
Muscle Fibre - Answers - run parallel to each other
- surrounded by connective tissue
- a muscle fibres is actually a single muscle cell that is multinucleated with a very large number
of mitochondria
Myofibrils - Answers - contractile element of skeletal muscle
- the cell is divided into myofibrils along the length of the muscle
-
What gives the muscles its striated pattern? - Answers light (I) and dark (A) bands
Myofibrils - 6 components to its structure - Answers 1. Dark band (A)
2. Light band (I)
3. H zone
4. M line
5. Z line
A band - Answers - dark bands
- made up of stacked thick and thin filaments
- middle is slightly lighter as the thin filaments don't reach this far from the ends
- lighter portion is called the H zone
What portion of the sarcomere has thick and thin filaments? - Answers the A band
I bands - Answers - light bands
- make up the portion of the thin filament that don't extend into the A band
- middle = z line
, - this region only has thin filaments
H zone - Answers - lighter portion of the A band
- contains proteins that hold the thick filament together in a stack
- myosin is made of 2 chains and 2 light chains
- H zone only contains the heavy chains (thick filaments)
M line - Answers - proteins that hold the thick filament together in a stack
- runs down the centre of the H zone
- at the middle of the sarcomere (m is in the middle of the alphabet)
Z line - Answers - vertical lines in the middle of the I band
- defines the end of the sarcomere (z is at the end of the alphabet)
Borders of the sarcomere - Answers - the distance from one z line to the other
muscle proteins in the thick filament - Answers Myosin
Myosin - Answers - motor protein (uses ATP)
- gold club looking structure with 2 heads
- head contains the actin binding site and the myosin ATPase
muscle proteins of the thin filament - Answers actin, tropomyosin, troponin
Actin - Answers - actin filaments are made up of individual actin molecules that come together
to form a double helix
Tropomyosin - Answers - a thin, double helix protein
- lies along the actin filament
- regulatory protein that covers the actin binding site to regulate the binding site, preventing the
interaction of actin and myosin
Troponin - Answers regulatory protein that is made up of 3 polypeptides that binds to actin,
tropomyosin, and calcium
What happens to a muscle when it contracts? - Answers it shortens
The sliding filament mechanism - Answers - thick filaments (myosin) are on the inside and thin
filaments (actin) are on the outside
3 components of the structure of skeletal muscle - Answers Muscle, muscle fibre, myofibrils
innervation of skeletal muscle - Answers somatic nervous system (voluntary movement)
Muscle - Answers - made of od individual muscle fibres
- the muscle fibres run the entire length of the muscle
Muscle Fibre - Answers - run parallel to each other
- surrounded by connective tissue
- a muscle fibres is actually a single muscle cell that is multinucleated with a very large number
of mitochondria
Myofibrils - Answers - contractile element of skeletal muscle
- the cell is divided into myofibrils along the length of the muscle
-
What gives the muscles its striated pattern? - Answers light (I) and dark (A) bands
Myofibrils - 6 components to its structure - Answers 1. Dark band (A)
2. Light band (I)
3. H zone
4. M line
5. Z line
A band - Answers - dark bands
- made up of stacked thick and thin filaments
- middle is slightly lighter as the thin filaments don't reach this far from the ends
- lighter portion is called the H zone
What portion of the sarcomere has thick and thin filaments? - Answers the A band
I bands - Answers - light bands
- make up the portion of the thin filament that don't extend into the A band
- middle = z line
, - this region only has thin filaments
H zone - Answers - lighter portion of the A band
- contains proteins that hold the thick filament together in a stack
- myosin is made of 2 chains and 2 light chains
- H zone only contains the heavy chains (thick filaments)
M line - Answers - proteins that hold the thick filament together in a stack
- runs down the centre of the H zone
- at the middle of the sarcomere (m is in the middle of the alphabet)
Z line - Answers - vertical lines in the middle of the I band
- defines the end of the sarcomere (z is at the end of the alphabet)
Borders of the sarcomere - Answers - the distance from one z line to the other
muscle proteins in the thick filament - Answers Myosin
Myosin - Answers - motor protein (uses ATP)
- gold club looking structure with 2 heads
- head contains the actin binding site and the myosin ATPase
muscle proteins of the thin filament - Answers actin, tropomyosin, troponin
Actin - Answers - actin filaments are made up of individual actin molecules that come together
to form a double helix
Tropomyosin - Answers - a thin, double helix protein
- lies along the actin filament
- regulatory protein that covers the actin binding site to regulate the binding site, preventing the
interaction of actin and myosin
Troponin - Answers regulatory protein that is made up of 3 polypeptides that binds to actin,
tropomyosin, and calcium
What happens to a muscle when it contracts? - Answers it shortens
The sliding filament mechanism - Answers - thick filaments (myosin) are on the inside and thin
filaments (actin) are on the outside
