Muscles 3

Question 1

Where is energy for contractions found?

Answer 1

Hydrolysis of ATP energises cross bridges

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

Question 2

Define fatigue.

Answer 2

Comes from repeated muscle stimulation.

Question 3

What does fatigue prevent?

Answer 3

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

Question 4

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

Answer 4

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

Question 5

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

Answer 5

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

Question 6

What 2 things characterise skeletal muscle fibre types?

Answer 6

Fast of slow shortening

Oxidative or glycolytic ATP forming pathways

Question 7

Give 5 features of oxidative fibres.

Answer 7

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

Question 8

Give 4 features of glycolytic fibres.

Answer 8

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

Question 9

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

Answer 9

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

Question 10

Define muscle recruitment.

Answer 10

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

Question 11

What is the order of muscle recruitment?

Answer 11

Slow oxidative, fast oxidative, fast glycolytic.

Question 12

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

Answer 12

Autonomic, somatic

Question 13

How are myosin and actin arranged in smooth muscle?

Answer 13

Diagonally

Question 14

Describe the smooth muscle cross-bridge cycle activation.

Answer 14

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

Question 15

Where can cytosolic calcium be sourced?

Answer 15

Sarcoplasmic reticulum

Extracellularly

Question 16

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

Answer 16

One, calcium

Question 17

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

Answer 17

Graded

Question 18

What 4 factors affect contractile activity?

Answer 18

Dynamic balance of:
Pacemaker activity
Autonomic neurotransmitters
Hormones
Stretch