1. MUSCULAR SYSTEM
Human Systems

2. Main Understanding
Describe in general, the action of actin and myosin in muscle contraction and heat production.

3. Introductory video Watch up to 2:20
Up to 2:20 to introduce the types of muscles

4. THREE (3) TYPES OF MUSCLE TISSUE
Smooth: Have 1 nucleus; Arranged in parallel lines; Contract involuntarily; Found in certain blood vessels, iris of the eye, digestive system (intestines); Does not fatigue easily
Cardiac: Cells are tubular and striated (bands of light and dark); Contraction is involuntary; Does not fatigue
Skeletal: Tubular and striated; Contraction is voluntary; Are very long; Have many nuclei because it needs a lot of energy and materials

5. Three Types of muscle Smooth: found in stomach, airways, blood vessels
Helps with involuntary functions moving fluids and material by contracting and relaxing
Not striated:
not striped

6. Three types of muscle 2. Cardiac muscle: heart muscle
Involuntary: pumps blood through your heart
Striated: striped muscle

7. Three types of muscle
3. Skeletal Muscle: the muscles used for movement
Mainly voluntary
Usually attached to bones and create movement by relaxing and contracting
Striated: has stripes

8. FUNCTIONS OF SKELETAL MUSCLES
Support – allow us to stand and remain upright
Move bones – allow us to move and have facial expression
Help maintain body temp – release large amounts of heat
Help protect organs and stabilize joints

9. COOPERATION OF SKELETAL MUSCLE
When muscles contract they shorten
They can ONLY pull
Because of this muscles must work together to bend joints (work in pairs - antagonistic muscles )
Example: bicep and tricep
Figure 10.2 pg 333

10. Skeletal muscle: Myofibrils
made of tiny parallel threads called myofibrils

11. MyoFibrils: Made of Sarcomeres
Myofibrils are made of repeating contractile units called sarcomeres

13. Muscle ↓
Muscle-fibre bundle
Muscle fibre
Myofibrils
Myofilaments

14. Video
Watch from 3:57- 4:36.

16. Sarcomeres
Made of two myofilaments (strands of protein): actin and myosin
Thin filaments: made of actin
Thick filaments: made of myosin
Sarcomeres separated by Z-lines

17. Video
Watch from 4:36- 5:12

18. Muscle Contraction in a sarcomere
Sliding filament theory: when muscle contraction occurs the myosin slides past the actin
Two body guards that prevent myosin attaching to actin: troponin and tropomyosin.
Step one:
Brain stimulates the muscle, releasing calcium
Calcium attaches to troponin which moves tropomyosin.
Frees up a space where myosin can attach

19. MUSCLE CONTRACTIONS Involve the actions of two types of myofilaments
Actin myofilament
Thin
Have two strands of actin molecules that wrap around each other

20. 10X longer than actin and a different shape
Myosin filament
Thick
Two strands of protein molecules wound around each other
10X longer than actin and a different shape

21. We will watch from 6:40- 9:15.
6:40- 9:15

22. Step Two: ATP binds to the myosin head,
ATP breaks down into ADP + Pi. The myosin head is in an extended position like a stretched spring

23. Step Three:
Myosin binds to actin and pulls, shrinking the sarcomere and contracting the muscle. This pulling is called a powerstroke
ADP +Pi are released

24. Step Four: A new ATP binds to the myosin head attached to the actin
The myosin is released from the actin

25. Cycle Repeats with Calcium Present
The ATP then breaks down into ADP + Pi allowing the myosin head to again become extended.
With calcium present, it can then reattach to actin and contract again

26. HOW MYOFILAMENTS CONTRACT
heads of myosin move first
are attached to actin myofilaments
bends back and inward pulling the actin myofilament
Requires ATP to work
sliding filament model

27. ROLE OF CALCIUM
at rest myosin heads are not bound to actin - blocked by tropomyosin
calcium is needed to move the tropomyosin
Calcium and troponin bind to make a complex which binds to tropomyosin, moving it out of the way

28. MUSCLES AND HEALTH Atrophy occurs when muscles are not used
reduction in size, tone and power
can be permanent
Hypertrophy
increase in size of muscle fibers
number of mitochondria increase
through exercise
improve strength endurance

29. Why do we shiver?
Muscles involuntarily contract in response to a cold core body temperature
Not very efficient
Part of the ATP is released as heat