1. Structural Overview

2.  excitability - responds to stimuli (e.g., nervous impulses)  contractility - able to shorten in length  extensibility - stretches when pulled  elasticity - tends to return to original shape & length after contraction or extension

3.  motion  maintenance of posture  heat production

4.  skeletal: ◦ attached to bones & moves skeleton ◦ also called striated muscle (because of its appearance under the microscope) ◦ voluntary muscle  Smooth: ◦ involuntary muscle ◦ muscle of the viscera (e.g., in walls of blood vessels, intestine, & other 'hollow' structures and organs in the body)  cardiac: ◦ muscle of the heart ◦ involuntary

6.  Skeletal muscles -> tendons (connective tissue)  Epimysium - Ensheaths the entire muscle  Skeletal muscles ->numerous subunits or bundles called fasicles (or fascicles).Skeletal muscles  Perimysium – Connective tissue surrounding Fascicles  Endomysium – Ensheath muscle cells.  Muscle cells -> Consist of many fibrils (or myofibrils).  Myofibrils – Composed of myofilaments.  Myofilaments – Thick & Thin myofilaments

9.  SARCOLEMMA has holes.  Holes -> TRANSVERSE TUBULES (or T- TUBULES)  T-Tubules -> Muscle cell and go around the MYOFIBRILS.  T-Tubules - DO NOT open into the interior of the muscle cell.  Function of T-TUBULES -> Conducts impulses from the surface down to Sarcoplasmic Reticulum.

10.  SR - like ER, hollow  Primary Function – Store Calcium Ions  Associated with the MYOFIBRILS  Ca "pumps" (active transport) for calcium so that calcium is constantly being "pumped" into the SR from the cytoplasm.  Relaxed muscle - high concentration of Ca in SR/ Low in Sarcoplasm  Impulse travels along the membrane of the SR, the calcium "gates" open &, therefore, calcium diffuses rapidly out of the SR & into the sarcoplasm where the myofibrils & myofilaments are located.  Key step in muscle contraction.

11. http://people.eku.edu/ritchisong/RITCHISO/30 1notes3.htm