Histo Muscle

Question 1

What are the 3 major types of muscle?

Answer 1

Skeletal, Cardiac, Smooth

Question 2

What germ layer does all muscle come from? What is the one exception to this rule?

Answer 2

mesoderm

iris comes from the ectoderm

Question 3

Describe the fibers of skeletal muscle.

Answer 3

have peripherally located nuclei…are multinucleated; elongated, striated

Question 4

Describe the contraction of skeletal muscle.

Answer 4

strong, quick, discontinuous, involuntary

Question 5

Describe the fibers of cardiac muscle.

Answer 5

They are striated, mono nucleated or sometimes binucleated, & there are intercalated discs that allow it to act like a synctium…the fibers are branched

Question 6

Describe the contraction of cardiac muscle.

Answer 6

strong, quick, continuous, voluntary

Question 7

Describe smooth muscle fibers.

Answer 7

an agglomeration of cells whose density depends on the amt of surrounding CT…no striations…centrally located cells.

Question 8

Describe the contraction of smooth muscle. What is it like in a relaxed state? In a contracted state?

Answer 8

weak, slow, involuntary
Relaxed State: elongated
Contracted State: all crunched up

Question 9

What do all types of muscle contain? What are these an example of?

Answer 9

Actin & myosin. Microfilaments.

Question 10

What is the structural organization of skeletal muscle?

Answer 10

Sacomeres–>Myofibrils–>muscle fiber=muscle cell–>fascicle–>muscle

Question 11

How does skeletal muscle develop?

Answer 11

primitive mesenchymal cells of the mesoderm–>myoblasts–>myotubes–>muscle fiber=muscle cell

Question 12

What are the 3 layers that cover muscle cells/muscle fibers?

Answer 12

Sarcolemma
Basal Lamina
Endomysium (CT)

Question 13

What covers fascicles?

Answer 13

perimysium

Question 14

What covers the entire muscle?

Answer 14

epimysium

Question 15

What are the 3 layers of the CT sheath around skeletal muscle? What are its functions? What produces it?

Answer 15

Endomysium, Perimysium, Epimysium
connects muscle cells that don’t reach the entire length
necessary to transmit forces from one end to the other
allows for blood vessels & nerves to travel w/ the muscle
fibroblasts make it.

Question 16

What are satellite cells? Where are they found?

Answer 16

stem cells capable of regeneration

found b/w the sarcolemma & the basal lamina

Question 17

What makes the Z disc? M line?

Answer 17

Z disc: cross-linking actin; M-line: myosin tails

Question 18

Explain the structure of a sarcomere.

Answer 18

Z disc, I band, A band, H zone, M line, H zone, rest of A band, I band, Z disc

Question 19

What are the I band, A band, & H band composed of?

Answer 19

I band: only actin; H band: only myosin; A band: myosin & actin & just myosin…essentially the entire length of myosin filaments

Question 20

What is the relationship of the I band & A band to polarized light?

Answer 20

I band has actin thin filaments & is isotropic to polarized light–light pass thru–light in color
A band has thick myosin filaments & is anisotropic to polarized light–light doesn’t pass thru as much–dark in color.

Question 21

What is the AI junction?

Answer 21

It is located b/w the A band & I band…it is an invagination of sarcolemma into muscle cells. Allows proper amt. of Ca++ to get into muscle for uniform contraction.

Question 22

What happens to the sarcomere during contraction according to the sliding filament theory?

Answer 22

Z discs move closer together
I band & H band get smaller b/c they are pure actin & myosin & w/ contraction there is more overlap.
A band stays the same.

Question 23

What are 2 important elements to keep in mind concerning skeletal muscle contraction?

Answer 23

Triggered by calcium.

All or none.

Question 24

At what age does the number of muscle fibers stop increasing? Keep in mind w/ pitching baseball!

Answer 24

14 years of age…about puberty

Question 25

How can you get stronger skeletal muscles?

Answer 25

Increasing thickness--hypertrophy thru repeated exercise Increasing CT Increasing Number of Cells--hyperplasia thru excessive exercise; suppression of myostatin; stimulation of satellite cells NOT the length of muscle cells

Question 26

What is myostatin?

Answer 26

cytokine produced by skeletal muscle; suppresses skeletal muscle growth

Question 27

What else is the epicardium called?

Answer 27

Visceral layer of the serous pericardium

Question 28

What are the layers of the heart (outside--inside) starting with the epicardium on the outside?

Answer 28

Epicardium Myocardium Subendocardial Space Endocardium

Question 29

What are cardiomyocytes derived from?

Answer 29

Mesoderm

Question 30

Where are Purkinje fibers found? What are they? What do they do?

Answer 30

Subendocardial space modified cardiomyocytes propagate contraction down to the apex of the ventricle--blood squeezes out of the pulmonary trunk & aorta

Question 31

What are the 3 types of cardiocytes in the myocardium?

Answer 31

Contractile Cardiocytes--contract & pump blood into circulation Myoendocrine cardiocytes--produces ANP nodal cardiocytes--responsible for rhythmic contraction--in SA & AV nodes.

Question 32

Where are purkinje fibers found?

Answer 32

after the AV node, under the endocardium, lining the interventricular septum

Question 33

How can Purkinje fibers be distinguished from cardiocytes?

Answer 33

Location Purkinje are larger Purkinje stain lighter b/c of the high glycogen content

Question 34

What is found in the subendocardial CT layer?

Answer 34

collagen & elastic fibers made from fibroblasts | blood vessels, nerves, Purkinje fibers

Question 35

What are the 2 main parts of the intercalated discs & what is found their?

Answer 35

Transverse (vertical): fascia adherens & desmosomes | Longitudinal (horizontal): gap jcns

Question 36

How can you differentiate smooth muscle from CT?

Answer 36

There are a ton of nuclei in smooth muscle.

Question 37

What is the exact location of the SA node?

Answer 37

SVC RA jcn

Question 38

What is the exact location of the AV node?

Answer 38

under the endocardium that covers the intertribal & inter ventricular septa.

Question 39

What is located inside of a dense body?

Answer 39

plaque plasma membrane thickening some microfilaments

Question 40

Which types of muscle require calcium?

Answer 40

skeletal, cardiac, & smooth muscle!!

Question 41

What takes up the calcium? What binds it?

Answer 41

Caveolae assist in taking up calcium. | Calmodulin bind the calcium

Question 42

What do smooth muscle cells look like in the relaxed state & the contracted state?

Answer 42

Relaxed: cigar, longitudinal Contracted: all crunched up

Question 43

What is the outside of smooth muscle like?

Answer 43

external basal lamina w/ gap jcns

Question 44

What is the contraction of smooth muscle like?

Answer 44

weak, slow, involuntary

Question 45

What is the nucleus situation of smooth muscle?

Answer 45

mononucleated. Centrally located nuclei.

Question 46

Which types of muscle have T-tubules?

Answer 46

T tubules are found in skeletal & cardiac muscle.

Question 47

Which types of muscle have gap jcns?

Answer 47

Cardiac & Smooth

Question 48

What binds calcium in each type of muscle?

Answer 48

Smooth muscle uses calmodulin. | Skeletal & cardiac muscle uses troponin C.

Question 49

Which types of muscle can undergo mitosis?

Answer 49

Only smooth muscle cells.

Question 50

Cardiac & smooth muscle don't have epimysium...what is their CT sheath situation?

Answer 50

They just have CT sheaths & endomysium.