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Flashcards in histology 7- muscle Deck (32)
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1

3 types of muscle tissue

skeletal
cardiac
smooth

2

skeletal muscle

-strong, quick discontinuous voluntary contractions
-long striated strings (muscle fibers)

3

cardiac muscle

-strong, quick continuous involuntary action
-only found in heart
-presence of larger nuclei and intercalated discs distinguish it from skeletal

4

smooth muscle

-weak, slow involuntary contraction
-non-striated, group of cells

5

special characteristics of muscle tissue

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

6

excitability

can be excited by electrical potentials

7

contractility

fibers condense unilaterally to move bones without stretching cell

8

extensibility

fibers can be overextended without stretching/deforming cells

9

elasticity

fibers are elastic, can stretch and deform

10

function of muscle tissue

-Production of movement
-Maintaining posture
-Stabilizing joints
-Generate heat (thermogenesis)

11

list the different types of skeletal muscle

type 1
type 2a
type 2b

12

type 1 skeletal muscle fibers

Slow, red oxidative fibers
-a.k.a. Slow twitch, fatigue resistant fibers
-Many mitochondria and lots of myoglobin
-Derive energy from aerobic oxidative phosphorylation of fatty acids
-Adapted for slow, continuous contractions over time

13

type 2a skeletal muscle fibers

Fast, intermediate oxidative-glycolytic fibers
-a.k.a. Fast twitch, fatigue resistant fibers
-Many mitochondria, lots of myoglobin and glycogen (intermediate)
-Derive energy from aerobic oxidative metabolism and anaerobic glycolysis
-Adapted for rapid contractions and short bursts of activity

14

type 2b skeletal muscle fibers

Fast, white glycolytic fibers
-a.k.a. Fast twitch, fatigable fibers
-Fewer mitochondria and myglobin, but LOTS of glycogen (pale color)
-Derive energy from anaerobic glycolysis
-movement

15

Describe the organization of muscle tissue from the organ level down to the myofilaments.

Molecules → myofilaments → myofibril → muscle fiber → muscle fascicle → skeletal muscle

16

Sarcomeres

-Interlocking rods of actin and myosin
-Z line (Z disc) endpoints of sarcomere
-M line: midpoint of sarcomere, myosin
-A band: length of myosin fibers in sarcomere, actin & myosin
-H band: (H zone) length of myosin fibers not surrounded by actin, shortens with contraction, myosin
-I band: length from ends of myosin fibers on adjacent sarcomeres, shortens with contraction, actin & titin

17

Describe the filament sliding hypothesis and changes in the appearance of the sarcomere during contraction. Filament sliding hypothesis in relaxed, partial contraction, and full contraction

relaxed muscle- sarcomere, I band, H zone all at relaxed length

partial contraction:
-thick (myosin) and thin (actin) filaments slide past one another
-I band and H zone almost nonexistent
-thick fibers meet at M line (here, M line = H zone)

full contraction:
-thick filaments overlap
-adjacent I bands overlap, H zone nonexistent
-shortest length of sarcomere

18

thick and thin filaments don’t _________, just interlock and slide against each other

change length

19

excitation-contraction coupling

1) Action potential generated along sarcolemma down t-tubules.
2) Action potential triggers Ca2+ release from terminal cisternae of sarcoplasmic reticulum
3) Ca2+ binds to troponin, cross-bridges form…contraction

20

Sarcoplasmic reticulum

-endoplasmic reticulum of muscle cells, stores and pumps Ca2+ ions

21

T-tubules

-invaginations of sarcolemma designed so action potentials can travel into cell

22

Terminal cisternae


-enlarged areas of SR that surround t-tubules. Stores Ca2+ to release when action potential travels down t-tubule

23

Triad

-structure (group) formed by T-tubule and 2 sarcoplasmic reticula/terminal cisterna

24

Describe the process of cross-bridge formation, the power stroke, and cross-bridge detatchment. Describe how this relates to rigor mortis.

1) Head of myosin cross bridge attaches to actin myofilament
2) Working stroke – myosin head pivots and bends to pull actin filament toward M line
-ADP and Pi released
3) New ATP attaches to myosin head, head detaches from actin filament
4) ATP hydrolysis splits ATP on myosin head, cocking of myosin head occurs
-Repeat

25

Rigor mortis-

caused by inability of ATP replenishment due to death. Muscles lock up.

26

List and describe the CT layers associated with skeletal muscle.

Endomysium -encases muscle fibers
Perimysium -encases muscle fascicle (bundle of fibers)
Epimysium -encases entire muscle (bundle of fascicles)

27

Describe how muscles attach to bones.

tendons
-continuous with bone and muscle
-extension of periosteum/epimysium

28

morphological features of cardiac muscle

-branched, uninucleated cells separated by permeable intercalated discs.
-mitochondria make up 25-40% of cell volume
-T-tubules: one per sarcomere at Z line
-SR: simple, small terminal cisternae, forms diads with T-tubules

29

morphological features of skeletal muslce

-multinucleated independent cells
-mitochondria only 2% of volume
-T-tubules: two per sarcomere at A-I junctions
-SR: complex, larger terminal cisternae, forms triads with T-tubules

30

Describe the structure and function of intercalated discs.

-fascia aderens (links actin filaments)
-macula adherens (desmosomes) stop separations during contraction via linking intermediate filaments
-gap junctions for intercellular communication (ion exchange)