Flashcards in CSCS Anatomy and Physiology Deck (37):
Name the connective tissues of the muscle from the muscle cell to the whole muscle
1. Endomysium (surrounds individual muscle cell)
2. Perimysium (surrounds the fasciculus-group of muscle cells)
3. Epimysium (surrounds the entire muscle)
What is the name of the fluid that is contained within a muscle cell?
Muscle cells are made up of hundreds of _____(1)_____, which are made up of contractile proteins known as _____(2)_____, of which there are two known as _____(3a)_____ and _____(3b)_____.
Which myofilament contains troponin and tropomyosin?
What is the functional unit of the muscle cell?
Sarcomere (this is also known as the contractile unit of the muscle cell)
The thin filaments are anchored to which part of the sarcomere?
Thin filament is another name for actin
Where in the sarcomere is myosin anchored to?
Myosin (also known as the thick filament) is anchored at the M bridge (which is the center of the H zone)
What area of the sarcomere ONLY contains actin filaments?
I - band
The H - zone corresponds with the presence of only which myofilament within a sarcomere?
Which are of the sarcomere is associated with the length of the myosin filaments?
A - band
Each actin filament is surrounded by _____(1)_____ myosin filaments, which itself is surrounded by ______(2)_____ actin filaments.
A sarcomere is the distance between two __________.
Z - lines
What is the definition of a motor unit?
A motor neuron (nerve) and all of the muscle fibers that it innervates.
How many motor nerves can a muscle be innervated by?
Only one. A motor nerve can innervate over a thousand muscle fibers but a fiber will only ever be innervated by one motor neuron.
Name the membrane of the muscle cell.
How does movement occur?
Force is generated in muscles by actin and myosin pulling on each other, force is transferred through levels of connective tissue to tendon, tendon pulls bone to move
What are the aspects of the myosin heads that allows for muscle contraction to occur?
1. Myosin head binds to actin allowing the myofilaments to pull across each other
2. Binds to ATP, making the energy molecule available for muscle contraction
3. Contains myosin ATP-ase, which hydrolyzes (breaks down) ATP, allowing for the use of the energy molecule for muscle contraction
Which protein on actin covers the binding site of the myosin head?
Tropomyosin, which is responsible for the inhibition of the actin-myosin binding site
Which protein is responsible for pulling tropomyosin off the binding site on actin?
Name the five steps involved in the sliding filament theory
Step 1: Resting phase
Step 2: Excitation-Contraction Coupling phase
Step 3: Contraction phase
Step 4: Recharge phase
Step 5: Relaxation phase
During which stage of the sliding filament theory is calcium stored in the sarcoplasmic reticulum?
Resting phase. During this phase there is little tension in the muscle due to very few myosin cross-bridges bound to actin
During the excitation-coupling phase, what actions occur to allow myosin to bind to actin
Calcium is released from the sarcoplasmic reticulum into the sarcoplasm and binds to troponin. Troponin shifts its position, pulling tropomyosin away from the actin active site and exposing it. The ATPase portion of the myosin head hydrolyzes ATP, thereby making energy available.
What two actions occur during the contraction stage of the sliding filament theory?
1. The head of the myosin tilts (powerstroke) and pulls on the actin molecule.
2. A new ATP binds to the emptied ATP binding site on the myosin head, causing the release of the actin-myosin bond.
What is the name of the stage of the sliding filament theory that is simply a repetition of the previous two stages?
What three items within the muscle must be continually available for measurable shortening of said muscle to occur?
What causes the muscle to move from the recharge phase to the relaxation phase?
The muscle is no longer activated via the motor neuron
What four actions occur during the relaxation stage of the sliding filament theory of muscle contraction?
1. Calcium is released from its binding site on troponin and taken back up into the sarcoplasmic reticulum.
2. Myosin is released from actin when the new ATP binds to the myosin head.
3. Troponin shifts back to resting position.
4. Tropomyosin shifts back to resting position, covering the active sites on actin.
What is the underlying determinant of how much force a muscle can produce?
The number of actin-myosin bonds
Which type of muscle contraction involves the Z-lines moving toward the center of the sarcomere?
Concentric contraction. This is a shortening of the muscle. During this type of contraction the H-zone and I-bands will shrink in length
What type of muscle contraction occurs when the I-bands increase in length?
Eccentric contraction. This involves the muscle lengthening. The H-zone will also increase in length during this type of muscle contraction
What is the definition of an isometric muscle action?
A contraction that involves myosin-actin binding, but no movement occurs. The sarcomere, I-bands and H-zone all remain unchanged in length.
During which type of muscle action does the external resistance exceed the internal force of the muscle?
An eccentric contraction. For a concentric contraction to occur, the muscle force must exceed the external resistance. During an isometric contraction, the muscle force and external resistance will be equal.
During what type of muscle action does the A-band remain the same length?
Any muscle action. The A-band is the area in which the myosin filament resides. As the length of the myosin filament never changes during any type of contraction, the A-band length will never change. Sorry, this is a trick question.
Define the two anatomical parts of the nervous system and how they are involved in movement.
The nervous system is divided into the central nervous system (brain and spinal cord) and peripheral nervous system (motor and sensory peripheral nerves). The CNS processes information coming from different regions of the body or from the external environment and sends out motor signals in response to the stimuli. The peripheral nervous system transmits these motor signals from the CNS to the muscles and sensory information from the body to the CNS.
Define the all-or-none principle
If a motor neuron fires, it activates all of the muscle fibers in the motor unit or none at all
Neurally, how does muscle action occur from the central nervous system to the muscle itself?
The central nervous system creates an action potential in the motor neuron, which then moves down the motor nerve to the neuromuscular junction. This action potential continues along the sarcolemma and into the sarcoplasmic reticulum through the transverse tubules, causing the release of calcium.