MNSR 7 - Anatomical Muscles Muscle Physiology

Question 1

Explain what a muscle, tendon, and ligament is.

Answer 1

Muscle: contracts
Tendon: connects muscle to bone
Ligament: connects bone to bone

Question 2

How are muscles connected?

Answer 2

Muscles are generally connected to two bones and have an origin (on one bone) & insertion point (on another bone). The insertion point is generally drawn towards the origin.

Question 3

Describe the structure of an individual muscle fiber.

Answer 3

Epimysium –> perimysium –> endomysium –> fascicles –> muscle fibers –> myofibers –> sacromere

Question 4

What are the three types of muscle?

Answer 4

Skeletal Muscle (striated): attached to bones, voluntary, low endurance, hexagonal with nuclei on the outside.
Cardiac Muscle: attached to the myocardium, involuntary, high endurance, has intercalated discs with gap junctions, 1-2 nuclei per cell
Smooth Muscle: attached to organs, involuntary, low endurance, centrally placed nuclei

Question 5

What is a Muscle Biopsy?

Answer 5

A needle used to get a sample of muscle.

Question 6

What is a motor unit?

Answer 6

The functional unit of skeletal muscle that is composed of a single motor neuron, and a fascicle of muscle fibers innervated by it. If a motor unit has fewer muscle fibers, dexterity is increased. If a motor unit has more muscle fibers, dexterity is decreased.

Question 7

What is the neuromuscular junction (NMJ)?

Answer 7

The neuromuscular junction is the connection between the muscle fiber and its motor neuron. There is one neuromuscular junction for each muscle fiber.

Question 8

What are the two ways a muscle contracts?

Answer 8

1. Isometric contraction:
   - length constant, tension changes
2. Isotonic contraction:
   - Tension constant, length increases

Question 9

What are the two types of isotonic contraction?

Answer 9

1. Concentric Isotonic Contraction: force generated by the muscle is greater than the load to be lifted, muscle shortens.
2. Eccentric Isotonic Contraction: force generated by the muscle is less than the load applied to it, muscle lengthens. Muscles are 10% stronger during eccentric contractions than during concentric contractions to prevent muscle necrosis.

Question 10

What are the three phases of muscle contraction?

Answer 10

1. Latent (0.005) (stimulus occurs before first visible reaction)
2. Contraction (0.04) (muscle shortens)
3. Relaxation (0.05) (muscle lengthens to original length)
4. Refractory Period

Question 11

Explain summation and the ways it can occur.

Answer 11

Summation is a second twitch that occurs during contraction & twitches becomes superimposed. There are two different types of summation:

• Multiple motor unit summation: increasing # of motor units involved
• Wave summation: increasing # contractions (tetanization can be reached in which contractions become very short)