CH 3: Muscular System

Question 1

the muscular system includes how many muscles?

Answer 1

650

Question 2

which muscle fiber type are the largest and produce the most amount of force?

Answer 2

type IIx

Question 3

muscle origin vs muscle insertion

Answer 3

muscle origin - closest to the head, less movable
muscle insertion - closest to the feet, more movable

Question 4

Epimysium

Answer 4

think of it as plastic wrap around a steak
protects muscle from friction against other muscles and bones
connected to fascia

Question 5

sarcomeres

Answer 5

functional units that can make the muscle fiber shorten (does so collectively as a sequence of actions)
lined up w/in the myofibril

Question 6

how do sarcomeres shorten?

Answer 6

due to the sliding of two muscle proteins: myosin and actin in a process called “cross bridge cycle”

think of mysosin as a rowboat and actin as the water, except the rowboat remains stationary and the water moves. This is also known as the sliding filament theory.

Question 7

sliding filament theory

Answer 7

muscle shortens bc the thick and thin filaments (myosin and actin) slide past each other

Question 8

what is Acetylcholine?

Answer 8

a neurotransmitter released in the neuromuscular junction that facilitates muscle contraction.

Question 9

describe what happens with acetylcholine

Answer 9

• the binding of acetylcholine results in calcium release w/in the muscle.
• the calcium release is fundamental to the cross bridge cycle

Note: when muscle is at rest, actin is wrapped by proteins that block interaction w/myosin. When calcium levels rise, it binds to these proteins moving them out of the way for mysosin to interact w/actin

Question 10

what fuels the cross bridge cycle?

Answer 10

ATP hydrolysis (ATP–>ADP) to release energy stored w/in the phosphate bond

Question 11

Two sources of calcium needed for muscle activation are found where?

Answer 11

extracellular space
intracellular space

Question 12

Intracellular calcium is released from where?

Answer 12

the muscle’s sarcoplasmic reticulum, which is tubules in muscle that store and release calcium

Question 13

what causes calcium elevation and muscle contraction?

Answer 13

a neural signal sent from brain in a process called excitation-contraction coupling.

Question 14

what is excitation-contraction coupling?

Answer 14

a process that starts w/a neural signal and ends w/a muscle contraction

Question 15

what is pulling force?

Answer 15

the force a muscle produces to shorten (think of it as “contracting”)

Question 16

what is resistance force?

Answer 16

an external force that opposes the force a muscle produces to shorten (ie the dumbbell during a bicep curl)

Question 17

describe agonist, antagonist, synergist

Answer 17

prime mover, opposite, indirect (respectively)

Question 18

what is Force-couple?

Answer 18

a type of synergy
- occurs when >=2 muscles concurrently generate force in linear directions to produce 1 mvmt. I.e., making a right turn on a bicycle requies pushing w/left and pulling w/right

note: ALL muscles work synergistically, which reaffirms the importance of an integrated (vs isolated) approach

Question 19

3 factors make muscle fiber type unique

Answer 19

Shortening velocity. can be improved w/exercises performed at high speed

Mitochondrial density. mitochondria fuel muscle action, so, the more mitochondria the better the capacity for contraction. A decrease in mitochondria density –>diabetes and cardiovascular disease

Capillary density. Capillaries allow the exchange of O2 and CO2. Increase capillaries=increase in O2 and decrease in CO2.

Question 20

what is capillarization?

Answer 20

the formation of new capillaries through endurance exercise

Question 21

describe the 3 factors that make fiber types unique for each of the fiber types

Answer 21

Type I
Shortening Velocity=slow
Mitochondria Density=High
Capillary Density=High

Type IIa
Shortening Velocity=fast
Mitochondria Density=High
Capillary Density=mod

Type IIx
Shortening Velocity=very fast
Mitochondria Density=low
Capillary Density=low

Question 22

How might a person’s muscle fiber ratio change?

Answer 22

not much but when it does it’s toward higher endurance (i.e. IIx to IIa, IIa to I)

Question 23

What causes DOMS?

Answer 23

1. When an exercise is performed for the first time
2. Increase in intensity
3. Increase in volume

Question 24

When it comes to muscle size changes, what are the two elements to consider?

Answer 24

Contractile elements (myofibrils)
Non-contractile elements (glycogen and semifluid plasma)

Question 25

what are two forms of hypertrophy?

Answer 25

1) Myofibrillar - growth of myofibrils, increases a muscle’s force potential

2) Sarcoplasmic - Increase in volume of glycogen and semifluid plasma; DOESN’T increase a muscles’s force potential

Question 26

of the two types of hypertrophy, which one increases a muscle’s force potential?

Answer 26

Myofibrillar hypertrophy, due to growth of myofibrils

Question 27

Describe the difference bw muscle protein synthesis and muscle protein breakdown

Answer 27

muscle protein synthesis forms muscle proteins FROM amino acids

muscle protein breakddown breaks down muscle proteins INTO amino acids

Question 28

When muscle protein synthesis > muscle protein breakdown, what happens?

Answer 28

hypertrophy

Question 29

When muscle protein synthesis < muscle protein breakdown, what happens?

Answer 29

atrophy

Question 30

What is fascia?

Answer 30

a safety net throughout the body acting as girdles and guy wires to create an interconnected structure.

Fascia also contain nerve endings which inform propioception