Slide set 5 Flashcards
Muscle cell is
Muscle fiber
Cell membrane in muscle is
Sarcolemma
Cytoplasm in muscle is
Sarcoplasm
Modified ER in muscle is
Sarcoplasmic reticulum
Skeletal muscles are usually attached to
Bones and tendons
What are flexor and extensor
Flexor muscles- brings bones together
Extensor- moves bones away
Antagonistic pair: flexor-extensor pair
Properties of skeletal muscles and their function
Responsible for moving the framework of the body
•Can contract rapidly but tires easily
•Remarkably adaptable
•Function: Maintain posture and body position
•Movement of the body as a whole or of its parts
•Stablilizejoints
•Heat production
•Contract only in response to a signal from a motor neuron
Skeletal muscles are surrounded by ___, muscles divide into ___, where you can find individual muscle fibers
Connective tissue
Muscle fascicle
What are epi,peri and endomysium
Epimysium—coarse sheath covering the muscle as a whole
–Perimysium—tough connective tissue binding together fascicles
–Endomysium—connective tissue membrane that covers skeletal muscle fibers
–These three fibrous components are continuous with eachother and with the tendon
Characteristic of muscle fibers to movement
Excitability—ability to be stimulated
Contractility—ability to contract, or shorten, and produce body movement
Extensibility—ability to extend, or stretch, allowing muscles to return to their resting length
What is the role of SR in muscle
Plays a role in Ca+regulation during contraction
What are T tubules
extend across the cell. They are formed from inward extension of the sarcolemma.
–T-tubules chief function is to allow electrical signals traveling along the sarcolemma to move deeper into the cell
–Requirement for contraction
What is the triad
formed from a triplet of tubules made of the sacroplasmic reticulum which surrounds the T-tubule
–This arrangement allows a signal traveling along the T-tubule to stimulate adjacent membranes on the SR
Muscle fibers contain many ____
Mitochondira and multiple nuclei
What is sacromere
Segment of myofibril between two successive Z lines
•Each myofibril consists of many sarcomeres
•Contractile unit of muscle fibers
Sacromerers are a part of
Myofibril
Z lines function
an anchor for the myofibrils
Muscle fibers are made up of smaller units ___, which are made up from _____ that can be thick and thin. Thick is made up from ____ and the thin from ____
Myofibrils, myofilaments, myacin, actin
The bands of sacromere that are made only of thin microfilaments are ___ and thick microfilaments are ___
I band
H zone
What is A band
Where there is an overlap of thick filaments and thin filaments + H zone
Sacroplasm contains
SR
Myofibrils
Mitochodnria
Glycogen granules (energy)
Thin filaments in addition to actin are made up from
troponin
tropomyosin
What microfilamants play regulational role on muscle contraction
Titin
Nebulin
Thick myosin filaments do not attach to ___
Z lines
What are myosin heads
Very important during muscle contraction to create “bridges”
Actin is
globular protein that forms two fibrous strands that twist around each other to form bulk of thin filament
tropomyosin and troponin are
Tropomyosin—protein that blocks the active sites on actin molecules
•Troponin—protein that holds tropomyosin molecules in place
Thin filaments attach to both ___
Z lines
nebulin helps to align
Actin
titin provides
Elasticity and stabalizes myosin
Phase 1 of muscle contraction is
Motor neuron stimulates muscle fiber
Action Potential arrives at axon terminal at neuromuscular junction
Ach released; binds to receptors on sarcolemma
Ion permeability of sarcolemma changes
Local change in membrane voltage (depolarization) occurs
Local depolarization (end plate potential) ignites AP in sarcolemma
Phase 2 of muscle contraction
Excitation-contraction coupling occurs
Action Potential travels across the entire sarcolemma
AP travels along T-tubules
Sarcoplasmic Reticulum releases Ca2+; Ca2+ binds troponin; myosin-binding sites (active sites) on actin exposed
Myosin heads bind to actin; contraction begins
The binding of the mysoin head triggers ATP hydrolysis to ADP and phosphate. Energy of broken bond transferred to the mysoin
•D-the release of stored energy provides the force needed for the head to move back to its original position
What two receptors are involved in sending the signal from T tubule to SR
DHP- dihydropyridine L-type calcium channel
RyR- ryanodine receptor-channel
How signal is transferred from T tubule to SR
Depolarization will cause RyR to open through DHP and it will cause Ca ions to leave SR into cytoplasm and bind to troponin to allow actin-myosin binding
usually what is the position of actin filaments constituents
The troponin complex (Yellow) on the actin filament is positioned so that the threadlike tropomyosin (purple) is blocking the active site on the actin (pink) located underneath it.
what is essential movement for muscle contraction
The myosin heads bend with a strong force when they bind the actin filaments
•This pulls the thin filaments past them
•Each head then release and this pulls again
In what direction pulling of myosin happens
As the myosin heads pull on the thin filaments, the Z lines (Z disks) get closer together—thus shortening the sarcomere.
What happens after the contraction
Immediately after Ca++ions are released, sarcoplasmic reticulum begins actively pumping them back into sacs
•Ca++ions are removed from troponin molecules on thin filament, shutting down contraction
What happens in muscle when they are at rest ( energy)
ATP from metabolism is used to make phosphocreatine from creatine
Muscle store very limited reserves of ATP, so what is the way out
They have phosphocreatine, which is hydrolyzed to creatine and ATP when muscles work, providing quick energy
ATP in muscles are needed for
Myosin ATPase (contraction)
Ca-ATPase (relaxation)
Na-K-ATPase(restores ions that cross cell membrane during action potential to their original compartments)
Type of muscle fibers
Slow-twitch fibers (type I or ST)
Fast twitch oxidative-glycolytic fibers(FOG or type IIA)
Fast-twitch glycolytic fibers (FG or type IIB):
Characteristics of slow-twitch muscles
Use oxidative phosphorylation (have more mitochondria)
-Appear red due to myoglobin ( red oxygen-binding pigment) -> legs
describe fast-twitch muscles
develop tension 2-3x faster than slow
-Pump Ca2+ into SR faster
•Fast twitch oxidative-glycolytic fibers(FOG or type IIA)
- Use oxidative phosphorylation (have more mitochondria
- Appear red due to myoglobin
Fast-twitch glycolytic fibers -eyes (FG or type IIB): rely on anaerobic glycolysis to produce ATP
- Leads to high H+ (acidosis), because of lactate
- Fatigue more easily
- Appear white (lower myoglobin)
- Larger in size
- Fewer blood vessels
- More likely to run out of oxygen after repeated contractions
- In sports like sprinting
Cardiac muscle properties
- Striated
- Branched, have T tubules that are larger than in skeletal and forms diads with and sparse (редкий) SR
- They are held together by intercalated disks that have gap junction, that allow for cytopalsmic connection-> contraction as a unit
- Does not taper like muscle fiber (waste)
What type of muscle is cardiac
Striated involuntary
Difference of cardiac muscle vs skeletal in work
Cardiac muscle sustains each impulse longer than in skeletal muscle
•Cardiac muscle does not run low on ATP and does not experience fatigue (more mitochondria)
•Cardiac muscle is self-stimulating
Smooth muscle characteristics
Smooth muscle is composed of small, tapered cells with single nuclei
–No T tubules are present, and only a loosely organized sarcoplasmic reticulum is present
–Ca++comes from outside the cell and binds to calmodulin (regulatory protein) instead of troponinto trigger a contraction
–No striations, because thick and thin myofilaments are arranged differently than in skeletal or cardiac muscle fibers; myofilaments are not organized into sarcomeres