Musculoskeletal System Flashcards
(30 cards)
What are muscle fibers?
Long, striated, multinucleated cells responsible for voluntary movements.
What do muscle fibers contain?
Myofibrils, which are bundles of contractile proteins
What is a sarcomere?
The basic contractile unit of a muscle, composed of thick (myosin) and thin (actin) filaments.
What is the sarcolemma?
Plasma membrane of a muscle fibre; Surrounds each muscle cell and helps to transmit the action potential from the neuron to the muscle fibre.
What is the sarcoplasmic reticulum?
A specialised form of the endoplasmic reticulum; Stores and releases Ca2+ ions, which are crucial for muscle contraction; SR surrounds each myofibril and releases Ca2+ in response to action potentials
What are T-tubules?
Invaginations of the sarcolemma that penetrate into the muscle fibre; Help transmit the action potential deep into the muscle fibre, ensuring that the signal reaches all parts of the muscle cell; Closely associated with SR, and play a role in the release of Ca2+.
What is the role of the sarcoplasmic reticulum?
Crucial in calcium storage and release
What is the role of the sarcolemma and T-tubules?
Facilitate communication and signal transmission for muscle contraction.
What is the role of ATP in muscle contraction?
ATP binds to myosin, is hydrolyzed to ADP, and provides the energy for the myosin head to change position and pull actin filaments.
What neurotransmitter is involved in muscle contraction?
Acetylcholine
What are the main proteins involved in muscle contraction?
Myosin (thick filaments) and actin (thin filaments).
What role does calcium play in muscle contraction?
Calcium binds to troponin, causing a structural change that moves tropomyosin and exposes binding sites on actin for myosin.
What triggers the release of calcium from the sarcoplasmic reticulum?
Membrane depolarisation
What is the role of troponin in muscle contraction?
Troponin binds calcium, which causes a conformational change that moves tropomyosin and exposes binding sites on actin.
What is the function of tropomyosin in muscle contraction?
Tropomyosin blocks the binding sites on actin in a relaxed muscle and moves to expose these sites when troponin binds calcium.
What is the first step in excitation-contraction coupling?
An action potential travels down a motor neuron to the neuromuscular junction.
What happens when the action potential reaches the neuromuscular junction?
The motor neuron releases the neurotransmitter acetylcholine into the synaptic cleft.
What does acetylcholine do once it is released into the synaptic cleft?
Acetylcholine binds to receptors on the sarcolemma (muscle cell membrane).
What is the result of acetylcholine binding to receptors on the sarcolemma?
It causes depolarization of the sarcolemma, leading to an action potential in the muscle fiber.
How is the action potential transmitted into the muscle fiber?
The action potential travels along the sarcolemma and down the T tubules.
What is the role of T tubules in excitation-contraction coupling?
T tubules transmit the action potential deep into the muscle fiber to the sarcoplasmic reticulum.
What happens when the action potential reaches the sarcoplasmic reticulum?
The sarcoplasmic reticulum releases stored calcium ions into the cytoplasm of the muscle fiber.
What is the role of calcium ions in muscle contraction?
Calcium ions bind to troponin, causing a conformational change that moves tropomyosin and exposes binding sites on actin.
What happens after the binding sites on actin are exposed?
Myosin heads bind to the exposed sites on actin, forming cross-bridges.
