1. 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)

2. 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

4. 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

5. 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

7. 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

9. 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]