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ABS - Histology > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

1
Q

General features of muscle tissue

A

Basic tissue type – the most abundant of the four (~40% body weight)
• Contractile properties - modified/controlled by nervous input.
• Highly vascularized.
• Derived from the embryonic mesoderm

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2
Q

Fiber:

A

individual muscle cell (not to be confused with connective tissue fibers which are extracellular, or nerve fibers which are multiple cellular extensions.)

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3
Q

• Sarcolemma:

A

plasma membrane of muscle cell.

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4
Q

• Sarcoplasmic reticulum:

A

smooth endoplasmic reticulum of muscle cell.

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5
Q
  • Cardiac muscle
A
  • Located in the heart
  • Involuntary control
  • Striated
  • Mono-nucleated
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6
Q
  • Smooth muscle
A
  • In hollow organs
  • Involuntary control
  • Non-striated
  • Mono-nucleated
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7
Q

Prefixes sarco- or myo - refer to

A

muscle

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8
Q

• Sarcoplasm:

A

cytoplasm of muscle cell

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9
Q
  • Skeletal muscle
A
  • Connected to bones
  • Voluntary control
  • Striated
  • Multi-nucleated
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10
Q

Muscle tissue develops from

A

myoblasts

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11
Q

What are the characteristics of muscle tissue developing from myoblasts?

A
  • Fusion of mononucleated embryonic myoblasts (multinucleated myotubes)
  • Skeletal muscles contract by the 7th week of human development
  • The number of fibers does not increase significantly after birth
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12
Q

Skeletal muscle has limited regenerative capacity mediated by the mononucleated satellite cells which?

A

proliferate and fuse after injury

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13
Q

What are Satellite cells?

A

Reserve myoblasts that can form new skeletal muscle fiber

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14
Q

What is Plasticity?

A

ability to change in size (but not number) depending upon use/disease

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15
Q

Atrophy

A
  • a decrease in the diameter of individual muscle fibers which occurs when muscles are not used or are denervated.
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16
Q

Hypertrophy

A
  • an increase in diameter of fibers after continuous muscle use.
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17
Q

Two types of plasticity?

A
  1. Atrophy

2. Hypertrophy

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18
Q

perimysium

A

contains bundles of muscle fibers

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19
Q

myofibrils

A

contraction

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20
Q

epimysium

A

covers the muscle

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21
Q

endomysium

A

seperates muscle fibers

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22
Q

Cytoskeletal Elements of Muscle Fibers: Actin and myosin

A

directly involved with contraction

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23
Q

Cytoskeletal Elements of Muscle Fibers: Titins

A

large proteins that act as microscopic “springs” which allow striated muscle to get back into shape after being stretched

24
Q

Cytoskeletal Elements of Muscle Fibers: Dystrophin

A

large sub-membrane protein in all types of muscle which cross links with actin (intracellularly) and with trans-membrane glycoproteins (sarcoglycans, dystroglycans) which connect with the laminins (extracellularly); this complex is believed to stabilize the sarcolemma and help transmit the force of contraction[“Trans-membrane Link Proteins”]

25
Q

A nerve induced muscle impulse spreads along T tubules causing Ca++ release from the sarcoplasmic reticulum into the sarcoplasm causing

A

contraction of the myofilaments

26
Q

Troponin

A

a globular protein, located at a specific site on each tropomyosin molecule, composed of three subunits: TnT, TnC and TnI

27
Q

TnT

A

which strongly binds to tropomyosin

28
Q

TnI

A

which inhibits the actin-myosin interaction

29
Q

TnC

A

which has the capacity to bind Ca++ and change the conformation (shape) of the complex Myofilaments

30
Q

Innervation: The motor unit consists of

A
  • a single nerve and all the muscle fibers it innervates
    • A single muscle fiber (cell) is innervated by only one motor neuron, but one neuron may innervate more than one fiber.
31
Q

What is a Neurotransmitter Vesicles?

A

found within terminal axonal bulbs; contain the neurotransmitter acetylcholine

32
Q

What is a Synaptic Cleft?

A

synaptic space between motor axon and skeletal muscle.

33
Q

What is the junctional folds?

A

area of the sarcolemma which contains acetylcholine receptors and cholinesterase which breaks down the neurotransmitter

34
Q

What is the end plate nuclei?

A

Stimulated by neuregulins (secreted by motor neurons) to transcribe AChR genes

35
Q

ATP is replenished by a variety of means:

A
  • creatine phosphate
  • stored glycogen
  • aerobic metabolism of glucose, fatty acids and other high-energy molecules
36
Q

Ia neuron

A

sends signals to spinal cord

37
Q

Gamma neurons

A

maintain degree of contraction in Intrafusal fibers

38
Q

Muscle Spindles

A

encapsulated structures that contain intrafusal fibers; dispersed among the extrafusal fibers of the muscle.

39
Q

Main functions of muscle spindles

A

proprioception, muscle tone, and reflexes.

40
Q

Extrafusal Fibers - majority, provides force

A
  • Red Fibers (Type I, Slow-Twitch)
  • White Fibers (Type II, Fast-Twitch)
  • Intermediate Fibers
41
Q

• Intrafusal Fibers - sensory feedback

A

Nuclear Chain Fibers

Nuclear Bag Fibers

42
Q

Extrafusal: Red Fibers (Type I, slow-twitch)

A

+ Contain large amounts of myoglobin (similar to hemoglobin; binds oxygen) which gives them a red color
+ Abundant mitochondria
+ Oxidative respiration - energy derived from oxidative phosphorylation of fatty acids
+ Relatively small diameter
+ Contract slowly, but continue to function over long periods of time (e.g. in maintaining posture)

43
Q

Extrafusal: White Fibers (Type II, fast-twitch, fatigue-prone)

A 
\+  Contain little myoglobin        
\+  Glycolytic respiration        
\+  Abundant glycogen        
\+  Relatively large caliber packed with myofibrils        
\+ Contract quickly but fatigue easily
44
Q

Growth in cardiac muscle

A

arises from differentiation and growth of single cells which do not fuse - beyond early childhood, cardiac cells do not have the ability to regenerate after injury (e.g. heart attack) - however, hypertrophy can occur (i.e. individual cells grow in size but not number).

45
Q

The cardiac muscle cells are located in the

A

myocardium (middle layer of the heart) which is bounded by the endocardium on the inside and the epicardium on the outside.

46
Q

The vagus nerves (parasympathetic) ____ the heart rate

A

decrease

47
Q

Natriuretic Peptides are produced by:

A

atrial (ANP) or ventricular (BNP)

48
Q

Function of Natriuretic peptides

A

Function: decrease blood pressure, acting to:

1) Promote kidney diuresis and natriuresis (loss of water and Na+).
2) Cause vasodilatation.
3) Inhibit central sympathetic outflow

49
Q

Structure of smooth muscle: spindle shaped -

A

each cell surrounded by basal lamina and reticular fibers that physically couple the cells together.

50
Q

Mononucleated - structure of smooth muscle

A
  • nucleus centrally located and elongated
51
Q

Most sarcoplasmic organelles are confined to a

A

conical region at each pole of the nuleus

52
Q

Dense Bodies distributed along the

A

sarcolemma - contain actinin (similar to Z-lines of striated muscle); they are anchoring sites for actin filaments and intermediate filaments (desmin, vimentin).

53
Q

Gap junctions between individual fibers make them

A

electrically coupled - the number of these junctions depend upon the type of smooth muscle.

54
Q

No T tubules -

A

numerous caveolae (“tiny caves”) on the cell surface that may be involved in sequestering Ca++.

55
Q

Characteristic presence of neurotransmitter-carrying vesicles termed

A

Varicosities

ABS - Histology (9 decks)

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