Tishk International University

Course Name: physiology

TOPIC: Muscle

Instructor: Dr. Ayad Sameen

Muscle Function

• Skeletal muscles are responsible for all locomotion• Cardiac muscle is responsible for coursing the blood

through the body• Smooth muscle helps maintain blood pressure, and

squeezes or propels substances (i.e., food, feces)through organs

• Muscles also maintain posture, stabilize joints, andgenerate heat

Types of Muscles

Motor Unit: The Nerve-Muscle

Contraction of Sarcomere

MUSCLE PHYSIOLOGYSKELETAL MUSCLESummary of Contraction Sequence

• AP get to end of axon • ACh released at neuromuscular junction • ACh diffuse across gap • Nicotinic ACh receptor at end-plates

react with ACh• Muscle cell membrane depolarized • AP travel along muscle cell membrane • T tubule depolarization, travel to sarcoplasmic

reticulum Ca++ release into cytoplasm

MUSCLE PHYSIOLOGY

SKELETAL MUSCLESummary of Contraction Sequence (cont)• Ca++ binds to troponin-tropomyosin• Myosin heads bind to actin • Myosin-ATPase activated • Cross-bridges attach & detach • Myosin & actin slide past each other• Sarcoplasmic reticulum pumps Ca++

back into lumen• Ca++ removed from tropin-tropomyosin `

complex & actin-myosin interaction inhihited

Thanks