CH 3: Muscular System Flashcards
(30 cards)
the muscular system includes how many muscles?
650
which muscle fiber type are the largest and produce the most amount of force?
type IIx
muscle origin vs muscle insertion
muscle origin - closest to the head, less movable
muscle insertion - closest to the feet, more movable
Epimysium
think of it as plastic wrap around a steak
protects muscle from friction against other muscles and bones
connected to fascia
sarcomeres
functional units that can make the muscle fiber shorten (does so collectively as a sequence of actions)
lined up w/in the myofibril
how do sarcomeres shorten?
due to the sliding of two muscle proteins: myosin and actin in a process called “cross bridge cycle”
think of mysosin as a rowboat and actin as the water, except the rowboat remains stationary and the water moves. This is also known as the sliding filament theory.
sliding filament theory
muscle shortens bc the thick and thin filaments (myosin and actin) slide past each other
what is Acetylcholine?
a neurotransmitter released in the neuromuscular junction that facilitates muscle contraction.
describe what happens with acetylcholine
- the binding of acetylcholine results in calcium release w/in the muscle.
- the calcium release is fundamental to the cross bridge cycle
Note: when muscle is at rest, actin is wrapped by proteins that block interaction w/myosin. When calcium levels rise, it binds to these proteins moving them out of the way for mysosin to interact w/actin
what fuels the cross bridge cycle?
ATP hydrolysis (ATP–>ADP) to release energy stored w/in the phosphate bond
Two sources of calcium needed for muscle activation are found where?
extracellular space
intracellular space
Intracellular calcium is released from where?
the muscle’s sarcoplasmic reticulum, which is tubules in muscle that store and release calcium
what causes calcium elevation and muscle contraction?
a neural signal sent from brain in a process called excitation-contraction coupling.
what is excitation-contraction coupling?
a process that starts w/a neural signal and ends w/a muscle contraction
what is pulling force?
the force a muscle produces to shorten (think of it as “contracting”)
what is resistance force?
an external force that opposes the force a muscle produces to shorten (ie the dumbbell during a bicep curl)
describe agonist, antagonist, synergist
prime mover, opposite, indirect (respectively)
what is Force-couple?
a type of synergy
- occurs when >=2 muscles concurrently generate force in linear directions to produce 1 mvmt. I.e., making a right turn on a bicycle requies pushing w/left and pulling w/right
note: ALL muscles work synergistically, which reaffirms the importance of an integrated (vs isolated) approach
3 factors make muscle fiber type unique
Shortening velocity. can be improved w/exercises performed at high speed
Mitochondrial density. mitochondria fuel muscle action, so, the more mitochondria the better the capacity for contraction. A decrease in mitochondria density –>diabetes and cardiovascular disease
Capillary density. Capillaries allow the exchange of O2 and CO2. Increase capillaries=increase in O2 and decrease in CO2.
what is capillarization?
the formation of new capillaries through endurance exercise
describe the 3 factors that make fiber types unique for each of the fiber types
Type I
Shortening Velocity=slow
Mitochondria Density=High
Capillary Density=High
Type IIa
Shortening Velocity=fast
Mitochondria Density=High
Capillary Density=mod
Type IIx
Shortening Velocity=very fast
Mitochondria Density=low
Capillary Density=low
How might a person’s muscle fiber ratio change?
not much but when it does it’s toward higher endurance (i.e. IIx to IIa, IIa to I)
What causes DOMS?
- When an exercise is performed for the first time
- Increase in intensity
- Increase in volume
When it comes to muscle size changes, what are the two elements to consider?
Contractile elements (myofibrils)
Non-contractile elements (glycogen and semifluid plasma)
