Muscle Tissue

Question 1

what germ layer does muscles tissue develop from?

Answer 1

mesoderm

Question 2

what are the three types of muscle tissue?

Answer 2

1. skeletal: strong, quick, discontinuous voluntary contractions
2. cardiac: strong, quick, continuous involuntary contraction
3. smooth: weak, slow, involuntary contraction

Question 3

what are the 4 special characteristics of muscle tissue?

Answer 3

1. excitability
2. contractility
3. extensibility
4. elasticity

Question 4

excitability

Answer 4

respond to stimuli by producing action potentials

Question 5

contractility

Answer 5

ability to generate force/tension when stimulated (requires ATP, thru actin/myosin binding), shortens when tension produced is overcoming tension opposed

Question 6

extensibility

Answer 6

ability to be stretched or extended

Question 7

elasticity

Answer 7

ability to return to the original length after shortening/stretching

Question 8

function of muscle

Answer 8

1. producing movement
2. maintaining posture: muscles contracted to fight gravity
3. stabilizing joints: other muscles move to support main movers
4. generate heat

Question 9

types of skeletal muscle fibers

Answer 9

1. type I: slow, red oxidative fibers
2. type IIa: fast, intermediate oxidative-glycolytic fibers
3. type IIb: fast, white glycolytic fibers

Question 10

type I: slow, red oxidative fibers

Answer 10

lots of mito and Mb (protein binds to O2, dark red), energy from aerobic OxPhos of Fas, for slow continuous contractions over long periods (posture mm)

Question 11

type IIa: fast, intermediate oxidative-glycolytic fibers

Answer 11

many mito and Mb and glycogen, energy from oxidative metabolism and anaerobic glycolysis, for rapid contraction and short bursts of energy

Question 12

type IIb: fast, white glycolytic fibers

Answer 12

few mito and Mb, lots og glycogen, energy from anaerobic glycolysis, for rapid contractions, fatigue quickly

Question 13

what is a sarcomere?

Answer 13

functional unit of muscles, between 2 z discs

Question 14

I band

Answer 14

thin (actin) filaments only

Question 15

A band

Answer 15

entire thick (myosin) filament and some thin filament

Question 16

H zone

Answer 16

thick filaments only (lighter color)

Question 17

M line

Answer 17

in middle of sarcomere, cross connecting cytoskeleton

Question 18

what is the filament sliding hypothesis?

Answer 18

explains shortening/contraction of sarcomeres

myosin pulls on actin, walk along actin, thick and thin filaments pull along and slide past one another

Question 19

what happens to the A band with contraction?

Answer 19

doesn’t change length because myosin doesn’t move

Question 20

what happens to I band and H zone with contraction?

Answer 20

get smaller and disappear

Question 21

sarcoplasmic reticulum

Answer 21

specialized SER, stores calcium that is released to initiate contraction

Question 22

t tubules

Answer 22

extensions of plasma membrane (sarcolemma) into cell (2 into each sarcomere at A/I junction)

Question 23

terminal cisternae

Answer 23

enlargement of SR (stores lots of calcium)

Question 24

triads

Answer 24

1 t tubule and 2 terminal cisternae, 2/sarcomere

Question 25

excitation

Answer 25

AP is generated and propagated along sarcolemma and down t tubules

AP triggers calcium release from terminal cisternae of SR, binds to troponin (changes shape to remove blocking action of tropomyosin)

actin active site is exposed

Question 26

contraction

Answer 26

myosin cross bridges alternately attach/detach to actin, pulling filaments toward center of sarcomere (powered by ATP->ADP), calcium is removed to SR via active transport after Ap ends

Question 27

what helps spread AP between sarcomeres

Answer 27

voltage gated channels

Question 28

cross bridge attach/detach

Answer 28

1. myosin head (high energy) config atatches to actin myofilament
2. powerstroke: ADP and Pi released, myosin head pivots and pulls on actin filament
3. myosin head bound to ATP (low energy) cross bridge detaches
4. ATP->ADP and Pi myosin head cocks and prepared to attach

Question 29

rigor mortis

Answer 29

12 hrs after death, terminal cisternae let out large amt of calcium, contraction occurs, no ATP production -> no release of myosin heads -> no relaxation

Question 30

CT layers of skeletal muscle

Answer 30

1. endomysium
2. perimysium
3. epimysium

Question 31

endomysium

Answer 31

areolar CT, surrounds each individaul myocyte, contains capillaries and nerves

Question 32

perimysium

Answer 32

surrounds a group of muscle fibers making bundles (fascicles)

Question 33

epimysium

Answer 33

dense irregular CT, surrounds entire muscles

Question 34

how does skeletal muscle attach to bones?

Answer 34

tendons

Question 35

cardiac muscle vs skeletal muscle

Answer 35

• less distinct striations
• cells are short, fat, branched, mononucleated, intercalated discs
• 25-40% cell vol is mito (SM is much less)
• only 1 t tubule/sarcomere at z line
• simpler SR and SM
• smaller terminal cisternae
• forms diads, not triads

Question 36

morphology of smooth muscle

Answer 36

cells are flat in center with nucleus centrally located, thin on ends, cork screws w/ contraction, nonstriated, uninucleated

Question 37

function of intercalated discs

Answer 37

connect adjacent cardiomyocytes

Question 38

structure of intercalated discs

Answer 38

1. fascia adherens: anchoring jnctn, links thin filaments
2. desmosomes (macula adherens): anchoring jnctn, links intermediate filaments
3. gap jnctns: communication jnctn, intracellular communication

Question 39

skeletal m characteristics

Answer 39

striated, large elongated cylindrical multinucleated cells, oval nuclei on periphery of cell (right at sarcolemma)