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Histology > Muscle Tissue Part 2 > Flashcards

Muscle Tissue Part 2 Flashcards

1
Q

Smooth muscle characteristics

A

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

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2
Q

Shape of smooth muscle cells

A

Fusiform cells. aka Elongated spindle-shaped

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3
Q

Where is the nuclei of smooth muscle cells?

A

Centrally placed. Long/cigar shaped with tapered ends

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4
Q

What does the sarcoplasm of smooth muscle cells consist of?

A

Myofilaments and organelles, numerous mitochondria

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5
Q

How are the myofilaments arranged in smooth muscle?

A

Randomly distributed throughout the cytoplasm

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6
Q

What do the thin filaments of smooth muscle anchor to?

A

Dense bodies

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7
Q

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

A

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

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8
Q

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

A

Caveolae

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9
Q

Communicating junctions

A

gaps in the smooth muscle to connect the muscle cells

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10
Q

Reticular fibers in smooth muscle

A

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

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11
Q

Thin filaments of smooth muscle

A

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

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12
Q

Caldesmon

A

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

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13
Q

Thick filament of smooth muscle

A

Myosin II

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14
Q

Composition of myosin II

A

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

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15
Q

When does smooth muscle myosin bind to actin?

A

Only when phosphorylated

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16
Q

Where does the neural stimulation of smooth muscle occur?

A

Thru the post ganglion of the autonomic system

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17
Q

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

A

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

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18
Q

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

A

Impulse transmission occurs via gap junctions

19
Q

What can elicit chemical stimulation in smooth muscle?

A

Hormones, angiotensin II, vasopressin

20
Q

What effect does mechanical stimulation of smooth muscle elicit?

A

Can lead to the initiation of muscular contraction

21
Q

What drives the contraction of smooth muscle?

A

High concentrations of Ca++

22
Q

Ca++’s effect on smooth muscle fibers

A

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

23
Q

What does myosin light-chain kinase do?

A

Phosphorylates the regulatory (light) chain of the myosin molecule

24
Q

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

A

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
Q

Smooth muscle relaxation

A

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
Q

Latch state

A

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

27
Q

Smooth muscle blood supply

A

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

28
Q

Active regeneration response

A

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

29
Q

Cardia muscle blood supply

A

Extensive blood supply thru a network of capillaries

30
Q

Regeneration of cardiac muscle

A

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

31
Q

Characteristics of cardiac muscle CELLS

A

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
Q

Intercalated disks

A

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

33
Q

Transverse portion of the intercalated disks

A

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

34
Q

Adherens junctions

A

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

35
Q

Desmosomes

A

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

36
Q

Lateral portion of intercalated disks

A

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

37
Q

T-tubules in cardiac muscle

A

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
Q

Diads

A

One T-tubule and its surrounding small terminal cisternae

39
Q

Purkinje fibers

A

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

40
Q

Nodes/bundles of Purkinje fibers

A

Sinoatrial node, atrioventricular node, bundle of His

41
Q

Layers of Arteries/Veins

A

Tunics: Tunica intima, tunica media, tunica adventitia

42
Q

Artery characteristics

A

Thicker walls, narrower lumens, usually round when cut

43
Q

Vein characteristics

A

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

44
Q

Lymphatic vessels

A

Very thin walls, only endothelial lining, may contain valves

Histology (8 decks)

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