HK 36800 Lecture 1: HK 368 Cumulative Final study guide first 9 lectures in course order

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HK 368 Cumulative Final study guide
Chapter 1: Structure and Function of Exercising Muscle
1. Muscle Fiber= Muscle Cell
-Multinucleated -range in diameter 10-12um -striated muscle
2. Epimysium (surrounds entire muscle and holds it together) > Perimysium (covers each
fascicle (bundle of fibers) > endomysium (surrounds each muscle fiber)
3. sarcolemma= plasmalemma + basement membrane (referred to plasmalemma)
-contains folds on surface for stretching - has junctional folds for transmission of
action potentials -helps to maintain acid-base balance -transport metabolites
-contains satellite cells (b/w plasmalemma and basement membrane) for growth and
development of skeletal muscle
4. sarcoplasm- fluid part of muscle fiber (cytoplasm) and contains dissolved proteins, minerals,
glycogen, fats, and organelles
-contains larger quantity of glycogen and myoglobin than cytoplasm of other cells
5. Transverse Tubules- extensions of plasmalemma that pass laterally through muscle fibers to
allow nerve impulses to be transmitted into individual myofibrils.
-also allows a pathway for substances to enter and waste products to leave fibers
5. sarcoplasmic reticulum- longitudinal network of tubules that parallel and loop around the
myofibrils
-stores calcium
6. Myofibrils- smaller unit in muscle fiber that contains sarcomeres
-each muscle fiber has hundreds to thousands of myofibrils -look like long strands of
sarcomeres
7. sarcomerebasic functional unit of myofibril and contractile unit of muscle.
-joined at Z disks (proteins for attachment and stability of thin filaments)
-H zone is visible when relaxed
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-I-band (LiGHT/thin) -A-band (dArk/both)
-H zone (thick) is middle of A band -M line (proteins for
attachment of thick filaments and stabilize structure of sarcomere) in
middle of H zone
-Thick filaments: myosin (2/3 of skeletal muscle protein)
-2 protein strands twisted and one strand has a globular
head (myosin head) to form cross-bridges that interact during muscle
contraction. Titin stabilizes myosin filaments and extend from Z disk to
M line
- Thin filaments: actin, tropomyosin, troponin.
-1 end is inserted into a Z-disk and the other extends towards center of
sarcomere. Nebulin anchors actin and regulates actin and myosin interactions. Tropomyosin lies
in grooves of actin and blocks active sites. Troponin
are attached to tropomyosin and bind calcium
Muscle fiber contraction starts with a signal from the nervous system
8. Alpha motor neuron: connects with and innervates muscle fibers
-1 alpha motor neuron + all muscle fibers it signals = motor unit
-Neuromuscular junction: synapse between alpha motor neuron and muscle fiber
9. Excitation-contraction coupling is a sequence of events that results in a muscle contraction
a. nerve impulse (action potential (AP)) from brain or spinal cord to alpha motor neuron
(AMN) > AP arrives at AMN’s dendrites to axon terminals located by plasmalemma >
acetylcholine is released and crosses synaptic cleft and binds to receptors on plasmalemma >
IF ENOUGH acetylcholine binds to receptors, the AP is transmitted through the muscle fiber
and ion gates open in muscle membrane to allow sodium to enter (depolarization)
10. Calcium ions are released from the sarcolemma after the AP travels through the T-tubules.
-this makes troponin move tropomyosin heads off the binding sites of actin which lets the
myosin heads attach to the binding sites
11. Sliding filament theory: think of rowing in a canoe
Myosin cross bridge activated > myosin head tilts (power stroke) and drags thin filament
toward center of sarcomere > thin filaments gets pulled past thick filaments and creates force >
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bond is weakened/blocked by tropomyosin > myosin head tilts and breaks from actin> rotates
back to original position > attaches to new active site further along actin > repeat until end of
myosin filaments reach Z disks or all calcium ions are pumped back into sarcolemma
-during this, thin filaments overlap H zone and make it no longer visible
-sarcomere, myofibril, muscle fibers all shorten and creates a contraction
12. ATP (adenosine triphosphate) provides energy needed for contraction
-myosin head contains binding site for ATP
~ Myosin head contains ATPase which splits ATP into ADP and an inorganic
phosphate and energy which is used to power the tilting of the myosin head
Muscle Fiber Types
13. Type I Fibers (slow twitch): 110 ms to reach peak tension when stimulated, red fibers, 50%
-have a slow form of ATPase -high level of aerobic endurance (produce ATP from
oxidation of carbs and fat) -walking, marathons, etc
14. Type II Fibers (fast twitch): 50ms to reach peak tension when stimulated, white fibers
-Have a fast form of ATPase and splits ATP quicker -more developed sarcoplasmic
reticulum (more calcium) -bigger alpha motor neuron (innervates more fibers)
-poor endurance -anaerobic (ATP formed through anaerobic pathways
-Type IIa- most frequently recruited besides Type I, 25%, generate more force than Type
I, Mile Run, 400 m swim, etc
-Type IIx- 25%, not easily activated by nervous system, highly explosive events (50m
sprint, 100m dash)
-Type IIc- 1-3%
15. Single-Fiber contractile velocity (Vo)
16. Muscle fiber recruitment follows the order of type I > type IIa > type IIx
Principle of Orderly Recruitment: motor units in a given muscle are ranked
Size Principle: the order of recruitment of motor units is directly related to the size of
their motor neuron
Muscle Contraction
17. 3 different types of contraction
-concentric: muscle shortening (thin filaments pulled toward center of sarcomere),
dynamic contraction
-static/isometric: force is generated but the muscle length doesn’t change (carrying a
briefcase). The myosin cross-bridges form and are recycled, producing force, but the external
force is too great for the thin filaments to be moved so they remain in their normal position
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Document Summary

Chapter 1: structure and function of exercising muscle: muscle fiber= muscle cell. Multinucleated -range in diameter 10-12um -striated muscle: epimysium (surrounds entire muscle and holds it together) > perimysium (covers each fascicle (bundle of fibers) > endomysium (surrounds each muscle fiber, sarcolemma= plasmalemma + basement membrane (referred to plasmalemma) Contains folds on surface for stretching action potentials -helps to maintain acid-base balance -transport metabolites. Contains satellite cells (b/w plasmalemma and basement membrane) for growth and development of skeletal muscle: sarcoplasm- fluid part of muscle fiber (cytoplasm) and contains dissolved proteins, minerals, glycogen, fats, and organelles. Contains larger quantity of glycogen and myoglobin than cytoplasm of other cells: transverse tubules- extensions of plasmalemma that pass laterally through muscle fibers to allow nerve impulses to be transmitted into individual myofibrils. Also allows a pathway for substances to enter and waste products to leave fibers: sarcoplasmic reticulum- longitudinal network of tubules that parallel and loop around the myofibrils.

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