Bsf Block 2: Muscle Tissue Histology (Miller)

Front 1

The two types of involuntary muscle are...

Back 1

smooth and cardiac muscle

Front 2

Is cardiac muscle striated?

Back 2

yes, although it is involuntary

Front 3

_______________ are muscle cell precursors, derived from somite myotomes, committed to the muscle cell lineage and eventually form _____________.

Back 3

-Myogenic cells
-myoblasts

Front 4

What are the embryonic uninucleate precursors to the mature muscle fiber?

Back 4

myoblasts

Front 5

What are the multinucleate immature muscle cells, each formed by the fusion of many (hundreds of) myoblasts called?

Back 5

myotubes

Front 6

What is the muscle cell contractile apparatus called?

Back 6

myofibril

Front 7

Do muscle fibers stop growing postnatally?

Back 7

No. developing muscle fibers increase in length and thickness and continue to add myofibrils

Front 8

A mature myofiber has a sarcoplasm nearly filled with...

Back 8

myofibrils

Front 9

The nuclei of the mature myofibril appears as what?

Back 9

long, oval and immediately adjacent to the sarcolemma

Front 10

The mitochondria of mature myofibers are found where?

Back 10

packed in the subsarcolemmal space and between myofibrils

Front 11

Mature skeletal muscle fibers normally vary from ____________ in diameter, and can change in response to exercise.

Back 11

10 to 100 μm

Front 12

Skeletal muscle is composed of many bundles of ________ filled with ______________.

Back 12

myofibers filled with myofibrils

Front 13

A single mature muscle cell is called a

Back 13

myofiber

Front 14

Myofibrils (inside myofibers) are how wide?

Back 14

1 to 2 μm

Front 15

What is responsible for the light and dark cross-striation pattern observed in skeletal muscle longitudinal sections?

Back 15

myofibrils

Front 16

Cytoskeletal intermediate filaments composed of ______________ attach adjacent myofibrils.

Back 16

desmin

Front 17

What is the repeating subunit of a myofibril that comprises the basic contractile unit of striated muscle?

Back 17

sarcomere

Front 18

Thick filaments are composed of __________ and thin filaments are composed of _________.

Back 18

-thick: myosin
-thin: actin

Front 19

Each myosin molecule is composed of __________ and __________.

Back 19

2 heavy chains and 2 light chains

Front 20

The myosin heavy chain is composed of...

Back 20

light meromyosin (the rod portion of the myosin) and heavy meromyosin (the globular head of the myosin). The portion connecting the light and heavy meromyosin is flexible

Front 21

How do the myosin light chains associate with the myosin heavy chains?

Back 21

two light chains associate with one heavy chain globular head

Front 22

Thick and thin filaments (can/cannot) be seen under a light microscope.

Back 22

cannot

Front 23

Thin filaments are composed of what 3 things?

Back 23

-actin
-tropomyosin
-troponin

Front 24

Filamentous actin (F-actin) is formed by the polymerization of many ________ molecules.

Back 24

G-actin

Front 25

Each thin filament is composed of __ F-actin chains wound together. This creates ____________ along the length of the bound F-actin chains.

Back 25

-2 F-actin chains double stranded

-creates 2 shallow grooves along the length of the double stranded F-actin

Front 26

Tropomyosin is found in the _______. What is its function?

Back 26

found in the shallow grooves in double stranded F-actin. INHIBITION: Functions to block the myosin head binding site on the actin during the resting (non-contractile) phase

Front 27

Troponin T does what?

Back 27

binds the entire tripeptide troponin complex to Tropomyosin

Front 28

Troponin I does what?

Back 28

Inhibits actin-myosin interactions by positioning the tropomyosin onto actin

Front 29

Troponin C does what?

Back 29

binds calcium

Front 30

Myosin is ONLY found in the ___ band.

Back 30

A band (dark, thick filaments)

Front 31

What is the H band and what is found there?

Back 31

It is the pale center of the A band. Only myosin (thick filaments) is there--the actin cannot overlap into this H band.

Front 32

What do the dark regions on either side of the H band represent?

Back 32

it is the overlap between thick and thin filaments (actin and myosin)

Front 33

What is the line that bisects the H band?

Back 33

the M line

Front 34

What is found in the I band?

Back 34

only actin/tropomyosin/troponin; no myosin

Front 35

What is the line that bisects the I band and what does it do?

Back 35

Z line. Made of alpha-actinin and is where the thin filaments (Actin) attach

Front 36

A sarcomere extends from what to what?

Back 36

from Z disc to Z disc. NOTE: this means that only HALF of each I band is considered part of the sarcomere

Front 37

Each myofibril is enveloped by a meshwork of....

Back 37

sarcoplasmic reticulum

Front 38

The sarcoplasmic reticulum (SR) is derived from what organelle?

Back 38

SMOOTH endoplasmic reticulum

Front 39

________________ are located at the junction overlap between the A and I bands of the sarcomere, and together with a pair of ___________ (bulbous enlarged areas of the sarcoplasmic reticulum) it forms an arrangement called a ____.

Back 39

-T tubules
-terminal cisternae
-triad

Front 40

Junctional feet, the connections between T tubules and the terminal cisternae, are composed of what 2 receptors?

Back 40

1. Voltage-sensitive proteins in the T-tubule membrane (DHP RECEPTORS)
2. Calcium release channels on the SR terminal cisternae (RYANODINE RECEPTORS)

Front 41

In the relaxed state, __________ partially covers the myosin binding site on actin and the ________ complex holds tropomyosin in the proper position along the F-actin groove.

Back 41

-tropomyosin

-troponin

Front 42

What carries a depolarization transversely along the myofiber?

Back 42

the T tubules, which are transverse invaginations of the sarcolemma

Front 43

What does a depolarization do to the myofiber?

Back 43

it changes the conformation of the DHP receptor, which opens the adjacent SR Calcium release channel (ryanodine receptor), causing an influx of calcium into the cytoplasm

Front 44

When calcium is let into the sarcoplasm after depolarization, what is the first thing that it does?

Back 44

it binds TnC, causing a dissociation of of TnI and actin...shifting tropomyosin deeper into the F-actin groove, exposing the myosin head binding sites on the G-actin allowing association and the eventual power stroke

Front 45

Contraction occurs only if ATP is available to supply the ___________.

Back 45

myosin head ATPase

Front 46

In contraction, the __________ filament slides over the _________ filament.

Back 46

thin slides over the thick since the thick (myosin heads) pulls on the thin, causing it to slide

Front 47

Cessation of neural impulses to muscles initiates relaxation by doing what physiologically?

Back 47

it closes the SR calcium release channels (ryanodine receptors). The remaining calcium in the sarcoplasm is pumped BACK into the SR.

Front 48

What is the calcium binding protein present in the terminal cisternae that concentrates calcium in preparation for the next contraction?

Back 48

Calsequestrin

Front 49

Rigor mortis occurs in the human body because ______ is no longer available...this keeps actin associated with myosin.

Back 49

ATP

Front 50

Sensory neurons innervating skeletal muscles are associated with ________________, a stretch receptor.

Back 50

muscle spindles

Front 51

What kind of receptors populate the post-synaptic region of the sarcolemma?

Back 51

acetylcholine receptors

Front 52

In muscles the require fine control, such as the fingers, each motor axon innervates (few/many) muscle fibers?

Back 52

each innervates only a few

Front 53

a motor neuron and all of the muscle fibers it innervates is called a...

Back 53

motor unit

Front 54

Although motor neurons can innervate many muscle fibers, each muscle fiber is innervated by only _____ motor neuron.

Back 54

one

Front 55

Slow-twitch fibers use ____________ for their energy demands. This gives them...

Back 55

they are the aerobic tissues. they use oxidative phosphorylation and therefore have many mitochondria

Front 56

Slow-twitch fibers appear _____ in color due to the presence of __________ and ________.

Back 56

-red
-myoglobin and large amounts of mitochondria

(NOTE: large amounts of myoglobin are necessary to supply the large amounts of mitochondria with oxygen)

Front 57

Fast-twitch fibers have a _________ cross-sectional area than slow-twitch fibers. Why?

Back 57

-greater area due to presence of many myofibrils

Front 58

Fast-twitch fibers derive their energy from what metabolic process?

Back 58

glycolysis

Front 59

Fast twitch fibers appear _____ in color due to what?

Back 59

white due to the absence of myoglobin (they don't need the oxygen as they don't have many mitochondria)

Front 60

Motor units are also named as the fiber types, since each motor unit is homogenous in fiber type. Muscle fiber type is controlled by the innervating motor neuron?????????

Back 60

??????????

Front 61

What is most commonly assayed for distinguishing muscle fiber types?

Back 61

Myosin ATPase activity

Front 62

When doing the myosin ATPase histochemical technique, what does adding acid do?

Back 62

it produces COLORLESS FAST TWITCH fibers....so all you see is the slow twitch as dark.

ACID = FAST TWITCH ABSENT

Front 63

When doing the myosin ATPase histochemical technique, what does adding base do?

Back 63

it produces COLORLESS SLOW TWITCH fibers...so all you see is the fast twitch as dark and slow twitch as colorless.

BASE = FAST TWITCH BOLDENED

Front 64

What protein is a Z-disc component involved in anchoring thin filaments, as well as a transsarcolemmal filaments at the myotendinous junction, important in transmitting muscle contractile force to a tendon?

Back 64

alpha-Actinin

Front 65

What protein binds Z-discs of adjacent myofibrils, thus keeping adjacent myofibrils in register?

Back 65

desmin

Front 66

What protein is a subsarcolemmal protein that is part of the linkage between the cytoskeleton and the extracellular matrix, offering structural support to the sarcolemma?

Back 66

dystrophin

Front 67

What is the is the largest protein discovered in humans, forming a longitudinal elastic lattice for myofibrils and assisting in holding thick filaments in place (traversing the Z disc all the way to the A band)?

Back 67

Titin (like a titan)

Front 68

What connective tissue covers the entire skeletal muscle?

Back 68

Epimysium

Front 69

What connective tissue surrounds a group of myofibers?

Back 69

perimysium

Front 70

What is a fasicle?

Back 70

a bundle of myofibers surrounded by perimysium

Front 71

What is the connective tissue covering each myofiber called?

Back 71

endomysium

Front 72

What is endomysium composed of?

Back 72

it's delicate: reticular fibers

Front 73

T or F. Myofibers can be regenerated through mitosis.

Back 73

False. Only through satellite cells can myofibers be salvaged or regenerated

Front 74

What are the small, uninucleate cells lying under the myofiber basal lamina that can fix/regenerate myofibers?

Back 74

satellite cells

Front 75

structures that inform the central nervous system of body position and movement are called...

Back 75

Proprioceptors

Front 76

What proprioceptor is composed of a group of about 2-to-10 specialized muscle fibers surrounded by a fluid-filled connective tissue capsule?

Back 76

muscle spindles

Front 77

What kind of fibers comprise the muscle spindle? How do they compare to other muscle fibers?

Back 77

intrafusal fibers. they are shorter and thinner than extrafusal fibers

Front 78

The center of each intrafusal muscle fiber found in proprioceptor cells is occupied by what?

Back 78

1. a bulging aggregation of nuclei
OR
2.a single row of nuclei

Front 79

Intrafusal fibers with a single row of nuclei are _______________ than those with a bulging aggregation of nuclei.

Back 79

thinner but more numerous

Front 80

Intrafusal fibers of proprioceptor muscle cells receive motor innervation at ___________ from __________.

Back 80

at their unencapsulated, myofibril containing distal portions by γ-efferent neurons

Front 81

Intrafusal fibers of proprioceptor muscle cells receive sensory innervation from __________ and __________.

Back 81

primary afferent neurons and secondary afferent neurons

Front 82

Primary afferent neurons in priprioceptor muscle cells respond to __________.

Back 82

rate of stretch

Front 83

Secondary afferent neurons in priprioceptor muscle cells respond to __________.

Back 83

duration of stretch

Front 84

In the spinal cord, the_____________________ synapse with alpha-motor neurons that innervate skeletal muscle extrafusal fibers.

Back 84

- afferent neurons of proprioreceptive cells

Front 85

The patellar tendon reflex is an example of the ________________________. Thus, muscle spindles detect ____________.

Back 85

proprioceptive response

detect changes in in muscle length

Front 86

proprioceptors found near the myotendinous junction composed of sensory neurons surrounded by collagen fibers in a capsule are called..................

Back 86

Golgi tendon organs (GTOs)

Front 87

Golgi tendon organs provide the spinal cord with information about...

Back 87

muscle tension

Front 88

When muscle tension is suddenly increased, ________ provide inhibitory feedback to stimulate relaxation.

Back 88

GTOs

Front 89

Smooth muscle exists in the dermis as ______________________ and in the GI tract as _______________.

Back 89

-dermis: small, scattered bundles of a few fibers
-GI tract: thick layers

Front 90

T or F. T tubules are present in smooth muscle.

Back 90

False. However, there IS a SR

Front 91

What are caveolae?

Back 91

depressions in the sarcolemma of smooth muscle cells that look like the beginnings of pinocytotic vesicles. They are involved in calcium sequestration

Front 92

The thin filaments of smooth muscle are composed of what?

Back 92

Actin, tropomyosin, but NO TROPONIN

Front 93

The intermediate filaments of smooth muscle are composed of what?

Back 93

desmin

Front 94

Besides no troponin, what are the other 2 major differences between the thin filaments of smooth muscle vs skeletal?

Back 94

smooth muscle actin is much longer and there is a LOT more actin in smooth muscle than in skeletal

Front 95

Where do the thin and intermediate filaments insert to form a contractile unit in smooth muscle?

Back 95

dense bodies and dense plaques

Front 96

What is found in dense bodies?

Back 96

alpha actinin

Front 97

What is found in dense plaques?

Back 97

alpha actinin, vinculin, talin

Front 98

What 2 extracellular components help physically transmit the force of contraction?

Back 98

a basal lamina and reticular fibers

Front 99

Explain the 5 steps of the smooth muscle contraction mechanism.

Back 99

1. Calcium released from SR/caveolae
2. Calcium binds to calmodulin
3. Calcium--calmodulin complex activates myosin light chain kinase (MLC kinase)
4. MLC kinase phosphorylates myosin light chain, unmasking the actin binding site on the myosin heavy chain globular heads
5. Actin can now interact with myosin

Front 100

Which contraction, smooth or skeletal muscle, takes a longer time to accomplish? Why?

Back 100

Smooth because the phosphorylation step is slow

Front 101

T or F. Smooth muscle contraction requires less ATP than skeletal muscle.

Back 101

True

Front 102

When smooth muscle cells contract, what two things get pulled towards one another?

Back 102

the dense bodies

Front 103

When a smooth muscle cell contracts, what transmits the force to the extracellular connective tissue (reticular fibers/basal lamina)?

Back 103

the attachments at the sarcolemma (dense plaques)

Front 104

When a smooth muscle cells is contracted, the nucleus takes on a _________________ appearance.

Back 104

"corkscrew"

Front 105

What causes muscle relaxation in smooth muscle cells?

Back 105

Calcium is pumped back into the caveolae

Front 106

The smooth muscle contraction mechanism can be controlled by what 2 things?

Back 106

1. innervation (duh)
2. hormones that act on cAMP

Front 107

What type of smooth muscle has each muscle fiber individually innervated? What are some examples?

Back 107

multiunit smooth muscle

iris of the eye and the vas deferens of the male reproductive tract (very rare)

Front 108

What type of smooth muscle allows impulses to be spread from cell-to-cell via gap junctions?

Back 108

visceral (unitary) smooth muscle. much more common than multiunit smooth muscle

Front 109

Increasing cAMP levels in smooth muscle cells through hormonal control leads to ___________ of the muscle cell. How?

Back 109

relaxation. cAMP inhibits MLC kinase. Does not need to eliminate the Ca--calmodulin complex...it skips that step

Front 110

How is smooth muscle regenerated?

Back 110

Mitosis. This is unlike skeletal muscle