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Histo Exam 1 > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

1
Q

Titin

A

large elastic proteins that anchors myosin to Z lines-help stabilize the centering of MYOSIN in the sarcomere.

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2
Q

Nebulin

A

elongated INELASTIC protein that is attached to Zlines and assists in anchoring ACTIN to Z lines

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3
Q

alpha actinin

A

protein that bundles actin into parallel arrays and anchors actin to z lines

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4
Q

tropomodulin

A

protein that caps the free end of actin and regulates its length

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5
Q

myomesin

A

myosin-binding protein that holds myosin in register at the M line- forms several distinct stripes on either side of the M line

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6
Q

Desmin

A

intermediate filament that forms a lattice around the sarcomere at the level of Z lines-stabilizes myofibrils by attaching Z lines to one another and to the plasma membrane.

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7
Q

Dystrophin

A

Links laminin (residues in external lamina of muscle cell) .

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8
Q

what happens when there is an absence in Dystriopin?

A

Associated with progressive muscle weakness (Duchenes’s muscular dystrophy)

-encoded on X chromosome; affects primarily in males

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9
Q

Transverse Tubules in skeletal muscle

A

present at A-1 junction (2 per sarcomere)

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10
Q

sarcoplasmic reticulum. Function and features

A
  • endoplasmic reticulum of muscle- generally lack ribosomes
  • role is to release to calcium
  • many calcium pumps
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11
Q

Specialized cisternae

A

form triads with T-tubles:TC+T+TC

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12
Q

What are the steps of sliding filament model

A

1.)excitation initiated by synapses (Ach)
2.)action potential propagates along sarcolemma and t tubules
3.)calcium released by terminal cisternae into sarcoplasma as a result of voltage-sensor proteins depolarizing and stimulating opening calcium channels in terminal cisternae
4)Calcium binds troponin-C,
5)Myosin/actin bind together weakly (binding has 2 effects..)
6)conformational change in myosin head, exposing ATP binding site-ATP BINDS TO MYOSIN
7)Binding releases myosin from actin
8)ATPase portion of myosin head cleave ATP
ATP-> ADP +Pi, myosin uses energy to recock for the next cycle
9)tropomyosin slides back over myosin/ actin binding site-troponin returns to its pre-contraction position

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13
Q

When calcium binds troponin what happens with myosin?

A

causing TnI to dissociate from actin molecules, allowing troponin complex uncover myosin-binding sites on the actin molecules

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14
Q

Myosin/ actin binding together weakly has What 2 effects ?

A

1) myosin affinity for actin increases
2) cocked myosin head moves actin along the thick filament, generating power stroke of muscle contraction- ADP is lost during this stage

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15
Q

Without ATP what happens?

A

actin and myosin will remain bound (rigor Mortis)

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16
Q

where is alpha motor neuronal axons located? what is its function?

A

ventral horn of spinal cord gray matter

  • supply a muscle cell
  • motor unit: alpha motor neurons and all the muscle cells it supples
  • schwann cells
  • motor end plate
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17
Q

How is Ach used in muscle?

A

Ach binds to Ach receptor muscles. This causes Na+ to open up, which causes the plasma membrane to be depolarized. this will cause voltage Ca2+ channels to open

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18
Q

neuromuscular spindle (aKA proprioceptor)

A
  • SENSORY structure located in skeletal muscle
  • detects degree of tension in the muscle
  • sphindle consist of specialized muscle fibers, nuclear bag and nuclear chain fibers collectively
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19
Q

Extrafusal fibers

A

normal skeletal muscle fibers

-alpha motor innervation

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20
Q

Intrafusal fibers (muscle spindle)

A

contain nuclear bag fibers, nuclear chain, ,modified muscle cells

  • modified muscle cell (part muscle can contract)
  • part sensory receptor (sense length, tension, velocity/rate)
21
Q

What is the difference between nuclear bag fibers and nuclear chain fibers?

A

Nuclear bag fibers are thicker: multinucleated region is expanded while nuclear chain fibers contain multiple nuclei in a row

22
Q

What is a modified muscle cell?

A
  1. Part muscle (myofibrils can contract)

2. part sensory receptor (sense length, tension, velocity/rate)

23
Q

primary afferent fibers

A
  • detect length and rate of contraction
  • ends are called Annulospiral Endings
  • wrap both bag and chain fibers
24
Q

secondary afferent fibers (length)

A
  • flower spray endings

- mostly chain fibers

25
Q

Gamma motor neurons

A

(are the efferent nerve fibers to intrafusal fibers)

  • contain a gamma motor end plate
  • innervate intrafusal fibers and regulate their tension; SENSITIViTY
  • Motor portion: permits intrafusal fiber contraction-maintains length/tension relationship with extrafusal fibers
26
Q

What makes the the cardiac muscle striated?

A

Due to myofilament arrangement similar to skeletal muscle.

27
Q

Developing cardiac muscles don’t form what?

A

anatomical syncytium

28
Q

To form long fibers, cardiac muscles are attached end to end by intercalated disks forming what?

A

functional syncytium

29
Q

How does cardiac muscle differ from skeletal muscle in morphology?

A

-Nucleus: large with blunt ends; are centrally located
-More mitochondria and found within myofilaments
-fibers: often branch instead of straight fibers
T-tubles are at the Zline
-intercalated disks
-sarcoplasmic reticulum: less extensive
-terminal cisternae: much smaller than skeletal muscle
-t-tubles form dyads at Z-lines. T-tubules are much larger than those found in skeletal muscle-one T-tubule per sarcomere in cardiac muscle.
-calcium comes from outside the cell.

30
Q

What is unique about smooth muscle compared to striated muscle?

A

slow in comparison and energy efficient

31
Q

What type of stimuli induces smooth muscle contraction besides alteration of calcium muscle?

A
  • hormones (oxytocine)
  • nerve impulses
  • stretch
32
Q

What role does caveloe play in smooth muscle?

A

sequestering calcium-equivalent to t-tubules of striated muscle

33
Q

What is the ratio of actin:myosin in smooth muscle and striated muscle?

A

smooth: 12:1
striated: 6:1

34
Q

What can smooth muscle synthesize?

A

collagen and elastin

35
Q

what are dense plaques?

A

pivot points for contraction

36
Q

smooth muscle has no

A

troponin and tubles

37
Q

Muscle fibers are composed of what?

A

myofibrils

38
Q

myofibrils

A

longitudinally arranged bundles of thick and then myofilaments.

39
Q

myofilament

A

actin and myosin filaments.

40
Q

A band

A

contains actin and myosin filaments-defined by length of myosin. (constant length-does not change length)

41
Q

I band

A

contains only actin (variable length)

42
Q

H band

A

contains only myosin (variable in length)

43
Q

M-line

A

myosin attachment line

44
Q

Z-line

A

sarcomere boundary-actin attachment line. z-lines contain alpha actinin, proteins that anchors actin to z-lines

45
Q

sarcomere

A

basic functional unit. portion of myofibril between 2 adjacent z lines

46
Q

What are the components that make up actin

A

-G:actin (monomer)
-F:actin (polymer of G-actin. forms double helix
-tropomyosin: double helix of 2 polypeptides
-Troponin: (3 subunits)
Tn-C:binds calcium
Tn-I: inhibits actin/ myosin binding
Tn-T: binds troponin complex to tropomyosin

47
Q

what are the myosin components

A
  • heavy meromyosin (S-1 binds actin)
  • light meromyosinbinds to other myosin molecules.
  • myosin myofilament consists of multiple myosin molecules linked together.
48
Q

What changes with contraction

A

H and I band (shorten) during contraction

A band remains the same

49
Q

cell to cell cohesion made of what type of junctions in cardiac cells

A

fascia adherens
macula adherens
gap junctions

Histo Exam 1 (16 decks)

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