1. Muscular System

2. List of muscles to know is posted in canvas.

3. Muscle Facts
The average human heart will beat 3,000 million times in its lifetime and pump 48 million gallons of blood.
Muscle is about 15% more dense than fat.
The tongue consists of 8 different muscles.
The masseter is the strongest muscle in the human body. It can exert as much as 975lb of force.
The human heart creates enough pressure when it pumps blood, that it could squirt blood 30 feet.
The smallest muscle in the body is the stapedius attached to the stapes in the ear.
It takes the interaction of 72 different muscles to produce human speech.

5. Function of Muscles to pull against bones to produce movement.
to maintain posture
to stabilize joints
to generate heat (mitochondria)
to pump blood through the body (heart muscle).

6. Types of Muscle Skeletal – striated & voluntary Smooth – involuntary
Cardiac – heart & involuntary
The word “striated” means striped. Skeletal muscle appears striped under a microscope.

7. Origin and Insertion
The origin of a muscle is a fixed bone for attachment.
The insertion is the bone that the muscle moves when it contracts.
The biceps and triceps are antagonistic muscles.

8. Gross Anatomy of a Muscle: Bundles
1. Actin & myosin myofilaments are bundled into myofibrils
2. Individual myofibrils (muscle cells) are bundled together into fibers.
3. Muscle fibers are bundled into fasicles
4. Fasicles are bundled into the whole muscle.

9. Linear view of muscle bundling…
Whole Muscle myofibril
Fasicle myofilaments
Muscle Fiber

10. Gross Anatomy Skeletal Muscle

11. Muscle Layers

12. Myofibrils are made of myofilaments
ACTIN = thin filaments (light bands)
MYOSIN = thick filaments (dark bands)

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

14. There are rules to muscle contractions…
Threshold stimulus: motor neuron releases enough acetylcholine into synaptic cleft to reach threshold
All-or-None Response: individual muscle fibers (and all the myofibrils within) will contract when stimulated.
Recruitment: more and more fibers contract as the intensity of the stimulus increases. (stimulus is acetylcholine) more stim=heavier object

15. Actin & myosin contractile units are called sarcomeres.
Contraction of
sarcomeres
contracts
muscle as
a whole.

16. When a muscle contracts the Z-line (sarcomere) shortens
When a muscle contracts the Z-line (sarcomere) shortens This is called the Sliding filament theory

18. Actin & Myosin Contraction Animation

19. As is the case with any body system…
Issues can arise!
-hypertrophy
-atrophy
-tetanus
-muscle cramp
-muscle fatigue
-oxygen debt

20. Hypertrophy - muscles enlarge (working out or certain disorders)
Atrophy - muscles become small and weak due to disuse

21. What is tetanus?
Tetanus causes cholinosterase to not break down the acetylcholine in the synapse.  This results in a person's muscles contracting and not relaxing.
A tetanus shot must be administered shortly after exposure to the  bacteria.
Once you develop tetanus, there is no cure.

22. Muscle Fatigue -  muscle loses ability to contract after prolonged exercise or strain
Muscle Cramp  -  a sustained involuntary contraction
Oxygen Debt  -  oxygen is used to create ATP, -- not have enough oxygen  causes Lactic Acid to accumulate in the muscles → Soreness

23. What is rigor mortis?
A few hours after a person or animal dies, the joints of the body stiffen and become locked in place. This stiffening is called rigor mortis. Depending on temperature and other conditions, rigor mortis lasts approximately 72 hours. The phenomenon is caused by the skeletal muscles partially contracting. The muscles are unable to relax, so the joints become fixed in place.

24. Body Worlds

25. Body Worlds

26. Body Worlds

27. Body Worlds

28. Body Worlds

29. Body Worlds