Chapter 9 Muscles

Creatine Phosphate

An energy storage molecule used by muscle tissue. The phosphate from creatine phosphate can be removed and attached to an ADP to generate ATP quickly.,

Maximal Stimulus

the strongest stimulus that produces increased contractile force; represents the point at which all the muscles motor units are recruited,

Myoglobin

"An oxygen-storing, pigmented protein in muscle cells. red pigment",

Special Characteristics of Muscles

"Excitability, Contractility, Extensibility, Elasticity",

Slow Oxidative Fibers

"Generally thinner, good blood supply, higher myoglobin content. Fatigue resistant. Important for long distance/duration exercise. Marathon runners 80%",

Fast Glycolytic Fibers

"Important for short-term intense, powerful movements. Prefer anaerobic glycolysis.",

Distinguish between unfused tetanus and fused tetanus

"Unfused tetanus-""the relaxation time between successive twitches will get shorter as the strength of contraction increases in amplitude."" On the other hand,Fused tetanus-""Smooth, sustained muscle contraction.""",

Muscle Twitch

"a single momentary muscle contraction, and is the response to a single stimulus.",

Fast Oxidative Fibers

"contract fast, moderate fatigue resistance; intermed. power (walking, sprinting) 60% sprinters",

small motor unit

"for fine motor control (hand, fingers, eye)",

Wave Summation

"if a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs",

Complete Tetanus

"if stimulation frequency is high enough, muscles never BEGIN to relax: continuous contraction",

Unfused Tetanus

"if the stimulus strength is held constant and the muscle is stimulated at an increasingly faster rate, the relaxation time between the twitches become shorter and shorter, the concentration of Ca2+ in the cytosol higher and higher, and the degree of wave sumation greater and greater, progressing to a sustained but quivering contraction",

Isotonic Contractions

"muscle length changes and moves the load, the tension remains relatively constant through the rest of the contractile period; come in two flavors concentric and eccentric",

Aerobic Respiration

"occurs in mitochondria, requires oxygen, involves sequence of chemical reactions, 95% of ATP used for muscle activity",

Latent Period

"the first few milliseconds following stimulation when excitation-contraction coupling is occuring; during this period, muscle tension is beginning to increase",

Refractory Period

(neurology) the time after a neuron fires or a muscle fiber contracts during which a stimulus will not evoke a response,

Muscle Tension

Force exerted on an object by contracting or lengthening muscle,

Lactic Acid

Produced in muscle cells from the reduction of pyruvate (under anaerobic conditions) to regenerate NAD+ so that glycolysis can continue. A rise in lactic acid usually accompanies an increase in physical activity.,

Threshold Stimulus

The minimal strength required to cause a contraction: 55 mv,

Incomplete Tetanus

______is repeated stimulation of the muscle so that the muscle is never allowed to completely relax. will yield increased tension,

Glycolysis

a metabolic process that breaks down carbohydrates and sugars through a series of reactions to either pyruvic acid or lactic acid and release energy for the body in the form of ATP,

Motor Unit

a motor neuron and all the muscle cells it stimulates,

Subthreshold Stimuli

action potentials may be reached when these summate and reach threshold,

Recruitment

an increase in the number of motor units being activated,

Temporal summation

cumulative effect as a result of repeated synaptic stimulation within a brief time,

Creatine Kinase

enzyme makes creatine phosphate + ADP into ATP,

Isometric Contractions

muscular contraction that increases tension but does not produce movement.,

large motor unit

occur in weight-bearing muscles,

Anaerobic Glycolysis

the overall process in which pyruvic acid generated during glycolysis is converted to lactic acid,

fused Tetanus

when stimulus frequency is so high that no muscle relaxation takes place between stimuli,

Anaerobic

without oxygen,

What is the difference between Isotonic and Isometric Contraction?

• In isotonic contraction, the tension is constant while the length of the muscle varies. In isometric contraction, the muscle length remains constant while the tension varies. • Isotonic twitch has a shorter latent period, shorter contraction period, and a longer relaxation period. In contrast, isotonic twitch has a longer latent period, longer contraction period, and a shorter relaxation period. • Temperature rise decreases isometric tension whereas it increases isotonic twitch shortening. • The releasing heat of isometric contraction is less and, therefore, isometric contraction is more energy efficient, whereas that of isotonic contraction is more and, therefore, is less energy efficient. • During isometric contraction, no shortening occurs and, therefore, no external work is done, but during isotonic contraction, shortening occurs and external work is done. • Isotonic contraction occurs in the middle of a contraction while isometric contraction occurs at the beginning and end of all contractions. • During the muscle contractions, isometric phase increases when load increases whereas isotonic phase decreases when load increases.