Muscle Tissue Part 2 Flashcards Preview

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Flashcards in Muscle Tissue Part 2 Deck (44):
1

Smooth muscle characteristics

Simplest type of muscular tissue. No cross striations. Contractile filaments are not well organized in cell. Specialized for slow/rhythmic prolonged contractions (visceral organs) or rapid/precise (eye). Are involuntary

2

Shape of smooth muscle cells

Fusiform cells. aka Elongated spindle-shaped

3

Where is the nuclei of smooth muscle cells?

Centrally placed. Long/cigar shaped with tapered ends

4

What does the sarcoplasm of smooth muscle cells consist of?

Myofilaments and organelles, numerous mitochondria

5

How are the myofilaments arranged in smooth muscle?

Randomly distributed throughout the cytoplasm

6

What do the thin filaments of smooth muscle anchor to?

Dense bodies

7

What are dense bodies of smooth muscles anchored to and by what are they anchored?

Dense bodies are anchored to intermediate filaments via desmin (analogous to Z-lines of skeletal muscle fibers)

8

What does the sarcolemma of smooth muscle posses a large number of ?

Caveolae

9

Communicating junctions

gaps in the smooth muscle to connect the muscle cells

10

Reticular fibers in smooth muscle

Cover the smooth muscle cells. Play an important role in the force transduction in the smooth muscle tissue

11

Thin filaments of smooth muscle

F-Actin, tropomyosin, Caldesmon (NO TROPONIN is present)

12

Caldesmon

Smooth-muscle specific actin-binding protein that mass the myosin-binding site on the actin fibers

13

Thick filament of smooth muscle

Myosin II

14

Composition of myosin II

2 heavy polypeptides and 4 light chains (2 essential and 2 regulatory)

15

When does smooth muscle myosin bind to actin?

Only when phosphorylated

16

Where does the neural stimulation of smooth muscle occur?

Thru the post ganglion of the autonomic system

17

How are neuromuscular junctions different in the smooth muscle compared to skeletal muscle?

The neurotransmitters are released near to the muscle cells and diffuse to the cells as opposed to precise release (skeletal muscle)

18

How do smooth muscle cells without terminal nerves receive neural impulses?

Impulse transmission occurs via gap junctions

19

What can elicit chemical stimulation in smooth muscle?

Hormones, angiotensin II, vasopressin

20

What effect does mechanical stimulation of smooth muscle elicit?

Can lead to the initiation of muscular contraction

21

What drives the contraction of smooth muscle?

High concentrations of Ca++

22

Ca++'s effect on smooth muscle fibers

Binds to calmodulin. Complex releases actin, thus opening the myosin-binding sites on F-actin. Complex activates myosin light-chain kinase

23

What does myosin light-chain kinase do?

Phosphorylates the regulatory (light) chain of the myosin molecule

24

What happens after the light chain of myosin in the smooth muscle in phosphorylated?

Myosin unfolds and the actin-binding site becomes open. Myosin binds to actin. Filaments slide. Cells shorten. Nucleus folds and becomes corkscrew-shaped. Slow action.

25

Smooth muscle relaxation

Ca++ pumped back into the sarcoplasmic reticulum. Calmodulin deactivates from Ca being disassociated and rebinds to myosin-binding site on actin. Uses 10% ATP that skeletal muscle uses

26

Latch state

For long-term contraction in smooth muscle. Used to sustain tone of blood vessels. Resembles rigor mortis

27

Smooth muscle blood supply

Blood supply is moderate via capillaries in connective tissue immediately surrounding the muscle cells

28

Active regeneration response

Smooth muscle cells can go thru mitosis and replace damaged/lost cells

29

Cardia muscle blood supply

Extensive blood supply thru a network of capillaries

30

Regeneration of cardiac muscle

limited regeneration. localized injury results in scar tissue of fibrous connective tissue. muscle function is lost in scar tissue area

31

Characteristics of cardiac muscle CELLS

Cylindrical cells arranged end to end. Centrally placed rounded nuclei. Large/flattened mitochondria densely packed between myofibrils. Form a long chain of muscle cells with intercalated disks between. Branching between fibers.

32

Intercalated disks

Junctions between individual muscle cells. Has a transverse and lateral portion.

33

Transverse portion of the intercalated disks

Runs at a right angle from the fiber. Provides mechanical stability for the tissue. Prevents cells from being pulled apart

34

Adherens junctions

In transverse portion of intercalated disks. Connect myofilaments of 3 neighboring cardiac muscle cells

35

Desmosomes

In transverse portion of intercalated disks. Connect intermediate filaments of 2 adjacent cells

36

Lateral portion of intercalated disks

Run parallel to myofilaments. Contains communicating/gap junctions. Provides ionic continuity between adjacent cells. Allows contraction signal to pass from cell to cell

37

T-tubules in cardiac muscle

Found at the Z-disks (NOT at junction of A and I bands)/ Sarcoplasmic reticulum not as well developed and have smaller cisternae than skeletal muscle.

38

Diads

One T-tubule and its surrounding small terminal cisternae

39

Purkinje fibers

Cardiac conducting cells that are modified for the conduction of electric impulses.

40

Nodes/bundles of Purkinje fibers

Sinoatrial node, atrioventricular node, bundle of His

41

Layers of Arteries/Veins

Tunics: Tunica intima, tunica media, tunica adventitia

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Artery characteristics

Thicker walls, narrower lumens, usually round when cut

43

Vein characteristics

Walls are not distinctly separate, bundles of smooth muscle, much thinner wall than arteries

44

Lymphatic vessels

Very thin walls, only endothelial lining, may contain valves