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Human Physiology > the muscular system > Flashcards

the muscular system Flashcards

1
Q

what are the 3 types of muscle?

A
  1. smooth
  2. cardiac
  3. skeletal
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2
Q

describe smooth muscle?

A

1) fusiform shaped (tapering at both ends)
2) involuntary contraction (slow wave motions)
3) not striated and has only one centrally located nucleus

functions:
digestion, breathing and circulation

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3
Q

describe caridac muscle?

A
  1. cardiomyocytes (main component)
  2. narrow and shorter than skeletal
  3. one nucleus and many mitochondria
  4. intercalated discs support synchronised contraction of cardiac tissue
  5. outside called sarcolemme
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4
Q

describe an intercalated disc?

A

z lines of sarcomere (longitudinal section of the tissue and how to separate it when describing):

desmosome - structural support

fascia adherens - mechanical support

gap junction - electrical synpases

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5
Q

describe the organisation of skeletal muscle?

A

elongated muscle cells - myocytes

multi nucleated

striated - banded pattern

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6
Q

what are the 4 characteristics of skeletal muscle?

A
  1. excitability - capacity to respond to stimulus
  2. contractility - ability to shorten in order to produce force
  3. extensibility - stretched to limited degree beyond normal length
  4. elasticity - recoil to orginial resting length folowing stretch
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7
Q

main functions of skeletal muscle?

A

movement
posture
stabilisation
generation of heat - byproduct and shivering

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8
Q

what is indirect movement of skeletal muscle?

A

tendons

immobile bone (origin)
moveable bone (insertion)
movement insertion to origin
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9
Q

what is direct movement of skeletal muscle?

A

periosteum - epimysium

perichondrium - epimysium (fibrous connective tissue)

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10
Q

anatomy of skeletal muscle?

A
  1. epimysium and perimysium - dense fibrous connective tissue
  2. endomysium - areolar connective tissue
  3. fascicle - bundle of fibres
  4. sarcolemma - plasma membrane
  5. connective tissue - elasticity
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11
Q

describe the thick filament in myofibril?

A

proteins

thick filament - myosin (tails points toward center of sarcomere) attached to M line and not contained in I band and interacts with actin in A band

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12
Q

what does titin do?

A
  1. keep thick and thin filmaments aligned (goes from one z line to another in myosin)
  2. resist muscle from overstretching
  3. recoil muscle to resting length after stretching
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13
Q

what does nebulin do?

A

anchoring actin to Z disc (Z line)

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14
Q

what does dystrophin do?

A

anchoring protein

attaches actin to membrane via protein complex

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15
Q

what happens in muscle dystrophy?

A

weaking and breakdown of skeletal muscle

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16
Q

what is a sarcomere?

A

1 z line to another z line

17
Q

describe the thin filament in myofibril tissue?

A

thin filament -
actin (series is F actin and attached to Z line),

troponin (complex consists of Tn-T, tropomyoin and calcium)

tropomyosin (keeps active site of G-actin closed)
- help at different parts of contraction phase of muscle

18
Q

what is in the A band?

A

one end of myosin to the other

19
Q

what happens i the z line during muscle contraction?

A

H zone disappears
A band remains unchanged (myosin and actin interacting)
I band narrows (only actin)

20
Q

what are the 2 main components of teh motor unit?

A
  1. alpha motor neuron

2. muscle fibres innervated by the AMN

21
Q

what is henneman’s size principle?

A

motor unit fibres are activated in a preset sequence (1 to IIa to IIx) depending on the motor neuron size from smallest to largest

recruitment based on the force requirement (e.g more for 60% 1RM than 20%) not velocitiy of movement

slow units are always recruited regardless of velocity

22
Q

describe type 1 fibre in motor unit?

A

slow contraction speed

adapted for aerobic respiration e.g
high capillary density and myoglobin content
lage aerobic metabolism capacity and blood supply
high mitochondrial density

23
Q

describe type 2 fibre in motor unit?

A

fast contraction speed

adapted for anaerobic metabolism:
less blood supply, mitochondria and myoglobin
high content of glcyogen and glycotic enzymes

type 2a = fast oxidative fibres

type 2x = fast glycotic fibres

24
Q

describe transverse tubules?

A 
dihydropyridine receptor ('door man'):
voltage gated calcium channel and L type calcium channel to let it bind with actin

ryanodine receptor: release of Ca from sarcoplasmic reticulum

mechanical coupled

25
Q

what is calsequestrin?

A

moderate capacity and high capacity for Ca

glycoprotein

26
Q

describe excitation contraction coupling?

A

Ca binds to troponin

shifts tropomyosin off myosin binding sites

enables myosin to bind to actin

27
Q

describe the sliding filament mechanism?

7 steps

A
  1. at rest, ATP molecule binds to myosin head and ATPase enzyme on myosin hydrolyses ATP to ADP
  2. reaction releases energy that points myosin head away (cocks) from M line into an extended, high energy position
  3. cocked myosin binds to active site on actin molecule called the cross bridge and Pi released, making bond stronger
  4. myosin releases ADP, bending myosin head and tugging actin along with it towards centre of sarcomere (power stroke)
  5. new ATP molecule binds to myosin head to release myosin from actin
  6. ATP hydrolysis by atpase cocks (points head from away M line) the myosin head again
  7. steps 3-5 repeated at a new active site further down the actin filament to shorten the sarcomere
28
Q

sliding filament mechanism in terms of sarcomere?

A

actin slides over
no change in myofilament length
ulls z lines together

a band no change
i band decreases
h zone disappears

29
Q

describe calmodulin?

A

calcium modulated protein

calcium binds to it which activates MLCK
this phosphorylates light chains in myosin heads and increases myosin ATPase activity

active myosin cross bridges slide along actin and create muscle tension

30
Q

describe skeletal muscle relaxation?

A

sarco(endo)plasmic ca-ATPase - membrane proteins

sodium/calcium exchanger

31
Q

describe calcium kinetics influencers?

A

K and Na

increased Mg

Pi

Ca

32
Q

what are the 7 steps of the sliding filament mechanism in simple terms?

A
  1. ATP binds to myosin head which hydrolyses to ADP
  2. energy so myosin cocks head
  3. binds with actin (cross bridge) and releases Pi
  4. releases ADP and pulls actin away
  5. new ATP attaches so actin released
  6. head cocks again
  7. steps 3-5 repeated

Human Physiology (9 decks)

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