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The Human Muscular System
Transcript of The Human Muscular System
A motor unit is the combination of a motor neuron and the muscle cell it innervates.
A muscle will only contract when they reach a minimal level of intensity called the threshold stimulus.
Structure of Skeletal Muscle
3 Parts of Major Skeletal Muscle:
Made up of skeletal muscle cells and connective tissue
Extend from bone to bone with joint in between
Muscles attach to bone by tendons
Bursae - lubracation for muscles to slide over bones more easily
Types of Skeletal
1. Twitch - quick, jerky response
2. Tetanic - more sustained and steady
The Human Muscular System
3 major types of muscle tissue:
Functions of Skeletal Muscle
Once activated, each fiber will always respond "all or none."
Muscle Movements by Contractions
(moving away from midline)
(away from midline)
Effects of Muscles
Exercise improves muscle tone and posture
Heart and Lungs are more efficient
Too much? Too little?
Types of Skeletal Muscle
Effects of Exercise
Movements produced by contractions
3. Isotonic - produces movement
4. Isometric - increases tension
Cardiac-composes the bulk of the heart and helps it to pumps blood.
Smooth-forms blood vessel walls and hollow internal organs, helps pump liquids though these vessels and organs.
Skeletal-attaches to bone
4 Types of Disorders
1. Strain -Tearing of Muscle Fibers
2. Sprain -ligament damage
3. Cramps - Muscle Spasms
4. Crush Injuries - Trauma to Skeletal Muscle
5. Stress Induced Muscle Tension - Headaches or Backache
ie. Flu: Muscle pain and stiffness
Polio: (Viral infection of nerves controls muscle movement) - can lead to paralysis and death
Muscle replaced by fatty tissue
X-linked (mostly in boys)
Rapid progression of weakness and atrophy
Autoimmune Muscle Disease
Major and Microscopic
Muscle fibers grouped into bundles
Fiber contains thick and thin myofilaments
Basic functional unit is called a sarcomere
Sarcomere is seperated by dark bands (Z-lines)
Schub, T., & Buckley, L. (2013). Muscular Dystrophy, Duchenne
Patton, K., & Thibodeau, G. (2014). The Human Body
Mostly found in males
Mutation of dystrophin gene on band Xp21
Dystrophin is what protects and stabilizes muscle fibers
Without sufficient dystrophin:
variation of sizes and loss of muscle fibers
muscle is replaced with connective tissue
1 out of 3500 males born with DMD
Signs & Symptoms
Begin from ages 2-6
Symmetrical muscle atrophy
Begins proximally and progresses distal
Hard time with stairs
There is no cure
Treatments are to control symptoms
No actual meds
Glucocorticoid - stablize progression & function, put off wheel chair
Creatine - improve quality of health
Ankle plantar flexor
Walking halts ~ 12 years old
Death between 20-25
Acacia & Amy