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z. nmsk 1 > Muscles > Flashcards

Muscles Flashcards

1
Q

What are the 3 types of muscles

A
  • smooth muscle (for contraction and dilation, usuall on vessels)
  • cardiac muscle
  • striated muscle
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2
Q

What are the functions of skeletal muscle

A
  • locomotion and breathing
  • postural support
  • heat production during cold stress
  • largest protein store in the body (body will use proteins in these muscles in malnourished)
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3
Q

What are the key structural points of skeletal muscle fibres (cells)

A
  • striated
  • syncytium (multi nucleated cells)
  • peripheral nuclei (nuclei found near the outside of the cell
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4
Q

What is a fasicle

A
  • an bundle of muscle fibres
  • multiple fasicles make up a muscle
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5
Q

what is epimysium

A

CT layer that surrounds the entire muscle

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6
Q

What is perimysium

A

CT that surrounds each fasicle

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7
Q

Why is CT important for muscles?

A

Functional (transfer of info) and protective

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8
Q

What is the sarcolemma

A

muscle cell membrane

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9
Q

what are myofibrils

A

rod-like structures that pack the filaments together. also known as a muscle fibre

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10
Q

what are myofilaments

what are the different kinds

A

threadlike strands within myofibrils
- Actin (thin filament) (proponin and propomyosin)
- myosin (thick filament)

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11
Q

what is a sarcomere

A

an individual unit conatining actin/myosin

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12
Q

Within a sarcomere, what are the different bands/lines called and what are they

A
  • I-bands: actin filaments alone
  • A bands: zones containing myosin
  • Z line (or disc): defines boundary between sarcomeres
  • M-line: transverse line in the middle of the sarcomere that binds the myosin filaments
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13
Q

What is the sliding filament theory

A
  • muscle shortening occurs due to the movement of the actin filament over the myosin filament
  • formation of cross-bridges between actin and myosin filaments
  • reduction in the distance between Z lines of the sarcomere
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14
Q

What is involved in cross bridge formation and how do they work

A
  • tropomyosin: located along the 2 chains of actin filaments and when calcium is low, blocks the binding of myosin to the actin and the fibre
  • troponin: complex that is attached to each tropomyosin
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15
Q

Why is calcium important for muscle function

A

stimulates muscle contraction

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16
Q

what does troponin do

A

captures calcium and undergoes a conformational change that lifes tropomyosin away from the actin filament

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17
Q

What are the 3 different fast muscle fibres

A
  • type 2a (fast oxidative)
  • tpye 2b (fast glycolytic)
  • type 2x (intermediate between a and b)
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18
Q

what are the slow muslce fibres

slow to contract

A

type 1 fibres (slow oxidative)

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19
Q

how are fibre type compositions within muscles analysed for identification

A
  • immunochemistry (looks for cell markers)
  • histochemistry (looks for ATPase activity which is positively correlated to muscle contraction velocity
  • fibres have specific metabolic profiles
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20
Q

what is muscle fatigue

A

decreased maximum contractile force
- ATP is required for formation of cross bridges
- when muscles fatigue, inorganic phosphate increases and calcium decreases

21
Q

What are the components of the motor unit

A
  • a single alpha motor neuron and all of the corresponding muscle fibres it innervates
22
Q

what are the key note about a motor unit

A
  • all fibres in a MU innervated simultaneously
  • all the same fibre type
  • MU size dictates the level of control
  • slow MU tend to be smaller and are recruited first during normal exercise
  • hennemans size principle (as force increases, more larger MU recruited)
  • in ballistic locomotion, faster MU can be recruited initially
23
Q

label

A
24
Q

What is acetylcholine and what is its function

A
  • the chemical intermdiary in the transfer of excitation from nerve to muscle
  • releases the synaptic vesicles (calcium triggers the release)
  • ACh is then released into the synaptic cleft where it combines with ACh receptors causing depolarisation of the muscle cell and activates the ion channel for Na ions
  • it is then rapidly broken down by acetylcholinesterase
25
Q

what is a t-tubule system

A
  • conducts action potentials from the cell surface to the core of the fibre
  • in direct contact with the sarcoplasmic reticulum (SR) surrounding the myofibrils
  • the membranes of the SR contain a type of Ca2+ channel called a ryanodine receptor
  • voltage-sensitive channels are coupled to RR
  • upon depolarisation they change conformation and open RR
26
Q

how does action potential influence Ca2+ Release

A
  1. action potentional in t-tubule
  2. openes calcium channels in sarcoplasmic reticulum
  3. calcium released: casues mroe channels to open (calcium induced calcium release) this drives muscle contraction
  4. calcium pumped back into sarcoplasmic reticulum, relaxing muscle
27
Q

whata re the receptors in the muscle

A
  • muscle spindle
  • golgi tendon organ
28
Q

what are muscle spindles receptive to and what are they

A
  • sensitive to stretch
  • provide information on muscle length
  • modified muscle fibres (intrafusal fibres, ONLY stretch and send data, do not take load)
29
Q

what are the golgi tendon organ receptors receptive to

A
  • monitor tension developed in muscle
  • prevents damage during excessive force generation
  • excessive stimulation results in reflex relaxation of muscle
30
Q

what is hypertrophy

A

cells increasing in size
in mucscles cells: increase in myofibrils and myofilaments to enlarge the muscle cells

this is how we get growth of muscles

31
Q

what is hyperplasia

A

increasing number of cells

32
Q

What is Atrophy

A

a reduction in muscle volume or mass which may be generalised or limited to certain muscles

33
Q

what factors cause hypertrophy and atrophy

A
  • anabolic factors (building the muscle with mechanical load or steroid)
  • catabolic factors (breaking down the muscle via disuse, denervation, disease, malnutrition)
34
Q

how does mechanical stimulus produce an increase in fibre size

A
  • IGF-1 (insulin like growth factor)
35
Q

what are the 4 types of muscle pathology

A
  • injury
  • nerve damage
  • disease
  • aging
36
Q

what is necrosis and how is it triggered in muscular injury

A

cell death
- in muscle injury when sarcolemma is torn or damaged there is an influx of calcium whihc triggers the nectrotic mechanisms

37
Q

what cells are responisble for repairing injured muscle cells and how do they work to repair damaged muscle

A

satellite cells
- activated following damage
- proliferate and differentaite to form muscle cells and daughter cells

they sit btwn the sarcolemma and endomysium

38
Q

what are the steps of nerve damage pathology in the muscles

A
  • motor nerve gets damaged
  • muscle lacks innervation
  • muscle uncergoes atrophy
39
Q

what is stringhalt disease

A
  • onset of excessive felxion in 1 or both hindlimbs
  • in severe cases causes muscle tetanises
  • muscle atrophy
40
Q

how do you detect muscle damage

A

myoglobinuria
- O2 binding protein in the muscle
- excessive amounts of myoglobin in the urine
- too much can cause kidney damage
creatine kinase
- enzyme used by muscles
- increased levels can indicate muscle damage or wasting (be careful with this one though as it can also be present shortly after moderate exercise)

41
Q

what are the 2 noted inflammatory muscle diseases

A
  • polymyositis
  • masicatory muscle myositis (MMM)
42
Q

what is polymyositis

A
  • generalized inflamatory myopthay
  • muscle damage is thought to be the result of cell-mediated immunity (immune system start to attack own muscles)
43
Q

what is masticatory muscle myositis

A
  • focal inflammatory myopathy that selectively affects the muscles of the mastication (chewing muscles)
  • clinical signs include lock jaw, fox like contour to the head and prominence of the zygomatic arch
44
Q

what is duchenne muscular dystrophy

A
  • occurs in humans dogs and mice
  • congenital and inherited disease
  • mutation of the gene coding for the membrane protein dystrophin (x-linked recessive disorder)
  • leads to degeneration/regeneration resulting eventually in the failure of the respiratory muscles
45
Q

what are the 2 noted hypothyroidism

A
  • hypothyroidism
  • cushings disease (hyperadrenocorticism)
46
Q

what is the effect of hypothyroidism to the muscles

A
  • problems with carbohydrate metabolism which interferes with glycolitic metabolism
  • muscle biopsies show atrophy type 2 fibres
  • clinical signs include weakness, stiffness, reluctance to move and decreased exercise tolerance and muscle wastage
47
Q

what is the effect of cushings diseas on the muscle

A
  • selective atrophy of type 2 fibres
  • breakdown of muscle proteins and inhibition of muscle protein synthesis
  • clinical signs include weakness, stiff gait, muscle atrophy an inability to walk in dogs
48
Q

what is an example of a nutrition myopathy

A

selenium and vitamin E deficiency
- clinical signs include still birth and weak calf (stiffness and inability to stand
- affects calves, lambs, swine and foals
- doesnt often affect carnivores
- can be treated with supplements over a course of 3 months but this is costly

49
Q

what is sarcopenia

A

atrophy associated with aging
- loss of motor axons
- denervation
- degeneration/regeneration
- loss of motor fibres
- motor-unit size
- fibrosis
- IGF-1

z. nmsk 1 (50 decks)

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