Muscle Tissue Part 2

Question 1

Smooth muscle characteristics

Answer 1

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

Question 2

Shape of smooth muscle cells

Answer 2

Fusiform cells. aka Elongated spindle-shaped

Question 3

Where is the nuclei of smooth muscle cells?

Answer 3

Centrally placed. Long/cigar shaped with tapered ends

Question 4

What does the sarcoplasm of smooth muscle cells consist of?

Answer 4

Myofilaments and organelles, numerous mitochondria

Question 5

How are the myofilaments arranged in smooth muscle?

Answer 5

Randomly distributed throughout the cytoplasm

Question 6

What do the thin filaments of smooth muscle anchor to?

Answer 6

Dense bodies

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Caveolae

Question 9

Communicating junctions

Answer 9

gaps in the smooth muscle to connect the muscle cells

Question 10

Reticular fibers in smooth muscle

Answer 10

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

Question 11

Thin filaments of smooth muscle

Answer 11

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

Question 12

Caldesmon

Answer 12

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

Question 13

Thick filament of smooth muscle

Answer 13

Myosin II

Question 14

Composition of myosin II

Answer 14

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

Question 15

When does smooth muscle myosin bind to actin?

Answer 15

Only when phosphorylated

Question 16

Where does the neural stimulation of smooth muscle occur?

Answer 16

Thru the post ganglion of the autonomic system

Question 17

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

Answer 17

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

Question 18

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

Answer 18

Impulse transmission occurs via gap junctions

Question 19

What can elicit chemical stimulation in smooth muscle?

Answer 19

Hormones, angiotensin II, vasopressin

Question 20

What effect does mechanical stimulation of smooth muscle elicit?

Answer 20

Can lead to the initiation of muscular contraction

Question 21

What drives the contraction of smooth muscle?

Answer 21

High concentrations of Ca++

Question 22

Ca++’s effect on smooth muscle fibers

Answer 22

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

Question 23

What does myosin light-chain kinase do?

Answer 23

Phosphorylates the regulatory (light) chain of the myosin molecule

Question 24

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

Answer 24

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.

Question 25

Smooth muscle relaxation

Answer 25

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

Question 26

Latch state

Answer 26

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

Question 27

Smooth muscle blood supply

Answer 27

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

Question 28

Active regeneration response

Answer 28

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

Question 29

Cardia muscle blood supply

Answer 29

Extensive blood supply thru a network of capillaries

Question 30

Regeneration of cardiac muscle

Answer 30

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

Question 31

Characteristics of cardiac muscle CELLS

Answer 31

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.

Question 32

Intercalated disks

Answer 32

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

Question 33

Transverse portion of the intercalated disks

Answer 33

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

Question 34

Adherens junctions

Answer 34

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

Question 35

Desmosomes

Answer 35

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

Question 36

Lateral portion of intercalated disks

Answer 36

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

Question 37

T-tubules in cardiac muscle

Answer 37

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.

Question 38

Diads

Answer 38

One T-tubule and its surrounding small terminal cisternae

Question 39

Purkinje fibers

Answer 39

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

Question 40

Nodes/bundles of Purkinje fibers

Answer 40

Sinoatrial node, atrioventricular node, bundle of His

Question 41

Layers of Arteries/Veins

Answer 41

Tunics: Tunica intima, tunica media, tunica adventitia

Question 42

Artery characteristics

Answer 42

Thicker walls, narrower lumens, usually round when cut

Question 43

Vein characteristics

Answer 43

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

Question 44

Lymphatic vessels

Answer 44

Very thin walls, only endothelial lining, may contain valves