Muscle 2 Flashcards Preview

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Flashcards in Muscle 2 Deck (33)
1

What does excess fatigue cause?

Rigor, new cross bridges cannot form

2

What does muscle fatigue depend on?

Length of contraction, fibre type and fitness of the individual

3

What factors contribute to fatigue?

Rising extracellular potassium levels - failure of cell depolarisation
Lactic acid - acidifies proteins
Increasing concentration of ADP + Pi delaying myosin detachment from actin
Decrease in glucose and glycogen
Dehydration
Central command fatigue - cerebral cortex cannot excite motor neurones - there is no will

4

Describe the ATPase activity of myosin in fast muscle fibre

High activity

5

Describe the features of oxidative muscle fibres

More mitochondria since more oxidative phosphorylation
More vascularisation to deliver oxygen and nutrients
Fibres are red with small diameters

6

Describe glycolytic fibres

Few mitochondria
More glycolytic enzymes and glycogen
Lower blood supply
White fibres with larger diameters

7

Describe the three types of muscle fibres and their resistance to fatigue

Slow oxidative - High resistance to fatigue
Fast oxidative - Intermediate resistance to fatigue
Fast Glycolytic - Low resistance to fatigue

8

What is recruitment?

When the load increases, Increasing the number of motor units - a cluster of fibres activated by the same action potential

9

What can lead to muscle mass loss?

Denervation atrophy (damaging the nerve or nmj)
Disuse atrophy

10

What is the effect of aerobic respiration on muscle development?

Increases mitochondria, vascularisation, fibre diameter, facilitation of oxidative phosphorylation

11

What is the effect of anaerobic respiration (strength training)?

Increase in diameter increase in glycolysis

12

What is smooth muscle innervated by?

The ANS and not the NS

13

Does smooth muscle have striations?

NO

14

Where can you find smooth muscles?

GI Tract, Uterus, airways, ducts

15

Describe the nucleus of smooth muscle?

Mononucleate

16

How are filaments arranged in smooth muscle?

Diagonally across the cell

17

Describe the cross bridge cycle in smooth muscle

Increase in calcium ions
Calcium binds to calmodulin
Calmodulin binds to Myosin Light Chain Kinase
Kinase phosphorylates the cross bridges activating them - bind to actin and cause contraction, ATP used to release the myosin from the actin

There is no blocking tropomyosin in smooth muscle

18

What causes the relaxation of the smooth muscle?

Myosin light chain phosphatase

19

What's the result of dephosphorylating the cross head when the myosin is still bound to the myosin?

Inhibits the cross bridge cycle, decreases the rate of ATP splitting, maintenance of tension with low ATP consumption, useful in blood vessel walls that need to stay open for long periods of time.

20

What are the sources of cytosolic calcium?

Sarcoplasmic reticulum, (less in smooth muscle, no t- tubules)
Extracellular Ca+ - Voltage activated calcium channels

21

What pumps calcium out the cell and into the SR?

Calcium ATPases - slower than in skeletal muscle

22

What factors affect contractile activity of smooth muscle?

Pacemaker activity
Autonomic neurotransmitters
Hormones
Local factors (paracrine agents, pH, osmolarity, Ions)
Stretch

23

How many action potentials is needed in skeletal muscle to saturate all troponin sites?

1

24

In smooth muscle what does the GRADE of contraction depend on?

The number of action potentials received, there is a constant level of contraction in smooth muscles

25

Where can you find single unit smooth muscle types?

GIT, uterus, Small blood vessels

26

How are cells in single unit muscle types linked?

Gap junctions

27

What evokes contraction in single unit smooth muscle

Stretch

28

How do cells coordinate their actions with one another in single unit muscle type?

Gap junctions allow signals to travel between cells
They contract synchronously
Contain pacemaker cells

29

Where do you find multiunit smooth muscle?

Arteries, airways hair

30

Does multiunit smooth muscle contain gap junctions?

Yes but only very few

31

Describe innervation by the ANS in multiunit smooth muscle

Rich

32

Does multiunit smooth muscle respond to stretch?

no

33

Why are muscles in organs a mixture of single an multiunit muscle?

An organ can have a mixture of properties in different areas