Muscle structure and function Flashcards
THe ________ is located between muscle fibers.
edomysium
_____ = thick filament, ______ = thin filament
myosin; actin
Depolarization of the T-tubule system causes Ca2+ release from the sarcoplasmic reticulum’s ________ sacs.
lateral
What does Ca2+ bind to in the actin filaments?
troponin-tropomyosin
During muscle contraction, actin combines with myosin ________ to split ATP with energy release.
ATPase
ATP binds to myosin _______, breaking actin-myosin bond.
crossbridge
When muscle stimulation ceases, calcium moves back into the SR lateral sacs through ______ ______ requiring ATP hydrolysis.
active transport
______ removal restores inhibitory action of troponin-tropomyosin.
calcium
What is sarcomere length at rest?
4 micrometers (10^-6)
What is sarcomere length during contraction ?
2.7 micrometers (10^-6)
What is the optimal sarcomere length?
between 2-2.2 micrometers
When the motor neuron signal arrives, where is Ash released?
NMJ
With Ca++ influx, _____ moves aside which allows myosin to bind to actin.
troponin
The crossbridge slides, then _______ is ejected, and ATP replaces ADP, causing crossbridge to release and spring back.
phosphate
What type of muscle is the strongest? Why?
Pennate; fibers are packed more closely together
With a ____ degree angle of clination, there is a corresponding 13% loss of strength, but you can pack more muscle into the area.
30
The longer the muscle, the (more/less) force it can exert.
less
The longer the muscle, the (slower/faster) it can exert a certain force.
faster
_______ muscles have faster working velocity and longer working range.
fusiform
_______ muscles have a higher peak force and shorter working range.
pennate
At a whole body level, optimal joint angle is influenced by _____ ______.
muscle length
Biomechanically, what is impacting optimal muscle length?
muscle moment arm
Every muscle generates muscle force most optimally at 90 degrees. (T/F)
FALSE (every muscle has a joint angle at which muscle force generation is optimal)
What two things influence the joint angle at which muscle force generation is optimal?
- Actin-myosin overlap
2. Joint biomechanics
When assessing muscle strength clinically with manual muscle tests, one must use the _________ ______ for that muscle.
standardized position
Type __ fibers have high aerobic capacity, low force and slow contraction speed.
1
Type __ fibers have fast contraction speed, high force and rapid cross bridge turnover, and high anaerobic capacity,
2
The MN cell body is located in the ___ matter in the SC.
grey
Voltage dependent Na+ channels open when initial depolarization reaches ____mV and this leads to an influx of Na+ leading to further depolarization until ____mV.
-50; +40
Voltage-dependent K+ channels open when depolarization reaches ____mV, leading to efflux of K+ which leads to ________ of the cell membrane.
+40; repolarization
Ratio of muscle fibers per MF is generally related to a muscles _______ _____.
movement function
__________ ______ principle = the motor units are recruited in a graded manner, from small to large,.
henneman’s size
Recruitment occurs ______ the motor units.
across
_____ _____ = modulation of firing rate of a motor unit (frequency of motor unit discharge)
rate coding
As firing rate increases, ________ occurs (initial small twitch like contraction will build to produce a constant higher force contraction)
summation
How is force modulated?
input from sensory receptors
How does the fore generate from a muscle meet the needs of a task?
Can increase the number of activated fibers of increase firing rate.
