1. The Muscular System
Topic 1.2

2. 1.25 Identify the location of skeletal muscles in various regions of the body
Muscle man diagram
IB SEHS SL Topic 1.2

3. 1.2.1 Outline the general characteristics common to muscle tissue
Contractility – shortening of the muscle
Extensibility – stretching of the muscle
Elasticity – returning back to normal after being stretched or shortened
Atrophy – wasting of muscle
Hypertrophy – increase in muscle
Controlled by nerve stimuli
Fed by capillaries
IB SEHS SL Topic 1.2

4. Topic 1.2.2 Distinguish between the different types of muscle
Smooth – involuntary, spindle-shaped, single nucleus (e.g. intestines)
Cardiac – involuntary, striated cells, single nucleus (e.g. heart)
Skeletal – voluntary, striated cells, multiple nuclei (e.g. muscles attached to tendons)
All types are needed for physical activity, but cardiac and skeletal are often the primary focus for IB SEHS.
IB SEHS SL Topic 1.2

5. Topic 1.2.3 Annotate the structure of skeletal muscle
Epimysium: connective tissue capsule.
Perimysium: within the muscle tissue there is branching connective tissue called perimysium.
Endomysium: the muscle cells themselves are individually wrapped in endomysium.
Myofibril: the muscle cells are filled with cylindrical structures called myofibrils.
These contain the myofilaments whose action is responsible for the contraction of the myofibrils and therefore the muscle as a whole.
Solomon & Davis
IB SEHS SL Topic 1.2

6. 1.2.3 Annotate the structure of skeletal muscle
IB SEHS SL Topic 1.2

7. 1.2.3 Annotate the structure of skeletal muscle
There are 2 kinds of myofilaments:
(Thick and Thin)
Myosin: thick filaments
Actin: thin filaments
A unit of thick and thin filaments is known as a Sarcomere.
These structures hold the key to muscle contraction. Because of the staggered thin and thick filaments it has the effect as one might pull a rope towards oneself hand over hand.
Solomon & Davis
IB SEHS SL Topic 1.2

8. Actin-Myosin
IB SEHS SL Topic 1.2

9. 1.2.3 Annotate the structure of skeletal muscle
Look on page 259
IB SEHS SL Topic 1.2

10. 1.2.4 Define the terms origin and insertion of muscles
Origin: the attachment of a muscle tendon to a stationary bone
Insertion: the attachment of a muscle tendon to a moveable bone.
IB SEHS SL Topic 1.2

11. Review Topic 1.2
IB SEHS SL Topic 1.2