بسم الله الرّحمن الرّحيم

Skeletal Muscle Mechanics By: Dr. Khurram Irshad

OBJECTIVES To Learn Structure of Skeletal Muscle Structure of Skeletal Muscle How muscle length shortens during the process of contraction How muscle length shortens during the process of contraction

Muscle Physiology Contraction Specialists Helps to maintain Homeostasis

Classification - Types i. Skeletal Muscles 40% of body weight i. Smooth Muscle 10% of body weight i. Cardiac Muscles

Classification of Muscles i. Striated - Skeletal muscles - Cardiac Muscle ii. Unstraited - Smooth muscles

i. Voluntary muscles - Skeletal muscles (Innervated by somatic nerves) nerves) ii. Involuntary muscles - Smooth muscles - Cardiac muscles (Innervated by autonomic nerves)

Structure of Skeletal Muscle

Molecular Basis of Skeletal Muscle Contraction Sliding Filament Theory

Cross Bridge Activity Rise in intracellular calcium ion Concentration Triggers cross bridge activity

Cross Bridge Cycle

The Tubules and Sarcoplasmic Reticulum

Simple (Single) Muscle Twitch

Excitation-Contraction Coupling

Skeletal Muscle Mechanics Muscles can produce contraction/power of different grades by 1. The number of muscle fibers contracting within a muscle. 2. Tension developed by each contracting fiber.

The number of muscle fibers contracting within a muscle

Tension develop by each contracting fiber  Frequency of stimulation.  The length of fiber at the onset of contraction.  The extent of fatigue.  The thickness of fiber.

Frequency of stimulation

The length of fiber at the onset of contraction

Source of energy required for skeletal muscle contraction and relaxation ATP Sources : 1. Stored ATP (only limited stores are available) 2. Creatine Phosphate (CP) 3. Oxidative Phosphorylation 4. Glycolysis.

Fatigue “Inability of a muscle to maintain a continuous tension for a prolonged period of time” Causes: i. Muscle Fatigue: - Accumulation of lactic acid - Depletion of energy stores

ii.Central Fatigue: iii.Neuro Muscular Fatigue:

Types of Muscle Contraction There are two types of muscle contraction. 1. Isotonic

ii. Isometric

Types of Muscle Fibers - Slow-oxidative (type I) fibers - Fast-oxidative (type IIa) fibers - Fast-glycolytic (type IIb) fibers

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