1. Topic 11.2 Movement
Bone and Muscle

2. Bones Bones and muscles work together to move the body
Bone and exoskeleton provide framework
Part
Function
Bones
Support body, attachment
Ligaments
Provide stability at joint; attach bone to bone
Tendons
Attach muscle to bone for movement
Nerves
Send impulses to muscles for relaxation & contraction

3. Skeletal muscle are antagonistic
Work in pairs
When one relaxes the other contracts
Example, biceps and triceps

4. Elbow Joint Joints are where two bones meet
Joints allow movement in different directions
Synovial joints: have synovial fluid to prevent friction
Elbow and knee are hinged synovial joint
Ball and socket joints (shoulder and hip)
Pivot joint (head)
Gliding joint (wrist)

5. Elbow joint

6. Parts & functions Structure Function Cartilage
Reduces friction and cushions ends of bones
Synovial fluid
Lubricates & prevents friction between ends of bones
Joint capsule
Seals the joint space & provides stability
Biceps
Flexor muscle, pulls the arm upward when contracted
Triceps
Extensor muscle pulls the arm downward when contracted
Humerus
Long upper arm bone
Radius
Shorter of the two bones in the forearm
Ulna
Longer of the two bones in the forearm

7. Muscle Types Three types of muscle tissue Skeletal or striated Cardiac
smooth

8. Skeletal muscle Composed of myofibrils (actin & myosin)
Arranged in unique ways for distinct functions
Sliding over each other
Basic unit of a muscle contraction is called a sarcomere

9. Each muscle cell can contain thousands of sarcomeres
Each sarcomere is made of a myofibril
Myofibril contains actin and myosin
Actin is the thin filament
Myosin is the thick filament

10. Stacked myofibrils are found within each cell surrounded by the muscle cell membrane called the sarcolemma
Contains T tubules (transverse)
Reach deep into the cell
Increase surface area of sarcolemma

11. Skeletal muscle can be very long so it is multinucleated
Also contain a special endoplasmic reticulum called the sarcoplasmic reticulum
Stores and releases calcium as needed to initiate a muscle contraction
Packed with mitochondria for energy

12. Sarcomere Functional unit of muscle cells
Composed of many repeating sarcomeres
Composed of sliding filaments
Part
Function
Z lines
Borders of the sarcomere
H zone
Region where only myosin is located
A band
Region where myosin overlaps with action (dark band)
I band
Regions where only actin is located (light band)

14. Contraction of skeletal Muscle
Initiated by and action potential from the nervous system
Steps are as follows:
1. action potential arrives at terminal button releasing a neurotransmitter (acetylcholine)
2. Neurotransmitter released into synapse
3. Neurotransmitter is attached to receptors on sodium gated channels on sarcolemma (depolarization)

15. 4. Action potential spreads through T-tubules of sarcolemma releasing calcium from sarcoplasmic reticulum
5. calcium attached to troponin (protein) causes tropomyosin to shift, exposing myosin binding sites
6. each myosin head binds an ATP and splits the ATP into ADP + Pi (inorganic phosphate) causing the myosin head to bend outwards
7. Each myosin head forms a cross-bridge with actin & releases the Pi. Release of Pi causes myosin heads to bend inward and slide the actin over the myosin (shortening sarcomere)

16. 8. Each myosin head binds a new ATP to break the cross-bridge
9. The cycle repeats until no more action potentials are sent and calcium is pumped back into the sarcoplasmic reticulum

17. Sliding filament Theory

18. Electron Micrograph of Skeletal Muscle