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Anatomy > 15 - MSK Muscle of A&P > Flashcards

15 - MSK Muscle of A&P Flashcards

1
Q

What are the three types of muscle

A

smooth
cardiac
skeletal

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2
Q

How do the types of muscle differ in

A

function
body location
morphology (shape)
method of activation

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3
Q

Where is smooth muscle found

A

lines hollow organs

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4
Q

Size of smooth muscle

A

small

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5
Q

What is the morphology of smooth muscle

A

no striation (no striping pattern)
one nucleus
spidle shaped
Contracts into a ball

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6
Q

Does smooth muscle have gap junctions

A

yes

all connected to each other (wave of contractions)

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7
Q

how is smooth muscle regulated

A

involuntary
ANS
pacemaker cells (set diff rates of contractions)
respond to stretching (contract to resist stretching)
hormones

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8
Q

Where is cardiac msucles found

A

heart

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9
Q

Size of cardiac muscle

A

large

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10
Q

What is the morphology of cardiac muscle

A

striated (striped) – makes heart more efficient pump
1-2 nuclei
branched

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11
Q

Does cardiac muscle have gap junctions

A

yes
intercalated disks

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12
Q

how is cardiac muscle regulated

A

involuntary
ANS
pacemaker cells
hormones

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13
Q

Where is skeletal muscle found

A

MSK system

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14
Q

Size of skeletal muscle

A

very large
slightly bigger than a strand of hair

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15
Q

What is the morphology of skeletal muscle

A

striated (striped)
multinucleated (5-5000 nuclei) –> because very large, needs many nuclei to make enough nutrients that cell needs
long and tubular

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16
Q

Does skeletal muscle have gap junctions

A

no
has fine tune control (can control specific muscle)

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17
Q

how is skeletal muscle regulated

A

voluntary
somatic NS

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18
Q

What us skeletal muscle made of

A

muscle fibers (myocytes/muscle cells)
peripheral nerves
vasculature (blood vessels)

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19
Q

Where do peripheral nerve axons originate from

A

lower motor neuron cell bodies in the ventral grey horn of the spinal cord –> goes through ventral or dorsal ramus

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20
Q

What does contraction of skeletal muscle do

A

accounts for all voluntary body movement

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21
Q

What are the three layers that skeletal muscle is wrapped in

A

1) endomysium
- surrounds individual muscle fibers
2) perimysium
- surrounds bundle of muscle fibres
3) epimysium
- surrounds the entire muscle

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22
Q

What is a tendon made of

A

all the layers of skeletal muscle tapering off to form tendon

continuous with the periosteum of bone

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23
Q

What are muscle composed made of

A

muscle fibers

24
Q

What are muscle fibres

A

filled with thousands of myofirbils

25
Q

What are myofibrils

A

millions of sacromeres in series

26
Q

What are sacromeres
What are they composed of

A

basic contractile unit (from Z to Z)
smallest unit in muscles

2 filaments:
- thick filament (myosin)
- thin filament (actin)

27
Q

What do the dark and light bands on sacromere structure do

A

gives rise to striations

28
Q

What do the bands mean on sacromere structure

A

light I band = actin only
dark A band = myosin and actin
dark H zone = myosin only

29
Q

What happens with muscle shortening

A

actin filaments pulled across myossin filaments to make distance between adjacent z discs to get smaller

thick filaments slide over thick filaments = contraction
both H zone and I band decrease in size during contraction

30
Q

What is titan

A

largest protein in the body
acts as a string to keep myosin in the centre

31
Q

What is the effect of exercise on muscle size

A

muscles enlarge with use (hypertrophy)
- exercise stimulates protein synthesis
(actin and myosin)
- Results in more sarcomeres and more myofibrils

32
Q

Do the number of muscle cells increase

A

no!

33
Q

What are the factors effecting muscle size

A

muscle is highly expensive tissue because highly metabolically active (gobbles a lot of ATP)

if you dont use muscle, muscle will stop using protein and break down over time –> atrophy (no nutrition)
- immobilization, weightlessness, denervation (interfering signals)

building up muscle by muscle use –> hypertrophy

34
Q

How does muscle contraction occur

A

sliding filament theory
- filaments slide past one another –> shortening

thin actin filaments slide over the myosin –> protein does not get smaller, but overlap between protein increases, making smaller

35
Q

What shortens during muscle contraction

A

sacromere (z-z line shorter), H zone, I band

36
Q

What stays the same during muscle contraction

A

A band

37
Q

What is myosin

A

contractile globular protein (two heads)
thick

38
Q

What is myosin composed of

A

composed of myosin molecules attached end to end to form a large myosin filament (tube-like structure)

globular heads contain actin binding sites and atp binding sites
- ATP provides energy to change the conformation (shape) of myosin heads

39
Q

What is actin

A

glubules that form two coiled chains - the thin filmanet

40
Q

What is actin made of

A

tropomyosin runs along actin - blocking myosin binding sites
troponin: holds tropomyosin in place regulated by Ca2+

41
Q

How does actin contract

A

Add Ca2+ into cytoplasm –> Ca2+ binds troponin –> changes its confirmation –> pulls tropomyosin away from the mysoin-binding sites –> allows actin-myosin interaction to occur

When Ca2+ is removed, tropomyosin moves back to block myosin-binding sites (no actin-myosin interaction)

42
Q

What is the contraction cycle

A

occurs as long as there is ATP (always present) and go signal (Ca2+)

cross bridge cycling: myosin bound to actin

  1. myosin heads hydrolyze (break down and store) ATP and become energized and oriented
  2. myosin head binds to actin to form a cross bridge
  3. myosin head pivots, pulling the thin filament past the thick filament toward centre of sacromere (power stroke)
  4. as myosin head binds ATP, the cross-bridge detaches from actin
43
Q

What is rigor mortis

A

absence of ATP preventing myosin from disengaging with actin

slight state of contraction
very stiff becasue of all the cross bridges formed

44
Q

What is excitaion-contraction coupling

A

process by which an electrical stimulus (excitation) triggers the release of calcium by the sarcoplasmic reticulum, initiating the mechanism of muscle sarcomere shortening (contraction(

45
Q

What happens during excitation

A

AP in neuron coming down to axon terminal causes release of neurotransmitter (acetylcholine)

binds to acetylcholine receptors (nicotinic receptors on skeletal muscles) –> ACh-receptors at the motor end plate are stimulated

AP generated in muscle fiber and propagates along sarcolemma

46
Q

How does AP in muscle contraction travel

A

AP travels as wave along the membrane and then must dive deep into the cell

AP propagated down T-tubules (transverse) = membrane invagination (allows go all the way down)
- T-tubules also have voltage gated ion channels (only way it would propagate): bring AP down

neurotransmission –> muscle action potential –> T-tubules –> SR (terminal cisternae) –> release of Ca2+ –> contraction

47
Q

What is the sarcoplasmic reticulum

A

organelle
smooth endoplasmic reticulum specialized in skeletal muscle to be a place where you store calcium internally within that cell

right beside t-tubule

48
Q

What is a triad

A

t-tubule and two sarcoplasmic reticulums surrounding it

49
Q

How does AP cause calcium release

A

t-tubule bring AP down –> DHP receptor: changes shape & attached to ryanodine receptor –> pulls on plug –> calcium flows from sarcoplasmic reticulum to cytoplasm –> contraction

50
Q

How to stop contraction

A

reuptake of Ca2+ in the SR
requires energy (pump using ATP) because concentration of Ca2+ very high in cytosol

SR Ca2+ pump

Takes a long time

51
Q

Describe the electrical nad mechanical events that occur in a skeletal muscle cell

A

muscle fibre action potential occurs in about 3ms
latent period of about 10ms before muscle fibre shortening (lag phase)
- time it takes for calcium to flow across, bind….

1 AP generates certain amount of force and then disappears because brief release from AP and then circum pump put all calcium back into SR - no calcium, no contraction

Twitch contraction: 1 AP = 1 muscle contraction

52
Q

What are the factors affecting force production

A
  1. muscle length
    - degree of overlap before actin and myosin before telling the muscle to contract in the first place (~ half)
    - if muscle is too contracted or too relaxed, can’t generate as much force if it there were some overlap between myosin and actin
  2. Action potential frequency
    - while muscle AP’s cannot be summed, calcium release events can
    - the greater the frequency of stimulation, the greater the summation of intracellular calcium
    Tetanic force:
  3. number of fibres per motor unit and the cross-sectional area of those muscle fibres
    - motor unit: single motor neuron –> all of the muscle fibres it innervates
    - different types of muscle fibres in a muscle group
53
Q

What is the size principle in motor unit recruitment

A

motor units are activated according to size; smallest to biggest

slow oxidative –> fast oxidative –> fast glycolytic

number of motor units recruited depends on force required for the task at hand

54
Q

What is slow oxidative (muscle fibre type)

A

slow oxidative: always recruited first in contraction cause can make ATP using oxygen (fatigue resistance) –> posture and enduarance

55
Q

What is fast oxidative-glycolytic (muscle fibre type)

A

fast oxidative-glycolytic: can make ATP using oxygen but can also break down glucose to make ATP in the absense of oxygen (less efficient) –> walking and sprinting

56
Q

What is fast glycolytic (muscle fibre type)

A

fast glycolytic: biggest, only glycolytic processes (dont make ATP), short bursts of activity –> power movements), dont last very long

Anatomy (18 decks)

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