skeletal muscle

• skeletal muscle is attached to the bone
• skeletal muscle is voluntary and conscious control
• a muscle is made up of a bunch of myofibrils and together they create a great amount of pressure, in which they are parallel to each other to maximise force
• sarcolemma is the cell surface membrane
• sarcoplasm is the cytoplasm
• sarcoplasmic reticulum is the endoplasmic reticulum
• sarcolemma has holes which is the entrance to the T-tubules which run close to the sarcoplasmic reticulum
• sarcoplasm contains mitochondria and myofibrils
• mitochondria provides ATP for muscle contraction
• myofibrils contain actin and myosin which slide past each other for muscle contraction
• the sarcoplasmic reticulum contains protein pumps which transport calcium ions into the lumen of the sarcoplasmic reticulum
• tendons attaches bones to the muscle
• the myofibrils is located in the sarcoplasm
• there are 2 types of protein filaments are: actin and myosin
• myosin are thick protein filaments
• actin are thin protein filaments
• H-band only thick myosin filaments
• I-band only thin actin filament present
• A-band some areas only contain myosin present and some area with overlap of actin and myosin
• A-band regions appear dark in images
• M-line is the attachment for myosin
• Z line is the attachment for actin filament
• sarcomere is the region between two Z lines
• role of calcium ions: 1. calcium ions diffuse into myofibrils from sarcoplasmic reticulum 2. this causes the movement of tropomyosin of myosin forming a cross-bridge 3. binding sites of actin are exposed 4. myosin head attaches to the binding sites on actin 5. hydrolysis of ATP on myosin head causes head to bend 6. bending causes pulling of actin 6. attachment of new ATP molecule causes myosin head to detach
• ATP allows binding of myosin to actin providing energy to move myosin head
• the sliding filament theory explains how muscles contract by shortening