Lecture 14: Muscle tissue

Question 1

Skeletal muscle characteristics

Answer 1

Multinucleated syncytium
Peripheral nuclei
Sarcomeric arrangment

Question 2

Myofiber type 1 characteristics

Answer 2

Intense staining for oxidative enzymes
Rich in NADH transferase, myoglobin, mitochondira
Primarily utilize oxidative phosphorylation
Produce slow, continuous contractions
Referred to as dark/red fibers

Question 3

Myofiber type 2 characteristics

Answer 3

Intermediate staining for oxidative enzymes
Utilize both aerobic and anaerobic respiration
Contract more rapidly than type 1
Resistance to fatigue

Question 4

Myofiber type 3 characteristics

Answer 4

Light staining for oxidative enzymes
Utilize primarily anaerobic respiration
Rich in ATPase
Contract very rapidly
Fatigue quickly
White/light fibers

Question 5

Smooth muscle characteristics

Answer 5

Single mononucleated cells
No sarcomeric arrangement
Cells innervated via ANS
Gap junctions connect

Question 6

Cardiac muscle characteristics

Answer 6

Mononucleated cells
Central nuclei
Branched cells
Sarcomeric arrangement
Intercalated discs
Not directly innervated

Question 7

Perimysium consists of

Answer 7

Fibroblasts and type I collagen

Question 8

Myofiber is a

Answer 8

Muscle cell

Question 9

Endomysium consists of

Answer 9

Basal lamina and reticular collagen fibers

Question 10

Basal lamina characteristics

Answer 10

Secreted by muscle cells
Anchors muscle fibers to eachother
Helps distribute the force of contraction

Question 11

“A” band consists of

Answer 11

Myosin/actin filaments

It is the length of the myosin filament

Question 12

H band consists of

Answer 12

Only myosin filament

Question 13

I band

Answer 13

Only actin filaments

Question 14

Banded pattern origin

Answer 14

Filaments of the sarcomere are organized in such a way as to create a repeated banding pattern

Question 15

Each myosin head has what regions

Answer 15

Actin binding region
ATP-binding region
Light-chain binding region

Question 16

Two pairs of light chains on myosin head

Answer 16

Similar to calmodulin but have lost ability to bind calcium
Essential light chains contribute to stability of myosin head
Regulatory light chains maintain stability of myosin II and are sites for phosphate binding

Question 17

F-actin

Answer 17

Polymer of G actin

Plus ends insert on Z disk

Question 18

Tropomyosin

Answer 18

Each tropomyosin sits in the groove between two actin strands of an actin filament
Each tropomyosin spans 7 actin monomers

Question 19

Troponin I

Answer 19

Inhibits binding between actin/myosin

Question 20

Troponin C

Answer 20

Binds calcium ions

Question 21

Troponin T

Answer 21

Binds to tropomyosin

Question 22

T-tubules are located

Answer 22

At the A-I junction

Question 23

aB-crystallin

Answer 23

Heat-shock protein that protects desmin from mechanical stress

Question 24

Dystrophin

Answer 24

One of the proteins that links the a-actinin/desmin complex to cytoplasmic side of sarcolemma
Anchors actin to sarcolemma
Reinforces sarcolemma during contraction

Question 25

Dystroglycan complex

Answer 25

Links dystrophin (intracellular) to laminin-2 (extracellular)

Question 26

a-actinin

Answer 26

Attaches thin filaments to the Z-line

Question 27

Nebulin

Answer 27

Extends from Z disc to actin filament | Serves as template to regulate length of actin filament

Question 28

Titin

Answer 28

Extends from Z-disk to middle of H-band and connects ends of thick filaments to Z-line Provides myosin with elasticity Centers thick filaments in sarcomere

Question 29

Desmin intermediate filaments

Answer 29

Framework of desmin filaments which surrounds the Z-line and extends into each sarcomere Links myofibrils laterally and to the sarcomere

Question 30

Plectin

Answer 30

Binds desmin filaments

Question 31

Satellite cells

Answer 31

Attach to myotubes before basal lamina is laid down Generally quiescent Function as stem cells Can become mitotic in times of stress Give rise to myogenic precursor cells-replace damaged muscle by differentiating into skeletal muscle fibers

Question 32

Neuromuscular spine components

Answer 32

``` Extrafusal fibers Intrafusal fibers--Nuclear bag/nuclear chain fibers. nuclear bag is sensory region Alpha motor neurons-to extrafusal fibers Gamma motor neurons-to intrafusal fibers Primary and secondary afferent fibers ```

Question 33

T-tubule system in cardiac muscle tissue

Answer 33

Not as extensive as in skeletal muscle | Only interacts with one cisterna

Question 34

Contents of intercalated discs

Answer 34

Macula adherentes Fascia adherents (anchor actin filaments of sarcomeres) Gap junction

Question 35

ANP

Answer 35

``` Secreted by cardiac muscle cells in atria Regulate fluid electrolyte balance Relax vascular smooth muscle -reduces blood volume/pressure Release is stimulated by atrial stretch ```

Question 36

Dense bodies in smooth muscle

Answer 36

Anchor actin filaments to eachother and cell membrane Contain A-actinin Interconnected by specific type of desmin Communicate force of contraction to cytoskeleton and cell membrane Found in cytoplasm and cell membrane

Question 37

Smooth muscle cells do not have

Answer 37

T-tubule system or extensive SR

Question 38

Smooth muscle cells dependent on

Answer 38

Extracellular calcium for contraction | -calcium transported by pinocytic vesicles

Question 39

Caveolae/lipid rafts

Answer 39

Permanent depressions of cell membrane involved in fluid/electrolyte transport Caveolin binds cholesterol in lipid rafts and initiates formation of caveolae Vesicles formed and detach to participate in trafficking

Question 40

Adrenergic and muscarinic receptors

Answer 40

Linked to G-proteins

Question 41

Nicotinic cholinergic receptor

Answer 41

Cation channel

Question 42

Smooth muscle sheet innervation

Answer 42

Smooth muscle sheets are mostly poorly innervated | Excitation is spread through gap junctions