Muscular Movement Flashcards Preview

PHYS5530M Physics of Biological Systems > Muscular Movement > Flashcards

Flashcards in Muscular Movement Deck (21)
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1
Q

Muscle Structure

Organ Level

A

-major skeletal muscles of the body

2
Q

Muscle Structure

Tissue Level

A

-neuromuscular junctions and fascicles

3
Q

Muscle Structure

Cellular Level

A

-myoblasts and myofibers

4
Q

Muscle Structure

Microscopic Level

A

-sarcomere and myofibrils

5
Q

Muscle Structure

Molecular Level

A

-actin and myosin

6
Q

From Single Cells to Fibers

A
  • each skeletal fibre is a single skeletal muscle cell / skeletal myocyte formed from the fusion of precursor cells:
    1) cell multiplication, dividing myocytes
    2) multiplication ceases and cells align
    3) aligned cells fuse, appearance of muscle specific proteins
    4) spontaneous contractiuons begin in the muscle fiber
7
Q

How do muscles grow?

A
  • mature cells can chage in size but new cells aren’t formed when muscles grow
  • more myofibril strands made of myosin and actin contractile proteins are created
8
Q

Muscle Cell Properties

A
  • lots of mitochondria for ATP / energy

- myofibrils composed of thick and thin filaments of myosin and actin

9
Q

Muscle Contraction

Actin and Myosin

A
  • actin filaments form the thin filaments
  • bundles of over 200 myosin II proteins form the thick filaments
  • upon activation, myosin II heads pull opposing actin filaments towards each other
10
Q

Muscle Contraction

Myosin Activation

A
  • in relaxed state, tropomyosin blocks the myosin binding sites on the actin preventing cross bridges from forming and keeping the muscle in the relaxed state
  • Ca2+ binding to troponin alters the shape of the tropomyosin which uncovers the myosin binding sites and allowing muscular contraction to occur
11
Q

Nerve Impulse to Muscular Movement

A
  • motor neurons carry signal from the brain along axons from the spinal cord to muscles
  • dendrites collect the sigl/nal
  • the axon passes it along to the muscular fiber
12
Q

Motor Neuron Junction

Steps

A

1) nerve impulse arrives at axon terminal
2) Ca2+ ions released into axon terminal
3) Ca2+ causes synaptic vesicles to release acetylcholine (ACh) via exocytosis
4) ACh binds to ion channels in the muscular fiber membrane allowing flow of Na+ ions into the muscles cell which reverses the membrane potential

13
Q

Diffusion and Distance Equation

A

= 2mDt

-where D is the diffusion constant, t is the diffusion time and m is the number of dimensions

14
Q

Pressure and Concentration Equation

A

Δp = Δc kb T

15
Q

Pressure and Tension

A

Δp = 2λ/R

-where λ is the tension and R is the radius of the cell

16
Q

Signalling into the Muscle Cell

A
  • ACh binding to receptors in the muscle cell membrane allows the flow of Na+ in which reverses the membrane potential
  • this propagates down the T (transverse) - tubules which are deep indents in the membrane into the cell through a chain reaction of voltage gated sodium channels
17
Q

Calcium Cycle

A
  • muscle cells usually maintain a low internal calcium concentration
  • a small increase in this concentration leads to contraction
  • to maintain the low concentration, calcium is actively pumped out of muscle cells or into organelles for storage
18
Q

Oubain

A
  • in cardiac muscle cells, an antiporter which couples extusion of Ca2+ to entry of Na+ into the cell is used
  • the drug is used to treat heart failure by inhibiting activity of Na-K pumps
  • this raises the intracellular concentration of sodium which reduces the activity of the Na-Ca exchanger
  • the intracellular calcium concentration is therefore maintained at a higher than usual level leading to higher cardio contractility
19
Q

What are most procces carried out by?

A

-molecular motors

20
Q

What dominate behaviour at a cellular level?

A
  • stochastic interactions

- probabilistic transitions

21
Q

What do cells use when they can’t rely on probabilistic events?

A

-the large free energy change of the ATP - > ADP reaction can be used to drive the system form equilibrium