1. 11.2 MUSCLES
& MOVEMENT
IB BIOLOGY

2. MOVEMENT: THE HUMAN MACHINE
• Joints
• Bones
• Nerves
• Muscles
• Tendons
• Ligaments

4. THE ELBOW

5. THE ELBOW
• Biceps – bends the arm (flexor)
• Triceps – straightens the arm (extensor)
• Humerus – anchors muscle (muscle origin)
• Radius/Ulna – acts as forearm levers (muscle insertion)
• Radius acts as a lever for the biceps
• Ulna acts as a lever for the triceps
• Cartilage – allows easy movement (smooth
surface), absorbs shock and distributes load
• Synovial fluid – provides food, oxygen, and lubrication to
the cartilage
• Joint capsule – seals the joint space and provides passive
stability by limiting range of movement

6. KNEE JOINT VS HIP JOINT

7. KNEE JOINT VS HIP JOINT
Similarities:
-
Both are synovial joints
-
Both are involved in the movement of the leg
Differences:

8. MUSCLE STRUCTURE
sarcomeres < myofibrils < muscle fibers = MUSCLES
muscle fibers – long multinucleate cells
Within each muscle fiber are cylindrical structures called
myofibrils
Myofibrils consist of repeating units called
sarcomeres, which have light and dark bands

9. STRIATED MUSCLE FIBER

10. STRIATED MUSCLE FIBER
Sarcolemma – specialized plasma
membrane
Sarcoplasmic reticulum – specialized
endoplasmic reticulum designed for muscle
contraction (contains high Ca2+)
Myofibrils – tubular fibers divided into
sections called sarcomeres, and made up of
two different myofilaments (actin & myosin)
Mitochondria – large numbers in order to
produce enough ATP for muscle contraction

11. STRIATED MUSCLE FIBER

12. SARCOMERES

13. SARCOMERES

14. SARCOMERES
H zone – area only occupied by the thick
filaments (myosin)
I bands (light) – regions occupied by
only thin filaments (actin)
A bands (dark) - are the region occupied
by both filaments (overlap)
Z lines – represent the extremeties of a
single sarcomere

15. SARCOMERES
H zone – area only occupied by the thick
filaments (myosin)
I bands (light) – regions occupied by
only thin filaments (actin)
A bands (dark) - are the region occupied
by both filaments (overlap)
Z lines – represent the extremeties of a
single sarcomere

16. SARCOMERES
I band
A band
H-zone

17. SARCOMERES
H-zone
I band
A band
I band

18. SARCOMERE
CONTRACTION

19. SARCOMERE
CONTRACTION

20. SARCOMERE
CONTRACTION
What do you expect to happen to the:
H zone?
A band?
I band?

21. SARCOMERE
CONTRACTION

22. SARCOMERE
CONTRACTION

23. SARCOMERE
CONTRACTION
Four Stages of Cross Bridge Cycle
1) Cross Bridge Formation
2) Power Stroke
3) Cross Bridge Detachment
4) Reactivation of Myosin Head