BIOL 1050H Lecture Notes - Lecture 3: Erector Spinae Muscles, Endoplasmic Reticulum, Skeletal Muscle
Muscles
Muscles
• Nearly half the body’s weight
• ~ 600 human skeletal muscles
• Muscle types:
• skeletal
• cardiac
• smooth
• Specialized for one purpose: transforming ATP into force/ motion
Functions of muscles
1. Movement (moving body; internal movements:
breathing (intercostals, diaphragm), circulation,
and digestion)
2. Stability (maintain posture by preventing
unwanted movements (e.g. erector spinae
muscles); stabilize joints (e.g. rotator cuff muscles
(SITS))
3. Control of body openings and passages (sphincters
are internal muscular rings that control movement
of food, blood, etc.)
4. Heat production (skeletal muscle produces as much as
85% of our body heat)
5. Glycemic control - Absorb and store glucose as
glycogen, helps regulate blood sugar
6. Communication (speech, writing, expressions)
Transverse tubules and sarcoplasmic reticulum
• T-tubules – invaginations of
the sarcolemma (cell
membrane)
• Sarcoplasmic reticulum (SR)
• Smooth ER forms a network
around each myfibril
• Ca++ stored here
• Membrane potential change in T-tubules trigger Ca++ release from SR
