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Science for Medicine KR > Muscle 2 > Flashcards

Muscle 2 Flashcards

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1
Q

What 2 processes does ATP power in muscle contraction?

A
  • unbinding of myosin to actin so that a new cycle may begin
  • Ca2+-ATPase in the sarcoplasmic reticulum. calcium gets pumped back into the sarcoplasmic reticulum and contraction ends
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2
Q

What causes muscle fatigue?

A

repeated muscle stimulation

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3
Q

What does muscle fatigue prevent?

A

muscles using up too much ATP

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4
Q

What 3 factors during high intensity, SHORT duration exercise can lead to muscle fatigue?

A
  • conduction failure due to increase in concentration of potassium ions
  • increase in lactic acid concentration which can acidify the proteins
  • increase in the concentrations of ADP and Pi inhibit X bridge cycle
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5
Q

What 3 factors during low intensity, LONGTERM exercise can lead to muscle fatigue?

A
  • dehydration
  • decrease in muscle glycogen
  • decrease in blood glucose
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6
Q

What is meant by ‘central command fatigue’?

A

cerebral cortex cannot excite motor neurones

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7
Q

How are skeletal muscle fibre types characterised?

A

based on whether the fibres are slow or fast shortening which is dependent on whether the oxidative or glycolytic ATP forming pathways are used

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8
Q

Comment on the ATPase activity of myosin in fast muscle fibres.

A

high

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9
Q

Comment on the ATPase activity of myosin in slow muscle fibres.

A

low

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10
Q

Give 4 properties of oxidative muscle fibres.

A
  • lots of mitochondria for oxidative phosphorylation
  • greater vascularisation to deliver more 02 and nutrients
  • contain myoglobin to increase oxygen delivery
  • fibres are red and have low diameters
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11
Q

Give 4 properties of glycolytic fibres.

A
  • few glycolytic fibres
  • greater glycolytic enzymes and glycogen
  • lower blood supply
    white fibres with larger diameters
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12
Q

What are the 3 types of muscle fibres? Comment on their susceptibility to fatigue.

A
  • Slow oxidative- resist fatigue
  • Fast oxidative - intermediate resistance to fatigue
  • Fast glycolytic - fatigue quickly
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13
Q

What is muscle fibre ‘recruitment’?

A

if there is an increase in load then we require to activate more motor units
the increase in number of active motor units is known as recruitment

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14
Q

In what order are the different types (oxidative etc) of muscle fibre activated?

A
  1. slow oxidative fibres
  2. fast oxidative
  3. fast glycolytic
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15
Q

What 2 factors is neural control of muscle tension dependent on?

A
  1. frequency of APs to motor unit

2. recruitment of motor units

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16
Q

What 2 things can lead to a decrease in muscle mass?

A
  • denervation atrophy - destroy nerve/NMJ

- disuse atrophy - muscle not used

17
Q

What causes muscle hypertrophy?

A

exercise

18
Q

What determines the type of muscle fibres you have?

A

the type of exercise you do

19
Q

What type of muscle fibre would you expect to have a lot of if you do a lot of aerobic exercise?

A

oxidative

20
Q

What type of muscle fibres would you expect to have if you do a lot of anaerobic (strength) exercise?

A

glycolytic

21
Q

How is smooth muscle innervated?

A

By the autonomic nervous system

22
Q

Give 3 general properties of smooth muscle appearance.

A
  • spindle shaped
  • mononucleate
  • not striated
23
Q

How does smooth muscle differ from skeletal muscle in terms of repair?

A

smooth muscle cells divide through life

24
Q

How do the myofilaments in smooth muscle differ in arrangement compared to skeletal muscle?

A

still have thick myosin and thin actin filaments that use the cross bridge, sliding filament model of contraction
- but filaments are arranged diagonally and are anchored to membranes and cell structures by dense bodies

25
Q

Describe the 6 steps involved in the smooth muscle X-bridge cycle activation.

A
  1. increase in calcium concentration
  2. calcium binds calmodulin
  3. calcium- calmodulin binds to Myosin Light Chain Kinase
  4. kinase phosphorylates myosin X bridge with ATP
  5. phosphorylated X bridges bind to actin filaments
  6. contraction and tension
26
Q

How does smooth muscle relax?

A

by action of myosin light chain phosphatase which dephosphorylates X - bridges

27
Q

How can smooth muscle maintain tension for a long time with low ATP consumption?

A

by x bridges being dephosphorylated when still being bound to actin
decreases the rate of ATP splitting and slows cross bridge cycle

28
Q

Where are the sources of cytosolic calcium in smooth muscle?

A

sarcoplasmic reticulum - less SR than in skeletal muscle and NO T tubules
extracellular calcium

29
Q

How is calcium removed from the cytosol?

A

by pumping it back in to the SR and out of the cell by calcium ATPases

30
Q

What does it mean that smooth muscle has ‘tone’?

A

it has a basal level of calcium in cells to enable a constant level of tension

31
Q

What are the 2 types of smooth muscle?

A

single or multiunit

32
Q

Where are single unit type smooth muscle types found? 3 places

A

small blood vessels, GIT and uterus

33
Q

Give 3 properties of single unit smooth muscle.

A
  • many cells linked by gap junctions
  • signals travel between cells
  • contract synchronously
34
Q

Give 3 examples of where multiunit smooth muscle is found?

A
  • airways
  • large arteries
  • hairs
35
Q

Give 3 properties of multiunit smooth muscle.

A
  • few or no gap junctions
  • richly innervated by ANS
  • don’t respond to stretch
36
Q

What types of smooth muscle are found in organs?

A

a mixture of single unit and multiunit

37
Q

Why is it beneficial to an organ that it have a mixture of the two types of smooth muscle?

A

it means that an organ can have a mixture of properties in different areas

Science for Medicine KR (37 decks)

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