Muscles, contraction and movement Flashcards Preview

HUBS191 Human Movement and Sensation > Muscles, contraction and movement > Flashcards

Flashcards in Muscles, contraction and movement Deck (75)
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1

function of cardiac muscle

pumping of blood

2

function of smooth muscle

to control the movement of fluid e.g. blood, urine, digestion

3

function of skeletal muscle

to move, maintain posture, generate heat

4

structure of skeletal muscle

  1. Tendon attaches muscle to bone
  2. fascia
  3. muscle
  4. epimysium
  5. muscle bundle
  6. perimysium
  7. fascicle
  8. endomysium
  9. muscle cell aka muscle fibre aka myocyte
  10. sarcoplasmic reticulum and T tubule
  11. myofibrils
  12. sarcomere
  13. myofilaments

5

T-tubule

invagination of Extracellular space that allows the action potential to enter the myofibril and initiate the release of Ca2+

6

triad

T-tubule sandwiched between two SR

7

sarcolemma

plasma membrane of the muscle cell

8

sarcoplasmic reticulum

ER of a muscle cell and stores calcium

9

sarcomere

myofilament between to Z-disks= basal contractile unit

10

thin filament

actin, tropomyosin, troponin; Globular actin forms a double helix strand surround by two thin strands of tropomyosin

11

thick filament

myosin and myosin head

12

NMJ vs synapse

  • In healthy humans, there is no IPSP or EPSP
  • if an action potential reaches the NMJ it will cause contraction;
  • Should call the cleft the NMJ cleft rather than the synaptic clefts

13

3 steps of skeletal muscle contraction

excitation, contraction, relaxation

14

steps of excitation

  1. AP reaches end of motor neuron, which causes Ca2+ entry into nerve terminal
  2. Neuronal action potential Acetylcholine (Ach) released from the nerve terminal in synaptic vesicles
  3. Synaptic vesicles release Ach, which diffuses into the synaptic cleft
  4. Ach stimulates Ach-receptors on the adjacent muscle fibre, initiating an impulse in the muscle fibre
  5. Depolarisation of muscle sarcolemma, initiating an action potential
  6. Electro-chemical-electro coupling
  7. Action potential on the muscle fibre- always sufficient to reach threshold in healthy individuals

15

steps of contraction

  1. AP travels over sarcolemma and T-tubules very quickly, which triggers the release of Ca2+ ions from the adjacent sarcoplasmic reticulum almost simultaneously along the myofibril
  2. Large Ca2+ release from the internal Ca2+ store- ions diffuse to the myofilaments to trigger cross-bridge formation
  3. Cross-bridge formation of myofilaments
  4. Myosin head is in its energised state, with ATP bound
  5. Ca2+- troponin interaction exposes active site
  6. Actin-myosin interact as a cross-bridge
  7. Energised myosin head pulls the actin in a power-stroke

16

steps of relaxation

  1. No new AP- sarcolemma repolarises
  2. Ca2+ no longer bind to Troponin; ion re-uptake into internal Ca2+ store
  3. Troponin active sites are hidden
  4. Actin and myosin are still bound but not enough Ca2+ ions to initiate new cross-bridges
  5. ATP must bind for actin and myosin to uncouple cross-bridge

17

sliding filament model

  • When inactive the filaments are not over one another
  • When activated the myofibril shortens as the z-lines move closer
  • Myofilaments do not change length themselves

18

motor unit

one somatic Motor Neuron and Muscle Fibres innervated by its branches

19

energy sources for contraction

Anaerobic and anaerobic

20

features of anaerobic respiration

- short term - fast energy production - no O2 required - ATP, creatine phosphate, glycolysis

21

features of aerobic respiration

- long term - steady - slower energy production - O2 required - Oxidative phosphorylation

22

why is energy required for relaxation?

Ca2+ re-uptake into SR and uncoupling of crossbridges

23

types of muscle fibres

red, white and intermediate (myosin type IIa)

24

features of red muscle fibres and example

high myoglobin (myosin type I), high aerobic enzymes - soleus

25

features of white muscle fibres and example

low myoglobin (myosin type IIx), low aerobic enzymes - eye

26

function of red (myosin type I) fibres

slow rate interaction with actin; slow force production; slow energy consumption; sustained by aerobic metabolism

27

function of white (myosin type IIx) fibres

fast rate interaction with actin; fast force production; fast energy consumption; use anaerobic metabolism

28

what is a twitch

the smallest tension a muscle can produce - a single AP in a single motor unit

29

what is treppe

- repeated stimuli - sustained levels of SR Ca2+ = more contraction - actin and myosin become more sensitive to Ca2+ - more sensitive at higher temperatures

30

what is tetanus

- rapidly repeated stimuli - closely spaced twitches - heat increases sensitivity - mechanical summation due to high Ca2+ in SR