Skeletal muscle - Nervous system Flashcards
(28 cards)
What are the two divisions of the autonomic nervous system?
- Parasympathetic: Controls digestion and rest functions.
- Sympathetic: Controls the fight or flight response (increases heart rate, blood pumping).
What is the somatic division responsible for?
Controls voluntary movements of the limbs, trunk, and head by acting on skeletal muscles
What are the two major divisions of motor pathways?
- Somatic division (controls skeletal muscles)
- Autonomic division (controls involuntary functions)
What are T-tubules (transverse tubules)? (Structure of skeletal muscle)
Invaginations of the sarcolemma (muscle cell membrane) that penetrate deep into the muscle fibers to help transmit signals
What are myofibrils?
Structural components of muscle fibers made up of two contractile proteins:
Actin (thin filaments) - 8 nm
Myosin (thick filaments) - 16 nm
Why do skeletal muscles appear striated?
The alternating bands of actin and myosin create a striped (striated) appearance under a microscope
What are the properties of muscle fibers?
- Irritability (can respond to stimuli).
- Conductivity (can transmit electrical signals).
- Contractility (can actively shorten using energy).
- Extensibility (can be stretched without damage)
What are the structural components of a muscle cell?
- Sarcolemma: Muscle cell membrane.
- Sarcoplasm: Muscle cytoplasm.
- Sarcoplasmic reticulum (SR): Stores calcium ions needed for contraction.
What is a sarcomere?
The functional unit of muscle contraction, made of repeating actin and myosin filaments
Where are thick and thin filaments located in the sarcomere?
- Thick filaments (myosin): Located in the center.
- Thin filaments (actin): Located on the edges
What are the components of thick filaments?
- Made of 200 myosin proteins.
- Myosin heads extend toward thin filaments, forming cross-bridges
What are the components of thin filaments?
- Actin: Main structural protein.
- Tropomyosin: Covers myosin-binding sites in relaxed muscle.
- Troponin: Holds tropomyosin in position.
What are elastic filaments, and what do they do?
- Titin: Anchors and stabilizes myosin filaments, helping sarcomeres recover after contraction.
- Nebulin: Stabilizes actin filaments.
What is the Sliding Filament Theory?
Muscle contraction occurs when myosin heads bind to actin, pulling the thin filaments inward and shortening the sarcomere
Why is ATP needed for muscle contraction?
- ATP energizes myosin heads, enabling them to bind to actin.
- Powers the power stroke, pulling actin filaments inward.
- Needed to detach myosin heads from actin for the next cycle
How do sarcomere arrangements affect contraction?
- Series arrangement: Increases degree of shortening.
- Parallel arrangement: Increases force generation
How do muscles store ATP?
- Muscles store small amounts of ATP.
- Creatine phosphate helps regenerate ATP quickly
What are myogenic and neurogenic muscle fibers?
- Myogenic: Contract spontaneously (e.g., heart muscle).
- Neurogenic: Contract only when stimulated by neurons (e.g., skeletal muscle)
What is the neuromuscular junction (NMJ)?
A specialized synapse where neurons communicate with muscle fibers to initiate contraction
What neurotransmitter is used at the NMJ?
Acetylcholine (ACh)
What is the motor end plate?
A specialized area of the sarcolemma that contains ACh receptors
What is a motor unit?
A single motor neuron and all the muscle fibers it controls
What happens at the Neuromuscular Junction during muscle activation?
- ACh is released from the motor neuron.
- ACh binds to receptors on the sarcolemma.
- Depolarization occurs, generating a muscle action potential.
- The signal spreads across the sarcolemma.
Where is calcium stored in muscle cells?
In the sarcoplasmic reticulum (SR)
