Muscle Test Prep

vocab

1. Muscle: the organ made of fascicles

2. Tendon: Structure that connects muscle to bone

3. Sarcomere: Structure where contraction happens

4. Perimysium: Connective tissue that wraps around each fascicle

5. Actin: Thin filament, slides toward the m-line during contraction

6. Sarcolemma: plasma membrane of a muscle fiber

7. Fascicle: A bundle of muscle fibers

8. Muscle fiber: Muscle cell

9. Myofibril: Long chains of sarcomeres that make up each muscle fiber

10. Myofiliment: structure of protein found in myofibril, can be actin or myosin

11. Tropomyosin: Protein that covers active site on actin

12. Epimysium: Connective tissue sheath that wraps around entire muscle

13. Myosin: Thick Filament, changes shape during the contraction cycle

14. Sarcoplasmic reticulum: Organelle that stores Ca+ in muscle fiber

15. Endomysium: Connective tissue sheath that wraps around each muscle fiber

16. synaptic cleft: space between neuron and the muscle

17. AchE: enzyme that breaks down Ach

18. Ca+: released from SR, initiates contraction cycle

19. troponin: binds Ca+ and starts contraction cycle

20. Synaptic Terminal: contains vesicles filled with Ach

21. Cross bridge: connection between myosin and actin

22. motor endplate: contains receptors for Ach

23. summation: stimulus applied before tension has completely relaxed

24. incomplete tension: tension peaks and falls repeatedly and builds up beyond twitch tension

25. complete tension: tension is steady and does not relax

26. muscle tone: tension in “resting” muscle, stabilizes bone and joints, prevents atrophy

Order of biggest to smallest

1. Tendon

2. Epimysium

3. Muscle

4. Perimisium

5. fascicle

6. endomysium

7. muscle fiber

8. sarcolemma

9. myofibril

10. myofiliments

Energy

Anaerobic glycolysis

• cytoplasm

• no O2

• primary source for peak energy use

• break down glucose from glycogen stores in skeletal muscle

Aerobic metabolism

• mitochontria

• O2

• primary source of resting muscle

• break down fatty acids = 2 ATP

• produce 34 ATP per glucose molecule

Describe how energy is produced and used in a muscle fiber during rest, moderate and peak activity

During a resting period, a muscle will use aerobic metabolism in order to acquire some energy. The process will happen in the mitochondria and will result in 36 total ATP. Fatty acids will be broken down and produce pyruvic acid for 2 ATP, then through Kreb’s cycle we will obtain 2 ATP, and lasting go through ETC resulting in 32 ATP.

Intermediate energy use is the most common. Muscles will generate ATP through aerobic breakdown of carbohydrates, lipides, or amino acids.

During peak activity, there is a lack of oxygen to support the mitochondria so we will use a process called glycolysis for ATP. The pyruvic acid will built up and then be converted to lactic acid. Energy will be provided by anaerobic reactions that generate lactic acid as a byproduct.

Compare and contrast fast verses slow twitch fibers in terms of structure and function

Fast twitches are stronger, but they burn out faster so they have more muscle fatigue. They also have more actin and myosin within their muscle fibers so they are bigger. Your body will also take your fibers and arrange them into sarcomeres for faster and powerful contractions. Fast twitches also have fewer mitochondrial and little blood flow and are made for anaerobic respiration. This muscle will be white and light colored.

Intermediate fibers are medium sized. They have low myoglobin. They have more capillaries than fast fiber and are slow to fatigue.

Slow twitch fibers are slow and steady, better for endurance because they are smaller and slower to fatigue. They will have less actin and myosin but more mitochondria. These fibers have myoglobin which gives them a red pigment.

Explain how a nerve cell stimulates a muscle fiber and describe in order the steps of muscle contraction

Steps of contraction

1. Action potenital is released

2. Ach is released into synaptic cleft

3. Ach binds to recpetors

4. Na+ gates open, second action potential is generated

5. Action potenital moves through T-tubules

6. SR released Ca+

7. calcium binds to t exposing the active site on the actin

8. pre=energized myosin head attaches to the active site on the actin forming a cross bridge

9. sarcomere shortens

10. removes Ach from receptors and recyles back to the synaptic terminal

11. sarcoplasmic reticulum reclaims calcium, tropomyosin covers active site

12. Muscle fiber relaxes

Important info

3 catagories of muscle tissue

1. skeletal

   • striated

   • voluntary

2. cardiac

   • striated

3. smooth

the ability of a muscle to respomd to stimuli from a nervous impulse is called

• excitability

we see the I and A band as the striations in skeletal muscle

Calcium is stored in the Sarcoplasmic Reticulum

3 phases of muscle twitch

1. latent

2. contraction

3. relaxation

when a muscle is stimulated until the relaxation phase is completely eliminated, the muscle is said to be in a state of complete tetanus

byproduct of anaerobic breakdown of glucose

lactic acid

Orgin - the end attachment to the bone that does not move is known as the orgin

Insertion- the end part that moves is called the insertion

Achilles - largest and strongest tendon in the body

5 functions of the muscle system

1. produce movement

2. maintain posture and body position

3. support soft tissue

4. guard body entrances and exits

5. maintain body temp

a muscle contraction that results in the shortening of a muscle is called a concentric contraction

H and I band narrows when skeletal muscle contracts