Describe the physiological steps of muscle fiber contraction and relaxation in w

Question

Describe the physiological steps of muscle fiber contraction and relaxation in which ATP would be used as an energy source. Be very specific and use correct anatomic and/or physiologic terminology (3)

     Describe two anaerobic metabolic pathways that could be used by muscle fibers to create ATP. Use chemical equations if necessary to describe the substrates used to produce ATP, and state approximately how many ATP molecules are produced by this method. (2)

Describe one aerobic metabolic pathway that could be used by muscle fibers to create ATP. Briefly describe the pathway, and approximately how many molecules of ATP are produced. (1)

Explain which type(s) of metabolism above would be used by “fast twitch” muscle fibers, and which type(s) would be used by “slow twitch” fibers. (2) Describe a type of activity that would most likely use fast twitch fibers, and explain why you think this (2). Describe a type of activity that would most likely use slow twitch fibers, and explain why you think this (2). (12 points total)

Explanation / Answer

1.

Physiological steps of muscle fiber contraction are:

(a) A neurotransmitter signal ACh begins the process of muscle fiber contraction. This depolarizes the local membrane of the fiber as Na+ ions which triggers an action potential that spreads to the rest of the membranes.

(b) The rest of the membranes are depolarized and the release of Ca++ is triggered.

(c) Ca++ then initiates the process of muscle contraction which is sustained by the presence of ATP.

Physiological steps of muscle fiber relaxation are:

(a) Motor neurons signals the muscle fibers to initiate relaxation.

(b) Repolarization of Sacrolemma and the T-tubules which closes the voltage gated calcium channels.

(c) Ca++ is pumped back intot he SR which leads to the relaxation of muscle fiber.

2.

Two anaerobic metabolic pathways for ATP production by muscle fbers are:

(a) Creatine Phosphate method

In this method ADP along with Creatine phosphate is converted into ATP and Energy is released. In this process Creatine phosphokinase acts as a catalyst.

ADP + CP --------------> ATP + C + Energy

In this process only 1 ATP molecule is produced and energy is supplied for about 15 seconds.

(b) Glycolysis

In this process glucose is converted into Lactic Acid and ATP is released. This process occurs in the absence of O2 so it is an Anaerobic process.

Glucose + Pi + 2 ADP ----------> 2 Lactic Acid + 2 ATP + 2 H2O

In this process 2 molecules of ATP are released.

Aerobic pathway

In this pathway Glucose is broken down into CO2 , H2O and releases energy in the form of ATP. The process occurs in the Mitochondria

Glucose + 6 O2 ----------> 6 CO2 + 6 H2O + 38 ATP.

So, 1 molecule of glucose releases 38 molecules of ATP.

Fast twitch muscle fibers required energy in quick doses so they use ANAEROBIC METABOLISM like GLYCOLYSIS.

Slow twitch muscle fibers on the other hand use AEROBIC METABOLISM.

Maintenance of posture by tonic muscles is an activity of slow twitch muscle fibers.

Strength training and power training activities require fast twitch muscle fibers.

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