Muscular System

Question 1

functions

Answer 1

1. body movement
2. stabilization of body position
3. substance movement throughout body (pumping force in veins/lymp)
4. generating heat

Question 2

muscle types

Answer 2

smooth, cardiac, and skeletal muscle

Question 3

smooth muscle

Answer 3

• present in organs, airways, blood vesseks
• involuntary
• 1 nucleus per cell
• not striated

Question 4

cardiac muscle

Answer 4

• present in heart
• involuntary
• 1 nucleus per cell
• striated (contains sarcomere)

Question 5

skeletal muscle

Answer 5

• present around bone
• voluntary
• many nuclei per cell
• striated (contain sarcomere)

Question 6

skeletal anatomy

Answer 6

muscle > muscle fascicles > muscle fibers (muscle cells) > myofibrils (contractile protein)

Question 7

sarcolemma

skeletal M. anatomy

Answer 7

cell membrane

Question 8

sarcoplasm

skeletal M. anatomy

Answer 8

cytoplasm of m. cells

Question 9

protective sheaths

skeletal M. anatomy

Answer 9

• epimysium (covers muscle)
• perimysium (covers muscle fasicles)
• endomysium (covers muscle fibers)

Question 10

sarcomere

Answer 10

functional unit inside myofibrils, contains thin (actin) and thick myosin filaments that cause contractions

Question 11

actin

Answer 11

• thin
• Z line/ I band

Question 12

myosin

Answer 12

• thick
• A band/ H zone

Question 13

sarcoplasmic reticulum (ER)

Answer 13

surrounds many sarcomeres arranged in fibers
* releases stored calcium into sarcoplasm when muscle cell is depolarized

Question 14

sarcolemma

Answer 14

wraps SR, sarcomeres, to form muscle
* contains T tubule –> makes AP faster

Question 15

Z line

Answer 15

• ends of sarcomere
• thin actin filaments branch from Z line to middle of sarcomere

Question 16

M line

Answer 16

• midpoints
• thick myosin filaments branch from M lines towards Z lines

Question 17

I band

Answer 17

only actin filaments

Question 18

A band

Answer 18

• actin and myosin overlap
• does NOT change size during contraction

Question 19

H zone

Answer 19

only myosin present

Question 20

muscle contraction stimulation

Answer 20

1. AP reaches motor end plate
2. Ach is released at neuromuscular junction
3. Ach bind to ligand-gated Na+ receptors –> Na+ enters cell = graded potential created
4. graded potential trigger voltage gated Na+ channels to open
   * can produce AP on muscles IF stimulus is large enough
   * AP travels to T-tubules and causes Ca++ release

Question 21

cross bridge cycling

Answer 21

1. initially actin/myosin unbound because tropomyosin blocks binding site on actin
2. neuron sends signal to muscle at neuromuscular synapse, releasing ACh
3. ACh causes AP in muscle cells which spread out quickly via T-tubules
4. due to AP, SR releases many Ca++ ions into muscle cell
5. Ca++ causes troponin to move tropomyosin, allowing myosin to bind to actin
   * myosin is attached to ADP + Pi in higher energy “cocked” position

Question 22

cross bridge cycling (6-9 steps)

Answer 22

6. release of ADP + Pi causes power stroke where myosin moves along actin
7. ATP binds causing release of actin from myosin
8. ATP is hydrolyzed to ADP + Pi causing myosin to become “cocked” again

Question 23

when does rigor mortis occurs?

Answer 23

when there is not more ATP to release myosin

Question 24

motor unit

Answer 24

all the muscle fibers innervated by a single neuron

Question 25

small motor unit

Answer 25

few muscle fibers for precise movement

Question 26

large motor units

Answer 26

many muscle fibers used in powerful movements

Question 27

type 1 (slow twitch) | type of fiber

Answer 27

* high myoglobin so looks red * slow to fatigue but slow contraction velocity--> slow oxidative (oxidative phosphorylation) * mitochondria are in higher numbers

Question 28

type 2 (fast twitch) | type of fiber

Answer 28

* low myoglobin so looks white * fast to fatigue, but fast contraction velocity * muscle cells don't divide, just grow more/thicker/longer sarcomeres * **type ll a**: fast oxidative glycolytic fibers * **type ll b**: fast glycolytic fibers

Question 29

twitch contractions

Answer 29

* contraction of a m. fiber through motor unti stimulation @ same size and duration * all or non principle: depolarization will cause all m. fibers to twitch if **above threshold** but will not cause any twitching if the depolarization is **below threshold**

Question 30

latent | twitch contraction phase

Answer 30

AP spreads over sarcolema and T-tubules, signaling SR to release Ca++

Question 31

contraction | twitch contraction phase

Answer 31

cross bridges form as Ca++ binds to troponin * muscle tension increases

Question 32

relaxation | twitch contraction phase

Answer 32

Ca++ is pumped back into SR * muscle tension decreases

Question 33

twitches can add up to create?

Answer 33

summation = larger overall contraction

Question 34

wave summation

Answer 34

* depolarizing motor unit during relaxation (can cause tetanus) * resulting depolarization is larger but can eventually cause fatigue

Question 35

motor unit summation

Answer 35

AP to different motor units at different times * small (most excitable), larger (least excitable)

Question 36

tetanus

Answer 36

stimulated frequently meaning no relaxation period * sustained until muscle fibers are fatigued

Question 37

muscle tone

Answer 37

caused by weak, involuntary twitches

Question 38

skeletal muscle types

Answer 38

agonists, antagonists, synergists