Muscle Contraction Flashcards
(47 cards)
What are the three types of muscle tissue?
Skeletal muscle, cardiac muscle, smooth muscle
These muscle tissues differ in structure, function, and control mechanisms.
What is the characteristic shape of skeletal muscle cells?
Long cylindrical and multinucleate
Skeletal muscle cells form from the fusion of separate embryonic cells.
How does cardiac muscle differ from skeletal muscle in terms of structure?
Branched and striated
Cardiac muscle is found in the heart and operates involuntarily.
What is the shape of smooth muscle cells?
Fusiform, long and tapered with one nucleus
Smooth muscle lacks striations and is found in hollow organs.
Where is skeletal muscle located in the body?
Attached to bones or skin
Skeletal muscle is under voluntary control.
Where is cardiac muscle located?
In the walls of the heart
Cardiac muscle is under involuntary control.
Where is smooth muscle found?
In the walls of hollow visceral organs
Smooth muscle also operates involuntarily.
What is the membrane surrounding a muscle cell called?
Sarcolemma
The cytoplasm inside a muscle cell is called sarcoplasm.
What are myofibrils?
Long slender contractile organelles in muscle cells
Myofibrils are composed of myofilaments.
What are myofilaments?
Smallest units contained inside myofibrils
They are made of proteins that contribute to muscle contraction.
What causes the striated appearance of skeletal muscle?
Arrangement of myofilaments in myofibrils
Dark and light stripes correspond to overlapping and non-overlapping myofilaments.
What are the two types of myofilaments?
Actin (thin) and myosin (thick)
Actin forms the light bands, while myosin forms the dark bands in striated muscle.
What is a sarcomere?
Smallest functional unit of a muscle cell
It is defined by the distance between Z discs.
What are the components of a sarcomere?
A band, I band, Z disc, M line, H zone
The A band contains overlapping filaments; the I band contains only actin.
What is the function of titin in muscle cells?
Connects myosin filaments to the Z disc
Titin helps maintain the structure of the sarcomere.
What initiates muscle contraction at the neuromuscular junction?
Release of acetylcholine (ACh)
ACh binds to receptors on the sarcolemma, leading to depolarization.
What is the role of calcium ions in muscle contraction?
Bind to troponin, exposing binding sites on actin
This allows myosin heads to attach to actin.
What is the sliding filament mechanism?
Thin filaments slide past thick filaments during contraction
Neither filament changes length; the sarcomere shortens.
What happens to the H zone and I band during muscle contraction?
H zone disappears and I band shortens
This indicates increased overlap of actin and myosin.
What is the action potential’s role in muscle contraction?
Triggers excitation-contraction coupling
It spreads along the sarcolemma and down T-tubules.
What is the role of tropomyosin in muscle contraction?
Blocks myosin-binding sites on actin in a relaxed state
It is moved away by troponin when calcium binds.
What is the function of the sarcoplasmic reticulum?
Stores and releases calcium ions
It regulates intracellular calcium levels during muscle contraction.
What is the relationship between the T tubules and the sarcoplasmic reticulum?
T tubules run between terminal cisternae of the sarcoplasmic reticulum
They facilitate rapid transmission of action potentials.
What is the significance of the M line in a sarcomere?
Holds myosin filaments in place
It is located in the center of the sarcomere.
