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Glycolysis is a series of reactions that occurs in the cytosol all cells. Glycolysis breaks ........... down into ...............and provides energy (ATP) for muscle contraction once immediate sources of energy are depleted.

glucose. 2 ATP


Glycolysis, or anaerobic catabolism, does not require



What happens to pyruvate if oxygen is abundant? What happens to pyruvate if oxygen is not abundant?

it will enter the mitochondria for oxidative catabolism. It will be converted into 2 lactic acid molecules.


Oxidative catabolism, or aerobic catabolism, requires oxygen directly. Oxidative catabolism allows for longer lasting muscle contractions because these reactions produce many more............. molecules than glycolysis.



Oxidative catabolism is the predominant energy source after .............. minute of contraction and provides nearly 100% of ATP after several minutes.



Some oxygen is supplied by the blood but the majority is bound to the oxygen- carrier .



When glucose levels are exhausted, what molecules can be catabolized to generate ATP?

fatty acids and amino acids


A ........... is the smallest unit of muscle contraction.

muscle twitch


What are the 3 phases of a twitch?

1. latent period:
2. contraction period:
3. relaxation period:


The ............ period begins at the onset of the latent period and ends at the beginning of the contraction period. During this time the muscle fiber is unable to respond to further stimuli.



Repeated stimulation of a fiber results in progressively greater tension production. Calcium ion levels remain elevated in the ............. as SR pumps cannot keep up with successive stimuli. Waves of contractions have additive effects known as ................ The tension produced depends on the frequency of motor neuron stimulation resulting in two possibilities: .............. or .............

cytosol, wave summation, unfused tetanus (roughly 80%), or fused tetanus (highest tension nearly 100%)


The length-tension relationship states that the optimal length of a sarcomere is about 100-120% of the natural length of the sarcomere. At this natural length a sarcomere can generate the greatest tension. The length of the sarcomere must be short enough to allow for a generous zone of overlap between thin and thick filaments. But the length of the sarcomere must be long enough for the thick filaments to pull the thin filaments toward the ........... line without running into the .............-discs.

m-line, z discs


What are two main classes of skeletal muscle fibers, and how are they classified?

1. Type 1: fibers are small diameter, slow-twitch fibers that contract slowly to produce less force for a longer period of time.
2. Type II fibers are large diameter, fast twitch fibers that fatigue quickly.


Compare the number of mitochondria, myoglobin and the blood supply in fast-twitch fibers to slow-twitch fibers

Slow-twitch fibers have low myosin ATPase activity, rely on oxidative catabolism and have large numbers of mitochondria, a well-developed blood supply, and myoglobin molecules; this gives them a characteristic "dark meat" red color.

Fast-twitch fibers have high myosin ATPase activity, less myoglobin, few mitochondria, white meat b/c less oxygenated blood.


What is a motor unit?

A single motor neuron and all the muscle fibers that it innervates


Motor units are considered either slow, composed of ............ fibers only; or fast, composed of .......... fibers only.. The number of fibers varies depending on the motor unit's function. Muscles requiring fine motor control have .......... motor units, and those requiring less control have .......... motor units.

type 1, type 2, small, large


As greater force is required more motor units must be stimulated, a process known as............



What is muscle tone? Why is muscle tone is vital?

A baseline level of involuntary activation of motor units. It stabilizes joints, maintains posture, generates heat, and ensures that muscles are ready to go when needed.


What are the 3 types of muscle contractions?

1. Isotonic concentric
2. Isotonic eccentric
3. Isometric


List the changes, primarily biochemical that result from endurance training.

able to better utilize fatty acids in ATP production, increased resistance to fatigue.


What is fatigue, and what causes it?

The inability to maintain a given level of intensity of a particular exercise. Caused by:
1.depletion of metabolites
2. decreased oxygen to muscle fibers.
3. accumulation of certain chemicals.
4. environmental conditions


What is EPOC and what causes it?

a mechanism that allows the body to recover from exercise-induced homeostatic imbalances. It's caused by the body's need to release heat, to restore cell's ion concentration, and restoration of blood pH


what are 3 functions of smooth muscle?

1. peristalis
2. formation of sphincters
3. regulation of flow


In smooth muscle cells, both thick and thin filaments are longer, and the thin filament lacks.......... Myosin heads are found along the entire length of the thick filament.



What two things do smooth muscle cells lack?

motor-end plates, and t-tubules


Smooth muscle cells respond to multiple stimuli including:

mechanical, hormonal, nervous system, and local pacemaker cell


Contraction of smooth muscle involves influx of extracellular calcium ions that bind to



the calcium ion and calmodulin complex activate an enzyme called?

myosin-light chain kinase (MLCK)


what is a latch state?

a state in which the smooth muscle cell maintains tension while consuming very little ATP


What are the 2 types of smooth muscle?

1. Single unit smooth muscle: found in all hollow organs.
2. Multi-unit smooth muscle cell: the more rare type, found in the uterus and eyes, made for precision