types of muscle contractions; metabolism

isotonic contractions

contraction where skeletal muscle changes length, resulting in motion

isotonic concentric contraction

muscle tension > load (resistance); muscle shortens

isotonic eccentric contraction

muscle tension < load; muscle elongates

isometric contractions

contraction where skeletal muscle develops tension that never exceeds load; muscle does not change length

heavier the load,

the longer it takes for movement to begin (load and speed inverse)

tension must ____ the load before ____ can occur

exceed, shortening

elastic forces

tendons recoil after a contraction. helps return muscle fibers to resting length

opposing muscle contractions

contraction where opposing muscles return a muscle to resting length quickly. assisted by gravity

ATP

the only energy source used directly for muscle contraction

ATP is generated by…

• direct phosphorylation of ATP by creative phosphate (CP)

• anaerobic metabolism (glycolysis)

• aerobic metabolism (citric acid cycle and electron transport chain)

phosphorylation

the process of adding a phosphate group to another molecule. produces a high-energy bond

direct phosphorylation of ADP by CP

at rest, skeletal muscle fibers produce more ATP than needed. ATP transfer energy to creatine, creating creatine phosphate and creatine kinase

creatine phosphate (CP)

used to store energy and convert ADP back to ATP

creatine kinase (CK)

enzyme that catalyzes the conversion of ADP to ATP

glycolysis

anaerobic process in which glucose is broken down from glycogen stored in skeletal muscles. produces 2 ATP/glucose molecule and 2 pyruvate molecules. occurs in cytoplasm

glycogen

stored form of glucose; large branching network

aerobic metabolism

primary energy source of resting muscles. provides 95% of ATP in a resting cell

role of mitochondria in aerobic metabolism

skeletal muscles at rest metabolize fatty acids and store glycogen and CP. during moderate activity, muscles. uses oxygen and organic substances (pyruvate, fatty acids) to produce ATP. at peak activity, pyruvate produced via glycolysis turns into lactate

citric acid (tricarboxylic, krebs) cycle

complex pathway that produces many important intermediaries used in the next pathway

electron transport chain and oxidative phosphorylation

final steps of aerobic respiration to produce ATP

recovery period

the time required after exertion for muscles to return to normal

cori cycle

lactate removal and recycling.

1. lactate is transferred from muscles to liver

2. liver converts lactate to pyruvate

3. most pyruvate molecules are converted to glucose

4. glucose is used to rebuild glycogen reserves in muscle cells

oxygen debt (excess post exercise oxygen consumption- EPOC)

occurs after exercise or other exertion; breathing rate and depth are increased because body needs more oxygen than usual to normalize metabolic activties.

hormones that increase metabolic activities in skeletal muscle

growth hormone, testosterone, thyroid hormones, epinephrine