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NMSK > Muscles > Flashcards

Muscles Flashcards

1
Q

What type of muscle is this? How do you know?

A

Skeletal muscle

  • Regular striations
  • Peripheral nuclei
  • Syncytium
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2
Q

What type of muscle is this? How do you know?

A

Cardiac

  • Syncytium appearance
  • Central nuclei
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3
Q

What type of muscle is this? How do you know?

A

Smooth

No striations

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4
Q

Myopathy

A

Disease of muscle tissue

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5
Q

Causes of muscle pathology

A

External trauma

e.g. crushing, laceration, extreme heat/cold leading to necrosis of fibres

Internal trauma

Muscle tear due to forceful contraction; myopathy/repeated eccentric contractions leading to overstretched sarcomeres and Ca2+ leakage

Nerve damage

Motor nerve crushed or divided

Neuropathy

Disease

Aging

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6
Q

What is sarcopenia?

A

Muscle atrophy associated with aging. Leads to:

  • Loss of motor axons
  • Denervation
  • Degeneration/regeneration cycle leads to loss of motor fibres
  • Increases motor unit size –> loss of dexterity
  • Fibrosis: build up of connective tissue in muscle
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7
Q

Outline how changes in intracellular storage/signalling can result in skeletal muscle pathology

A
  • If sarcoplasmic reticulum can’t hold onto calcium –> unregulated muscle contraction
  • If Calcium ATPase runs all the time –> hydrolyses much ATP, producing much heat –> so animal overheats quickly
  • Leak of calcium may cause unregulated muscle contraction/prevent normal muscle contraction
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8
Q

Agonist

A

Muscle that produces a certain effect

Antagonist: muscle that produces the opposite effect

Example of antagonistic pair: bicep & tricep

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9
Q

Synergistists

A

Muscles that neither faciliate nor directly oppose the effects, but modify the action of the agonist e.g. by unlimiting an unwanted side effect

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10
Q

Fixators

A

Muscle that are employed to stabilise joints rather than promote movement

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11
Q

Origin

A

The most proximal/central attachment

Moves the least

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12
Q

Insertion

A

The more distal/peripheral attachment

Moves the most

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13
Q

Isotonic contraction

A

activated muscles shorten when contraction occurs

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14
Q

Isometric contraction

A

when the activated muscles generate force without shortening e.g. animal pushes against heavy object that doesn’t move

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15
Q

Why is the length of the sarcomere an indicator of contractile force?

A

As contraction increases, length of sarcomere decreases

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16
Q

Tetanic contraction

A

Sustained full contraction with the inability to relax

17
Q

What could be responsible for muscle fatigue?

A
  • Increases levels of inorganic phosphate (due to creatine phosphate degradation) adversely affects cross-bridge function
  • Accummulation of lactic acid
  • Reduced release of Ca2+ from sarcoplasmic reticulum
  • Empty glycogen stores
  • Psychological factors
18
Q

Method of energy metabolism in Type 1 (slow-twitch) fibres?

A

Oxidative phosphorylation

19
Q

Method of energy metabolism in Type II fibres?

A

Oxidative phosphorylation

20
Q

Method of energy metabolism in Type IIb fibres?

A

Glycolysis

21
Q

Characteristics of Type I muscles fibres?

A
  • Slow-twitch
  • Small
  • Many mitochondria
  • Fatigue-resistant
  • Much myoglobin, many cytochrome complexes, little glycogen
  • e.g. in marathon runners
22
Q

Characteristics of Type IIa fibres

A
  • Intermediate speed
  • Medium fibre length
  • Many mitochondria
  • Fatigue-resistant
  • High myoglobin content, high levels of glycogen
    • Capable of anaerobic glycolysis
  • e.g. in hockey players
23
Q

Characteristics of Type IIb muscle fibres

A
  • Fast-twitch
  • Large fibres
  • Few mitchondria
  • Less fatigue resistant
  • High anaerobic enzyme activity
  • Much glycogen stored
  • e.g. Short distance sprinters, weightlifters
24
Q

Compare the vasculature of muscles and tendons

A

Muscles have a generous blood supply

Muscle contraction squeezes veins, promoting circulation

Tendons are poorly vascularised due to their low metabolic needs

25
Q

Myoglobin

A

A red protein containing haem, which carries and stores oxygen in muscle cells. It is structurally similar to a subunit of haemoglobin.

26
Q

What is the neurotransmitter at the neuromuscular junction?

A

Acetylcholine

27
Q

Motor unit

A

a single alpha motor neuron and all of the corresponding muscle fibres that it innervates.

28
Q

What can be said about the fibres within a motor unit?

A
  • They will all be innervated simultaneously
  • They will all be of the same fibre-type
29
Q

True/False: the size of the motor unit dictates the level of control

A

True

Smaller motor units (e.g. 1 axon to 1 muscle fibre) enable fine muscle control

30
Q

What is the name given to the membrane of the muscle fibre?

A

Sarcolemma

31
Q

Excitation contraction coupling

A

The process by which an electrical stimulus triggers the release of calcium by the sarcoplasmic reticulum, initiating the mechanism of muscle contation by sarcomere shortening.

32
Q

Describe how excitation contraction coupling occurs

A
  • The system of T-tubules conduct action potentials from the cell surface to the core of the fibre
  • The t-tubules are in direct contact with the sarcoplasmic reticulum that surrounds the myofibrils
  • The membranes of the sarcoplasmic reticulum contain ryanodine receptors which are types of Ca2+ channels
  • Voltage-sensitive channels are coupled to these receptors
  • Upon depolarisation, the channels change conformation and open the ryanodine receptor
33
Q

How is muscle length regulated?

A
  • Using muscle spindles
  • Muscle spindles = specialised muscle fibres
  • Use reflex arcs to maintain muscle length when it changes –> myotatic reflex
  • Therefore used to automate movement
34
Q

How is muscle tension regulated?

A
  • Golgi tendon organs monitor the tension developed in the muscle
  • They prevent damage during excessive force generation –> excessive force leads to reflex relaxation of muscle to avoid rupture (reverse myotatic reflex)
35
Q

Describe the clinical relevance of the ryanodine receptor (malignant hyperthermia)

A

NMSK (26 decks)

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