Skeletal muscle contraction Flashcards
A muscle is made up of what?
Made up of multiple fassicles
What is perimysium?
Connective tissue surrounding an individual fascicle.
What is Endomysium?
The delicate connective tissue around each myofiber.
What is a fascicle?
A bundle of myofibers
What is the Sarcolemma (Plasmalemma)?
The cell membrane of a muscle fiber
What is a myofiber (muscle cell)?
An individual multi-nucleated muscle cell
What is a myofibril?
A chain of sarcomeres within a myofiber
What is a myofilament?
The actin and myosin filaments that make up a sarcomere. These are the contractile fibers.
List the characteristics of fast twitch muscle fibers.
These are WHITE fibers
- Contract rapidly and have less endurance
-Few mitochondria
Primarily use anaerobic respiration, resulting in the buildup of pyruvic and lactic acids
- Little myoglobin
- Large concentration of ATPase
List the characteristics of slow twitch fibers.
These are RED fibers.
- contract slowly, but have lots of endurance (fatigue resistant)
- lots of mitochondria
- Primarily use aerobic respiration
- Lots of myoglobin (reason why they are red)
- Small concentration of ATPase
What is the function of ATPase?
Cleave the phosphate groups from ATP
What is a motor unit?
A neuron (single nerve cell) and all of the myofibers it innervates
Which of the following terms refers to a chain of sarcomeres?
A. Muscle.
B. Myofiber
C. Myofibril
D. Myofilament
C. Myofibril
Which of the following sarcomeric bands does not undergo a change in length during concentration of skeletal muscle?
A. A-band
B. H-band
C. I-band
D. J-band
A. A-band
Which of the following sarcomeric bands is composed completely of actin filaments?
A. A-band
B. H-band
C. I-band
D. J-band
C. I-band
Dihyropyridine (DHP) channels are part of which of the following structures?
A. Sarcoplasmic reticulum
B. Plasmalemma
C. T-tubules
D. Z-discs
C. T-tubules
Ryanodine-sensitive calcium ion release channels are part of which of following structures?
A. Sarcoplasmic Reticulum
B. Plasmalemma
C. T-tubules
D. Z-discs
A. Sarcoplasmic Reticulum
Which of the following represents the facto by which the concentration of calcium ions increases in the cytosol after the release from the sarcoplasmic reticulum?
A. 10
B. 50
C. 100
D. 1000
C. 100
Which of the following maintains an optimum calcium concentration gradient to facilitate return of calcium to the SR?
A. Calsequestrin
B. SERCA
C. DHP
D. Ryanodine
A. Calsequestrin
Fast twitch fibers have which of the following characteristics?
A. They are reddish in color compared to slow twitch fibers
B. They have more mitochondria than slow twitch fibers
C. They have more myoglobin than slow twitch fibers
D. They are more fatiguable than slow twitch fibers
D. They are more fatiguable than slow twitch fibers
Which of the following represents an example of an eccentric contraction?
A. The triceps muscle during the throwing of a ball
B. The triceps muscle while raising the body from the floor during a push
C. The triceps muscle while lowering the body to the floor during a push-up
D. The biceps muscle while raising the body during a pull-up
C. The triceps muscle while lowering the body to the floor during a push-up
What is motor unit recruitment?
The activation of additional motor units to accomplish an increase in contractile strength in a muscle.
What is summation?
The adding together of individual twitch contractions to increase the intensity of over muscle contraction.
What is multiple fiber summation?
Summation by increasing the number of motor units contracting simultaneously.
What is frequency summation?
Summation by increasing the frequency of contraction.
Why does tetany/ tetanization occur?
Tetany/ tetanization occurs because enough calcium ions are maintained in the muscle sarcoplasm, even between action potentials, so that the full contractile state is sustained without allowing any relaxation between the action potentials. Occurs during frequency summation
Isometric contraction
Contraction in which the muscle does not shorten. Usually results form an increase in tension
Isotonic contraction
contraction in which the muscle shortens against a fixed load (constant tension).
Eccentric
Isotonic contraction which occurs when the muscle lengthens
Concentric contraction
Isotonic contraction which occurs when the muscle shortens.
List the 3 ways that ATP is used during a muscle contraction. Which one requires the most ATP utilization?
- sliding filament mechanism
- Pumping calcium ions from the sarcoplasm back into the SR
- Pumping sodium (Na+) and potassium (K+) ions through the sarcolemma to reestablish the resting potential
The sliding filament uses most of the ATP during muscle contractions
what is epimysium?
Connective tissue surrounding entire muscle
What are T-tubules?
> invaginations of the sarcolemma
> lie close to the cisternae of sarcoplasmic reticulum
> forms triads with cisternae
> two per sarcomere
What is the sarcoplasmic reticulum?
> endoplasmic reticulum of the muscle cell
Z discs?
> anchor actin filaments
> located at each end of a sarcomere
I bands?
> composed entirely of actin
> width changes during contraction
A bands?
> composed of actin AND myosin
> width does not change during contraction
H bands
> composed entirely of myosin
> width changes during contraction
During contraction, Actin filaments do what?
> form the I bands which become narrower in width
