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Learn Human BodyExercise Physiology

Learn Human Body

Exercise Physiology

Energy systems of human body-

Physiology of Muscle -

Energy systems of human body-

Terms used in energy system

ATP -Adenosine Triphosphate: When a muscle fiber contrcts and exerts force,the energy used to drive the contraction comes primarily from a special substance in the cell known as ATP.It is a complex chemical compound formed with the energy released from food and stored in all cells, particularly muscles. Only from the energy released by the breakdown of this compound can the cells perform work. The breakdown of ATP produces energy and ADP.
PC -Phosphate-creatine: A chemical compound stored in muscle, which when broken down aids ADP to manufacture ATP, The combination of ADP and PC produces ATP.
LA - Lactic acid: a fatiguing metabolite of the lactic acid system resulting from the incomplete breakdown of glucose.
Aerobic - "means with oxygen." .The aerobic production of ATP occurs inside the mitochondria.
Anaerobic-"means without oxygen". The anaerobic production of ATP occurs outside the mitochondria, but inside the cell.

Energy Systems

• ATP-CP system-ATP stores in the muscle last for approximately 5-10 seconds and then another high energy source called PC begins to break down.PC has only one high-energy phosphate bond. The energy released from breakdown of PC is used to resynthesis ATP,which then break down to provide energy for exercise.ATP-CP system last for about 25-30 secs.To develop this energy system, sessions of 25 seconds of high intensity work at near peak velocity are required
• Anaerobic glycolysis (lactic acid) system-Once the CP stores are depleted the body resorts to stored glucose for ATP. The breakdown of glucose or glycogen in anaerobic conditions results in the production of lactic acid and hydrogen ions. The accumulation of hydrogen ions is the limiting factor causing fatigue in runs of 300 meters to 800 metres.This energy system lasts for approximately 1-2 minutes, until the accumulation of lactate and other metabolic (IONS) by-product causes fatigue. These activity include middle distance sprints like 400-600- and 800 meters runs.
• Oxygen (aerobic) system- The aerobic energy system utilizes proteins, fats and carbohydrate (glycogen) for resynthesising ATP, although protein is not a significant fuel source during most types of exercise. The carbohydrates, fat and small portion of protein is utilized by this energy system during exercise are completely metabolized, leaving only carbon dioxide (which is exhaled) and water as metabolic by products. This system requires 2-3 minutes to adjust to changing exercise intensity.

Physiology of Muscle -

Terms used in Muscle Physiology

Motor nerve - Nerve conducts impulse from the CNS to the peripheral signaling muscles to contract or relax.
Motor units - Motor units consist of motor nerve and all of the muscle fibers supplied by that nerve.
Muscle fiber - It is a single cell of muscle.
All or none principle - When the fibers of a motor unit are called on to contract, all of the muscle fibers in unit contract together with maximum force.
Muscle endurance - Ability of muscle to contract repeatedly against a resistance.
Neuromuscular junction - The site where the motor neuron and muscle fiber meet is the neuromuscular junction.
Sarcomere - Repeating unit of a muscle fiber.
Actin - Contractile (muscle) protein in myofibril (contractile protein in muscle fiber).It is also called thin filament.Actin contains two other proteins called troponin and tropomyosin.
Myosin - Contractile (muscle) protein in myofibril (contractile protein in muscle fiber).it is also called thick filament.

Sliding filament theory - ( Theory behind muscle contraction)

Skeletal Muscle Contraction -Muscle contraction involves several components that result in the shortening of sarcomeres, and the pulling of the muscle against its attachments.Role of Myosin and Actin ,Myosin consists of two twisted strands with globular cross-bridges projected outward along the strands.Actin is a globular protein with myosin binding sites; tropomysosin and troponin are two proteins associated with the surface of the actin filaments. According to the sliding filament theory of muscle contraction, the myosin crossbridge attaches to the binding site on the actin filament and bends, pulling on the actin filament; it then releases and attaches to the next binding site on the actin, pulling again.


Stimulus for Contraction

• The motor neuron must release the neurotransmitter acetylcholine from its synaptic vesicles into the synaptic cleft in order to initiate a muscle contraction.
• Protein receptors in the motor end plate detect the neurotransmitters, and a muscle impulse spreads over the surface of the sarcolemma and into the T tubules, where it reaches the sarcoplasmic reticulum.
• Upon receipt of the muscle impulse, the sarcoplasmic reticulum releases its stored calcium to the sarcoplasm of the muscle fiber.
• The high concentration of calcium in the sarcoplasm interacts with the troponin and tropomyosin molecules, which move aside, exposing the myosin binding sites on the actin filaments.
• Myosin cross-bridges now bind and pull on the actin filaments, causing the sarcomeres to shorten.
• After the nervous impulse has been received, acetylcholinesterase rapidly decomposes the acetylcholine.
• Then, calcium is returned to the sarcoplasmic reticulum, and the linkages between myosin and actin are broken.
• Energy Sources for Contraction -Energy for contraction comes from molecules of ATP. This chemical is in limited supply and so must often be regenerated