Muscular System Types of Muscle Tissue 40 of
- Slides: 18
Muscular System
Types of Muscle Tissue • • 40% of the mass of human body is muscle 1. skeletal muscle – attached to bones Voluntary movements Have striations (striated muscle) Consciously controlled by CNS Large, many nuclei, 1 mm-30 cm Long and slender (muscle fibers)
Types of Muscle Tissue • 2. Smooth Muscle – not under voluntary control • Spindle shaped, 1 nuclei, no striations • Stomach, blood vessels, intestines • Function without nervous stimulation
Types of Muscle Tissue • 3. Cardiac Muscle – found in heart • Striated, one nuclei (can have two) • Not under direct control of the CNS
Muscle Contraction • Muscle fibers → myofibrils → filaments
Muscle Contraction • Striations are alternating thick and thin filaments. • Thick are called myosin. • Thin are called actin. • Arranged in units called sarcomeres • Separated by regions called Z lines
Muscle Contraction • Contracts when the think filaments slide over the thick filaments. • http: //www. youtube. com/watch? v=z. Qocs. LRm 7_ A • 1. Myosin attaches to actin forming cross-bridge • 2. ATP causes the myosin cross bridge to change shape and pulls actin towards the center • 3. The cross bridge is broken and the myosin binds to another site on the actin, and the cycle begins again.
Control of Muscle Contraction • Impulses from motor neurons control the contraction of skeletal muscles fibers. • Motor neurons and skeletal muscles come into contact at a place called a neuromuscular junction.
Control of Muscle Contraction • Neuron releases a neurotransmitter called acetylcholine. • Acetylcholine diffuses across synapse and produces an impulse in the muscle fiber which will release calcium ions. • Actin and myosis will now interact. • Takes only a millisecond for this to happen
Control of Muscle Contraction • Muscle will remain contracted until acetylcholine stops being released and is destroyed.
How Muscles and Bones Interact • Muscles only pull in one direction • Muscles are joined to bone by tendons. • Most skeletal muscles work in opposing pairs. When one muscle contracts, the other relaxes. • Biceps contract, triceps relax.