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Histo > Muscle > Flashcards

Muscle Flashcards

1
Q

All muscle tissues are involved in what two functions?

A

Movement

Heat production

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2
Q

All muscle tissue contractions depend on myofilaments, which are composed of

A

Thin filaments - actin

Thick filaments- myosin

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3
Q

Satellite cells

A

Unfused prescursor myoblasts/ stem cells that persist in muscle; They fuse with present muscle fibers to support growth with additional nuclei

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4
Q

Why do skeletal muscles have limited regeneraitive capacity?

A

Skeletal muscle cells DO NOT undergo mitosis; they have satellite cells with limited capability to divide & repair

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5
Q

Organization of skeletal muscle

A

Fascicle > Muscle fibers > Myofibrils > Myofilaments > Thin & Thick filaments

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6
Q

Muscle fibers (aka muscle cells) are bound by

A

Connective tissue (epimysium, perimysium, endomysium)- not cell junctions

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7
Q

Fascicle

A

Group of muscle cells held together by perimysium

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8
Q

Visible characteristics of skeletal muscle

A
  • Polygon shaped cross-section; Rectangular longitudinal section
  • Peripheral nuclei
  • Striated
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9
Q

Epimysium- what is its composition and function?

A

Dense irregular connective tissue that ensheaths the entire muscle and carries vascular and nerve supply

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10
Q

Endomysium wraps around

A

Each individual muscle fiber/ cell

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11
Q

Thick filaments

A
  • Myosin II: 2 heavychains, 4 light chains
    • Light chains contain actin, ATP binding sites, ATPase, and motor activity
  • Lined up tail-to-tail to form bipolar thick filaments
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12
Q

What’s the black stuff?

A

Mitochondria

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13
Q

Thin filaments- F-actin, tropomyosin, troponin

A

Tropomyosin masks myosin-binding sites on F-actin

Ca+ binds torponin C to pull off tropomyosin, exposing the myosin-binding sites for the thick filament

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14
Q

A sarcomere (contractil eunit of skeletal muscle) is either

A

Distance between 2 adjacent Z lines

I band + A band

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15
Q

A band composition

A

Full length of thick filaments with some overlap from thin filaments

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16
Q

I band composition

A

Only thin filaments

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17
Q

H band composition

A

Only thick filaments; appears lighter because it lacks thin filaments

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18
Q

M line function

A

Holds thick filaments in place and links them to one another

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19
Q

What happens in muscle contraction

A

Sarcomere shortens, so

  • Z lines brought closer
  • I band shortens
  • H band shortens
  • A stays teh same*
20
Q

Sliding filament theory

A
  1. ATP-myosin hydrolyzes -> binds actin
  2. Pi is released -> conformational change (cock)
  3. ADP is released -> power stroke
  4. New ATP binds -> release actin
21
Q

Transverse tubules

A

Invaginations of the plasma membrane at A-I band junctions that propagate impulses down into all levels of the muscle cell

Serves as voltage-sensor proteins

22
Q

Sarcoplasmic reticulum

A

Terminal cisternae; stores Ca2+ via gated Ca2+ release channels

Two of these and 1 T-tubule form a triad together

23
Q

Dystrophin

A

Links actin to endomysium through dystrophin-associated glycoprotein complex

Ensures that shortening of myofibers is transmitted to surrounding connective tissue, resulting in muscle contraction

24
Q

Rigor mortis

A

Lack of ATP –> can’t release actin, so there’s no detachment and muscles stiffen

25
Q

Motor unit of skeletal muscle

A

Motor neuron (from ventral horn of spinal cord) + all the muscle fibers it innervates

Less muscle fibers, finer movement

26
Q

Neuromuscular junction (motor-end plate)

A

Where synapse occurs between motor nerve and muscle fiber; point of contact between axon & muscle fiber

27
Q

Initiation of contraction

A
  1. Action potential arrives
  2. Synaptic transmission at neuromuscular junction
  3. Propagation of AP along sarcolemma
  4. Hyperpolarization of T-tubules
  5. Conformational change of voltage-sensor proteins
  6. Gated Ca++-release channels open
  7. Ca++ released into sarcoplasm from SR
  8. Troponin binds Ca++
  9. Myosin-actin interaction
28
Q

Myasthenia gravis

A

Autoimmune disorder attacking Ach receptors on post-synaptic sarcolemma. (The body tries to fix this by digesting affected receptors, but replaces them with less responsive receptors.)

–> ptosis

29
Q

Fiber types of skeletal muscle

A
  • Type I : slow oxidative; fatigue resistance; red
  • Type IIa: fast oxidative; glycolytic; intermediate
  • Type IIb: fast glycolytic; fatigue-prone; white
30
Q

Sprinting is associated with what type of fiber?

A

Type IIb

Fast glycolytic; fatigue prone

31
Q

Contrasting red (type I) vs white (type II) fibers- Vascularity, size, SR mitochondria, myoglobin, etc

A

Type I is smaller and has less SR, but is otherwise more rich in everything else

32
Q

Myotendinous junction

A

Where the connective tissues surrounding skeletal muscle fibers become continuous with the dense collagenous (Type I collagen) tissue of tendon

33
Q

Sensory Receptors vs Golgi Tendon Organs

A

Sensory receptors penetrate the muscle spindle itself to detect stretch/tension of extrafusal muscle fibers and relay it to the CNS –> maintain posture & regulate opposing muscle groups

GTO: Encloses sensory axons penetrating among the collagen bundles in tendons at the myotendinous junction to send info about stretch and tension to the CNS

34
Q

What is the cursor pointing at?

A

Muscle spindles are located in the connective tissue island between muscle fascicles

35
Q

Visible characteristics of cardiac muscle

A
  • Branching
  • Intercalated discs
  • Central nuclei
36
Q

Cardiac muscle is held together by

A

Gap junctions

demosomes: intermediate filaments for cell adhesion

Adhering junctions to actin filaments of sarcomeres

37
Q

How to differentiate between skeletal and cardiac muscle on a cross section?

A

Cardiac = centrall located nuclei

38
Q

Contracitle apparatus of smooth muscle

A
  • Myosin filaments (side-polar) and actin filaments
    • But no troponin, no specific patterns (like sarcomeres)
  • Dense bodies- bind to intermediate filaments (vimentin, desmin), actin, and the membrane
    • Similar to Z-discs
  • Caveolae: dyad
    • Similar to T-tubule system
  • Gap junctions

Actin anchors to dense bodies, which also attach IF to the sarcolemma

39
Q

Regeneration of smooth muscle

A

High proliferative capacity (hyperplasia)

Arises from vascular pericytes

40
Q

Side-polar thick filament of smooth muscle

A
41
Q

3 ways to initiate smooth muscle contraction

A

Mechanical (stretching)

Depolarization (neuronal)

Chemical (vasopressin, angiotensin II , etc)

42
Q

Visible characteristics of smoth muscle

A
  • longitudinal
    • fusiform, small
    • no striations
    • corkscrew-shape dnucleus when contracted
    • central nucleus
  • cross-section
    • central nucleus with little cytoplasm
    • variable nuclear profile
43
Q

Regulation of smooth muscle contraction by calcium

A

Note: no troponin involved

44
Q

How to differentiate between smooth muscle and dense irregular connective tissue?

A

Smooth muscle has more cells & nuclei; whereas, in dense irregular connective tissue has more collagen, less cells

45
Q

White matter vs gray matter of spinal cord

A

White matter of spinal cord - no neurons

Gray matter of spinal cord - neurons

46
Q

Muscle spindles

A

Encapsulated proprioreceptors that help control body posture and coordinate the action of opposing muscles; consists of

  • Connective tissue capsule
  • Intrafusal muscle fibers
  • Sensory nerve fibers penetrating those fibers
47
Q

What kind of muscle is this

A

Nuclei are peripheral -> skeletal

Histo (20 decks)

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