1. Muscular System

2. Intro to Muscles Nearly half our weight comes from muscle tissue
There are 650 different muscles in the human body

3. Three Main Functions Responsible for body movement
Responsible for body form and shape (posture)
Responsible for body heat and maintaining body temperature

4. 4 Characteristics of a Muscle
CONTRACTILITY – the capability or quality of shrinking or contracting
EXCITEABILITY– the ability to respond to certain stimuli by producing impulses
EXTENSIBILITY – the ability to be stretched.
ELASTICITY – ability of muscle to return to its original length when relaxing.

5. Types of Muscle
Skeletal – striated, voluntary, multinucleated, long and run parallel to eachother, found on bones
Smooth – non-striated, involuntary, single nucleus, tapered, found in many organs, contract using peristalsis
Cardiac – striated, involuntary, 1-2 nuclei, long and branched, found in heart, contain intercalated discs, rhythmic contractions
The word “striated” means striped. Skeletal muscle appears striped under a microscope.

6. Muscles and Muscle Fiber Structure
Individual muscles are separated by FASCIA, which also forms tendons
**Tendonitis – inflammation of the tendons
Muscle fibers (cells) are arranged in bundles called FASCICLES

7. EPIMYSIUM = outermost layer, surrounds entire muscle.
PERIMYSIUM = separates and surrounds fascicles (bundles of muscle fibers)
ENDOMYSIUM = surrounds each individual muscle fiber
This model of the muscles uses straws to represent fibers.
Green = endomysium Yellow = perimysium Blue = epimysium

8. Muscle Layers

9. Epimysium
Perimysium
Endomysium

10. It is important to remember the hierarchy
ACTIN (light)
FASCICLES
MUSCLE FIBERS
MYOFIBRILS
FILAMENTS
MUSCLE
MYOSIN (dark)
Wrapped in EPIMYSIUM
Wrapped in PERIMYSIUM
Wrapped in ENDOMYSIUM

11. Muscles / Cells Sarcolemma = muscle fiber membrane
Sarcoplasm = inner material surrounding fibrils  (like cytoplasm)
Myofibrils  = individual threads within muscle fiber made of myofilaments

12. Nucleus
Sarcolemma
Mitochondrion
Sarcoplasm
Myofibril

13. Myofibrils are made of
MYOSIN = thick filaments
ACTIN = thin filaments

14. Myofilaments ACTIN (thin) and MYOSIN (thick)
  form dark and light bands
A band = dArk • thick (myosin)
I band = lIght • thIn (actin)

16. Z-line – the borders that separate and link adjacent sarcomeres
H-zone – region where only myosin is found and actin does not overlap
A-band – the dark striations
I – band – light striations

17. SLIDING FILAMENT THEORY (MODEL) - theory of how muscle contracts
This occurs as the thin filament (actin) slides past the thick filaments (myosin)

18. Explanation of Skeletal Muscle and Sliding Filament Theory
Start at 1:40

19. How Muscles Work with the Nervous System
NEUROMUSCULAR JUNCTION - where a nerve and muscle fiber come together

20. Neuromuscular Junction
Synaptic cleft – the gap between the motor neuron and the muscle fiber
Synaptic vesicles – where NEUROTRANSMITTERS are stored before being released into the synaptic cleft

21. Motor neurons stimulate muscle fibers to contract
Motor neuron secretes neurotransmitter known as ACETYLCHOLINE
One motor neuron connected to muscle fibers make up a motor unit

22. Energy Source
-ATP is produced by CELLULAR RESPIRATION; occurs in the MITOCHONDRIA

23. Other Terms 1. All-or-None Response 2. Motor Unit 3. Recruitment
4. Muscular Hypertrophy
5. Muscular Atrophy
6. Muscle Cramp
7. Origin & Insertion
8. Hernia
9. Ligaments vs. Tendons
10. Strain vs. Sprain

24. 2. Motor Unit The muscle fiber + the motor neuron
1. All-or-None Response
Fibers do not contract partially, they either do or don't
2. Motor Unit
The muscle fiber  +   the motor neuron 

25. 4. Hypertrophy - muscles enlarge (working out or certain disorders)
3. Recruitment
More fibers contract as the intensity of stimulus increases
4. Hypertrophy  - muscles enlarge  (working out or certain disorders)
5. Atrophy - muscles become small and weak due to disuse
Cardiomyopathy

26. 6. Muscle Cramp - a sustained involuntary contraction
7. Origin and Insertion
Origin = the immovable end of the muscle
Insertion = the movable end of the muscle

27. 9. Hernia – protrusion of an organ or tissue through a weak muscle or opening 11. Ligaments vs. Tendons Ligaments – bone to bone Tendons – muscle to bone

28. 10. Strain vs. Sprain
Strain – tear in muscles/tendons from excessive use
Sprain – tear in ligaments

29. Treatments (R.I.C.E.)
Rest
Ice
Compression
Elevation