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Flashcards in Muscle 2 Deck (37):
1

What 2 processes does ATP power in muscle contraction?

- 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

2

What causes muscle fatigue?

repeated muscle stimulation

3

What does muscle fatigue prevent?

muscles using up too much ATP

4

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

- 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

5

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

-dehydration
- decrease in muscle glycogen
- decrease in blood glucose

6

What is meant by 'central command fatigue'?

cerebral cortex cannot excite motor neurones

7

How are skeletal muscle fibre types characterised?

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

8

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

high

9

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

low

10

Give 4 properties of oxidative muscle fibres.

- 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

11

Give 4 properties of glycolytic fibres.

- few glycolytic fibres
- greater glycolytic enzymes and glycogen
- lower blood supply
white fibres with larger diameters

12

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

- Slow oxidative- resist fatigue
-Fast oxidative - intermediate resistance to fatigue
- Fast glycolytic - fatigue quickly

13

What is muscle fibre 'recruitment'?

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

14

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

1. slow oxidative fibres
2. fast oxidative
3. fast glycolytic

15

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

1. frequency of APs to motor unit
2. recruitment of motor units

16

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

- denervation atrophy - destroy nerve/NMJ
- disuse atrophy - muscle not used

17

What causes muscle hypertrophy?

exercise

18

What determines the type of muscle fibres you have?

the type of exercise you do

19

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

oxidative

20

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

glycolytic

21

How is smooth muscle innervated?

By the autonomic nervous system

22

Give 3 general properties of smooth muscle appearance.

- spindle shaped
- mononucleate
- not striated

23

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

smooth muscle cells divide through life

24

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

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

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

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

How does smooth muscle relax?

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

27

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

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

28

Where are the sources of cytosolic calcium in smooth muscle?

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

29

How is calcium removed from the cytosol?

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

30

What does it mean that smooth muscle has 'tone'?

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

31

What are the 2 types of smooth muscle?

single or multiunit

32

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

small blood vessels, GIT and uterus

33

Give 3 properties of single unit smooth muscle.

- many cells linked by gap junctions
-signals travel between cells
- contract synchronously

34

Give 3 examples of where multiunit smooth muscle is found?

- airways
- large arteries
- hairs

35

Give 3 properties of multiunit smooth muscle.

- few or no gap junctions
- richly innervated by ANS
- don't respond to stretch

36

What types of smooth muscle are found in organs?

a mixture of single unit and multiunit

37

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

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