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Muscle Structure Flashcards

1
Q

What is the typical vasculature of a muscle like?

A

Sometimes a single artery enters the muscle belly
Sometimes two or more arteries will enter and join up
Intramuscular arteries expand into capillaries

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2
Q

What is the typical vascularature of a muscle

A

Some have just one artery running into muscle belly
Some have more than one artery and they meet up
Intramuscular arteries expand into capillaries

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3
Q

What is an anastomosis?

A

surgical connection between two structures. It usually means a connection that is created between tubular structures, such as blood vessels or loops of intestine.

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4
Q

What is the inervature of the muscle like/

A

Single nerve branches out into connective tissue
Have motor neurons and sensory neurons
Has neuromuscular junctions

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5
Q

What are synergists/

A

Muscles that don’t facilitate or oppose a movement, but may effect it

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6
Q

What are fixators?

A

Muscles that stabilise a joint but doesn’t move it

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7
Q

What is the orgiin

A

Most proximal POA

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8
Q

What is the insertion?

A

Most distal POA

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9
Q

Where are skeletal muscles located?

A

Trachea, arteries

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10
Q

What are the 4 functions of skeletal muscle?

A

Locomotion and breathing
Posture and support
Heat production during cold stress
Largest protein store in the body

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11
Q

What is the structure of skeletal muscles like

A

Striated
Synctium (multinucleated)
Peripheral nuclei (at edge)

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12
Q

What are fasicles?

A

Bundles of muscle fibres

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13
Q

How big is each muscle fibre/

A

10-100 um in diameter
Up to 30cm in length

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14
Q

What is the epimysium

A

Surrounds whole muscle

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15
Q

What is the perimysium>

A

Surrounds bundles of muscle fibres (fascicles)

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16
Q

What is the endomysium

A

Surrounds individual muscle fibres

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17
Q

What is the sarcolemma?

A

Muscle cell membrane

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18
Q

What are Myofibrils

A

Myofibrils are long filaments that run parallel to each other to form muscle (myo) fibers. The myofibrils, and resulting myofibers, may be several centimeters in length. The muscle fibers are single multinucleated cells that combine to form the muscle. Myofibrils are made up of repeating subunits called sarcomere
Tubular structures that pack the fibres

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19
Q

What are myofilamwnts?

A

Threadlike strands within the myofibrils
Actin and myosin

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20
Q

What is the I band?

A

Actin alone

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21
Q

What is the A band

A

Myosin and actin (ambos)

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22
Q

What is Z lime?

A

End of sarcomere
Defines boundaries

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23
Q

What is H zone

A

Myosin only

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24
Q

How do muscles contract?

A

Calcium binds to troponin
Causes tropomyosim to change shape and move away from myosin binding site on actin
Cross bridge bwteeen actin and myosin forms
ATP —> ADP + P breaks cross bridge

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25
What are the three different types of fast fibres
Type IIa Type IIb Type 11x
26
How can you distinguish between different muscle fibre types
Each fibre type has a specific immunohistochemistry Specific histochemistfy (ATPase activity) Specific metabolic profiles
27
What is the following like for type I fibres? (Slow oxidative) Size of motor unit Itodhondira Fatigue resistant Speed of contraction Typical functions
Small Many High Low Posture
28
What is the following like for type IIa fibres? (Fast oxidative) Size of motor unit Itodhondira Fatigue resistant Speed of contraction Typical functions
Intermediate Many Intermediate Moderate Walk, run
29
What is the following like for type IIx fibres? (Fast glycolytoc fibres) Size of motor unit Itodhondira Fatigue resistant Speed of contraction Typical functions
Large Moderate Low High Jump, throw
30
What is the following like for type II b fibres? (Very fast glycolytic fibres) Size of motor unit Itodhondira Fatigue resistant Speed of contraction Typical functions
Very large Few Very low Very high Jump, throw
31
What is muscle fatigue and what are the causes of it?
Decrease in maximum contractile force No ATP for formation of cross bridges Increase in inorganic phosphate Decrease in Ca2+
32
What is a motor unit?
Single motor neuron and all of the muscle fibres it innervates All fibres innervated simulataneously All same fibre type
33
How does the neuromuscular junction work?
Action potential at end of neuron stimulates Ca2+ channels to open Ca2+ channels open and causes vesicles carrying acetylcholine to move to membrane Acetylcholine moves across synapse and binds to Na+ channels Na+ enters in membrane of muscle
34
What breaks down acetylcholine
Acetylcholinesterase
35
What will happen if drugs act at Ach receptor
Muscle will stay relaxed
36
What do antiacetylcholineestersse drugs do
Prevent breakdown of acetylcholine so more activation of muscle
37
What do t tubules do?
Help spread single from motor neuron throughout muscle
38
What channel does sarcoplasmic reticulum contain?
Ryanodine receptor for Ca2+
39
How do t tubules help muscle contraction
Action potential in t tubules Opens Ca2+ in sarcoplasmic reticulum Ca2+ releases indices more Ca2+ to be released Them Ca2+ pumped back into SR
40
What are the two types of receptors in muscles/
Muscle spindles Golgi tendon organ
41
What are muscle spindle fibres
Provide information on length of muscle and how quickly it is changing (velocity) Sensory neurons in fibres to detect this Uensitive to stretch
42
What are Golgi tendon organs?
Monitor tension developed in muscle Prevents damage during excessive force generation
43
What is an aponeurosis
A flat sheet of muscle with flat tendons
44
What is the structure of a smooth muscle like?
Single centrally located nucleus No striations
45
Where would you find smooth muscle
In viscera (internal organs) Blood vessels Uterus wall
46
What controls each type of muscle
Skeletal- somatic Cardiac/ smooth- autonomic
47
What can stimulate smooth muscle to contract
Hormones Neuronal communication
48
What is the structure of skeletal muscle like?
40cm in length 100um in diameter Multinucleated at periphery Striations
49
What are the two types of skeletal muscles
Slow twitch Fast twitch
50
What is the structure of cardiac muscle like?
Up to 90um in length Up to 15um in diameter One or two nuclei in centre of cell Show striations Cardiomyocytes are often branched for cell to cell connectiin
51
What happens to muscle structure is immobilised?
Sarcomeres deleted
52
What is hypertrophy and hyperplasia?
Hypertrophy- cells increasing in size Hyperplasia- increasing number of cells
53
How do muscles grow?
Due to hypertrophy Muscle fibre increases in size, increase in myofibrils and myofilaments
54
What factors can cause hypertrophy in muscles?
Building up the muscle Anabolic steroids
55
What factors cause atrophy (breakdown of muscles)
Disuse Denervation Disease Malnutrition
56
How does a mechanical stimukus increase muscle size?
IGF 1 causes: satellite cell profilerstiom Protein synthesis (myosin and actin)
57
What is the problem with IGF 1?
Cause cause too much cell proliferation, so results in tumour production
58
Why does necrosis of muscle cells occur?
Torn/ damaged sarcolemma Influx of Ca2+, which triggers necrotic mechanisms
59
What is the function of satellite cells and where are they?
Activated following damage Profilerste and differentiate to form muscle cells and daughter cells In between sarcolemma and endomysium
60
What is stringhalt?
Onset of excessive Flexion in one or both hind limbs Causes severe muscle spasms (tetanises) Muscle atrophy Most likely by nerve damage, and muscles stay fully contracted
61
What is neuropathy of the laryngeal muscles?
Only affects left muscles, as left recurrent laryngeal nerve goes round aorta so more likely to get damaged Affects ability to open glottis (opens into windpipe) Turbulent air flow, so causes roaring
62
How can you detect muscle damage?
Myoglobinuria —>check urine for myoglobin (like heamoglobin in muscle, binds to O2), too much can indicate muscle damage and could cause kidney damage Creatine kinase —> enzyme used by muscles, but not specific. Increase levels can indicate muscle damage or wasted
63
What is polymyosistois?
Generalised inflammatory myopathy Due to over active immune response, from cell mediated
64
What is masticating muscle myositis?
Focal inflammatory myopathy, only affects muscles in jaw for chewing Lock jaw Prominence of zygomatic arch (cheekbone)
65
What is Duchenne Muscular dystrophy?
Congenital/ inherited myopathy Occurs in dog, humans and mice Mutation in the gene coding for membrane protein dystrophin Links to degeneration of respiratory muscles
66
What are the two examples of endocrine myopathies
Hypothyroidism —> stiffness, weakness, muscle wastage, atrophy of type II fibres Cushing disease —> muscle weakness, stiff gait, muscle atrophy and inability to walk in dogs. Atrophy of type II Fibres, inhibition of muscle protein synthesis
67
What is selenium/ vitamin D deficiency
Still birth/ weak calf Doesn’t usually affect carnivores
68
What is sarcopenia
Atrophy associated with ageing Due to loss of motor neurons Degeneration Loss of motor fibres Fibrosis—> build up of connective tissue

NMSK (47 decks)

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