MUSCLE ENERGETICS

Frank starling Law Greater the initial length of the Sarcomere, Greater will be the Force of Contraction

LENGTH-TENSION Diagram (Frank-Starling Law) Greater the initial length of the Sarcomere, Greater will be the Force of Contraction Z Z M A X I U

Energy Sources & metabolism in skeletal Muscles ATP- (Immediate source) Phosphocreatinine Anaerobic glycolysis Aerobic Glycolysis

Muscle Contraction In muscular system contraction means muscle fibers generating tension with the help motor neurons and while under tension the muscle may shorten ,lengthen or remain the same.

Muscle tension: The force exerted on an object by a muscle is known as muscle tension Muscle Load: The force exerted on the muscle by an object is the muscle load.

Characteristics of Whole Muscle Contraction . Isotonic. Length changes but Tension remains constant. Two Forms of Isotonic Cont. 1. Concentric (Muscle shortens while lifting the weight) 2. Eccentric ( while putting the weight back, the muscle lengthens) Or walking down hill Types of Contraction

Types of Contraction Isometric. Tension is increased but Length remains constant. .e.g Isometric Contraction in the heart

Isometric versus Isotonic contraction Latent period is longer in isotonic contraction as compared to isometric contraction

Characteristics of Whole Muscle Contraction Simple Muscle Twitch; Comprised of 3 phases: Latent Period. Contraction Phase Relaxation phase

Isometric Contractions for different Types of muscles

Treppe (Stair-Case Phenomenon) When a series of maximal stimuli are delivered to Skeletal muscle just below the tetanizing frequency, the tension developed by each Twitch increases (Second stimulus elicits a stronger response) Perhaps due to increase in intracellular Ca2+.

TETANIZING FREQUENCY How many times you are stimulating the nerve fiber per second to obtain full tetanization. 10-15 stimuli/sec

SUMMATION The adding together of individual twitch contractions to increase the intensity of overall muscle contraction is called summation. Multiple fiber summation Frequency summation----Tetanization

Motor Unit Single Motor Neuron & all Muscle Fibers it innervates constitute a single Motor Unit. α- motor N

Some Diseases related to Muscles

MUSCLE FATIGUE Prolonged and strong contraction of a muscle leads to muscle fatigue. Characteristics of Fatigued muscle 1.Decreased shortening velocity 2. Slower rate of relaxation

Onset and rate of development of Fatigue include 1. Type of skeletal muscle fiber that is active. 2. Intensity and duration of contraction. 3. Degree of individual fitness.

TYPES OF FATIGUE High frequency fatigue Includes high frequency short duration exercise e.g weight lifting. Low frequency fatigue Includes low intensity long duration exercise e.g long distance running. Central command fatigue

Causes of high frequency fatigue Conductive fatigue Lactic acid build up Inhibition of cross bridge cycling. Causes of low frequency fatigue Decreased muscle glycogen low blood glucose Dehydration Junctional fatigue

Central command fatigue Appropriate regions of cerebral cortex fail to send excitatory signals to the motor neurons.

Fatigue results mainly from inability of the contractile and metabolic processes of the muscle fiber to continue supplying the same work output.