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KPE260 > L10 > Flashcards

L10 Flashcards

1
Q

Provide a brief summary of skeletal muscle characteristics

A
  • striated
  • controls body movement
  • attaches to bone
  • voluntary control (responds to somatic motor neurons)
  • multinucleated
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2
Q

Provide a brief summary of cardiac muscle characteristics

A
  • main goal is to move blood
  • cardiac muscles provide own contraction
  • striated muscles
  • non voluntary (responds to autonomic NS, contraction, modulated by endocrine system)
  • uninucleated
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3
Q

Provide a brief summary of smooth muscle characteristics

A
  • primary muscles of internal organs and tubes
  • influences the movement in and out of the body
  • involuntary control
  • non striated
  • uninucleated
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4
Q

Explain:

Origin
Insertion
Flexor
Extensor

A

Origin- closest to midline or stationary more
Insertion- more distal to midline, or mobile bone
Flexor- brings bones together
Extensor- moves bones away

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5
Q

What is another name for muscle cells— what’s are satellite cells?

A

Muscle cells are called muscle fibres, and satellite cells are stem cells which can specialize

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6
Q

What’s the purpose of T-Tubules in fibres?

A

To allow for AP to penetrate nearest internal structure of the fibre. These are extensions fo the sarcolemma thats associated with the end of the SR

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7
Q

Thin filaments—>_____
Thick filaments—> ____
Regulatory proteins—> ___, ____
Accessory proteins—> ____, _____

A

Thin filaments—> actin
Thick filaments—> myosin
Regulatory proteins—> troponin and tropomyosin
Accessory proteins—> titin and nebulin

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8
Q

What is the contractile unit of the myofibril?

A

The sarcomere is the contractile unit of the myofibril.

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9
Q

What components of the sarcomere causes contraction? Name and describe the components.

A

Z-disks= have actin filaments bonded together

I-Band= made of thin (actin) filaments only

A-Bands= darker regions where both thin and thick filaments overlap

H-Zone= within the middle of the A band, has thick filaments only

M-Line= only area where thick myosin filaments bind

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10
Q

What are the two types of accessory proteins that muscle fibres consist of? What are the functions?

A

Titin- this is an elastic protein which stabilizes position of contractile elements. Elasticity returns stretched muscles to their resting length

Nebulin- inelastic protein which aligns filaments, stabilizes position, lines with the thin filaments attached to Z disk

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11
Q

When muscles contract the sarcomere ______

When muscles lengthen the sarcomere ______

A

When muscles contract the sarcomere shrinks

When muscles lengthen the sarcomere lengthens

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12
Q

Instead of shrinking in size, during contraction myosin heads and actin do what?

A

Slide past each other

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13
Q

When the sarcomere is under contraction, what happens to the

Z-Disks
I-Bands 
A-Bands 
H-Zone
M-Line
A 
Z-Disks= nothing changes, still has actin filaments 
I-Bands= smaller in size, but still contain actin 
A-Bands= nothing changes, actin just moves closer to the M line 
H-Zone= smaller in size, still contains myosin heads 
M-Line= nothing changes, still has myosin
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14
Q

Three basic steps for a skeletal muscle to contract

A
  1. Event at neuromuscular junction
  2. Excitation contraction (E-C coupling)
  3. contraction-relaxation cycle
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15
Q

What are the contraction steps involving calcium?

A
  • calcium is released from terminal cisternae (within SR)
  • calcium binds to troponin
  • troponin pulls tropomyosin away from actin binding sites
  • myosin binds to actin and pulls on its heads
  • cycle repeated until lack of calcium and ATP is present
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16
Q

What are the contraction steps involving ATP?

A
  • ATP binds to myosin and decreases affinity for actin
  • ATP hydrolyses provides energy for myosin head to rotate and reattach to actin
  • ATPase break ATP into ADP and Pi
  • power stroke begins in response to Ca and Pi
  • myosin releases ADP and makes room for ATP
  • cycle continues
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17
Q

Contractile cycle summary in 4 steps, name them.

A
  1. ATP binds to myosin, relabeling actin from myosin
  2. Myosin hydrolyses ATP, energy from ATP puts myosin head into cocked position
  3. Power stroke begins when tropomyosin moves away from binding sites
  4. Myosin releases ATP at end of power stroke
18
Q

Provide the ten steps for E-C coupling

A
  1. When neuron is activated, signal is relayed to muscle via Ach
  2. Ach is released in synaptic cleft and binds to Ach receptors in motor end plate
  3. Depolarization of Na+ channels which allow for change in membrane potential
  4. Change in membrane potential allows for AP to occur
  5. AP in muscle fibre transported via T-tubules in motor end plate to muscle fibre
  6. Ap travels to DHP (voltage gated) channels that change physical form
  7. DHP receptors are connected to RyR receptors that connect to SR
  8. DHP, RyR and SR allow for opening and release of Ca+ into cytoplasm from [high] to [low]
  9. Ca+ binds to troponin which moves tropomyosin out of binding sites
  10. myosin heads then attach to actin and begin powerstroke
19
Q

What is a latent period and why is it caused?

A

A latent period is just before the contraction phase of a muscle where there is a delay in between AP and contraction.
- may be caused by time required for calcium release and binding of troponin

20
Q

Name the type of energy systems for skeletal muscles and their descriptions.

A

Phosphocreatine= breakdown produces a short burst of energy
Carbohydrates= most rapid and efficient store of energy
Anaerobic glycolytic= produces lactic acid, quick system, no oxygen required, small amount of energy released
Aerobic respiration= slow, oxygen needed, large amount of energy released

21
Q

Name the various types of fatigue in skeletal muscles and their causes

A

Central fatigue= due to CNS

Peripheral fatigue= if you utilize all glycogen you will get tired and there will be an Imbalance (K+ leaving cells) we alter likelihood of generating AP.

  • with this, short duration and maximal exertion leads to increased level of Pi
  • maximal exercise leads to ion imbalance—> K+ alters membrane potential
22
Q

Explain the difference and characteristics of slow twitch and fast twitch fibres? Which ones are stronger? Which has more mitochondria?

A

Slow twitch fibres (type I)= not as powerful as other fibres, myosin are slow with hydrolization and rely on oxidative phosphorylation. Has more mitochondria and capillaries for rapid oxygen consumption.

Fast twitch fibres= these develop tension faster, split ATP rapidly and hydrolyze quicker. 
TYPE IIA (FOG)- oxygen is present, uses oxidative glycolic metabolism 
TYPEIIB (FG)- oxygen is not present, relys on anaerobic glycolysis
23
Q

What does chronic stimulation allow for?

A

The transition between fibres to a certain extent (type IIB-type IIA)

24
Q

Tension generated is directly proportional to _______

A

Tension generated is directly proportional to number of cross bridges
- sarcomere contracts with optimal force at optimal length

25
Q

Explain the difference between tetanus and summation

A

Summation: stronger contractions when the muscle does not relax completely between AP. Force of contraction increases with summation

Tetanus: means a maximal contraction. more motor units= increase in contraction force

26
Q

What does the term asynchronous mean?

A

It is used to describe different contractions over different times

27
Q

If one motor unit is stimulated, what happens to the remaining ones?

A

A muscle may vary with types and numbers of motor units. If one motor unit becomes stimulated, all of them do.

28
Q

What are isotonic contractions? Give examples.

A

These are contractions that move loads. Two examples of these types of contractions are concentric (shortening) and eccentric (lengthening) contractions. Sarcomere shortens or lengthens more allowing for muscle to shrink or grow.

29
Q

What are isometric contractions?

A

These are contractions that generate force, but not a sufficient amount. The sarcomere shortens while elastic elements stretch resulting in little change over length. These are not able to move loads.

30
Q

What are two types of acquired muscle disorders

A

Inherited disorders= Duchenne muscular dystrophy

Macardles disease= glycogen does not get converted to glucose 6 phosphate

31
Q

Smooth muscles vary from skeletal and cardiac in many ways. Describe how the following are specialized to smooth muscles

By location: __________
By contraction patterns: __________
By communication with cells:____________

A

By location: vascular, GI, respiratory, urinary, reproductive, ocular
By contraction patterns: phasic (can observe) and tonic (cannot observe)
By communication with cells: visceral single units or uniting smooth muscles that have to excited each one individually

32
Q

What kind of junction are single unit smooth muscles connected by?

A

They are connected via gap junctions, the cell contracts as a whole unit.

33
Q

Give an example of multi smooth muscle units and why they’re not electrically linked.

A

An example is ocular eye muscles, these cells must be stimulated independently to allow for fine motor control.

34
Q

What is special about these characteristics within smooth muscles?

Sarcomere 
Actin 
Myosin
Troponin 
Cytoskeleton 
Sarcoplasmic Reticulum
A

Sarcomere- Smooth muscles do not have sarcomere
Actin- there is more actin within smooth muscles
Troponin- smooth muscles lack troponin, has calmodulin instead
Myosin- filaments are longer, entire surface of filaments covered with myosin heads
Cytoskeleton- there is an extensive cytoskeleton that has intermediate filaments and dense bodies
Sarcoplasmic Reticulum- amount of SR varies and is less organized. No T-tubules but caveolae.

35
Q

Provide the 5 steps for myosin smooth muscle phosphorylation contractions

A
  1. Increase in cytosol Ca+, initiates contraction from SR to ECF
  2. Ca+ binds to calmodulin
  3. Initiates cascade resulting in phosphorylation of myosin light chains
  4. Dephosphorylation due to myosin light chain phosphorylate
  5. relaxation occurs, MLCP controls calcium sensitivity
36
Q

Name four ways skeletal and smooth muscles differ in their contraction

A
  1. Ca+ comes from SR not ECF
  2. An AP is not required for Ca+ release
  3. There is no troponin, so Ca+ initiates contraction through a cascade via calmodulin inducing phosphorylation of myosin light chains
  4. de-phosphorylation of MLC by Myosin phosphate
37
Q

What are the three ways calcium enters the cell in smooth muscles

A
  1. Voltage gated Ca+ channels
  2. Ligand gated Ca+ channels
  3. Stretch activation Ca+ channels
38
Q

At slow wave potentials, AP_____________

At pacemaker potentials, AP____________

A

At slow wave potentials, AP doesn’t occur at constant phase

At pacemaker potentials, AP occurs at constant rate

39
Q

Explain paracrine signals

A

Histamines that constrict smooth muscles of airway and nitric oxide relaxes smooth muscle of blood vessels.

40
Q

Name the sympathetic and parasympathetic system receptors and descriptions

A

Sympathetic:
α-receptors= contraction within blood vessels
ß ₂-receptors= relaxes airway

Parasympathetic:
M-receptors= contract within airway, walls of stomach, relaxes within GI tract, relaxes via NO

41
Q

Compare cardiac muscles and Skeletal muscles

A
  • striated
  • sarcomere structure
  • electrically linked
  • some exhibit pacemaker effect
  • under parasympathetic and sympathetic controls
42
Q

Contrast cardiac and skeletal muscles

A
  • gap junction is intercalated disk
  • muscle fibres are shorter
  • may be branches
  • have single nucleus

KPE260 (7 decks)

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