Anatomy - Ch 10 (Muscular Tissue)
skeletal tissue
-voluntary -Striated -multinucleated
Muscle tone is ________.
a state of sustained partial contraction
power stroke
action of myosin pulling actin inward (toward the M line)
Tropomyosin
covers myosin binding sites on the G actin molecules
Sarcoplasm
cytoplasm of a muscle fiber Presence of glycogen and myoglobin
red muscle fibers
dark red with high myoglobin
Transverse tubules (T-tubules)
deep invaginations of the sarcolemma that extend into the sarcoplasm and are filled with interstitial fluid
Connective tissue coverings
endomysium - surrounds each muscle fiber (inner) perimysium - surrounds bundles of muscle fibers called a fascicle (middle) epimysium - binds fascicles together (outer) ALL MERGE TO FORM TENDONS
excitation-contraction coupling
events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract
Aponeurosis
flat tendon sheet that attaches muscle to muscle
white muscle fibers
low myoglobin content
Which of the following is a main characteristic of a skeletal muscle fiber?
multinucleated & started appearance
Each muscle fiber is made up of several structures called?
myofibrils
Which protein forms the thick filaments of a skeletal muscle fiber?
myosin
aerobic respiration
requires oxygen
M line
supporting proteins that hold the thick filaments together in the H zone
Which dense connective tissue attaches skeletal muscles to bones?
tendons
Myosin
thick filament; stationary
Actin
thin filament; only one that moves
I band
thin filaments only
Myofibrils
- Microscopic elongated contractile elements found in striated muscle cells like skeletal muscles - Made up of thick filaments (myosin) and thin filaments (actin) - rod-like structures hat extend the length of the cell and contain repeating units called sarcomeres (Z to Z)
Contraction - Sarcomere shortening
(HI) Bands H-band I-band
Titin
- A series elastic component protein responsible for allowing the sarcomere to stretch and recoil. - Holds myosin fibers in place laterally
sarcoplasmic reticulum
- Organelle of the muscle fiber that stores calcium - Forms terminal cisterns on ends of T-tubules
Z disc
- provides anchorage for thin filaments and elastic filaments - separates the sarcomeres from each other
concentric isotonic contraction
-muscle shortens -reduce the angle of a joint -tension is great enough to overcome resistance
Troponin
A protein of muscle that holds tropomyosin in place and forms a regulatory protein complex controlling the interaction of actin and myosin and that when combined with calcium ions permits muscular contraction
muscular tissue
Accounts for 40-50% of total body mass
Myoglobin
An oxygen-storing, pigmented protein in muscle cells.
Tendons
Connect muscle to bone
Myofibrils are built of 3 kinds of proteins:
Contractile - generate force during contraction Regulatory - help switch the contraction process on and off Structural - keep thick and thin filaments aligned
What moves myosin head ?
Myosin hinge
Myology
Study of the nature, structure, function, and diseases of the muscles.
H zone
The region at the center of an A band of a sarcomere that is made up of myosin only. The H zone gets shorter (and may disappear) during muscle contraction.
10,000 sarcomeres per
myofibril
Sarcolemma
plasma membrane of a muscle fiber (cell)
myosin and actin
protein filaments
3 types of muscle tissue
skeletal, cardiac, smooth
A band
thick and thin filaments
anaroebic respiration
without oxygen
Cardiac tissue
-Involuntary -striated and branched muscles -circulates in heart -single nucleus -Intercalated discs -Desmosomes and gap junctions -Natural pacemaker (Autorhythmicity)
Smooth tissue
-Located in the walls of hollow internal structures such as intestines, stomach and blood vessels -Involuntary -Non-striated -Single nucleus -Tapered cells
slow oxidative fibers
-Type I Fibers -contract slowly -have slow acting myosin ATPases -fatigue resistant -dark red (high myoglobin) -many large mitochondria generate ATP by aerobic cellular respiration
fast oxidative glycolytic fibers
-Type IIa (LARGERST) -Combine high myosin-ATPase activity with high oxidative capacity and intermediate glycolytic capacity -ATP by aerobic AND anaerobic cellular respiration
fast glycolytic fibers
-Type IIb -white color (low myoglobin) -few mitochondria -contract quickly and have fast myosin ATPase -easily fatigued -ATP by anaerobic cellular respiration
eccentric isotonic contraction
-muscle lengthens -the resistance being greater than the force the muscle is producing
nerve impulse transmission
1. Action potential arrives at presynaptic membrane. 2. This change in voltage opens Ca2+ channels to allow Ca2+ to flow in. 3. This causes synaptic vesicles carting the neurotransmitter (AcH) to fuse with membrane. 4. AcH binds to receptors (sodium-channels). 5. They open and sodium influx generates a muscle action potential.
2 types of isotonic contractions
1. Concentric 2. Eccentric
contraction cycle
1. Contraction Cycle Begins: Calcium is released from SR 2. Active-Site Exposure: Calcium binds to troponin ands moves tropomyosin away 3. Cross-Bridge Formation: myosin head binds to the G actin filaments 4. Myosin Head Pivoting (power stroke): myosin head pivot towards the M line and release ATP. This shortens the sarcomere to contract muscle. 5. Cross-Bridge Detachment: ATP binds to myosin head to break cross-bridge 6. Myosin Reactivation: ATP provides the energy to reactivate the myosin heads ands return them to their original position
4 key functions of muscular tissue
1. Producing body movements - walking and running 2. Stabilizing body positions - stabilize joints 3. Storing and moving substances - sphincters 4. Producing heat - thermogenesis
4 properties of muscle tissue
1. excitability - production of action potential by chemical or electrical stimuli 2. contractility - contract forcefully when stimulated by action potential 3. extensibility - ability to stretch with out damaging 4. elasticity - ability to return to its original shape
Triad
2 terminal cisternae and t tubule
isotonic contraction
tension developed in the muscle remains almost constant while the muscle changes its length