Unit-III Muscular System

Muscular System The muscular system is the anatomical system of a species that allows it to move. The muscular system makes up nearly half the weight of the human body, this is why when we train we sometimes put on weight instead of losing it. We put on muscle weight.

Muscular System Functions 1. Body movement (Locomotion) 2. Maintenance of posture 3. Respiration 4. Communication (Verbal and Facial) 5. Constriction of organs and vessels 6. Heart beat 7. Production of body heat

Muscles Muscles are all made of the same material, a type of elastic tissue (sort of like the material in a rubber band). Thousands, or even tens of thousands, of small fibers make up each muscle.

Types of Muscle 1. Skeletal Muscle 2. Smooth Muscle 3. Cardiac Muscle

Skeletal muscles 1. Attached to bones 2. Makes up 40% of body weight 3. Responsible for locomotion, facial expressions, posture, respiratory movements, other types of body movement 4. Voluntary in action; controlled by somatic motor neurons

Skeletal muscle

Structure of Skeletal muscle

 Skeletal muscle attached to bones via strong bands of connective tissue called tendons.  Skeletal muscle is organised into bundles of muscle cells or fibres. that are held together by a sheath of connective tissue.

Structure of Skeletal muscle  Each muscle fibre is a single cell with many nuclei. Around each cell is plasma membrane called the sarcolemma which contains sarcoplasm (cytoplasm).  Each cell/fibre is comprised of many smaller myofibrils arranged lengthwise.

Smooth Muscle

Smooth Muscles 1. In the walls of hollow organs, blood vessels, eye, glands, uterus, skin. 2. Some functions: propel urine, mix food in digestive tract, dilating/constricting pupils, regulating blood flow, in some locations, autorhythmic. 3. Controlled involuntarily by endocrine and autonomic nervous systems.

Structure of Smooth Muscles 1. Smooth muscle fibers have a fusiform shape and, like striated muscle, can tense and relax. 2. However, smooth muscle containing tissue tend to demonstrate greater elasticity and function within a larger length-tension curve than striated muscle.

Smooth Muscles This ability to stretch and still maintain contractility is important in organs like the intestines and urinary bladder. In the relaxed state, each cell is spindle- shaped, micrometers in length.

Cardiac Muscles 1. Heart: major source of movement of blood 2. Autorhythmic 3. Controlled involuntarily by endocrine and autonomic nervous systems

Structure of Cardiac Muscles Cardiac muscle is dense and packed tightly. The muscle fibers are striated and branched and have intercalated discs.

Muscle Fiber A cylindrical, multinucleate cell composed of numerous myofibrils that contracts when stimulated.

Types of Muscle Fiber Muscle Fiber Fast Twitch Muscle Fiber Slow Twitch Muscle Fiber

Types of Muscle Fiber Fast/White Twitch Muscle Fiber Fast twitch fibers, as the name suggests, contract more quickly than slow twitch muscle fibers and, as a result, they produce more power and strength. Fast/White Twitch Muscle Fiber Fast twitch fibers, as the name suggests, contract more quickly than slow twitch muscle fibers and, as a result, they produce more power and strength. Slow/Red Twitch Muscle Fiber Slow twitch fibers, as the name suggests, contract more slowly than fast twitch muscle fibers and they can contract for a longer period of time. Slow/Red Twitch Muscle Fiber Slow twitch fibers, as the name suggests, contract more slowly than fast twitch muscle fibers and they can contract for a longer period of time.

Muscle Fiber

Characteristics Of Muscle Tissue Excitability: capacity of muscle to respond to a stimulus. Contractility: ability of a muscle to shorten and generate pulling force. Extensibility: muscle can be stretched back to its original length. Elasticity: ability of muscle to recoil to original resting length after stretched.