Muscle tissue

Question 1

What is a muscle fascicle composed of?

Answer 1

Bundles of muscle fibers

Question 2

What are myofibrils?

Answer 2

The principal cytoplasmic component of the muscle fiber: branched rod-like structures that extend the full length of the fiber. Made of sarcomeres.

Question 3

What is the structure of myofibrils?

Answer 3

Repeating segments of identical sarcomeres. Ultrastructurally, composed of 2 types of myofilaments: actin and myosin.

Question 4

What is the sarcolemma?

Answer 4

The muscle’s name for the plasmalemma.

Question 5

The ____ bands are dark and the ___ bands are light.

Answer 5

A bands are dark

I bands are light

Question 6

Striations are oriented ____ to myofibril axis.

Answer 6

Perpendicular

Question 7

What defines the size/borders of a sarcomere?

Answer 7

Z line to Z line

Question 8

What makes up the bulk of the sarcoplasm (muscle cell cytoplasm)?

Answer 8

Myofibrils

Question 9

How many nuclei do cardiomyocytes have?

Answer 9

1 occasionally 2

Question 10

What is the sarcoplasmic cone?

Answer 10

The lighter staining portion in a cardiomyocyte when the myofibril moves around the nucleus.

Question 11

How do intercalated discs appear?

Answer 11

Thin basophilic lines that mark the junctions between myocytes. Perpendicular to the long axis.

Question 12

What is the function of intercalated discs?

Answer 12

Unique characteristic of cardiac muscle. Serve to link the ends of cardiac muscle electrically and physically.

Question 13

Describe the shape/appearance of smooth muscle.

Answer 13

Small, non-striated, spindle-shaped cells each with a single, elongated, centrally located nucleus.

Question 14

What are satellite cells?

Answer 14

Myoblast stem cells that lie in contact with adult fibers, enclosed within the fiber’s external (basal) lamina.

Question 15

Can the number of muscle fibers increase after birth?

Answer 15

No

Question 16

What is cachexia?

Answer 16

Severe wasting of muscle accompanying disease states such as cancer and immunodeficiency.

Question 17

Can muscle regenerate if injured?

Answer 17

If the basal lamina and satellite cells remain intact.

Question 18

How much muscle mass and muscle strength is lost from age 20 to 80?

Answer 18

30% mass, 30-40% strength

Question 19

What is normal age-related reduction in muscle called?

Answer 19

Sarcopenia

Question 20

How is muscle lost due to age?

Answer 20

Loss of muscle fibers and atrophy of remaining fibers.

Question 21

What do myoepithelial cells do?

Answer 21

Help expel fluids from glands

Question 22

When are myofibroblasts useful?

Answer 22

Wound healing

Question 23

What are pericytes?

Answer 23

Contractile/phagocytic/stem cells around blood vessels.

Question 24

What are type I muscle fibers? Describe it.

Answer 24

Red.
Slow-twitch, oxidative.
Capable of repeated contraction without fatigue

Question 25

What are type IIa muscle fibers? Describe it.

Answer 25

``` Intermediate. Fast-twitch Glycolytic-oxidative Fatigue resistant Can convert to one or the other with training ```

Question 26

What are type IIb muscle fibers? Describe it.

Answer 26

White Fast-twitch Glycolytic Strong and fast but fatigues easily

Question 27

What part of the muscle sequesters calcium?

Answer 27

Sarcoplasmic reticulum using calsequestrin

Question 28

What does nebulin do?

Answer 28

Provides a template for precise filament assembly. Controls the length of actin filament.

Question 29

What does titin do?

Answer 29

Confers elasticity on the sarcomere, anchors the myosin to the z line.

Question 30

What does desmin do?

Answer 30

An intermediate filament keeps sarcomeres in a vertical array (i.e. all A bands/I bands lined up)

Question 31

Is muscle contraction a shortening of fibers?

Answer 31

No! sliding of filaments past one another.

Question 32

Maximum range of contraction is related to muscle _____. Maximum strength is related to muscle ______.

Answer 32

Length, diameter

Question 33

On PAS stain, how do red and white fibers appear?

Answer 33

Red stain small and pale White stain large and dark PAS stains glycogen

Question 34

In a cytochrome oxidase stain, how do red and white fibers stain?

Answer 34

``` Red = small and dark White = large and light ```

Question 35

What type of fiber predominates in postural fibers?

Answer 35

Red

Question 36

What type of fiber predominates in sprinting (e.g. gastrocnemius)?

Answer 36

White

Question 37

What determines what a muscle subtype will be?

Answer 37

The neuron that innervates

Question 38

Myoblasts fuse to form a _____, which then assembles in a row to form a ______ which eventually forms a muscle ______.

Answer 38

Syncytium, myotube, muscle fiber

Question 39

In a muscle fiber, remaining myoblasts are called what?

Answer 39

Satellite cells. Along with nuclei, move to periphery when the fiber fills with central myofibrils

Question 40

No new muscle fibers are formed after ~______ weeks of gestation

Answer 40

24

Question 41

What type of muscle contains a lot of mitochondria?

Answer 41

Cardiac

Question 42

T-tubules are larger in diameter and located at z-lines in _____ .

Answer 42

Cardiac muscle

Question 43

Cardiac muscle has _____s instead of triads.

Answer 43

Dyads

Question 44

Is cardiac muscle or skeletal muscle more dependent on extracellular calcium?

Answer 44

Cardiac

Question 45

What is ANP?

Answer 45

Granules located primarily in the atria that are released in response to the stretch of the atrial wall. Acts on kidneys to reduce fluid (and thus return to the heart).

Question 46

What are cardiac conducting cells?

Answer 46

Purkinje fibers. Large cells with many gap junctions and lots of glycogen that initiate electric signaling.

Question 47

What are unique gross properties of smooth muscle?

Answer 47

Capable of mitotic division Can secrete fibers and nonfibrillar ECM Exhibit plasticity

Question 48

In contrast to skeletal muscle, smooth muscle nuclei are...

Answer 48

centrally located

Question 49

What are the fine structures of smooth muscle?

Answer 49

``` Dense plaques (membrane) and dense bodies (within cell) that attach actin. Contain many gap junctions electrically connect cells ("nexus") Cytoplasm dominated by cytoplasmic filaments ```