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Histo Final Exam Extravaganza! > Muscles > Flashcards

Muscles Flashcards

1
Q

Epimysium

A

outside layer of connective tissue surrounding entire bundle of muscle, contains dense irregular connective tissue with blood vessels and fibroblasts

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2
Q

perimysium

A

connective tissue surrounding fascicle, contains dense irregular connective tissue, blood vessels and nerves

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3
Q

fascicle

A

bundle of myocytes

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4
Q

Endomysium

A

layer of connective tissue surrounding each muscle cell, contains reticular fibers, nerve fibers, and capillaries

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5
Q

a muscle cell

A

Myocyte
Muscle fiber
Myofiber

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6
Q

Satelite cells

A

located between myocytes

Involved in growth and addition of muscle cells

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7
Q

Skeletal Muscle structrue

A

Peripherally multinucleated cells

Thicker muscle= more nuclei

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8
Q

Myofibrils

A

strands of protein inside myofiber, think myosin and thin actin filaments necessary for contraction

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9
Q

Myoblasts

A

precursor muscle cells

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10
Q

striations

A

caused by overlap of myofibrils

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11
Q

Sarcomere

A

structural unit of myofibril

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12
Q

z line

A

boundaries between adjacent sarcomeres

attachment of actin filiments

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13
Q

A band

A

dark band, corresponds to myosin filaments

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14
Q

H zone

A

Lighter zone inside of A band. Contains only myosin filaments

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15
Q

I band

A

Light area on each side of z line where actin does not overlap myosin

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16
Q

Tropomyosin

A

at rest, prevents myosin binding to actin (located on actin)

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17
Q

Troponin

A

Holds tropomyosin in place:

Ca binds to troponin and pulls on tropomyosin exposing myosin binding site on actin

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18
Q

Myosin

A

binds actin, binds ATP, hydrolyses ATP

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19
Q

How does overlap of myofibrils impact force production?

A

To much or too little overlap will cause less force production. The force production changes during the range of motion as a result.

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20
Q

Sarcolemma

A

plasma membrane of myocyte that can conduct action potentials

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21
Q

T-tubules

A

invagination of plasma membrane that transport action potential

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22
Q

Sarcoplasmic reticulum

A

internal membrane compartment that stores, releases, and reclaims Ca

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23
Q

synaptic cleft

A

gap where neurotransmitters (acetylcholine) are released by presynaptic motor neuron

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24
Q

motor unit

A

one motor neuron and all the muscle fibers it innervates

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25
Q

Small motor unit

A

low force, high precision

26
Q

Large motor unit

A

high force, low precision

27
Q

Order of motor unit recruitment

A

small first and then move onto large

28
Q

red skeletal muscle

A

slow oxidative, small diameter, endurance, extensive blood supply, more myoglobin, higher affinity for oxygen creates red color, more mitochondria, more intracellular lipid, ready energy supply, contract and fatigue slowly

29
Q

White skeletal muscle

A

fast glycolytic, more extensive sarcolemma, rapid Ca release and contraction, more glycogen, faster ATPase, recruited fast, contracts quicker, fatigue easily

30
Q

Myogenesis

A

During development myoblasts proliferate and fuse together to become myoctes

31
Q

myotubes

A

(immediate) precursor to muscle cell)

32
Q

atrophy

A

muscle size decreases: myonuclear loss, decreased myofibrillar proteins, decreased myofiber cross sectional area

33
Q

hypertrophy

A

muscle size increases: myonuclear addition, increased myofibrillar proteins, increased myofiber cross-sectional area

34
Q

hyperplasia

A

adding more cells

35
Q

myostatin

A

regulates muscle growth by preventing hypertrophy, can also impact cardiac muscle

36
Q

isotonic contraction

A

same tone/ force, muscle moves

37
Q

concentric phase

A

part of isotonic contraction, more heat, less force, muscle shortens

38
Q

eccentric phase

A

Part of isotonic contraction, less heat, more force, more damage, lengthen muscle, rip apart actin and myosin without ATP

39
Q

isometric contraction

A

same length, increased muscle tone but no movement, important for posture and stabilization, increased activation of motor neuron, better maintenance of muscle mass

40
Q

external rhabdomyolysis

A

(race horses), sarcolemma rips apart and contents (myoglobin) leak due to too much physical activity, myoglobin clogs up kidneys, can’t filter blood leading to kidney failure, can occur due to burns

41
Q

Cardiac myocyte

A

single centrally located nucleus, fibers branch and anastomose, more mitochondria than skeletal muscle, intercalated discs

42
Q

Why do cardiac myocytes have more mitochondria than skeletal muscle?

A

Provides high aerobic capacity, can use mandy energy substrates

43
Q

Intercalated discs

A

cell junctions, desmosomes=mechanical link between cells, gap junctions= electrical link between cells

44
Q

paricardium

A

double-walled sac surrounding the heart, full of collagen

45
Q

Connective tissue of cardiac muscle

A

reticular fibers surround each cell (endomysium), myocyte groups divided by thick bundles of connective tissue (perimysium). No analogous epimysium.

46
Q

Where are natriuretic peptides secreted and why?

A

Secreted by atrial myocytes to cause loss of water and sodium in kidney causing ECF volume to decrease and decrease blood pressure. Promote relaxation of smooth muscle in vessel walls
Note: this is a chemical response where baroreceptors are a separate autonomic response

47
Q

Which cardiac myocyte is larger?

A

Ventricular myocytes because they have a higher pressure gradient to overcome.

48
Q

Purkinje Fibers

A

Modified cardiac myocytes, impulse conducting fibers, noncontractile,
more cytoplasm and fewer myofibrils, no myoglobin (pale cytoplasm), have SR but lacks T tubules

49
Q

Contraction of cardiac muscle

A
  1. Ca released from SR
  2. cross bridge formation between actin and myosin
  3. Resting potential in unstable so ions leak across membranes *difference

electrical coupling between cells causes spread of action potential

50
Q

Smooth muscle characteristics

A

single centrally located nucleus, spindle shaped, each cell surrounded by reticular fibers, tissue rich in blood vessels and nerves, lack striations, involuntary

51
Q

Organs with smooth muscle

A

lines intestines, stomach, esophagus, uterus, gallbladder, and urinary bladder,

52
Q

Filaments of smooth muscle

A

arranged in various orientations (no striations or sarcomeres), tropomyosin but no troponin on actin

53
Q

dense bodies

A

anchor myofilaments to ECM and other cells in smooth muscle

54
Q

How is tone of smooth muscle different than skeletal muscle?

A

Smooth muscle always has some overlap of myofilaments/ tone, so there is always partial contraction/ force production

55
Q

contraction of smooth muscle

A

evets take longer, under control of autonomic nervous system, when myosin is phosphorylated it binds to action and muscle shortens, contraction slower and more sustained

56
Q

How does myosin become phosphorylated in smooth muscle?

A

Caused by an increase in intracellular Ca which binds to calmodulin which activates calcium calmodulin complex which phosphorylates myosin light-chain kinase (MLCK) which phosphorylates myosin which binds action creating a cross bridge.

57
Q

Channels responsible for calcium regulation in smooth muscle

A

stretch-activated and ligand gated cation channels, and voltage dependent calcium channel

58
Q

Unitary smooth muscle

A

cells linked by gap junctions (like cardiac), all cells act as a unit
eg. stomach

59
Q

multi-unit smooth muscle

A

no gap junctions, individual cells get own innervation, allows for precise contraction, eg. iris

60
Q

How are arteries and veins differently shaped?

A

Arteries are more circular because smooth muscle holds them up, but veins have less smooth muscle so they are irregularly shaped

61
Q

Fibroblast nuclei vs. myocyte nuclei

A

fibroblast nuclei are located near empty space and darker than lighter muscle nuclei in the muscle cells

62
Q

appearance of smooth muscle vs dense connective tissue

A

dense connective tissue nuclei are usually outside the fibers, smooth muscle fibers are cells, while connective tissue “fibers” are cables of acellular collagen

Histo Final Exam Extravaganza! (9 decks)

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