1. Specify the functions of skeletal muscle tissue.
Produce skeletal movement, Maintain body position and posture, Support soft tissues, Guard openings, Maintain body temperature and Store nutrient reserves
2. Describe the organization of muscle at the tissue level.
Muscles have three layers of connective tissues:
Epimysium: exterior collagen layer, Separates muscle from surrounding tissues
Perimysium: surrounds muscle fiber bundles (fascicles)
Endomysium: surrounds individual muscle cells (muscle fibers), contains capillaries and nerve fibers contacting muscle cells, contains myosatellite cells (stem cells) that repair damage
Endomysium, perimysium, and epimysium come together: at ends of muscles, to form connective tissue attachment to bone matrix (i.e., tendon (bundle) or aponeurosis (sheet))
3. Explain the characteristics of skeletal muscle fibers, and identify the structural components of a sarcomere.
Internal Organization of Muscle Fibers:
The sarcolemma: The cell membrane of a muscle fiber (cell), Surrounds the sarcoplasm (cytoplasm of muscle fiber), A change in transmembrane potential begins contractions
Transverse tubules (T tubules): Transmit action potential through cell, Allow entire muscle fiber to contract simultaneously, Have same properties as sarcolemma
Myofibrils: Inside muscle fibers, Made up of bundles of protein filaments (myofilaments), Myofilaments are responsible for muscle contraction. Types of myofilaments: thin filaments: made of the protein actin. thick filaments: made of the protein myosin.
Sarcoplasmic reticulum (SR): A membranous structure surrounding each myofibril, Similar in structure to smooth endoplasmic reticulum, Forms chambers (terminal cisternae) attached to T tubules, Cisternae have high concentration of Ca2+
Sarcomeres: Smallest functional unit in muscle fiber, The contractile units of muscle, Structural units of myofibrils, A striped or striated pattern within myofibrils, Alternating dark, thick filaments (A bands) and light, thin filaments (I bands). The A Band: M line: The center of the A band, At midline of sarcomere. The H Band: The area around the M line, Has thick filaments but no thin filaments. Zone of overlap: The densest, darkest area on a light micrograph, Where thick and thin filaments overlap. The I Band: Z lines: The centers of the I bands, At two ends of sarcomere. Titin: Are strands of protein, Reach from tips of thick filaments to the Z line,
Stabilize the filaments
4. Identify the components of the neuromuscular junction, and summarize the events that occur at the synapse.
Is the location of neural stimulation, Action potential (electrical signal), Travels along nerve axon, Ends at synaptic terminal: Synaptic terminal: releases neurotransmitter (acetylcholine or ACh), into the synaptic cleft (gap between synaptic terminal and motor end plate)
5. Explain excitation-contraction coupling and the contraction cycle.
Action Potential: Generated by increase in sodium ions in sarcolemma, Travels along the T tubules, Leads to excitation–contraction coupling: AP releases Ca2+ from terminal cisternae in triad, Contraction occurs in muscle due to sliding of muscle filaments
6. Describe the mechanisms responsible for tension production in a muscle fiber and in a skeletal muscle. Identify the factors that affect the amount of tension produced at the level of the muscle fiber and skeletal muscle.
The all–or–none principle: As a whole, a muscle fiber is either contracted or relaxed
Tension of a Single Muscle Fiber: Depends on: The frequency of stimulation, Amount of Ca2+ released, Resting length at time of stimulation, Overlap between thick & thin filaments
Tension Production by Muscles Fibers: Length–Tension Relationships: Number of pivoting cross-bridges depends on:Amount of overlap between thick and thin fibers. Optimum overlap produces greatest amount of tension: Too much or too little reduces