Act 15: Vertebrates Muscular System

• Vertebrate muscle is made up of three muscle cells (myocytes): smooth, cardiac, skeletal.
• Smooth myocytes - fusiform, uninucleate cells found as part of lining of viscera.
• Cardiac myocytes - striated branching cylindrical cells w/ 1-2 nuclei and found in the heart
• Skeletal - unbranching striated cylindrical cells w/ multinucleations.
• Intercalated disc - gaps between cardiac muscle and responsible for pumping heart.
• Skeletal muscle attached at two ends of bone: origin and insertion.
• Origin - fixed point
• Insertion - mobile point
• When skeletal muscle moves, an action is oroduced.
• Closely positioned muscles are ANTAGONISTIC.
• Flexor - contraction of muscle
• Extensor - opposite muscle of flexor
• Levator - raises
• Depressor - lowers
• Abductor - drags part away from axis
• Adductor - moves part towards the axis
• Constrictor/sphincter - closes opening
• dilator - enlarges/ widens opening
• Some muscles can also be synergistic (teamwork)
• Mylohyoid - muscle that raises the floor of mouth when breathing and swallowing
• Subhyoid - lowers the floor of the mouth