Muscle tissue Flashcards Preview

Cells to Tissues > Muscle tissue > Flashcards

Flashcards in Muscle tissue Deck (49):
1

What is a muscle fascicle composed of?

Bundles of muscle fibers

2

What are myofibrils?

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

3

What is the structure of myofibrils?

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

4

What is the sarcolemma?

The muscle's name for the plasmalemma.

5

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

A bands are dark
I bands are light

6

Striations are oriented ____ to myofibril axis.

Perpendicular

7

What defines the size/borders of a sarcomere?

Z line to Z line

8

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

Myofibrils

9

How many nuclei do cardiomyocytes have?

1 occasionally 2

10

What is the sarcoplasmic cone?

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

11

How do intercalated discs appear?

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

12

What is the function of intercalated discs?

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

13

Describe the shape/appearance of smooth muscle.

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

14

What are satellite cells?

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

15

Can the number of muscle fibers increase after birth?

No

16

What is cachexia?

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

17

Can muscle regenerate if injured?

If the basal lamina and satellite cells remain intact.

18

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

30% mass, 30-40% strength

19

What is normal age-related reduction in muscle called?

Sarcopenia

20

How is muscle lost due to age?

Loss of muscle fibers and atrophy of remaining fibers.

21

What do myoepithelial cells do?

Help expel fluids from glands

22

When are myofibroblasts useful?

Wound healing

23

What are pericytes?

Contractile/phagocytic/stem cells around blood vessels.

24

What are type I muscle fibers? Describe it.

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

25

What are type IIa muscle fibers? Describe it.

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

26

What are type IIb muscle fibers? Describe it.

White
Fast-twitch
Glycolytic
Strong and fast but fatigues easily

27

What part of the muscle sequesters calcium?

Sarcoplasmic reticulum using calsequestrin

28

What does nebulin do?

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

29

What does titin do?

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

30

What does desmin do?

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

31

Is muscle contraction a shortening of fibers?

No! sliding of filaments past one another.

32

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

Length, diameter

33

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

Red stain small and pale
White stain large and dark

PAS stains glycogen

34

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

Red = small and dark
White = large and light

35

What type of fiber predominates in postural fibers?

Red

36

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

White

37

What determines what a muscle subtype will be?

The neuron that innervates

38

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

Syncytium, myotube, muscle fiber

39

In a muscle fiber, remaining myoblasts are called what?

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

40

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

24

41

What type of muscle contains a lot of mitochondria?

Cardiac

42

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

Cardiac muscle

43

Cardiac muscle has _____s instead of triads.

Dyads

44

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

Cardiac

45

What is ANP?

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).

46

What are cardiac conducting cells?

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

47

What are unique gross properties of smooth muscle?

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

48

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

centrally located

49

What are the fine structures of smooth muscle?

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