Role of ATP ATP (provided by mitochondria) When a phosphate bond is broken off, this yields - energy plus leftover ADP ATP > ADP + P + ENERGY Energy supplies (in the order that they are used by the muscles) ATP (stored) – is quickly used (within about 5 seconds) Phosphorylation – using Creatine Phosphate (which is made by the body and stored within muscle) to supply a phosphate to the leftover ADP from the previous step. It is quickly used (within about 5 more seconds)

Glucose/Glycogen – stored form of glucose, in the liver. When broken down (glycolysis), it releases 2 ATP’s and 2 molecules of pyruvic acid. Anaerobic activity-pyruvic acids turns to lactic acid and contribute to fatigue and soreness in the muscles. Activity can only be sustained for about 60 seconds. Aerobic activity- pyruvic acids enter into the citric acid cycle (in the mitochondria), which leads to the production of 36 ATP’s Fat – provides the most energy, but is a last resort

O2 supply and cell respiration hemoglobin – pigment responsible for carrying O2 molecules in the blood and giving blood its color myoglobin – pigment in muscle, responsible for storing O2, gives muscle its color (dark meat in poultry and fish) lactic acid – a by-product of muscle activity (contributes to soreness, fatigue in muscles) - can be converted into glucose when combined with O2 - but O2 is not available during exercise b/c the body cannot metabolize it from the air fast enough - lactic acid accumulates in the muscles - must wait until after exercise (when O2 is available) to convert it into glucose this whole process is known as Oxygen Debt

Muscular Responses Twitch- Response of a single muscle fiber to the Ach released by a single action potential. Short delay following to Stimulus [Ach] Result from higher stimulus intensity Muscle Contraction Length -affects force of contraction Too stretched out= actin/myosin can’t reach and no contraction Too close [sarcomere compressed]= no more shortening

characteristics of two types of muscle fibers Type I (slow-twitch; oxidative; red) endurance activities found in muscles with high amounts of myoglobin (pigment that stores oxygen in the muscles) - makes the muscle appear a darker red color (dark meat in poultry) Rich in mitochondria Type II ( fast-twitch, glycolytic, white) quick, explosive, sprint-type activities not much myoglobin - makes the muscle appear a lighter color (white meat in poultry), fewer mitochondria Accumulate lactic acid

Thyroid gland [Endocrine] connection between different systems (endocrine - skeletal - muscular) of the body Thyroid gland [Endocrine] - produces calcitonin, which encourages movement of calcium from bloodstream into the bones [Skeletal] - if thyroid is overactive - too much calcium into the bones lowers blood calcium so that the muscles could potentially be deprived of calcium, which means they may not be able to contract properly [Muscular]