Muscles

Question 1

Myocyte

Answer 1

= muscle fiber

individual muscle cell

Question 2

sarcoplasm

Answer 2

muscle cytoplasm

Question 3

sarcolemma

Answer 3

plasma membrane or plasmalemma

Question 4

what are the 3 types of mucles?

Answer 4

1. skeletal
2. smooth
3. cardiac

all mesodermally derived

Question 5

skeletal muscle

Answer 5

responsible for movement, voluntary moto control

Question 6

syncytia

Answer 6

skeletal muscle cells are multinucleated to form this

Question 7

myoblasts undergo fusion into i

Answer 7

multinucleated myotube

Question 8

myotubes

Answer 8

synthesize contractile proteins which assemble into sarcomeres

Question 9

What happens to nuclei when it migrates to periphery of cell

Answer 9

lose ability to proliferate

Question 10

endomysium

Answer 10

Individual muscle fibers surrounded by connective tissue

Question 11

fascicles (= fasciculi)

Answer 11

“bundles”

fibers bound together

Question 12

perimysium

Answer 12

• Fascicles surrounded by connective tissue perimysium

- many fascicles together form muscle

Question 13

epimysium

Answer 13

Entire muscle surrounded by epimysium, continuous with tendinous attachment

Question 14

what do blood vessels and neurons tend to follow in connective tissue?

Answer 14

epi- and perimysia for support

Question 15

two major types of biers in skeletal muscles

Answer 15

1. slow twitch

2. fast twitch

Question 16

Type I, Slow Twitch Fibers

Answer 16

• “Slow” myosin
• Small fibers with large amount of myoglobin
• Use 1’ aerobic respiration for oxidative metabolism
• Large # of mitochondria (=> ATP for energy)
• Resistant to fatigue, but generate only moderate M tension
• Common in peripheral limbs

Question 17

Type II, Fast twitch, fibers

Answer 17

• “Fast” myosin
• Largefibers with less myoglobin & fewer mitochondria
• Use 1’ anaerobic glycolysis for energy production
• Abundant glycogen
• Extensive sarcoplasmic reticulum for rapid Ca release
• Fatigue rapidly, but generate high M tension for short bursts of activity

Question 18

Intermediate fibers consists of what tyoes?

Answer 18

Type IIA and Type IIB

Question 19

Type IIA

Answer 19

oxidative & fatigue resistant

Question 20

Type IIB

Answer 20

glycolytic & fatigue sensitive

Question 21

intermediate metabolites (e.g., lactic acid)

Answer 21

• During peak periods of exertion, both Type I & Type II fibers metabolize glycogen via anaerobic glycolysis to produce ATP
• Results: precipitate as crystals in Mm => tearing of Mm fibers & pain after heavy exertion

Question 22

Oxygen debt

Answer 22

ischemia& Mm cramps, even cell death

Question 23

rhabdomyolysis

Answer 23

breakdown of actin and myosin

Question 24

myoglobinuric nephrosis

Answer 24

subsequent kidney failure

Question 25

Extremem exertion may lead to what?

Answer 25

rhabdomyolysis and myoglobinuric nephrosis

Question 26

during normal exercise, muscle fibers delvelop___

Answer 26

micro tears

Question 27

hypertrophy

Answer 27

With exercise, Mm cells ↑in size

• Due to ↑in # of mitochondria, & ↑in volume of contractile proteins; splitting/ branching of individual Mm fibers
• Production of new Mm fibers relatively rare

Question 28

atrophy

Answer 28

With disuse, Mm cells ↓in size

- Due to immobilization (e.g., splint, cast), denervation(N damage => Mm atrophy)

Question 29

sarcopenia

Answer 29

With ↑age, also get progressive loss of skeletal Mm fibers

-not replaced => ↓# & ↓Mm mass

Question 30

muscle size changes due to 2 possibilities

Answer 30

1. hypertrophy
2. atrophy
3. Age

Question 31

Response to injury for skeletal muscles?

Answer 31

• limited ability to regenerate following injury
• Regeneration 1’ due to satellite cells, small myogenic cells adjacent to sarcolemma
• Proliferate following injury, differentiate into myoblasts

Question 32

intrafusal fibers

Answer 32

Modified skeletal Mm fibers associated with modified Nerve endings

• neuromuscular spindles
• neurotendinous spindles

Question 33

Neuromuscular spindles

Answer 33

(= muscle spindles)—located within belly of Mm; sensitive to changes in length

Question 34

Neurotendinous spindles

Answer 34

(=Golgi tendon organs)—located within tendon; sensitive to changes in tension

Question 35

postural reflexes

Answer 35

Both prevent overstretching & tearing of Mm

Question 36

Ultrastructure

Answer 36

• Individual Mm fibers composed of myofibrils

- Actin & myosin present in ~ 2:1 ratio in skeletal Mm

Question 37

myofibrils

Answer 37

composed of numerous myofilaments, or contractile proteins, in parallel bundles

Question 38

2 types of myofilaments:

Answer 38

1. Actin (thin)

2. Myosin (thick)