Chapter 6 : The Muscular System – Introductory
Worksheet
Intro:
1. Approximately what percent of a 120 pound person is skeletal muscle? 42%
A) Muscle Tissue
1. What is another name for a muscle cell? Muscle
Fiber
2. What are the three different names given to the type of muscle tissue that attaches to bones? a) Skeletal b) Voluntary c) Striated
3. For the three different types of muscle tissues, fill in the correct spaces in the table below.

Muscle
Type
Location and Function
A Cardiac HEART – Branched striated fibers connected with intercalated discs to allow them to beat in unison
B Skeletal SKELETON – Long multinucleated cylindrical cells with striations that contract to move joints
C Smooth Short tapered non-striated fibers that slowly contract to change the diameter of blood vessels and gut organ shapes
3. In the diagram above identify and label the nuclei, striations and intercalated disks when present. (use a ruler and write names of those structures)

4. What term is given for the shortening of muscle cells?
CONTRACTION

B) Structure of Skeletal Muscle
5. What name is given to the strong fibrous connective tissue that connect muscles to bones?
TENDONS
6. What are the two points of attachment of a muscle called, and describe the location of each site in comparison with the two bones and the joint.
The tendons that fasten onto the more stationary bone is called the ORIGIN.
The other attached tendon onto the more mobile bone is called the
INSERTION. These tendons are generally found on the opposite sides of a joint.
7. Use the word bank to correctly label the diagram below.

1.
SCAPULA
A\\\
2. TRICEP ORIGIN
3. PROXIMAL
TRICEP TENDON
4.TRICEPS MUSCLE
BODY
5. DISTAL
TRICEP TENDON
6. TRICEP
INSERTION on ULNA
7. HINGE JOINT
8. ULNA
9. Biceps Origin
10. Ball + Socket
11. PROXIMAL BICEP
TENDON
12. HUMERUS
13. BICEP MUSCLE
BODY
14. Distal Bicep Tendon
15. BICEP INSERTION
16. RADIUS
- Humerus
- Radius
- Ulna
WORD BANK
- Triceps Muscle Body
- Distal Tricep Tendon
- Distal Bicep Tendon
- Proximal Tricep Tendon - Tricep Origin
- Scapula - Tricep Insertion
- Hinge Joint
- Proximal Bicep Tendon
- Bicep Origin
- Bicep Insertion
- Biceps Muscle Body
- Ball and Socket Joint
8. Describe the structure and function of a bursa. A
Small fluid-filled sac that lies between bones and the tendons that rides over those bones. They act to cushion and reduce friction around the tendon.

9. Use the glossary in the back of the book (pp 529

) to define the following terms:
A) Actin: The contractile protein found in the THIN myofilaments of skeletal muscle
B) Myosin : The contractile protein found in the
THICK myofilaments of skeletal muscle
C) Sarcomere: Contractile unit of muscle; length of a myofibril between to Z-Lines.
D) Myofilament: Ultramicroscopic thread-like structures found in myofibrils .
10. Label the diagram below.
1.
Sarcomere
2.
Actin
3.
Myosin
4.
Z-Line

11. A muscle is made up of many contractile cells called muscle fibers. Use the diagram below to study the microscopic anatomy of a muscle. Use the picture to answer the following questions? a) What is a muscle bundle? A bundle is a bundle of muscle fibers that are wrapped up with perimysium.
Many bundles run together to form the Muscle Body. b) What is the difference between a muscle fiber and a myofibril? A muscle fiber is a muscle cell, myofibrils consists of 100’s of arranged packages of myosin and actin.
c) What happens to the amount of overlapping between the bands of myosin and actin as a muscle contracts?
As the myosin pulls actin under its arms, the amount of overlap increases.

12. What element must be present to form the bridges between actin and myosin? CALCIUM (Ca ++)
C) Function Of Skeletal Muscle
13. List the three primary functions of the muscular system. a) MOVEMENT b) HEAT PRODUCTION c) POSTURE / MUSCLE TONE
*** Also some protection

14. Which bone tends to move the origin or the insertion?
INSERTION bone
15. When using the arms to curl weights in the gym, which of the following muscles (Brachialis,
Triceps brachii, and Biceps brachii) fits each of the categories below. See pp. 143-144. a) Prime Mover: BICEPS Brachii b) Antagonists: TRICEPS Brachii c) Synergists : BRACHIALIS
16. What is tonic contraction and what is its purpose?
Tonic contraction is when enough muscle fibers are contracting to steady the position of parts of the body to oppose gravity. This helps maintain posture and tone, without creating any significant movement.
17. When ATP is broken down to ADP, during muscle activity, what two things happen to the energy that is released? a) Most of the energy goes into contraction of
Myosin heads pulling or locking onto actin. b) Some of this energy is just wasted as heat.

D) Fatigue
18. What is produced when muscles switch from aerobic (oxygen) respiration to anaerobic (without oxygen) respiration?
Lactic Acid is produced along with O
2
debt.
E) Motor Unit
19. Define the following: a) Motor Neuron: The type of nerve cells that innervate and stimulate muscles and glands.
b) Neuromuscular Junction: The point of contact between the nerve fiber ending and the actual muscle fiber.
c) Motor Unit: The combination of a single motor neuron and all of the muscle fibers it innervates.
F) Muscle Stimulus
20. A muscle fiber will only contract once a certain level of stimulation has been reached, what is this called?
This is called the THRESHOLD STIMULUS
LEVEL or “All or None Law ”

21. If muscle cells are said to respond in an “all or none” mechanism, why is it that you can gently curl both a 1-pound weight and a 25-pound weight?
When you gently lift something, you only recruit and activate a few motor units (5) that call on their muscle fibers (10 each = total of 50). When you lift something heavy you activate way more motor units (500) that each call on their muscle fibers (10 each = total of 5000).
G) Types Of Muscle Contraction
22. Other than Tonic Contraction, list the four other types of muscle contractions.
Type Of
Contraction
Description Of Contraction
(Give Example For last two types)
TWITCH A single stimulation of a muscle fiber, causing it to quickly jerk and then relax.
TETANIC When the muscle fiber is stimulated multiple times over a very short period the muscle fiber has a much smoother contraction as the stimuli blend together
ISOTONIC Any type of contraction of muscle that results in fluid movement of the joint.
Example : Normal Exercise.
ISOMETRIC When muscle contracts to increase tension but movement does not occur.
Example: Holding a curled barbell steady.

H) Effects of Exercise
23. The pictures below represent hypertrophy and atrophy, correctly label each.
ATROPHY HYPERTROPHY
24. How does aerobic training increase muscle endurance?
Aerobic training increases stamina in two ways, firstly, the muscle tissue develops better vascularization with capillaries. Secondly, the actual muscle fibers develop more mitochondria
(sarcosomes)