muscle contraction Flashcards
A muscle group is a single organ containing what?
Blodd vessels (one artery and at least one vein), nerves (motor neuron with branched axon ends at muscle fibers), adipose and connective tissue, bundles of muscle fibers (fasicle) and each fiber is a single cell.
What is present in a muscle cell, a.k.a, a muscle fiber?
Multinucleus, mitochondria, glycosome, myoglobin, myofibrils: (actin and myosin), sarcoplasmic reticulum.
Describe the myofibrils?
They are divided into repeating units of sarcomere. They contain two types of myofilaments proteins: the actin filaments (thin), myosin (thick).
What are the parts of a unit of sarcomere?
The M-line, the Z-line, the A band, the I band, the H-zone.
What is the M-line?
The M-line is the line where myosin are connected together.
What is the Z-line?
The line at one end of a sarcomere where actin are attached together.
What is the H-zone?
It is the area with myosin only.
What is the A-band?
It is the whole area where there is myosin.
What is the I band?
It is the area with actin only.
What is the first step of muscle contraction?
The depolarization in sarcolemma. An action potential is initiated and it travels through the sarcolemma into the T-tubules.
What is the second step of muscle contraction?
The depolarization in the T-tubules. It triggers the Ca++ release.
What is the third step of muscle contraction?
The Ca++ binds to troponin, proteins on actin. It moves the protein, and allows myosin to bind.
What are the fourth and fifth steps of muscle contraction?
It is the movement of the filaments. If a binding site is available on actin, activated myosin will bind to actin and release a Pi. Then, ADP released from myosin. Myosin head rotates and the actin filaments moves= contraction. ATP binds to the myosin head and the myosin detaches from the actin. ATP is hydrolysed into ADP and Pi, which activates the myosin. The contraction ends when Ca++ is pumped back into the SR.
