the muscular system

Question 1

what are the 3 types of muscle?

Answer 1

1. smooth
2. cardiac
3. skeletal

Question 2

describe smooth muscle?

Answer 2

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

Question 3

describe caridac muscle?

Answer 3

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

Question 4

describe an intercalated disc?

Answer 4

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

Question 5

describe the organisation of skeletal muscle?

Answer 5

elongated muscle cells - myocytes

multi nucleated

striated - banded pattern

Question 6

what are the 4 characteristics of skeletal muscle?

Answer 6

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

Question 7

main functions of skeletal muscle?

Answer 7

movement
posture
stabilisation
generation of heat - byproduct and shivering

Question 8

what is indirect movement of skeletal muscle?

Answer 8

tendons

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

Question 9

what is direct movement of skeletal muscle?

Answer 9

periosteum - epimysium

perichondrium - epimysium (fibrous connective tissue)

Question 10

anatomy of skeletal muscle?

Answer 10

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

Question 11

describe the thick filament in myofibril?

Answer 11

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

Question 12

what does titin do?

Answer 12

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

Question 13

what does nebulin do?

Answer 13

anchoring actin to Z disc (Z line)

Question 14

what does dystrophin do?

Answer 14

anchoring protein

attaches actin to membrane via protein complex

Question 15

what happens in muscle dystrophy?

Answer 15

weaking and breakdown of skeletal muscle

Question 16

what is a sarcomere?

Answer 16

1 z line to another z line

Question 17

describe the thin filament in myofibril tissue?

Answer 17

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

Question 18

what is in the A band?

Answer 18

one end of myosin to the other

Question 19

what happens i the z line during muscle contraction?

Answer 19

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

Question 20

what are the 2 main components of teh motor unit?

Answer 20

1. alpha motor neuron

2. muscle fibres innervated by the AMN

Question 21

what is henneman’s size principle?

Answer 21

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

Question 22

describe type 1 fibre in motor unit?

Answer 22

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

Question 23

describe type 2 fibre in motor unit?

Answer 23

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

Question 24

describe transverse tubules?

Answer 24

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

Question 25

what is calsequestrin?

Answer 25

moderate capacity and high capacity for Ca | glycoprotein

Question 26

describe excitation contraction coupling?

Answer 26

Ca binds to troponin shifts tropomyosin off myosin binding sites enables myosin to bind to actin

Question 27

describe the sliding filament mechanism? | 7 steps

Answer 27

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

Question 28

sliding filament mechanism in terms of sarcomere?

Answer 28

actin slides over no change in myofilament length ulls z lines together a band no change i band decreases h zone disappears

Question 29

describe calmodulin?

Answer 29

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

Question 30

describe skeletal muscle relaxation?

Answer 30

sarco(endo)plasmic ca-ATPase - membrane proteins sodium/calcium exchanger

Question 31

describe calcium kinetics influencers?

Answer 31

K and Na increased Mg Pi Ca

Question 32

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

Answer 32

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