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PHARM 110 midterm 1 > Muscle Tissues > Flashcards

Muscle Tissues Flashcards

1
Q

Define EPIMYSIUM connective tissue

A

Dense irregular tissue around ENTIRE MUSCLE

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2
Q

Define PERIMYSIUM connective tissue

A

Fibrous tissue surrounding fascicles

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3
Q

Define endomysium connective tissue

A

fine areolar tissue surrounding each muscle fibre

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4
Q

How do skeletal muscle attach DIRECTLY

A

Epimysium of muscle is fused to the periosteum of bone or perichondrium of cartilage

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5
Q

How do skeletal muscle attach INDIRECTLY

A

connective tissue that extends like a tendon

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6
Q

What band are thick and thin filaments? and what is their ratio in skeletal muscle? ratio in smooth muscle

A

thick: Band A
thin: Band I and can overlap band a sometimes

Skele: Ratio is 6 thin: 1 thick
Smooth: 13 thin: 1 thick

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7
Q

What do Z discs do

A

anchors THIN filaments and connects myofibrils

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8
Q

What is the H zone

A

region where thick and thin filaments do not overlap
- only contains thick filaments

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9
Q

What is the M line

A

the line of protein myomesin that holds thick filaments together
- involved in muscle contraction

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10
Q

What is the role of myosin heads in thick filaments

A

2 heads that act as cross bridges during contraction
- Binds actin
- Binds ATP
- Uses ATP as energy source (ATPase enzymes)

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11
Q

What are tropomyosin and troponin

A

regulatory proteins bound to actin

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12
Q

What forms triads and what do they do

A

Triads = T tubules + terminal cisternae
triads encircle each sarcomere

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13
Q

What is in the SR

A

pairs of terminal cisternae & calcium ions

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14
Q

What is in the space between T tubules (voltage sensors) and SR cisternae membranes

A

Integral membrane proteins

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15
Q

What are SR foot proteins?

A

gated channels that regulate Ca2+ release from the SR cisternae

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16
Q

How does calcium release.. what leads before that

A
  • DHP receptor (on T tubule) interact with Ryanodine receptor (on SR) to release Ca2+ from the SR terminal cisternae
  • E-C coupling: AP is transmitted along the sarcolemma.. leading to sliding of myofilaments
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17
Q

What does the relaxed state of the skeletal muscle look like

A

Thin and thick filaments overlap only slightly

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18
Q

How is the sarcomere affected by contraction

A
  • thin filaments bind to myosin heads towards M line (H zone decreases)
  • I band (thin) shortens
  • A band (thick) length stays the same

** occurs when TENSION generated by cross bridges on thin filaments EXCEEDS the forces opposing shortening

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19
Q

What are the 6 events of neuromuscular Junction

A
  1. Action potential arrives at axon terminal of motor neuron
  2. Voltage-gated Ca2+ channels open and Ca2+ enters the axon terminal
  3. Ca2+ causes synaptic vesicles to release Ach
  4. Ach diffuses across synaptic celft and binds to receptors in the sarcolemma
  5. Ach binding opens ion channels to allow simultaneous passage of Na+ into the muscle fiber K+ out
  6. ACh effects are terminated by its enzymatic breakdown in the synaptic cleft by acetylcholinesterase.
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20
Q

What are skeletal muscles stimulated by

A

Somatic motor neurons

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21
Q

What are the events in generating an action potential

A
  1. Local depolarization: generates END PLATE potential (Na+ entry)
  2. Generation of action potential
  3. Repolarization: K+ exits
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22
Q

What are the events in E-C (excitation-contraction) coupling

A
  1. Action potential is spread along the sarcolemma and down the T tubules (voltage-sensors)
  2. Calciums ions are released from the SR terminal cisternae via binding of DHP receptor and Ryanodine receptor
  3. Calcium binds to troponin and removes the blocking action of tropomyosin
    - Active sites are exposed for the myosin
  4. Myosin cross bridge occurs
    - then muscle contracts
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23
Q

What is the latent period in EC coupling

A

Time between AP initiation and the beginning of contraction
- events of EC coupling

24
Q

What happens at low intracellular Ca2+

A

Tropomyosin blocks the active sites on actin
Myosin cannot attach to the active site

25
Q

What happens at high intracellular Ca2+

A

Ca2+ binds to troponin and moves tropomyosin away from active sites
- cross bridge cycle occurs (conformational change)
- when simulation stops Ca2+ is backed into SR and contraction ends

25
Q

What happens at high intracellular Ca2+

A
26
Q

What happens in Cross Bridge cycling (last step of E-C coupling)

A
  1. Cross bridge formation:
    • high-energy myosin head attaches to thin filaments
  2. Working (power) stroke:
    • myosin head pulls thin filaments towards M-line (conformational change)
  3. Cross bridge detachment:
    • ATP attached to myosin head and detaches (need ATP to relax muscles)
  4. “Cocking” of the myosin head:
    • energy from hydrolysis of ATP cocks the myosin head back to high-energy state
27
Q

What is isotonic contraction (2 types)

A
  • changes in length of muscle, tension exceeds the load

Concentric: shortening muscle
Eccentric: lengthening muscle

28
Q

What is isometric contraction

A
  • no changes in length of muscle, tension does not exceed load
29
Q

What is unfused (incomplete) tetanus

A

Increase of frequency of stimulus however only partial relaxation (not all Ca2+ back into SR)

30
Q

Describe Length-tension relationship

A

Excessively stretched arm (starting point)
- Sarcomere stretched ~ 170%
Half contraction of bicep (resting length)
- Most optimal length tension ~100% stretch
Fully contracted bicep
- Sarcomere greatly shortened ~75% (overlap of thin filaments)

31
Q

What is the relationship between the amount of resistance and speed of contraction

A

Inverse

32
Q

What is the energy source for direct phosphorylation of ADP and how long does it last; does it need oxygen
- ratio of ATP produced

A

Creatine phosphate (15 sec), no oxygen use, 1 ATP per CP

33
Q

What is the energy source + oxygen use of anaerobic pathway and how long
- ratio of ATP produced

A

Glucose (60 sec), no oxygen, 2 ATP per glucose

34
Q

What is the energy source + oxygen use of aerobic pathway and how long
- ratio of ATP produced

A

Glucose, pyruvic acid, free fatty acids (hours); oxygen required, 38 ATP per glucose, CO2, H2O

35
Q

How does muscle fatigue in HIGH intensity SHORT duration

A

Na+ K+ pumps cannot restore ionic imbalances quick enough, interfering with EC coupling

36
Q

How does muscle fatigue in LOW intensity LONG duration

A

SR is damaged and interferes with Ca2+ regulation and release

37
Q

Slow oxidative fibres?
1. Primary ATP synthesis
2. Myoglobin content high/low
3. Recruitment #
4. Type of activity
5. Colour

A
  1. Aerobic
  2. High
  3. First
  4. Endurance type; maintaining posture
  5. Red
38
Q

Fast oxidative fibres?
1. Primary ATP synthesis
2. Myoglobin content high/low
3. Recruitment #
4. Type of activity
5. Colour

A
  1. Aerobic
  2. High
  3. Second
  4. Springing/walking
  5. Red to pink
39
Q

Fast glycolytic fibres?
1. Primary ATP synthesis
2. Myoglobin content high/low
3. Recruitment #
4. Type of activity
5. Colour

A
  1. Anaerobic glycolysis
  2. low
  3. third
  4. Short-term; intense
  5. White
40
Q

What happens as LOAD increases:
Latent period?
Speed of contraction?
duration of contraction?

A

Latent period: INCREASE
Speed of contraction : SLOW
duration of contraction: SHORT

41
Q

What are the 2 layers in smooth muscle

A

longitudinal and circular

42
Q

What happens as recruitment increases:
speed of contraction?
duration of contraction?

A

Speed of contraction : FAST
duration of contraction: LONG

43
Q

What happens to the organ when longitudinal layer and circular layer contracts

A

Longitudinal: organ dilates (become wider) and shortens
Circular: organ constricts and elongates

44
Q

What is the only connective tissue found in smooth muscle

A

endomysium

45
Q

Where are the 2 sources of Ca2+ muscle contraction

A

Extracellular & inside cell (SR)

46
Q

What is the stimuli for smooth muscle

A

Sympathetic nerve

46
Q

What is the stimuli for smooth muscle

A

Sympathetic nerve

47
Q

What is the protein that binds to calcium called in smooth muscle

A

Calmodulin; NO TROPONIN

48
Q

Steps of contraction of smooth muscle

A
  1. Calcium enters the cytosol from ECF or from SR intracellular
  2. Calcium binds to calmodulin and activates it
  3. Activated calmodulin activates myosin (light chain) kinase (MLCK)
  4. Activated calmodulin phosphorylates and activates myosin II
  5. Cross bridges events occur and shortening begins
49
Q

Properties of contraction of smooth muscle

A
  • very energy efficient (slow ATPases)
  • can maintain long contractions
50
Q

How does relaxation occur in smooth muscle

A
  • Calcium detaches from calmodulin
  • Active transport of Calcium into SR and ECF
  • Dephosphorylation of myosin to reduce myosin ATPase activity
51
Q

Special features of smooth muscle:
Stress-relaxation response?
Length-tension relationship?

A
  1. Can adapt to new length
  2. Can contract between half and twice its resting length
52
Q

What is found in a SINGLE unit smooth muscle

A
  1. coupled via gap junctions
  2. Rhythmic contractions
  3. Spontaneous ATP
  4. Adapt to new length
53
Q

What is found in a MULTI unit smooth muscle

A
  1. Rare gap junctions
  2. Independent contractions
  3. has motor units

PHARM 110 midterm 1 (5 decks)

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