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Chapter 12

Fasicle Bundle of muscle cell
Muscle fiber (cells) In fasicle
Myofirbil Protein filaments *aids in muscle contraction
What are the components of muscle fiber? Sarcolemma,multinucleated, sarcoplasm,myofibrils, sarcoplasmic reticulum, transverse tubules, mitochondria
Sarcolemma Cytoplasm membrane of the muscle cells (outer layer of cell, phospholipid bilayer)
sarcoplasm Equivalent to cytoplasm
sarcoplasmic reticulum Equivalent to smooth ER, surrounds ea. myofibrils *releases Ca to form a crossbride
transverse tubules (T Tubules) connected to sarcolemma. Helps transmit AP from sarcolemma deep inside muscle
Types of myofibril Thin and Thick filaments
Thin and Thick filaments *Run parallel to long axis of muscle cell *orderly arranged
What are thin filaments made of? Protein called actin
What are thick filaments made of? Protein called myosin
Sarcomere Function and location Function unit of muscle contraction in muscle cells *located between 2 Z-lines (where thin filaments are attached)
Where does striation of sarcomere come from? arrangement of thin and thick filaments
Crossbridge process Myosin head binds with actin and pulls it causing contraction and sarcomere to shorten
Sliding filament mechanism Explains how muscles shorten *thin filaments slides towards center of thick filaments cntracting sarcomeres
Excitation contraction coupling sequence of events that link AP to contraction in muscle cell *requires Ca *depends on neural input
Steps to Excitation contraction coupling 1. AP in sarcolemma 2. AP travels down tubule 3.AP triggers release of Ca from sarcoplasmic reticulum 4.Ca binds to troponin to expose myosin-binding sites 5. cross bridge cycling occurs
Troponin and tropomyosin regulate contraction via calcium binding *tropomyosin long *troponin pearl strands
calcium in muscle contraction triggers contraction by reaction with movement of troponin and tropomyosin on their thin filaments and this enables the myosin molecule heads
isotonic contraction muscle maintains the same tension as it shortens. Ex)walking
isometric contraction same length. muscle does not shorten but individual muscle fibers will shorten
Recruitment of motor unit dependent on FORCE production (in exercise) needs of the muscle and proceeds from the ‘smallest‘ motor units in size to ‘largest’
SMOOTH MUSCLE contracts blood vessels, GI tract, bladder, uterus *smaller than skeletal *autorythmic, involuntary *controlled by ANS & Endocrime *non-striated
cardiac muscle Autorythmic, involuntary *controlled by ANS & Endocrime
What happens when Ca is released from sarcoplasmic reticulum *Ca bind to troponin *changes shape to move tropomyosin to allow myosin head to bind actin and form crossbridge *myson head is activated when atp binds to it and turns into ADP
Created by: izis



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