Human Physiology-Muscle

What are the four functions of muscle?

movement, stability, control body openings/passages, heat generation, and glycemic control 

Movement (muscle function) 

externally visible, internal movements (propulsion of digestive tract and expulsion of urine), and important roles in communication (speech, writing, etc.) 

Stability (muscle function)

prevent unwanted movement (posture and holding bones/joints in place)

Control body (muscle function)

Sphincter muscles (control admission of light to eye, movement of materials in body, blood movement/waste elimination)

Heat generation (muscle function) 

Body heat (enzyme function and metabolism) 

Glycemic Control (muscle function)

Aids regulation of blood glucose, absorbs, stores, uses glucose (old age —→ decreased muscle mass/function—→ increase risk of type 2 diabetes)

All muscle cells have the following characteristics to function: 

Excitability

-Excitability: stimulated - chemical signals, stretch etc., electrical changes across plasma membrane

-Conductivity: local electrical stimulation initiates waves of excitation that travel to muscle fiber —→contraction

-Contractility: shortens when stimulated—→ movement 

-Extensibility: capable of being stretched between contraction 

-Elasticity: return to its original rest length after being stretched 

Muscular Tissue and Cells

Skeletal, cardiac, smooth

Muscular System

Refers only to skeletal

Specialized for one major purpose (chemical energy —→ ATP—→ mechanical energy of motion)

Skeletal Muscle Fibers 

-Voluntary

-Striated (alternating light and dark bands —> overlapping arrangements of internal boss) 

-Usually attached to one or more bones 

-Multiple nuclei 

-Cell type-muscle fiber (myofiber) 

Gross Anatomy: Tubes within Tubes

-myofilaments (thick-myosin, thin-actin)

-myofibrils

-muscle fiber (myofiber) —→ plasma membrane: sarcolemma + endomyosin (CT)

-Bundled into: muscle fascicles (perimysium (CT)) and muscle (epimysium (CT))