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What are the key minerals involved in bone hardening?
Ca2+, PO4-, and other ions
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What are the 3 main functions of bones?
Mechanical functions, maintainance of mineral levels, and blood production.
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What blood cells do bones produce and where?
Eukaryocytes, leukocytes, and megakaryocytes(platelets) and they are produced in the bone marrow.
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Bones are composed of what 2 different compounds?
A hard inorganic material, Hydroxylapatite and a tough fibrous collagen.
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Bones help maintain levels of Calcium and phosphorous by storing and removing them but what is so important about the maintainance of these levels?
Calcium is vital for cells to stick together and for muscle contraction. And phosphorous is a very vital mineral in complex chemicals such as DNA and RNA.
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Skeletal Muscle attaches to bones via?
tendons
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Flexor and Extensor muscles do what?
Flexors make the bones bend at a joint and extensors make them straighten at a joint.
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Muscles only exert force how? and do so in response to what?
Contraction; nerve signal
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What is Skeletal muscle involved in?
Voluntary motor responses and locomotion
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What is skeletal muscle made out of?
A grouping of cells(muscle fibers) bound together by connective tissue
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Muscle fiber =?
1 muscle cell
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A muscle cell in striated muscle contains what?
Myofibrils- cylindrical bundles of actin and myosin proteins
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What is one repeating unit of actin and myosin proteins in striated muscle called?
A sacromere
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The sacromere banding pattern is due to what?
To the ordered arrangement of contactile protein filaments.
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A thick filament in a sacromere is called what?
A myosin contracting protein
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A thin filament in a sacromere is called what?
A actin contractin protein + other regulatory proteins called tropomyosin and troponin
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Actin is what?
Thin filaments; molecules that form 2 intertwined helical chains and each molecule contains a binding site for myosin.
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Actin is closely associated with what 2 regulatory proteins?
Tropomyosin and troponin
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Myosin is what?
A thick filament; protein with 2 heads and a tail. Tails of myosin molecules aligned to form thick filament. 2 Heads form cross-bridges with actin.
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How many heads do myosin protein molecules have and what are there bonding sites for?
2 heads, and actin proteins and ATP
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Muscle increase due to exercise are mainly due to an increase in what?
The number of myofibrils; very few cells added
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During muscle contraction when does the Sacromere get shorter?
When the thin actin filaments slide passed the stationary myosin thick filaments.
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What happens during muscle contractions?
Myosin cross bridges (heads) attach to actin and pull thin filament toward center of sacromere
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What is the cross bridge cycle?
A sequence of events between time when crossbridge binds to a thin filament and when it is set to repeat the process.
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What are the 4 steps to the Cross-bridge cycle?
- 1. Cross bridge binds to actin
- 2.Cross birdge moves and filament slides past each other- power stroke
- 3. ATP binds to myosin cause cros bridge to detach
- 4.Hydrolysis of ATP re-energizes the cross-bridge
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What does tropomyosin do to regulate the contraction of muscles?
Rod-shaped molecule arranged along the lenth of actin thin filaments and in the absence of calcium it covers myosin-binding sites
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What does Troponin do to regulate muscle contraction?
When it binds to calcium it drags tropomyosin off of myosin binding site, cross bridges form and contraction begins. The removal of calcium is reverses process and contraction stops.
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Low cytosolic Calcium=
Relaxed muscles and clocks binding sites on actin
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High Cytosolic Calcium=
Muscles will contract as long as their is adequate ATP. Power stroke; exposes binding site on actin
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What is the Sarcoplasmic Reticulum?
Is a membrane network that surrounds myofibrils and is where Calcium is stored and released
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What happens when Calcium is released into the cytosol?
Triggers muscle contraction. Binds regulatory proteins on actin, opens bindinding sites.
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What muscle type cell produces action potential?
Skeletal muscle cells
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How is action potential initiated?
By neural impulses
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What is a neuromuscluar junction?
A junction of motor neuron's axon and muscle fiber cell
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Axon terminals contain what?
Vesicles of acetycloline (ACh)
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why is the muscle fiber under the axon terminal folded into junction folds?
to increase surface area
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What is an ACh receptor on a muscle?
Ligand-gated ion channel
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