Flashcards in Skeletal Muscle Contraction (Lecture 4) Deck (69)
Fill in the Blank:
_______is made up of multiple fascicles?
Muscle is made up of multiple fascicles.
True or False:
The connective tissue surrounding individual fascicle is called the perimysium.
What is a fascicle made up of?
A bundle of myofibers.
What is the connective tissue covering that is around each myofiber?
What is another name for the cell membrane of a muscle fiber?
What is another name for an individual multinucleated muscle cell?
Myofiber (= muscle cell)
What is a myofibril?
A chain of sarcomeres within a myofiber.
What is a myofilament?
Actin and myosin filaments that make up a sarcomere.
How many T-tubules are there per sarcolemma?
2 per sarcomere
What is a t-tubule and what structure does it lie close to?
T-tubule is an invagination of the sarcolemma and it lies close to the cisternae of the sarcoplasmic reticulum.
What band is replaced by the M-line at full muscle contraction?
What two bands have a width that changes with muscle contraction?
H Band and I Band
What band is entirely composed of actin, entirely composed of myosin, and which is composed of both actin and myosin?
I Band --> composed entirely of actin
A Band --> composed of actin and myosin
H Band --> composed entirely of myosin
Which band length does not change during muscle contraction?
What is the main function of the Z discs?
To anchor the actin filaments at both ends of the sarcomere.
Which molecule is the thick filament and which is the thin filament?
Thin Filament --> actin
Thick Filament --> myosin
What type of receptor is the dihydropyridine (DHP) receptor?
Voltage-sensitive L-type calcium channel
Where is the dihydropyridine (DHP) receptor primarily located?
DHP receptor is located on the sarcolemma t-tubules.
What does the DHP receptor do to the ryanodine receptor?
Causes a conformational change in the ryanodine receptor.
Does a large or small amount of calcium flow in to the cytosol through DHP receptors?
NO, a minute amount of calcium flows into the cytosol through the DHP receptor.
What is the epimysium?
The connective tissue surrounding the entire muscle.
What are the two types of muscle contraction?
Isometric and Isotonic
What are the two different forms of isotonic muscle contraction?
Eccentric and concentric
*eccentric --> contraction occurs when the muscle lengthens
*concentric --> contraction occurs when the muscle shortens
What is the difference between isometric and isotonic muscle contraction?
*Isometric contraction -> occurs when there is an increase in tension but not in length (cross-bridges are still formed and that is what builds tension, but no muscle length change).
*Isotonic contraction -> the muscle length changes. Either it shortens (concentric) or lengthens (eccentric.
What determines the myofiber type of a muscle?
The innervating neuron.
What are the two types of myofibers?
*Dark, slow fibers (red fibers)
*Light, fast fibers (white fibers)
How are fiber types classified, mainly?
On endurance (resistance or fatigue) and speed of contraction.
What are the four characteristics that fast (white; light) fibers?
1) fewer mitochondria
2) little myoglobin
3) larger concentration of ATPase
4) primarily use anaerobic respiration resulting in a buildup of pyruvic and lactic acids (glycolysis)
Fill in the blank:
____twitch fibers contract rapidly but have less endurance.