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CAPS 390 > L12. Muscles Part 2 > Flashcards

L12. Muscles Part 2 Flashcards

1
Q

Other names for a muscle cell is

A

Muscle fiber

Myofiber

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2
Q

What is the sacrolemma?

A

It is the plasma membrane of the muscle cell

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3
Q

What is the sarcoplasm?

A

Cytoplasm of the muscle cell ( myofiber/muscle fiber)

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4
Q

What is the sarcoplasmic reticulum

A

Smooth ER found in striated and smooth muscle fibers

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5
Q

Describe the skeletal muscle

A
  • voluntary

- controlled by motor neurons

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6
Q

What is a motor unit

A

motor unit= motor neuron + the motor end plate+ all muscle fibers that motor neuron innervates

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7
Q

Can a motor neuron innervate more than one muscle fiber (cell)

A

Yes

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8
Q

What is the motor end plate?

A
  • highly excitable
  • specialized domain on the sarcolemma
  • responsible for initiating the action potential across the myofibre causing muscle contraction
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9
Q

What is the neuromuscular junction?

A

junction between the axon terminal of he motor neuron and the motor end plate

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10
Q

Where are the acetocholyene receptors found?

A

on the sarcolemma

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11
Q

Memorize picture on L12 .4b

A

L12 .4b

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12
Q

Describe the excitation-contraction process

A
  1. neurotransmitter vesicles fuse with the pres-synaptic membrane
  2. acetocholine binds with the receptors on the sarcolemma
  3. action potential is generated down the sarcolemma into the T-tubules ( 2 SR cristae wedge the t-tubules)
  4. causes the release of Ca2+ from the SR
  5. the Ca2+ in the sacroplasm binds to troponin, shifts the tropomysoin to release myosin binding sites in the actin
  6. myosin binds to these sites, myosin pulls the actin filaments towards the center of the sacromere (ATP hydrolysis allows this process)
  7. end of the A.P the Ca2+ is returned to the SR via active transport
  8. troponin without Ca2+ shifts back to block the sites
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13
Q

What does botox do?

A

inhibits acetylcholine release by axon terminals

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14
Q

What clinical disease does botox cause?

A

botulism: causes muscle paralysis and respiratory failure

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15
Q

What is the Duschenne Becker Muscular Dystrophies

A
  • mutation of the dystrophin gene on the X-chromosome
  • muscle wasting
  • mental retardation
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16
Q

What are the symptoms for Duschenne Becker

A
  • limited fine movement
  • breathing difficulties ( diaphragm muscle weak)
  • scoliosis ( curve spine)
  • thick low leg muscle
  • muscle weakness affects the feet, hips, belly, shoulders and elbows.
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17
Q

What is the role of dystrophin

A

no dystrophin, no link between actin , sarcolemma and BM

18
Q

What happens in DMD ( duchene muscular dystrophy)

A

the link between actin cytoskeleton and the basal filament is lost ( as no dystrophin links actin to sarcolemma which has dystroglycan complex linked to BM)

19
Q

What is the protein missing in DMD?( duchene muscular dystrophy))

A

dystrophin

20
Q

Why is there an enlarged calf muscle in duchene muscular dystrophy

A

macrophages and fats accumulate without the dystrophin. there is an increase in C.T and adipose tissues

21
Q

(histology): what is different between DMD and normal cells

A
  • disorganized sacromeres
  • no dystrophin
  • present of CT and adipocytes around muscle cells
22
Q

What joins the cardiac muscle fibers?

A

intercalated disks

23
Q

Features of the cardiac muscle

A
  • found in heart
  • forms thick layer (myocardium)
  • intrinsic rhythmicity
  • involuntary muscle (spontaneous contraction)
  • short and branched striated fibers ( cardiac fibers/ cardiomyocytes)
  • one nucleus / fiber
24
Q

What is a cardiomyocyte?

A

short branched striated fibers (AKA cardiac fibers)

25
Q

What are intercalated disks

A
  • junctions between 2 cardiomyocytes ( cardiac fibers)

- steplike pattern

26
Q

How many types of intercalated disks are there, what are they?

A

2 types
LAT: runs parallel to myofilaments

TR: transverse part, runs right angle to myofibers

27
Q

what does the transverse part of the intercalated disk contain

A
  • Zonular adherens: adhere actin myofilaments of the terminal sacromeres to the plasma membrane
  • Desmosomes: binds fibers together to prevent their separation during contraction
28
Q

what does the lateral part of the intercalated disk contain

A

Gap junctions : flow of info between fibers

29
Q

What is in a diade of a cardiac fiber?

A

1 t-tubule with a junction towards 1 terminal SR cisternae

30
Q

Characteristics of smooth muscle

A
  • communicate solely by gap junctions
  • no t-tubules
  • involuntary
  • non-striated fibers, spindle-shape, tapered
  • found in GI tract, respiratory tract, blood vessels
  • one nucleus per fiber
31
Q

What is the role of smooth muscles in blood vessles?

A

control constriction and dilation

32
Q

what is the tunica media made up of

A

smooth muscles + elastic tissues

33
Q

Compare the tunica media in arteries and veins

A

arteries have a thicker tunica media

34
Q

What muscles are involved in peristalsis

A

Longitudinal and circular ( both smooth)

35
Q

what are circular muscles

A

muscle fibers that run around the circumference of the organ

36
Q

What are longitudinal muscles

A

muscle fibers that run parallel to the long axis of the organ

37
Q

What is peristalsis

A

Rhythmic contractions of the smooth muscles that propel food through the digestive tract

38
Q

Name the 3 layers of muscles in the smooth muscle of the stomach ( pg 13 b)

A

longitudinal ,circular and oblique

39
Q

What are the contractile units of a smooth muscle

A

myosin and actin filaments taht connect to the dense plaque on the sarcolemma and dense bodies in sacroplasm

40
Q

Thin filaments in the smooth muscle are:

A
  • obliquely arranged
  • attached to dense plaques in sarcolemma
  • attached to dense bodies in sarcoplasm

CAPS 390 (35 decks)

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