Lecture 14

Question 1

What are the 3 muscle tissues?

Answer 1

Skeletal Smooth Cardiac

Question 2

What are the major characteristics of skeletal m.?

Answer 2

• Multinucleated syncytium (share cytoplasm) - Peripheral nuclei - Derived during embryonic development from myotube–. - myocyte - striated - sarcomeric development - each fiber innervated by 1 motor axon - motor unit

Question 3

What are the major characteristics of smooth m.?

Answer 3

• mononucleated, centrally
• spindle shaped nuclei
• no sarcomeric arrangements - no striations or banding
• gap junctions connect cells
• don’t respond “all-or-none” innervated via ANS/enteric
• Involuntary/visceral
• meshwork of actin and myosin bundles (not in nuclear area)
• Dense bodies present
• Caveolae and lipid rafts

Question 4

What are the major characteristics of cardiac m.?

Answer 4

• mononucleated - centrally positioned nuclei - branched cells –> sarcomeric arrangement - communicate via gap junctions - intercalated discs - not directly innervated

Question 5

What are the 3 types of Fibers?

Answer 5

1) Type I = Slow/Red

• stain darker for oxidative enzymes
• High NADH transferase, high myoglobin
• use OP -

slow continuous contractions

• fatigue resistance

2) Type IIA = intermediate

• stain intermediate
• both aerobic and anaerobic respiration

3) Type IIB = Fast/White

• light stain for oxidative enzymes
• gylcolysis
• high ATPase
• rapid contractions
• fatigue quickly

Question 6

When Ca+2 is present: Ca+2 binds _______ and pulls back ______ exposing myosin binding site on actin.

Answer 6

Troponin

Tropomyosin

• Troponin 1 inhibits binding b/w actin and myosin
• Troponin C binds Ca+2 ions

Troponin T binds tropomyosin

Question 7

Enlargements of the SR (sacroplasmic reticulum) are called the ________ and hold _____ ions.

They sit next to _______ which are extensions of sarcollemma down into the sarcoplasm. What do these provide?

Answer 7

• cisternae
• Ca+2 ions
• T-tubules
• Provide electrochemical gradient coupling for contraction by transferring the AP into Ca+2 release

Question 8

AB-crystallin is a heat shock prtn that protects ______, which links myofibrils laterally and to the sarcolemma (stabilizing the myofibril).

_________ is a structural prtn that anchors actin to the sarcolemma, without it DMD occurs.

______ complex links dystrophin (intracellular) to laminin-2 (extracellular).

____ gives myosin elastiticy and centers it in the sarcomere.

____ attaches thin filaments to Z-line.

____ which extends from Z disc to end of actin filament (regulating the length).

____ protein binds desmin.

Answer 8

• desmin
• dystrophin
• dystroglycan complex
• titin
• alpha-actinin
• nebulin
• plectin

Question 9

What cells are capable of replacing damaged muscle tissue?

Where are they located?

What do the attach to embyrologically?

Answer 9

• Satellite cells
• just beneath the cell membrane
• myotube (before basal lamina is laid down)

Question 10

_____ fibers are located outside of the neuromuscular spindle and are part of ____ motor neurons.

___ fibers are located inside of the neuromusclular spindle and are part of ____ motor fibers.

Answer 10

Extrafusal, alpha

Intrafusal, beta

Question 11

Is the T-tuble system in a cardiac cell more or less extensive than in the skeletal m cell?

Describe why?

Answer 11

• Less
• each T-tuble interacts with one cisternae (whereas in skeletal muscle one T-tuble interacts with 2)
• forms diad located at level of Z-lines (where as in skeletal m it forms a triad at the I band-A band interface

Question 12

Intercalated discs are special to what type of muscle?

What forms the transverse component? What forms the longitudinal component?

Answer 12

Cardiac

Macula adherentes (desmosomes) - link desmin of adjoing cardiac m cells

Gap jxns

Question 13

What horomone is secreted by cardiac muscle and what causes its release?

What does it do?

Answer 13

• Atrial Natriurectic Peptide
• atrial stretching
• relaxes vascular sm m –> decreases BP

Question 14

1) Does smooth muscle tissue have a T-tuble system?
2) Describe the SR (in basic terms)
3) Sm m cells are connected by what?
4) What anchors actin filaments to each other and the cell membrane in sm m cells?
5) What stimulates the formation of calveolae? Describe this.

Answer 14

1) No
2) less extensive – depends on extraccellular Ca+2 being transported into SR by pinocytic vescicles
3) Gap jxns (this is how excitation spreads in smooth m cells)
4) Dense bodies (they have alpha- actinin)
5) Calveolin binds cholesterol in lipid rafts —> invagination of CM creates vesices (calveolae)
- assist in vesicular trafficking