ENERGY FOR MUSCLES

Question 1

What happens when muscles cannot produce enough oxygen to produce ATP?

Answer 1

• they hit the anaerobic, or lactic acid threshold

Question 2

What happens in the anaerobic reactions?

Answer 2

• glycolysis breaks down to yield pyruvic acids, which would normally enter the citric acid cycle
• however, when the oxygen level is low, the pyruvic acid reacts to produce lactic acid
• the lactic acid enter the blood stream and proceeds to the liver
• the liver converts the lactic acid to glucose

Question 2

What happens in the anaerobic reactions?

Answer 2

• glycolysis breaks down to yield pyruvic acids, which would normally enter the citric acid cycle
• however, when the oxygen level is low, the pyruvic acid reacts to produce lactic acid
• the lactic acid enter the blood stream and proceeds to the liver

Question 3

What happens to lactic acid within the body?

Answer 3

• it disassociate to lactate ion (lactate) and hydrogen ion

- both these leave the muscle cells by facilitated diffusion

Question 4

What happens when lactic acid accumulates?

Answer 4

• oxygen debt builds up

Question 5

What is oxygen debt?

Answer 5

• oxygen debt includes the amount of oxygen cells require to convert the accumulated lactic acid to glucose, as well as the sufficient amount of ATP and creatine phosphate to restore original concentrations
• oxygen debt also reflects the restoration of oxygen to blood and tissue oxygen levels to pre-exercise levels

Question 6

How does exercise change the metabolic capacity of oxygen?

Answer 6

• high intensity exercise will learn to synthesized more glycolysis for ATP, and will synthesize more glycolytic enzymes as it’s capacity for glycolysis increases
• stimulates capillaries to extend into muscles, supplying more nutrients to the muscle fibers
• also adds to the mitochondria, which split and enlarged to increase their abundance

Question 7

What is muscle fatigue?

Answer 7

• a muscle exercised for a long time may lose its ability to contract, which is called “fatigue”
• is caused by decreased blood flow, imbalances in the sarcolemma from repeated stimulation, and psychological loss of the desire to continue activity

Question 8

What is a cramp?

Answer 8

• a sustained, painful, involuntary muscle contraction

Question 9

How does muscle tissue contribute to body heat?

Answer 9

• it makes up so much mass in the body that it is a source of heat
• less than half of the energy released in cellular respiration is transferred to ATP; the rest becomes heat
• blood transports the heat from muscle contraction throughout the rest of the body to maintain body temperature

Question 10

What is a threshold stimulus?

Answer 10

• when an action potential reaches an all-or-nothing point that sends an impulse throughout the muscle fiber that releases enough calcium ions from the SR to activate cross-bridge formation and contraction
• a general action potential conducted down a motor neuron releases enough ACh to bring the muscle fiber to threshold and generates an impulse

Question 11

What is the contractile response of a single muscle fiber to single impulse called?

Answer 11

• a twitch
• defined by a period of contraction, during which the fiber pulls at its attachments
• followed by a period of relaxation, during which the pulling force declines

Question 12

What is a latent period?

Answer 12

• time between the application of a stimulus and the beginning of a response in a muscle fiber

Question 13

Define summation

Answer 13

increased force of contraction by a skeletal muscle when a twitch occurs before the previous twitch relaxes

Question 14

Define tetany

Answer 14

continuous, forceful skeletal muscle contraction with little or no relaxation

Question 15

What is a motor unit?

Answer 15

• a motor neuron and the muscle fibers it controls constitute a motor unit
• the fewer muscle fibers in a motor unit means more precise movement (the eyes, produces very slight but precise movement)
• larger motor units include many muscle fibers that are larger scale

Question 16

What is recruitment in relation to motor units?

Answer 16

• increase in number of motor units taking part in a contraction
• if only the easily stimulated motor neurons are involved, fewer motor units will take part in contraction
• at higher intensities of stimulation, more motor units are activated

Question 17

What is multiple motor unit summation?

Answer 17

• the number of activated motor units involved in responding to a stimuli

Question 18

How does sustained contraction work?

Answer 18

• during sustained contractions smaller motor units, whose neurons have smaller-diameter axons, are more easily stimulated and recruited first
• larger motor units, whose axons are larger in diameter, respond later and with greater force
• summation and recruitment together can produce a sustained contraction of increasing strength

Question 19

Define muscle tone

Answer 19

• is a state of slight or partial contraction that is present in muscles at all times
• lack of muscle tone can result in loss of consciousness!

Question 20

What happens in isometric contraction?

Answer 20

• the force generated is not sufficient to move the load, and as a result the length of the muscle doesn’t change

Question 21

What happens in isotonic contraction?

Answer 21

• the force of the contraction is greater than the load, and the muscle shortens (concentric contraction)
• if the strength of the isotonic contraction is less than the load, the muscle lengthens (eccentric contraction)