Muscles

Functions All body movements Moves bones Pumps blood Move food through digestive system Air movement

Types of Muscle Tissue 1) Skeletal Muscles Responsible for voluntary movements Skeletal movements Striated (alternating light and dark bands)

Skeletal Muscle, cont’d Muscle Fibers Myofibrils Actin (thin filaments) & Myosin (thick filaments)

Skeletal Muscle

Types of Muscle Tissue 2) Smooth Muscle Involuntary Found in intestines and blood vessels Move food through intestines through peristalsis peristalsis

Types of Muscle Tissue 3) Cardiac Muscle Involuntary Striated w/centrally located nuclei Found in Heart Never gets tired

Muscle Contraction Thin filaments (Actin) in the muscle fiber slide over the thick filaments (Myosin) to contract the muscle Muscle fibers contracting Cardiac muscle contracting

Cardiac Muscle How would you characterize this muscle? The nuclei are centrally located, striations are present, and there is branching of the muscle fibers. Several intercalated discs are indicated by the white arrow heads. In Virtual Microscopy, look in the upper left corner of the section to find longitudinally cut fibers.

Skeletal Muscle How would you characterize this muscle? The nuclei are peripheral, striations are present, and there is no branching of the muscle fibers. Even when you cannot visualize striations, the peripherally placed nuclei allow you to differentiate skeletal muscle from both cardiac and smooth muscle.

Smooth Muscle How would you characterize this muscle? The nuclei are centrally located, there are no striations, and the muscle fibers do not branch. Another good clue that this is smooth muscle is that when smooth muscle contracts, the nuclei take on a corkscrew appearance.

Muscle Tone Skeletal muscles remain in a state of partial contraction Responsible for keeping head upright, and your back and legs straight

Antagonistic Relationship Skeletal muscles work in opposing pairs When one muscle contracts, the other relaxes Example of antagonistic relationship: biceps/triceps Example of antagonistic relationship: biceps/triceps

Interesting Facts Muscles make up about 40% of a male’s weight and about 35% if you are female The largest muscle in your body is the gluteus maximus Muscular strength reaches its peak between the ages of 20 and 30

Cellulite