Skeletal muscle structure and function Flashcards
3 main muscle types (and type of movement)
- smooth: mainly found in the hollow organs
- under non voluntary movement - cardiac: found in heart
- under non voluntary movement - skeletal: applies force to bones
- under voluntary movement
primary function of skeletal muscles
Develop force via contraction for movement, posture and support of the body
the 3 secondary functions of skeletal muscles
- support and protection for soft internal organs
- provide voluntary control over major openings
- converts energy into heat which is used to maintain core temperature (homeostasis)
definition of (muscle) fibers
individual muscle cells
definition of fascicles
fibers that are bundled together
definition of muscles
fascicles that are bundled together
what are muscle fibers made of
bundles of myofibrils
what are sarcomeres
the repeating units that make up myofibrils
2 myofilaments that make up sarcomeres
actin - thin filaments
myosin - thick filaments
sarcolemma definition
cell membrane that lines the muscle fiber
transverse tubules (T tubules) definition
tube like extensions of the sarcolemma
sarcoplasmic reticulum (SR) definition
an extensive network associated with the T tubules at regular intervals
excitation-contracting coupling definition
the pairing of a signaling event (excitation of the muscle cell) with the mechanical event (contraction of the muscle cell)
the 3 main proteins in signaling even
(of excitation-contracting)
-the voltage-gated sensor (DHPR)
-the ryanodine receptor (RyR)
-the SR calcium ATPase (SERCA)
what is the voltage-gated sensor (DHPR)
receives signals from the t-tubules and interacts with the ryanodine receptors
what is the ryanodine receptor (RyR)
a passive calcium channel on the SR that can open to allow calcium out into the cell
what is the SR calcium-ATPase (SERCA)
an active calcium pump that uses ATP to move calcium back into the SR against its concentration gradient, ending the excitation
explain the signaling stage of EC-coupling
The signal is coming from the nerves running throughout the muscles.
The signals running through the T-tubules activates the DHPR.
The active DHPR interacts with RyR, causing them to open.
explain what triggers contraction in the EC-coupling
Once the RyR is open, due to the interaction with active DHPR, calcium will come flooding out of the SR into the cell.
Calcium then diffuses throughout the cell, activating myofilaments and causing contraction.
explain the relaxation process in the EC-coupling
The SERCA pump senses the rise in intracellular calcium.
SERCA then burns some ATP to produce energy to pump calcium back into the SR (against its concentration gradient)
This removes calcium from the cell, stopping the signaling event - relaxing the muscle.
