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Anatomy and Physiology > A & P - Muscles > Flashcards

A & P - Muscles Flashcards

1
Q

describe the structure of a cardiac muscle cell

A

small, branched cells
interconnected by selectively porous jucnctions (intercalated discs)
central nucleus
straited

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2
Q

how are cardiac muscles innervated?

A

cardiac self-contractile pacemaker cells

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3
Q

how are cardiac muscles regulated?

A

autonomic/involuntary nerves

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4
Q

what is the function of cardiac muscle?

A

blood circulation

hydrostatic blood pressure

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5
Q

describe the structure of smooth muscles

A

small, spindle shaped
single centre nucleus
non-striated

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6
Q

where would smooth muscle be found in the body?

A

blood vessel walls
hollow organs
respiratory, digestive, cardiovascular and repro. tracts

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7
Q

how is smooth muscle innervated?

A

self-contractile (dig. tract)

autonomic/involuntary nerves

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8
Q

what is the function of smooth muscle?

A

move food, urine and repro secretions

regulation of airway and blood vessel diameter

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9
Q

describe the structure of skeletal muscle

A

very long
striated
multinucleus

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10
Q

where in the body would skeletal muscle be found?

A

throughout

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11
Q

how is skeletal muscle innervated?

A

somatic/voluntary motornerves

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12
Q

what is the function of skeletal muscle?

A 
movement/stabilisation of skeleton
guards entrance/exit of dig, resp, urinary tracts
generates heat
protects organs
stores nutrients
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13
Q

where would the origin of a skeletal muscle be?

A

where fixed end of muscle meets bone

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14
Q

where would the insertion of a skeletal muscle be?

A

where moveable end of muscle meets bone

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15
Q

if skeletal muscle was described as synergist what would this mean?

A

muscles work together in same direction

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16
Q

if skeletal muscle was described as antagonist what would this mean?

A

muscle works in opposite direction to given muscle (eg. tricep/bicep)

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17
Q

if a particular skeletal muscle was described as the prime mover (agonist) what would this mean?

A

that muscle is responsible for a particular movement

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18
Q

if skeletal muscle was described as the fixator muscle what would this mean?

A

the muscle stabilises the origin of an agonist muscle (eg. scapula)

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19
Q

name the three layers of skeletal muscle, inner to outer

A

endomysium
perimysium
epimysium

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20
Q

describe the structure of epimysium in skeletal muscle

A

surrounding muscle
dense collagen layer
separates from nearby tissue

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21
Q

describe the structure of perimysium in skeletal muscle

A

divides muscle into fascicles

contains collagen, elastic fibres, nerves, blood vessels

22
Q

describe the structure of endomysium in skeletal muscle

A

flexible layer inside fascicle

contains fine capillaries and nerves

23
Q

name the three types of skeletal muscle and describe them in terms of metabolism, endurance and contractility

A

type I - slow contraction, low force, high endurance, aerobic metabolism
type IIa - fast contraction, medium force/endurance, mixed metabolism
type IIb - fast contraction, high force, low endurance, anaerobic metabolism

24
Q

what does muscle size depend on? what alters this?

A

abundance of type I vs. II muscle fibres

altered by : genes, sex, age, training

25
Q

describe the size of the muscle produced by type I and II fibres

A

type I : smaller muscles

type II : bigger muscles

26
Q

what is myopathy?

A

heterogeneous group of disease with various causes (when muscle go wrong)

27
Q

name some causes of myopathy

A 
gene mutation
metabolic origin
inflammation
autoimmune
drugs
infection
28
Q

what is affected in myopathy?

A

just the muscle - not the neuromuscular junction or nerve

29
Q

what innervates muscle fibres?

A

motorneurones (MN)

30
Q

how do motorneurones and muscle fibres communicate?

A

in close proximity at neuromuscular junction (NMJ)

chemical signals used

31
Q

describe the innervation of muscle at the NMJ

A
  1. electrical signal in MN axon
  2. Ca2 channels open in pre-synaptic MN
  3. Ca2 enters - fusion of vesicles containing ACh with membrane
  4. ACh released into synaptic cleft - binds with ACh receptors on muscle cell
  5. ACH degraded in synaptic cleft by ACh esterases
  6. opening of ACh gated ion channels on muscle cell allows Na+ and K+ to flood muscle cell - electrical signal
  7. muscle contracts
32
Q

what is myasthenia gravis?

A

severe muscle weakness - NMJ affected

33
Q

what are the causes of myasthenia gravis?

A

auto immune - antibodies attack ACh receptors
congenital - transfer of antibodies to baby from mum (reversible)
genetic - mutation affecting ACh production or signalling

34
Q

what are the symptoms of myasthenia gravis?

A

abnormal muscle fatigue - in prolonged/repetitive contraction
variation in severity - daily basis/overtime

35
Q

what are the treatments for myasthenia gravis?

A

prevention ACh degradation needed (ACh esterase inhibitor, steroids, immune suppress)
thymectomy - removal of thymus (antibodies made here)
plasmapheresis and immunoglobulin therapy

36
Q

what is the term used for the cell membrane of a muscle cell?

A

sarcolemma

37
Q

what does the term sarcoplasm mean?

A

cytoplasm relating to a muscle cell

38
Q

what does sarcoplasm contain?

A

long, protein rich fibres called myofibrils

39
Q

what does a myofibril consist of?

A

many parallel protein strands:
thin - actin
thick - myosin

40
Q

what is a sarcomere?

A

arrangement of thin and thick strands making up the basic contractile unit

41
Q

how many sarcomeres are in one myofibril?

A

10,000

42
Q

describe the sliding filament mechanism

A
  1. ATP turns into ADP releasing energy -converts myosin head to ‘cocked’ state (potential energy)
  2. calcium binds to troponin - exposes sites on actin so myosin can grab actin (cross bridges formed)
  3. myosin pushes on actin - actin moves (power stroke complete)
  4. ATP binds to myosin making it release actin
43
Q

which two elements are needed for the sliding filament mechanism to work?

A

ATP

Ca2+

44
Q

where is the ATP needed for the sliding filament mechanism obtained from?

A

creatine phosphate
aerobic metabolism
anaerobic metabolism

45
Q

what is ATP needed for in the sliding filament mechanism, what happens without it?

A

ATP needed to release myosin from actin binding site

without ATP strands are permanently cross linked (rigor mortis)

46
Q

where is the Ca2+ needed for the sliding filament mechanism obtained from?

A

at rest Ca2+ is stored in the sarcoplasmic reticulum (SR)

AP triggers release of Ca2+ - this binds to actin causing a structural change making binding site available

47
Q

what can affect the active reuptake of Ca2+ by the sarcoplasmic reticulum?

A

myopathies and myotoxicity (induced by statins) affect the reuptake of Ca2+ affecting the sliding filment mechanism

48
Q

what is excitation-contraction coupling?

A

mechanism whereby excitation of muscle cell causes contraction nearly simultanously

49
Q

what would happen if the sarcomere where too stretched or too contracted?

A

reduced number of cross bridges = reduced tension

50
Q

what is an isometric contraction?

A

muscle develops tension but does not shorten (during no movement of object)

51
Q

what is an isotonic, concentric contraction?

A

muscle shortens, tension remains constant (during upward movement)

52
Q

what is an isotonic, eccentric contraction?

A

muscle lengthens while maintaining tension (during downward movement)

Anatomy and Physiology (15 decks)

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