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PHA112 > Muscoskeletal System 1 > Flashcards

Muscoskeletal System 1 Flashcards

1
Q

define excitability?

A

capacity of muscle to respond to stimulus

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2
Q

define contractility?

A

ability of muscle to shorten + generate pulling force

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3
Q

define extensibility?

A

muscle can be stretched back to original length

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4
Q

elasticity?

A

ability of muscle to recoil to original resting length after stretched

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5
Q

what are the different types of muscle?

A
  • skeletal
  • smooth
  • cardiac
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6
Q

skeletal

A
  • makes up 40% body weight
  • responsible for locomotion, facial expressions, posture, respiratory movements
  • controlled by somatic motor neurones (VOLUNTARY)
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7
Q

smooth

A
  • in walls of hollow organs, blood vessels, eyes etc
  • functions: properly urine, mix food in digestive tract, dilate/constrict pupils, regulate blood flow
  • controlled by endocrine + autonomic nervous systems (INVOLUNTARY)
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8
Q

cardiac

A

controlled involuntarily by endocrine + autonomic nervous systems

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9
Q

what is the epimysium?

A

dense regular connective tissue surrounding entire muscle

  • separates muscle from surrounding tissues + organs
  • connected to deep fascia
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10
Q

what is the perimysium?

A

collagen + elastic fibres surrounding group muscle fibres = fascicle

contain blood vessel + nerves

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11
Q

what is the endomysium?

A

loose connective tissue that surrounds individual muscle fibres

contains blood vessels, nerves + satellite cells

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12
Q

motor neurones

A
  • stimulate muscle fibre to contract
  • neurone axons branch so each muscle fibre = innervated
  • forms NMJ (myoneural junction)
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13
Q

sarcolemma

A

= cell membrane

surrounds sarcoplasm

  • has abundance of myoglobin
  • has openings called Transverse T tubules
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14
Q

what are T tubules?

A

narrow tubes that extend into sarcoplasm at right angles to surface

filled with extracellular fluid

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15
Q

what are myofibrils?

A

cylindrical structures in muscle fibre

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16
Q

a bundle of protein filaments is known as…

A

myofilaments

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17
Q

what are the 2 myofilaments?

A

actin (thin)

myosin (thick)

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18
Q

what is the sarcomere?

A

region between two z lines

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19
Q

what is the I band?

A

zone of thin filaments not superimposed by thick filaments

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20
Q

what is the A band?

A

entire length of single thick filament

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21
Q

what is the H zone?

A

zone of thick filaments not superimposed by thin filaments

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22
Q

what is the M line?

A

middle of sarcomere

23
Q

what is the sarcoplasmic reticulum?

A

smooth ER

forms chambers = terminal cisternae on either side of T tubule

24
Q

a single T tubule + 2 terminal cisternae form …

A

triad

25
Q

what is tropomyosin?

A

elongated protein that winds along groove of F actin double helix

26
Q

troponin is composed of 3 subunits, what are they?

A
  • Tn-I site ; binds to actin
  • Tn-T site ; binds to tropomyosin
  • Tn-C site ; binds to ca2+ ions
27
Q

the tropomyosin/troponin complex regulates the…

A

interaction between active sites on G actin + myosin

28
Q

describe the myosin heads?

A
  • form cross bridges with actin
  • attached to rod portion by hinge region that can bend + straighten during contraction
  • have ATPase activity —> breaks down ATP
29
Q

what are the components of the synapse (NMJ)?

A
  • synaptic knob (swollen at end of axon terminal)
    contains ACh
  • motor end plate (region of sarcolemma that abuts synaptic knob - highly folded)
  • synaptic cleft
30
Q

what is the function of the motor end plate?

A
  • inc surface area to allow more ACh receptors

- contains AChE that breaks down ACh and causes relaxation

31
Q

what is the synaptic cleft?

A

tiny gap between synaptic knob + sarcolemma of muscle fibre

32
Q

what are the 4 actions involved in muscle contraction + relaxation?

A
  • excitation
  • excitation-contraction coupling
  • contraction
  • relaxation
33
Q

describe the sliding filament theory?

A
  • calcium binds to troponin
  • troponin moves, moving tropomyosin, exposing actin active site
  • myosin head forms crossbridge + bends towards H zone
  • ATP allows release of cross bridge
34
Q

muscle contraction summary

A
  • nerve impulse reaches NMJ
  • ACh released from motor neurone
  • ACh binds with nicotinic receptors in muscle membrane to allow na+ ions to enter
  • na+ influx generates AP in sarcolemma
  • AP travels down t tubule
  • SR releases ca2+
  • ca2+ binds to troponin, to move troponin tropomyosin complex
  • binding site in actin exposed
  • myosin head attaches to binding sites = power stroke
  • atp detached myosin head + energises for another contraction
  • when AP cease, muscle stop contracting
35
Q

functions of ATP in skeletal muscle contraction

A
  • energises cross bridges
  • providing energy for force generation
  • dissociates cross bridges bound to actin
  • energises ca2+ pumps that actively transport ca2+ back into SR
  • lowers cytosolic ca2+ levels —> relaxation
  • runs na+-k+ pump in sarcolemma
  • maintains resting membrane potential of sarcolemma
36
Q

ATP is produced from 3 sources, what are they?

A
  • creatine phosphate
  • aerobic respiration
  • anaerobic respiration (glycolysis)
37
Q

what are the 2 types of skeletal muscle fibre?

A

fast twitch

slow twitch

38
Q

slow twitch/ high-oxidative fibres

A
  • contract slowly
  • moderate power output
  • consume atp at moderate rate
  • rich blood supply
  • more mitochondria
  • smaller in diameter (minimise diffusion distance)
  • large amount myoglobin
  • more fatigue resistant
39
Q

fast twitch/ low oxidative fibres

A
  • rapid movement
  • anaerobic resp (glycolysis)
  • less blood supply (pale colour)
  • fewer mitochondria
  • fatigue rapidly
  • lower limbs in sprinter, upper limbs of most people
  • contain myosin
40
Q

what is a motor unit?

A

motor neurone and all muscle fibres it supplies

41
Q

muscles that control fine movements have …

A

small motor units

42
Q

large weight bearing have…

A

large motor units

43
Q

back muscle motor unit ratio

A

1:100

44
Q

finger muscle motor unit ratio

A

1:10

45
Q

eye muscle motor unit ration

A

1:1

46
Q

what is the force of contraction affected by?

A
  • relative size of muscle
  • number of muscle fibres contracting
  • degree of muscle stretch
47
Q

relative size of muscle

A
  • larger muscles have larger + more muscle fibres
  • larger fibres generate more force
  • more muscle fibres generate more force
48
Q

number of muscle fibres contracting

A

greater no of motor units generate more force than smaller no of motor units

49
Q

degree of muscle stretch

A

muscles contract strongest when muscle fibres = 80-120% normal resting length

50
Q

smooth muscle features?

A
  • cells not striated
  • smaller fibres
  • more actin
  • no sarcomeres (not arranged symmetrically)
  • cavoeolae- indents in sarcolemma
  • dense bodies instead of Z disks
51
Q

what is the longitudinal layer?

A

muscle fibres run parallel to organs long axis

52
Q

what is the circular layer?

A

muscle fibres run around circumference of organ

53
Q

role of ca2+ ions?

A

ca2+ binds to calmodulin + activates it

activated calmodulin activates MLCK enzyme

activated kinase transfers P from ATP to myosin cross bridge

phosphorylated cross bridge interacts with actin —> shorten

smooth muscle relaxes when intracellular ca2+ drop

PHA112 (37 decks)

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