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Fundamentals Of Life Science > Anatomy and Microanatomy of Muscle > Flashcards

Anatomy and Microanatomy of Muscle Flashcards

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1
Q

What are the four types of tissue?

A
  • connective
  • muscle
  • nerve
  • epithelial
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2
Q

What are the four properties of muscles?

A
  • contractibility
  • excitability
  • extensibility
  • elasticity
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3
Q

What is Contractibility?

A

ability of muscle cells to forcefully shorten and generate pulling force

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4
Q

What is Excitability?

A

ability to respond to a stimulus, from a motor neuron or a hormone

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5
Q

What is Extensibility?

A

ability of a muscle to be stretched

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6
Q

What is Elasticity?

A

ability to recoil to the muscle’s original size after being stretched

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7
Q

What are the functions of muscles?

A
  • movement
  • maintenance of posture
  • respiration and digestion
  • heat generation
  • communication
  • constriction of organs and blood vessels
  • pumping blood
  • protection
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8
Q

What are the three types of muscle?

A
  • smooth
  • cardiac
  • skeletal
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9
Q

Describe skeletal muscles

A
  • striated
  • somatic
  • voluntary
  • attached indirectly or directly to bone
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10
Q

What is fascicle?

A

a group of muscle fibres/cells

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11
Q

What is a muscle fibre?

A

groups of myofibrils

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12
Q

What is a skeletal muscle composed of?

From Out to In

A

Muscle - Group of Fascicles
Fascicle
Muscle Fibre
Myofibril

+Connective tissue

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13
Q

What are Myoepithelial cells?

A

Expel secretions from glands

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14
Q

What are Myofibroblast cells?

A

Secrete collagen in the process of healing and repair

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15
Q

What are Pericytes?

A

Cells that surround blood vessels of muscels.

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16
Q

What is the Epimysium?

A

Connective tissue surrounding the whole muscle

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17
Q

What is the Perimysium?

A

Connective tissue around fascicles

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18
Q

What is the Endomysium?

A

Connective tissue around individual muscle fibres.

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19
Q

Describe a skeletal muscle cell anatomically

A

long, cylindrical unbranched multinucleate contractile cell

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20
Q

How are the skeletal muscle cells arranged?

A

In parallel

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21
Q

Can muscle cells be regenerated if damaged?

A

yes by proliferation and differentiation of stem cells

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22
Q

What is the myofibril composed of?

A

longitudinal myofilaments

  • actin
  • myosin
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23
Q

Is actin thin or thick?

A

thin

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24
Q

What is the M line?

A

the line in the middle of the sarcomere

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25
Q

What is the A band?

A

the length of the thick filament (myosin)

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26
Q

What is the I band?

A

the space between thick filaments (Mainly Actin)

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27
Q

What is the Z line?

A

lines that separate sarcomeres

28
Q

What does myosin consist of?

A

heavy chain tail

light chain head

29
Q

What does actin consist of?

A
  • tropomyosin

- troponin (Ca binding site)

30
Q

What is the T tubule system?

A

a transverse extension of sarcolemma around each myofibril

31
Q

Where are the T-Tubule systems found?

A

At the junction of A and I bands

32
Q

Describe the sliding filament mechanism

A
  1. myosin heads hydrolyse ATP and become reorientated and energised
  2. myosin heads bind to actin forming crossbridges when Pi group is released
  3. Myosin heads rotate towards the centre of the sarcomere (power stroke) upon release of ADP
  4. As myosin heads bind ATP the cross bridges detach from actin
33
Q

Describe how muscle contraction occurs?

A
  1. sarcolemma becomes depolarised
  2. rapid dissemination by T tubule system
  3. Release of Ca^2+ ions from terminal cisternae into sarcoplasm surrounding myofilaments
  4. Ca^2+ ions bind to troponin which changes shape, moving tropomyosin on actin to reveal actin binding sites
  5. Myosin head attaches to form cross bridge
  6. pivots and slides thin filament towards the sarcomere centre which causes a muscle contraction
34
Q

What happens to the sarcomere during contraction?

A
  • I band and H zone shorten

- Z lines become closer together

35
Q

What is the efferent to muscles?

A

Motor nerves

36
Q

What is a motor unit?

A

A number of muscle fibres innervated by one motor neurone

37
Q

What is the neuromuscular junction?

A

structure where the motor neurone communicates with the skeletal muscle fibre

38
Q

What are the parts of the NMJ?

A

Axonal terminal
Motor end plate
Separated by synaptic cleft

39
Q

What are the afferents from muscles?

A
  • golgi tendo organs

- muscle spindles

40
Q

What is the role of the golgi tendon organs?

A

To detect changes in the tension within tendons (proprioceptors). Inhibits motor nerve activity if there is excessive tension

41
Q

What is the role of muscle spindles?

A

-Sensory recepters/proprioceptors that detect change in length and stretch of muscles

42
Q

What are the three types of muscle fibres?

A
  • type I
  • type IIA
  • type IIB
43
Q

What is the structure and function of type I fibres?

A

Slow Twitch

  • red oxidative fibres
  • many mitochondria
  • abundant myoglobin
  • mainly gets energy from aerobic oxidative phosphorylation
  • adapted for slow continuous contractions over prolonged periods (Posture)
44
Q

What is the structure and function of IIA?

A

Fast/Intermediate Twitch

  • oxidative glycolytic fibres
  • many mitochondria
  • reasonable amount of myoglobin
  • contains glycogen
  • energy source = both oxidative phosphorylation and anaerobic glycolysis
  • adapted for rapid contractions and short bursts of activity (athletics)
45
Q

Structure and function of IIB?

A

Fast Twitch

  • glycolytic fibres
  • few mitochondria
  • few myoglobin
  • abundant glycogen
  • mainly gets energy from glycolysis
  • adapted for rapid contractions but fatigue quickly (Eye muscles and Digits)
46
Q

What are the different ways to organise muscle fasciculi?

A
  • parallel fasciculi
  • covergent fasciculi
  • pennate fasciculi
  • circular fasciculi
47
Q

What are some skeletal muscle clinical correlations?

A

Myasthenia Gravis

Duchenne Muscular Dystrophy

48
Q

What is Myasthenia Gravis?

A

a chronic autoimmune neuromuscular disorder

causes weakness of skeletal muscle due to a lack of nAChRs at the NMJ since they’re blocked by Abs

49
Q

What is muscular dystrophy?

A

genetic disorder which causes breakdown of skeletal muscle

50
Q

Describe smooth muscle anatomically

A
  • non-striated, visceral, involunary
  • small elongated cells with tapered ends
  • single central nucleus
  • cells arranged in sheets or bundles
  • supporting collagenous tissue between cells
  • contract or stretch
51
Q

Describe the contractions of smooth muscle

A
  • continuous contraction of low force
  • can contract independent of innervation
  • contractions are modulated by autonomic nervous system, hormones and local metabolites
52
Q

Do smooth muscles have T tubules?

A

no they have gap junctions (also don’t have a sarcomere)

53
Q

What is the structure of a smooth muscle cell?

A
  • contractile proteins (actin and myosin) arranged in a criss-cross lattice
  • they are inserted to anchoring points along with desmin-intermediate filaments and cell membrane
54
Q

How does the sliding filament work in smooth muscles?

A

calcium calmodulin complex (calcium from cytoplasm) activates enzyme myosin light chain kinase which phosphorylates myosin and binds to actin for filament sliding contraction

55
Q

What are some smooth muscle clinical correlations?

A

Multisystemic Smooth Muscle Dysfunction Syndrome

Generalised weakness and poor functioning of smooth muscle

56
Q

What is cardiac muscle structurally and functionally an intermediate to and why?

A
  • skeletal and smooth
  • contractions are strong and use a lot of energy
  • contractions are continuous and inherently contractile (involuntary)
57
Q

Describe a cardiac muscle cell

A
  • long cylindrical
  • one or two nucleus usually central
  • striated
  • intercalculated disks
  • supported by delicate collagenous tissue with rich capillaries
58
Q

What control the cardiac muscle contractions?

A

Pacemakers SA and AV nodes

59
Q

How does myocardium contraction work?

A

Cells have slow leak of Ca ions from SR

Automated contractions modulated by SA/AV and hromones

60
Q

What is the functional Syncytium of cardiac muscle?

A

Intercalated discs for electrical and mechanical coupling with the adjacent cell.

61
Q

What is special about cardiac muscels structure?

A

Has branching myofibrils and a T-tubule system.

62
Q

What are some Cardiac muscle clinical correlations?

A

Angina Pectoris marked by Ischemia of cardiac muscle

Myocardial infarction

Arrhythmias

Myocarditis

Myocardial fibrosis

63
Q

What is Ischemia?

A

an inadequate blood supply to an organ or part of the body, especially the heart muscles.

64
Q

What is an arrhythmia?

A

Abnormal heart rhythm

65
Q

What is Myocarditis?

A

Inflammation of cardiac muscle

66
Q

What is Myocardial Fibrosis?

A

excess ECM from fibroblasts causing scarring and damage.

Fundamentals Of Life Science (26 decks)

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