Muscles 3 Flashcards Preview

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Flashcards in Muscles 3 Deck (18)
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1
Q

Where is energy for contractions found?

A

Hydrolysis of ATP energises cross bridges

ATP also powers calcium ATPase to pump calcium ions out of the sarcoplasmic reticulum for relaxation.

2
Q

Define fatigue.

A

Comes from repeated muscle stimulation.

3
Q

What does fatigue prevent?

A

Muscles using up vast amounts of ATP which can cause rigour.

4
Q

What 3 factors cause fatigue in high intensity, short duration exercise?

A

Conduction failure due to an increase of potassium
Increase in lactic acid acidifies proteins
Increase in ADP and Pi inhibits cross bridge cycle, delaying myosin detachment from actin

5
Q

What 4 factors cause fatigue in long-term, low intensity exercise?

A

Decrease in muscle glycogen
Decrease in blood glucose
Dehydration
Central command fatigue

6
Q

What 2 things characterise skeletal muscle fibre types?

A

Fast of slow shortening

Oxidative or glycolytic ATP forming pathways

7
Q

Give 5 features of oxidative fibres.

A
Many mitochondrial
Oxidative phosphorylation
Vascularization for more oxygen
Myoglobin increase
Fibres red and small diameter
8
Q

Give 4 features of glycolytic fibres.

A

Few mitochondria
Lots of glycolytic enzymes and glycogen
Lower blood supply
White fibres with large diameters

9
Q

What are the 3 types of muscle fibres and their association with fatigue?

A

Slow oxidative - resists fatigue
Fast oxidative - intermediate resistance
Fast glycolytic - fatigues quickly

10
Q

Define muscle recruitment.

A

An increase in load meaning more motor units need to be activated.

11
Q

What is the order of muscle recruitment?

A

Slow oxidative, fast oxidative, fast glycolytic.

12
Q

Smooth muscle is innervated by ______ nervous system but not ______ nervous system.

A

Autonomic, somatic

13
Q

How are myosin and actin arranged in smooth muscle?

A

Diagonally

14
Q

Describe the smooth muscle cross-bridge cycle activation.

A
Increase in calcium concentration
Calcium binds to calmodulin
This binds to myosin light chain kinase
Kinase phosphorylates myosin
Phosphorylated cross bridge binds to actin
Contraction and tension
15
Q

Where can cytosolic calcium be sourced?

A

Sarcoplasmic reticulum

Extracellularly

16
Q

In skeletal muscle ______ action potential releases enough ______ to saturate all troponin sites.

A

One, calcium

17
Q

In smooth muscle, only some sites are activated. This can be ______ depending on the number of action potentials reaching the cell.

A

Graded

18
Q

What 4 factors affect contractile activity?

A
Dynamic balance of:
Pacemaker activity
Autonomic neurotransmitters
Hormones
Stretch