Human Physiology: Muscle Energy and Types

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Questions and Answers

What is the main energy system used during maximum intensity activities lasting no longer than 10 seconds?

Anaerobic glycolysis

Lactic acid system

Aerobic system

ATP/PC system (correct)

Which process helps in removing blood lactate during anaerobic activities?

Cori cycle (correct)

Glycogenolysis

Oxidative phosphorylation

Beta oxidation

What type of physical activities predominantly rely on the aerobic energy system?

400m sprints

Weightlifting

Long-distance running (correct)

100m sprints

Which of the following statements about the anaerobic glycolysis system is true?

It is used for high intensity activities lasting about 1 minute. Signup and view all the answers

What is formed when AMP is deaminated by AMP deaminase?

IMP and ammonia Signup and view all the answers

What is the primary function of muscle tissue?

To convert chemical energy into mechanical energy Signup and view all the answers

Which type of muscle is under voluntary control?

Skeletal muscle Signup and view all the answers

Which type of muscle fiber is characterized by a high capacity for ATP production via oxidative phosphorylation?

Both B and C Signup and view all the answers

Which of the following describes slow twitch (Type I) muscle fibers?

High resistance to fatigue and a red color due to myoglobin Signup and view all the answers

What structure surrounds the sarcoplasm of a muscle cell?

Sarcolemma Signup and view all the answers

Which of the following characteristics is true about fast twitch type IIb muscle fibers?

Low levels of myoglobin and few mitochondria Signup and view all the answers

What role does creatine phosphate play in muscle cells?

It assists in the quick regeneration of ATP during short bursts of activity Signup and view all the answers

Which type of muscle tissue is primarily responsible for involuntary movements?

Both B and C Signup and view all the answers

What is the main source of energy production during high-intensity activity?

Anaerobic glycolysis Signup and view all the answers

Which amino acids are involved in the synthesis of creatine?

Glycine and arginine Signup and view all the answers

What role does creatine kinase (CK) play in energy metabolism?

It converts creatine into phosphocreatine Signup and view all the answers

What happens to creatinine once it is formed in the body?

It is excreted in the urine Signup and view all the answers

Which CK isoenzyme is primarily found in the brain?

CK-BB Signup and view all the answers

How does the amount of creatinine excreted in urine relate to muscle mass?

It decreases with decreased muscle mass Signup and view all the answers

What substances react to form creatine phosphate?

Creatine and ADP Signup and view all the answers

During exercise, ATP is broken down into which metabolites?

ADP and AMP Signup and view all the answers

Study Notes

Creatine Metabolism, High Energy Phosphates, and Muscle Energy Supply

Creatine metabolism, high energy phosphates, and muscle's energy supply are interconnected.
Muscle is the primary biochemical transducer that converts chemical energy into mechanical energy.
Muscles maintain a constant supply of chemical energy, primarily ATP and creatine phosphate.
Neural control of muscles regulates speed, force of contraction, duration of activity, and return to original state.

Muscle Types

Muscles are categorized into smooth, skeletal, and cardiac.
Skeletal muscles (attached to bone for movement) are striated.
Cardiac muscles are striated, responsible for heart function.
Smooth muscles (lining digestive tract and blood vessels) are non-striated.
Skeletal muscles are under voluntary nervous control; smooth and cardiac muscles are involuntary.

Skeletal Muscle Structure

Skeletal muscle fibers run the length of muscles and are multinucleated.
These fibers contain numerous mitochondria for ATP production, crucial for muscle contraction and relaxation.
Muscle fibers consist of myofibrils arranged in parallel (sarcomeres).
Myofibrils are embedded in sarcoplasm (cytoplasm of fiber) and surrounded by sarcolemma (excitable plasma membrane).
Sarcoplasm contains glycogen, glycogenolysis enzymes, glycolytic enzymes, ATP, and creatine phosphate.

Skeletal Muscle Classification

Muscle fibers are classified as slow-twitch (Type I) or fast-twitch (Type II).
Slow-twitch fibers are rich in mitochondria and myoglobin (red color) and are highly oxidative (aerobic).
They contract slowly, sustain contractions, and resist fatigue, suitable for repeated low-intensity activities (jogging, walking).
Fast-twitch fibers (Type II) are further subdivided into Type IIa and Type IIb.
Type IIa fibers are intermediate, and faster contracting, and have high myoglobin content (red).
Type IIb fibers have few mitochondria and low myoglobin (white), rely primarily on anaerobic glycolysis (fast, but unsustainable), and fatigue quicker.
Fast-twitch fibers are used for short bursts of high-intensity activities (sprints, heavy weightlifting).

Creatine Synthesis

Creatine is not an essential nutrient, naturally produced in the human body from amino acids (glycine and arginine) or found in meat in the diet.
Creatine synthesis begins in the kidneys and is completed in the liver.
Glycine combines with arginine in the kidneys to form guanidinoacetate, which then travels to the liver.
In the liver, guanidinoacetate is methylated by S-adenosyl methionine to create creatine.
Creatine then travels in the bloodstream to tissues (brain, heart, skeletal muscle).
Creatine reacts with ATP to form creatine phosphate.
The reaction is catalyzed by creatine phosphokinase (CK) and is reversible, enabling cells to use creatine phosphate to regenerate ATP.
The amount of phosphocreatine is proportional to muscle mass.

Creatine Kinase (CK)

CK is necessary for converting creatine to phosphocreatine.
Different CK isoenzymes (CK-MM, CK-MB, CK-BB) are located in various tissues.
CK levels are clinically important; increased levels indicate damage or injury in skeletal muscle or heart tissue (e.g., crush injuries, myocardial infarction).

Creatinine Metabolism

Creatine phosphate is unstable, spontaneously converting to creatinine.
Creatinine cannot be further metabolized and is excreted in urine.
Daily creatinine excretion is constant, directly related to muscle mass.
Decreased muscle mass (e.g., muscular dystrophy, paralysis) leads to lower creatinine excretion.
Kidneys play a key role in creatinine metabolism. Damaged kidneys cause creatinine to build up in the blood. (Serum creatinine is used to assess kidney health).

ATP Metabolites

During exercise, ATP is broken down to ADP.
Some ADP is reconverted to ATP through adenylate kinase reaction forming ATP and AMP (AMP is an auxiliary source of energy).
AMP is further broken down to IMP and ammonia.
AMP can also be dephosphorylated into adenosine, which acts as vasodilator increasing blood supply to the muscle.

Energy Systems

The body uses various energy systems (ATP-PC, anaerobic glycolysis, aerobic) depending on the activity's intensity and duration.
ATP-PC is predominant during short-duration, high-intensity exercises (e.g., sprints).
Anaerobic glycolysis (lactic acid system) is the primary supplier of energy for short-term, high-intensity activities (e.g., 400 m sprint).
Aerobic energy system provides energy for longer-duration, low-to-moderate intensity activities (e.g., endurance activities).

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Description

Explore the intricacies of muscle energy supply and metabolism in this quiz. Learn about the various muscle types, including skeletal, cardiac, and smooth muscles, and their physiological roles. Test your knowledge on how chemical energy is converted into mechanical energy and the structure of skeletal muscles.