Micro Muscle Lecture

Front 1

Mucle arrises from what type of tissue organ (endoderm, mesoderm, or ectoderm?)

Back 1

Mesoderm

Front 2

Four ways to classify muscle include

Back 2

type: skeletal, cardiac, smooth
voluntary vs involuntary
striated vs smooth
contractile components/ myofilaments

Front 3

Skeletal muscle cells (one fiber) is a cylindrical _____with _______nuclei

Back 3

Syncytium
-multiple, peripherally located

Front 4

Syncytium definition

Back 4

a cell divides without undergoing cytokinesis

Front 5

In skeletal muscle the fibers are_____packed, (organized/disorganized), (striated or smooth)

Back 5

tightly packed, organized cytoplasmic protein filaments and striated

Front 6

Connective tissues assocated with skeletal muscle include three layers

Back 6

epimysium, perimysium, endomysium

Front 7

Epimysium

Back 7

Connective tissue around entire muscle

Front 8

Perimysium

Back 8

Connective tissue around groups of myofibers

Front 9

Endomysium

Back 9

Connective tissue around individuals myofibers

Front 10

Is there an extensive or lacking capillary network in skeletal muscle

Back 10

an extensive capillary network to meet the high energy requirement of skeletal muscle demands

Front 11

Connective tissue type on skeletal muscle

Back 11

cross-sectional view of muscle: A. epimysium B. perimysium C. endomysium D. myofibrils E. sarcolemma of one muscle fiber F. collagen fibers

Front 12

How do you distinguish the I band from the A band on skeletal muscle?

Back 12

Dark = A band
Light = I band
dArk vs lIght

Front 13

A Sarcomere is a _____unit that runs from __line to ___line

Back 13

single contraction unit that runs from z line to z line

Front 14

The Sarcolema of a muscle fiber can be thought of the

Back 14

plasma membrane of the cell

Front 15

The Sarcoplasmic reticulum of a muscle fiber can be compared to the ____ of a generic cell

Back 15

Endoplasmic reticulum
where Ca++ is released for contraction

Front 16

Differences in the myofilament of the I and A bands

Back 16

I band has no myosin included and the A band has both myosin and actin

Front 17

Distinguish between the A, H, and A band

Back 17

I band is actin, troponin, and tropomysin (stains light -more eosinophilic)
H band is thick and myosin only
A nad is both actin and myosin with a darker stain

Front 18

Which band changes in lenght during a contraction/ shortening of the sarcomere?

Back 18

The H band width becomes shorter and there is no changein teh A band

Front 19

Name the most superficial connective tissue around a microfiber?

Back 19

Endomyosin

Front 20

What are the three thin filaments/ muscle proteins

Back 20

actin (2 strands of fibrous actin in 2xhelix)
tropomyosin (fibrous, located b/w strands of actin 2x helix)
Troponin (regulatory components, located along actin 2x helix and attached to tropomyosin) Troponin C is associated with Ca++

Front 21

What is the thick filaments/ muscle protein

Back 21

myosin- has ATP-ase activity within strand and 2 heavy chain tails connected together

Front 22

How does a muscle contraction take place?

Back 22

acetylcholine released from a motor nerve binds to its receptors on the muscle cell,
a wave of depolarization spreads along the sarcolemma into the transverse tubules (these extend
into the interior, so the depolarization wave goes deep into the myofiber), a calcium channel called
DHPR is activated, opening a calcium channel on the SER called the ryanodine receptor, Ca++ is
released from the sarcoplasmic reticulum, Ca++ binds to a protein called ‘troponin’ and allows
myosin to interact with actin, which is necessary for energy + ADP to be formed from ATP; the
energy causes the myosin head to bend, pulling actin along the myosin filament.

Front 23

What is the difference between a ‘motor endplate’ and a ‘motor unit?’

Back 23

motor endplate is the myoneural junction: the synapse between the motor axon and
the skeletal fiber; the neurotransmitter is acetylcholine, and there is an enzyme,
acetylcholinesterase, in the synaptic space that inactivates acetylcholine. The ‘motor unit’ is one
alpha (lower) motor neuron in the spinal cord ventral horn and all the myofibers it innervates

Front 24

What is the neurotransmither that initiates depolarization which spreads via t-tubules

Back 24

Acetylcholine (ACh)

Front 25

What are the t-tubules?

Back 25

Transverse tubules are invaginations of the cel membrane that extend b/w myofibrils

Front 26

What are the terminal cisternae?

Back 26

Expansions of the SER and located adjacent to T-tubules

Front 27

Depolarization of sarcolemma is conducted down T-tubule to the triad junction where the _____ activates the_______ on the sarcoplasmic reticulum

Back 27

DHPR- dihydropyridine receptor activating the RyR (ryanodine receptor)

Front 28

An actin-myosin complex forms when _____binds to Calcium and the thick and thin filaments "slide" across one another as the myosin changes conformation when it______

Back 28

Troponin C
Hydrolyzes ATP

Front 29

Muscle Fibers can be classified by fnxts and colors including ___-

Back 29

Red fibers(Type 1= endurance)
White fibers (Type II = sprint)
Intermdt fibers (type IIa)

Front 30

What is the difference between ‘red’ (type I) myofibers and ‘white’ (type II) myofibers?

Back 30

Red fibers (type I) are slow twitch but long-endurance, look more ‘red’ because they have
a higher content of myoglobin and cytochromes, more mitochondria and have aerobic metabolism.
White fibers (type IIb) are fast twitch but of short duration – they tire rapidly, have anaerobic
metabolism, low content of myoglobin and cytochromes and have fewer mitochondria. There are
actually fibers intermediate between these two called type IIa.

Front 31

True or False: The red:white fiber ratio in muscle can be modified

Back 31

yes by training and use

Front 32

Muscle Spindle is located_______and serves to _______

Back 32

b/w endomysium and perimysium and is part of the regulation mechanism of muscle contraction

Front 33

What is a muscle spindle?

Back 33

stretch receptors found usually in the c.t. of muscle. They contain miniature
versions of skeletal muscle called “intrafusal fibers” (hence, regular fibers are called “extrafusal
fibers”). They are innvervated by gamma motor neurons (not alpha motor neurons like those
going to extrafusal fibers). They send sensory information to the spinal cord

Front 34

The sensory nerves in the muscle spindle can ____

Back 34

sense if the muscle is straight or contracted and detect the degree of the stretch of the intrafusal fibers

Front 35

The gamma efferent (motor) nerves in muscle spindle maintain ___

Back 35

tension in the intrfusal fibers

Front 36

Cardiac muscle is (smooth/ striated ) and (voluntary/voluntary)

Back 36

striated and involunatry

Front 37

Distinguishing characteristics of cardiac vs skeletal muscle include

Back 37

smaller, branched cells, only one centrally located nucleus per cell (some have 2) and intercalated discs (joining cells for end-end communication)

Front 38

What are ‘satellite’ cells?

Back 38

Spindle-shaped cells that lie within the basal lamina but outside the sarcolemma.They retain the ability to divide (remember,
the nuclei of the myofiber cannot divide). Thus after injury, especially in young animals, satellite
cells can form some new myofibers

Front 39

What are the cardiac intercalated discs?

Back 39

an electron dense junctional comples that contains gap junctions and desmosomes that transmit contractile stimuli and create the functional syncytium

Front 40

What are the three types of junctions within the intercalted disks?

Back 40

Fascia adherens
Desmosomes
Gap Junctions

Front 41

What are the differnt functions of the three types of junctions of the intercalated disks?

Back 41

Fascia adherens- provide intercellular adhesion, anchors actin filaments
Desmosomes- provide interacellular adhesion (prevent separation during contraction)
Gap Junctions- allow for rapid communication of electric and chemcial signals

Front 42

For the cardiac muscle contraction the intrinsic conduction system is carried out by_________

Back 42

Purkinje Fibers and low electrical reistance of gap jnxts

Front 43

What are the purkinje fibers?

Back 43

modified cardiac myocytes that are specializaed for orchestrated contraction

Front 44

Purkinje Fibers

Back 44

Modified cardiac myocytes specialized for the orchestrated contraction

Front 45

Distinguishing characteristics of smooth muscle

Back 45

non-striated
involuntary
cells are spindle-shaped
One nucleus per cell (elongated and oval)
scant CT separated them
unorganized myofilaments

Front 46

The analogous structure in smooth muscle for T-tubules is the

Back 46

caveoli

Front 47

The analogous structure in smooth muscle that holds filaments in register is the

Back 47

dense bodies

Front 48

Smooth muscle contraction also involves the myosin and actin interaction but is also regulated by different types of ___

Back 48

surface receptors that activate diff second messenger systems. this involves phosphorylation of myosin light chains

Front 49

How do the three types of muscles regenerate themselves?

Back 49

skeletal muscle-uses satellite cells and connective tissue scars
Cardiac-very little regeneration (transplating stem cells)
Smooth muscle (normal cell division)

Front 50

smooth muscle

Back 50

smooth muscle

Front 51

TEM skeletal muscle

Back 51

TEM skeletal muscle

Front 52

comparison chart

Back 52

chart

Front 53

does smooth muscle contain gap jnxts?

Back 53

yes

Front 54

What is the morphology of smooth muscle cells?

Back 54

They are long, spindle-like cells (you usually can’t see this on H&E because they blend
together and form a smooth mass); they have one centrally-positioned, elongated nucleus, (which
may appear folded due to contraction after death). Smooth muscle is non-striated and involuntary

Front 55

muscle spindle

Back 55

muscle spindle= stretch receptors found usually in the c.t. of muscle. They contain miniature
versions of skeletal muscle called “intrafusal fibers” (hence, regular fibers are called “extrafusal
fibers”). They are innvervated by gamma motor neurons (not alpha motor neurons like those
going to extrafusal fibers). They send sensory information to the spinal cord