Muscles = _____ group of tissues in our body
_____% of our body mass
_____ muscle = 35 to 40%.
Muscles = largest group of tissues in our body
50% of our body mass
skeletal muscle = 35 to 40%.
Cardiac muscle cells
Connected to each other by _____ _____.
Intercalated discs _____ cardiac muscle cells together, preventing _____ when the heart _____. Allow cells to _____ for the heart muscle to contract in _____.
Muscle
Made up of many _____ _____ that are held together by _____ tissue.
Cardiac muscle cells
Connected to each other by intercalated discs.
Intercalated discs bind cardiac muscle cells together, preventing separation when the heart contracts. Allow cells to communicate for the heart muscle to contract in coordination.
Muscle
Made up of many muscle fibres that are held together by connective tissue.
Myoblasts
_____ (_____-_____) and _____ (_____ _____) cells
Myofibre
Combined _____ (A single muscle cell is AKA muscle fibre or myofibre)
Single cylindrical, large, _____, _____ (multinucleated) cell.
Adults = _____-_____ diameter, _____ cm length
Myoblasts
Undifferentiated (non-specialized) and mononucleated (single nucleus) cells
Myofibre
Combined myoblast (A single muscle cell is AKA muscle fibre or myofibre)
Single cylindrical, large, elongated, multinucleated (multinucleated) cell.
Adults = 20-100μm diameter, 20 cm length
Muscles are organized in levels:
Muscles are made up of _____ = groups of _____ _____.
Muscle fibres are made up of _____ = which _____.
3 layers of connective tissue:
_____ wraps around the muscle.
_____ wraps each _____.
_____ wraps each individual _____ _____.
Muscles are organized in levels:
Muscles are made up of fascicles = groups of muscle fibres.
Muscle fibres are made up of myofibrils = which contract.
3 layers of connective tissue:
Epimysium wraps around the muscle.
Perimysium wraps each fascicle.
Endomysium wraps each individual muscle fibre.
Striations (the striped appearance):
From contractile proteins _____ inside the _____
Located in the _____, the _____ (_____) and _____ (_____) filaments are arranged in a pattern; a repeat of this pattern = _____ (_____ unit that _____).
A and I Bands in a sarcomere:
Thick filaments (_____) are in the _____ of the sarcomere, forming the _____ band.
Thin filaments (_____), at each _____ of the sarcomere _____ to a _____ _____ (protein _____).
The other ends of the _____ overlap with the _____, helping the sarcomere contract.
Striations (the striped appearance):
From contractile proteins arrangement inside the myofibrils
Located in the cytoplasm, the actin (thin) and myosin (thick) filaments are arranged in a pattern; a repeat of this pattern = sarcomere (functional unit that contracts).
A and I Bands in a sarcomere:
Thick filaments (myosin) are in the center of the sarcomere, forming the A band.
Thin filaments (actin), at each end of the sarcomere anchored to a Z line (protein network).
The other ends of the actin overlap with the myosin , helping the sarcomere contract.
Sarcomere structure:
Sarcomere = between two _____ _____, a _____ _____ of skeletal muscle
Z line = Edge of a _____, anchors _____.
A band = _____ _____ in the _____ where _____ is located
H zone = _____ of the _____ _____ with no overlap with _____.
I band = _____ area on _____ sides of the _____ _____, containing only _____ and does not overlap with _____.
In a sarcomere, each myosin filament connects with _____ actin, and each actin connects with _____ myosin.
Sarcomere structure:
Sarcomere = between two Z lines, a functional unit of skeletal muscle
Z line = Edge of a sarcomere, anchors actin.
A band = dark band in the middle where myosin is located
H zone = center of the A band with no overlap with actin.
I band = lighter area on both sides of the A band, containing only actin and does not overlap with myosin.
In a sarcomere, each myosin filament connects with 6 actin, and each actin connects with 3 myosin.
Titin fibres:
Acts like _____ to anchor _____ to the _____ _____
Largest _____ in the human body: _____ amino acids long
Molecular weight of _____ million _____
Tropomyosin and troponin:
_____ proteins that control muscle _____.
Bind to _____ and controls when _____ can attach, ensuring the muscle _____ only at the right time.
Titin fibres:
Acts like springs to anchor Myosin to the Z lines
Largest protein in the human body: 27,000 amino acids long
Molecular weight of 3 million daltons
Tropomyosin and troponin:
Regulatory proteins that control muscle contraction.
Bind to actin and controls when myosin can attach, ensuring the muscle contracts only at the right time.
Cross-bridge:
Part of the _____ that grabs the _____ and pulls it toward the _____ of the _____ (by _____), causing the _____ to _____.
Muscle contraction:
Contraction doesn’t always mean the muscle gets _____.
Contraction = the muscle is _____ and generates _____.
Relaxation = the muscle stops _____ _____.
Cross-bridge:
Part of the myosin that grabs the actin and pulls it toward the center of the sarcomere (by flexing), causing the actin to slide.
Muscle contraction:
Contraction doesn’t always mean the muscle gets shorter.
Contraction = the muscle is activated and generates force.
Relaxation = the muscle stops generating force.
Sliding Filament Mechanism:
When many cross-bridges pull at once, _____ pulls _____, causing the filaments to slide past each other.
This sliding _____ the sarcomere, which may shorten the whole muscle if the load allows it.
Calcium:
In all muscle types, _____ controls whether _____ can bind to _____.
Calcium allows _____-_____ _____, which causes _____.
A change in _____ _____ (an _____ _____) triggers the release of _____ inside the _____ _____.
When the signal stops, calcium is _____ _____, and the muscle _____
Sliding Filament Mechanism:
When many cross-bridges pull at once, myosin pulls actin, causing the filaments to slide past each other.
This sliding shortens the sarcomere, which may shorten the whole muscle if the load allows it.
Calcium:
In all muscle types, calcium controls whether myosin can bind to actin.
Calcium allows cross-bridge cycling, which causes contraction.
A change in membrane potential (an action potential) triggers the release of calcium inside the muscle fibre.
When the signal stops, calcium is pumped away, and the muscle relaxes
Structure of the actin molecule:
1 actin molecule = 1 _____ (_____ polypeptide), 1 actin helix = many _____ linked together.
The actin molecule _____ with other actin molecules, resulting in a _____ _____ to make _____ _____ _____.
Each actin molecule has a _____ _____ for _____.
Structure of the actin molecule:
1 actin molecule = 1 globule (single polypeptide), 1 actin helix = many globules linked together.
The actin molecule polymerizes with other actin molecules, resulting in a helix shape to make long actin filament.
Each actin molecule has a binding site for myosin.
Regulatory molecules: _____ and _____:
Tropomyosin - _____ actin molecules long
Blocks/partial covers the _____ _____ _____ on actin during _____.
Troponin keeps _____ in place so it can block _____ from binding to _____
Troponin - 3 subunits: _____, _____, _____.
T, _____ = Attaches to _____.
I, _____ = Keeps _____ in place, blocking _____ from actin.
C, _____ = Binding site for _____.
Tropomyosin and troponin work together to block _____ from binding _____ in a _____ muscle.
Regulatory molecules: Troponin and Tropomyosin:
Tropomyosin - 7 actin molecules long
Blocks/partial covers the myosin binding site on actin during relaxation.
Troponin keeps tropomyosin in place so it can block myosin from binding to actin
Troponin - 3 subunits: T, I, C.
T, tropomyosin = Attaches to tropomyosin.
I, Inhibitory = Keeps tropomyosin in place, blocking myosin from actin.
C, Calcium = Binding site for calcium.
Tropomyosin and troponin work together to block myosin from binding actin in a relaxed muscle.
Structure of the myosin molecule:
2 large _____ _____ _____ + 4 smaller _____ _____ forms a large molecule with 2 _____ _____ and 1 _____ _____.
Each globular head has a binding site for _____ and _____ (acts like _____)
Heavy chain: 1 _____, 1 _____, which connects to _____ _____
Light chain: _____ _____ that _____ the _____ (also a site of _____)
Structure of the myosin molecule:
2 large polypeptide heavy chains + 4 smaller light chains forms a large molecule with 2 globular heads and 1 long tail.
Each globular head has a binding site for actin and ATP (acts like ATPase)
Heavy chain: 1 tail, 1 head, which connects to light chains
Light chain: Specialized proteins that stabilize the head (also a site of regulation)
Cross-bridge cycle (muscle contraction):
Myosin _____ to the actin.
Myosin _____ the actin (_____ _____).
Myosin _____ the actin.
Myosin _____ _____ to _____, so it can _____ again and _____ the cycle
Cross-bridge cycle (muscle contraction):
Myosin attaches to the actin.
Myosin pulls the actin (power stroke).
Myosin releases the actin.
Myosin uses energy (ATP) to reset, so it can attach again and repeat the cycle
