Action potentials are propagated from the surface to the interior of a muscle fiber by way of
the T tubules
The triads of a muscle fiber consist of
two terminal cisternae and a T tubule
In a relaxed muscle fiber, the active sites of actin are blocked by
Each end of a sarcomere is marked by
a Z disc
When there is not enough oxygen to create ATP by aerobic respiration, a muscle fiber can produce ATP by borrowing phosphate groups from
Which of the following is considered to be a regulatory protein of the myofilaments?
Chicken legs have dark meat because of an abundance of oxygen storage pigment in their fibers. The pigment is called _____ and the fibers are _____.
myoglobin; slow twitch
Which of these processes occurs during the contraction of skeletal muscle?
Z discs move closer together.
Oxygen debt is the amount of extra oxygen needed after an exercise to do all of the following except
lower the metabolic rate to a resting level.
Which of the following is not found in the thin filaments of striated muscle?
In contrast to red muscle fibers, white fibers
fatigue more quickly
The loss of muscle mass from disuse is called
Posture is maintained mainly by ___ fibers because they fatigue _____.
Endurance training favors all of the following changes in the skeletal muscles except
less reliance on fat as an energy source
A motor unit is
one nerve fiber and all the muscle fibers innervated by it
If a poison inhibits the activity of acetylcholinesterase, a muscle
may be unable to relax
The fibrous tissue that surrounds each muscle cell or fiber is called ____ and its function is to endomysium; insulate adjacent muscle cells from one another
You are working out with weights and after a while you notice that your muscles are becoming larger. This can be best explained because
muscle cells enlarged because of increased number of myofibrils
In skeletal muscle fibers, the elastic filaments are called _____ and their function is to
titin; return the muscle cell to its resting length after contraction
In a resting muscle or nerve cell, there are excess _____ ions in the extracellular fluid and excess _____ ions in the intracellular fluid.
The resting potential across the sarcolemma of a skeletal muscle cell is about _____ millivolts (mV)
In an action potential, the _____ voltage regulated gates open first followed by the ____ voltage regulated gates opening
A molecule of ATP is needed twice for each complete cycle of a power stroke. ATP is needed to
release the low-energy myosin head and hydrolyze ATP to form the high-energy myosin head.
As a muscle relaxes, calcium moves back into the sarcoplasmic reticulum by a process called
primary active transport
The amount of force produced by a muscle is proportional to all of the following factors except one. Identify the exception.
resting sarcomere length
In a resting muscle, most of the ATP generated by aerobic respiration comes from
In your quadriceps femoris, which is a powerful muscle group that extends the knee, you have the following proportion of slow-twitch and fast-twitch fibers: 85% slow-twitch and 15% fast-twitch. You most likely perform best at
running long-distance events
The movement of your fingers is controlled by muscles which have a greater proportion of
fast glycolytic fibers with small motor units
You are examining a cross-sectional slide of a muscle, and you noticed the following characteristics in most of the muscle fibers: smaller diameter, abundant mitochondria, abundant myoglobin, and low levels of glycogen reserves. This muscle is predominantly made up of fibers that are
type I and slow oxidative
Lifting a box off the floor unto a table is called a _____ contraction of your biceps brachii while lowering the box onto the floor is called a _____ contraction of your biceps brachii.
Which of the following supports the sliding filament theory of muscle contraction
The distance between the Z lines decreases during contraction.
In skeletal muscle, groups of muscle cells are called _____ and are surrounded by a connective tissue sheath called the ______.