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PHYL2062 > Muscle Physiology L1: Muscle Contraction > Flashcards

Muscle Physiology L1: Muscle Contraction Flashcards

1
Q

What are the 3 types of muscles?

A
  1. Skeletal
  2. Cardiac
  3. Smooth
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2
Q

What is skeletal muscle?

A
  • Controlled by somatic NS
  • Voluntary
  • Striated
    • Organization of contractile proteins (in cell)
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3
Q

Skeletal muscle is controlled by the _____ NS.

A

somatic

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4
Q

Skeletal muscle is _____ (voluntary/involuntary).

A

voluntary

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5
Q

Skeletal muscle is _____ (striated/unstriated).

A

striated

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6
Q

Skeletal muscle as a organisation of _______ proteins (in cell).

A

contractile

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7
Q

What is cardiac muscle?

A
  • Influenced by autonomic NS
    • Parasympathetic and sympathetic neurons
  • Involuntary
  • Striated
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8
Q

Cardiac muscle is influenced by the _____ NS.

A

autonomic sympathetic and parasympathetic

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9
Q

Cardiac muscle is _____ (voluntary/involuntary).

A

involuntary

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10
Q

Cardiac muscle is _____ (striated/unstriated).

A

striated

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11
Q

What is smooth muscle?

A
  • Influenced by autonomic NS
    • Parasympathetic and sympathetic neurons
  • Involuntary
  • Unstriated
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12
Q

Smooth muscle is influenced by the _____ NS.

A

autonomic sympathetic and parasympathetic

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13
Q

Smooth muscle is _____ (voluntary/involuntary).

A

involuntary

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14
Q

Smooth muscle is _____ (striated/unstriated).

A

unstriated

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15
Q

Muscle cells contain many parallel _______.

A

Myofibrils

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16
Q

Why is mitochondria important in muscle cells?

A
  • ATP plays a massive role in contractions.
  • ATP produced by power house (mitochondria)
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17
Q

Skeletal muscle activity is controlled the ______ motor neurons.

A

somatic (spinal cord/brainstem)

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18
Q

What is a motor unit?

A

One motor neuron + muscle cell (it targets/innervates)

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19
Q

How is an action potential generated in a muscle cell?

A

Step 1: Neuromuscular junction

  • A type of chemical synapse
  • ACh acts on nicotinic receptor –> end plate potential
    • Which always triggers an AP (muscle cell)
  • Voltage-gated Na2+ channels –> start in adjacent membrane

Step 2 and 3: AP enters T tubule and triggers Ca2+ release from sarcoplasmic reticulum into skeletal muscle cell

Step 2:

  • AP has to travel through many layers
  • To propel AP (as fast as possible) tubules

Step 3:

  • Sacroplasmic reticulum sits next to myofibrils
  • Myofibrils- thick and thin filaments
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20
Q

What is step 1 of how an action potential is generated in a muscle cell?

A

Step 1: Neuromuscular junction

  • A type of chemical synapse
  • ACh acts on nicotinic receptor –> end plate potential
    • Which always triggers an AP (muscle cell)
  • Voltage-gated Na2+ channels –> start in adjacent membrane
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21
Q

What is step 2/3 of how an action potential is generated in a muscle cell?

A

Step 2/3: AP enters T tubule and triggers Ca2+ release from sarcoplasmic reticulum into skeletal muscle cell

Step 2:

  • AP has to travel through many layers
  • To propel AP (as fast as possible) tubules

Step 3:

  • Sacroplasmic reticulum sits next to myofibrils
  • Myofibrils- thick and thin filaments
22
Q

What is a sacromere?

A

Basic contractile unit in skeletal muscles

23
Q

What is the sliding hypothesis in a sacromere?

A
  • Actin slide over the myosin
  • Each time this occurs, the actin moves close and closer
24
Q

In a sarcomere without ATP, relaxation ____ (occurs/can’t occur)

A

can’t occur

  • Eg. when dead –> can’t relax (rigor mortis)
25
Q

What is the Z line in a sacromere?

A

Slightly darker bands

26
Q

What is a power stroke? (How do muscles contraction?)

A

Calcium ions triggering actin and myosin interaction resulting in POWER STROKE.

  • There is a specific sequence of events that results in the excitation contraction coupling
27
Q

What are the 7 steps of a muscle contraction (power stroke)?

A
  1. Action potential enters the T-tubule
  2. AP then activates the sarcoplasmic reticulum to release Ca2+
  3. Ca2+ binds to troponin
  4. Troponin-Ca2+ complex pulls the tropomyosin exposing the binding sites on actin
  5. Myosin heads bind to actin and with the release of Pi from ADP, Myosin head bends resulting in the power stroke
  6. New ATP binds to Myosin head releasing the bond between Myosin and Actin
  7. Ca2+ is pumped back into the SR
28
Q

What is step 1 of a muscle contraction (power stroke)?

A
  1. Action potential enters the T-tubule
29
Q

What is step 2 of a muscle contraction (power stroke)? (After AP enters T-tubule)

A
  1. AP then activates the sarcoplasmic reticulum to release Ca2+
30
Q

What is step 3 of a muscle contraction (power stroke)? (After Ca2+ is released)

A
  1. Ca2+ binds to troponin
31
Q

What is step 4 of a muscle contraction (power stroke)? (After Ca2+ binds to troponin)

A
  1. Troponin-Ca2+ complex pulls the tropomyosin exposing the binding sites on actin
32
Q

What is step 5 of a muscle contraction (power stroke)? (After tropomyosin exposes the binding sites on actin)

A
  1. Myosin heads bind to actin and with the release of Pi from ADP, Myosin head bends resulting in the power stroke
33
Q

What is step 6 of a muscle contraction (power stroke)? (After myosin bind with actin to produce the power stroke)

A
  1. New ATP binds to Myosin head releasing the bond between Myosin and Actin
34
Q

What is step 7 of a muscle contraction (power stroke)? (after the bond between actin and myosin is released )

A
  1. Ca2+ is pumped back into the SR
35
Q

What is cross bridging cyling?

A
  • 6 actin filament
  • 6 array of heads (myosin) –> attach –> pull actin filament –> sarcomere shortens
36
Q

What are the 4 mechanisms of neurotransmission release in the excitation-contraction coupling in skeletal muscles?

A
  1. Action potential in motor neuron
  2. Release of ACh at the neuromuscular junction
  3. ACh action at nicotinic receptors (post-synaptic membrane) triggers an end-plate potential
  4. AP initiated in skeletal muscle membrane
    • If released threshold potential- potential that activates voltage
37
Q

What are the 5 mechanisms of muscle contraction in the excitation-contraction coupling in skeletal muscles after the 4 mechanisms of neurotransmission release?

A
  1. AP enters T-tubules
  2. Ca2+ release from sarcoplasmic reticulum
  3. Ca2+ triggers crossbridge cycling
  4. Sarcomeres shorten
  5. Muscle contracts
38
Q

How does cellular structure affects skeletal muscle function?

A

Increased contraction –> up to a point –> then starts to decrease contraction

39
Q

What happens at A?

A

Max no. of contraction

40
Q

What happens at B?

A

Active sites away from possible myosin heads = few interaction = decreased tension

41
Q

What happens at C?

A
  • No interaction between actin and myosin
  • Eg. cardiac failure
    • Actin and myosin are further away
    • Hard to empty blood as decrease tension
    • Heart expands more
    • Cycle continues
42
Q

What happens at D?

A
  • Pushed together
  • Actin sites don’t align = decreased tension
43
Q

What are intrafusal fibres?

A
  • Have stretch receptors –> stretched
  • AP form a code to spinal cord
44
Q

What are extrafusal fibres?

A
  • Alpha motoneuron (shortening)
  • Stretch receptors= signals to brain
45
Q

What are GTO afferents?

A
  • Sensory axons
  • Interweaved collagen fibres
  • Close to tendon
    • Acts as a relive value when too much tension in muscle
46
Q

In a muscle, the more it stretches = _____(more/less) AP

A

more

47
Q

In a muscle, the more it relaxes = _____(more/less) AP

A

less

48
Q

Stretch receptors are activated by _______ motor neurons.

A

Gamma

49
Q

What is a stretch receptor reflex? (using quads- monosynaptic and polysynaptic reflex)

A

Monosynaptic reflex –> quad muscle contraction –> bring back to approx. length

Polysynaptic reflex –> inhibits (contraction) of semitendinosus from flexing

Both occur at the same time

50
Q

How does is ATP produced in skeletal muscles?

A

PHYL2062 (17 decks)

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