Lecture 12: Muscle 6

Question 1

Fatigue

Answer 1

the decreased capacity of a muscle to do work and its reduced efficiently of performance that normally follows a period of activity

Question 2

Three main types of fatigue

Answer 2

• Muscle
• Neuromuscular
• Central

Question 3

Muscle fatigue

Answer 3

Occurs when exercising muscle can no longer respond to stimulation with the same degree of contractile activity

Question 4

Two possible causes of muscle fatigue

Answer 4

• Accumulation of lactic acid

- Depletion of energy stores

Question 5

Accumulation of lactic acid may inhibit

Answer 5

key enzymes in the energy-producing pathways or excitation-contraction process

Question 6

Depletion of energy stores

Answer 6

ATP is not present in sufficient amounts

Question 7

Muscle fatiguw time of onset varies with

Answer 7

• Type of muscle fiber

- Intensity of muscle activity

Question 8

Where does neuromuscular fatigue occur

Answer 8

neuromuscular junction

Question 9

Neuromuscular fatigue

Answer 9

• Also called synaptic fatigue
• Active motor neurons are not able to synthesize Ach rapidly enough to sustain chemical transmission of action potentials from motor neurons to muscle

Question 10

What type of fatigue is rare under normal conditions?

Answer 10

neuromuscular fatigue

Question 11

Central fatigue

Answer 11

-Occurs when CNS no longer adequately activates the motor neurons supplying the working muscle
Also known as psychological fatigue

Question 12

What three things happen during intense muscular activity

Answer 12

• Blood vessels in muscles dilate
• Blood flow increase
• Oxygen delivery increase

Question 13

When muscular exertion is very great, oxygen cant be supplied to muscles fast enough which means

Answer 13

cellular respiration cant produce enough atp. It starts to get derived from non-oxidative sources such as anaerobic glycolysis

Question 14

Oxygen debt

Answer 14

Recovery period where after intense muscular activity has stopped, the rate of breathing accelerates and continues for a period of time and O2 consumption is above resting level
Extra O2 is used to restore metabolic conditions to the resting level

Question 15

The extra O2 in oxygen debt is used to (3)

Answer 15

• Convert lactic acid to pyruvic acid then to glucose in the liver. Glucose is used to help restore glycogen levels in muscle fibers and liver. Pyruvic acid is used for ATP production
• Resynthesize creatine phosphate
• Replace the O2 removed from myoglobin

Question 16

Three steps in contraction-relaxation process the require ATP

Answer 16

1. Splitting of ATP by myosin ATPase provides the energy for the power stroke of the cross-bridge
2. Binding (but not splitting) of a fresh molecules of ATP t myosin permits detachment of bridge from the actin filament at the end of a power stroke so that the cycle can be repeated. This ATP is subsequently split to provide energy for the next stroke of the cross bridge
3. Active transport of Ca back into the SR

Question 17

Three sources of ATP

Answer 17

• Creatine phosphate
• Oxidative phosphorylation
• Glycolysis

Question 18

Creatine phosphate

Answer 18

• First energy storehouse tapped at the onset of contractile activity
• Supports short bursts of high-intensity contractile effort such as sprints

Question 19

Where does oxidative phosphorylation take place

Answer 19

in mitochondria, if sufficient O2 is present

Question 20

ATP yield of oxidative phosphorylation

Answer 20

36 per glucose molecule

Question 21

O2 required by oxidative phosphorylation is delivered by

Answer 21

the blood

Question 22

Increased O2 is made available by (4)

Answer 22

• Deeper, more rapid breathing
• Heart contracts more rapidly and forcefully
• Dilated of blood vessels supplying active muscle
• In some muscle fibers (red), there is an abundance of myoglobin which stores O2 and increases the rate of O2 transfer from blood into muscle fibers

Question 23

Glycolysis ATP yield

Answer 23

2 per glucose

Question 24

Does glycolysis require O2?

Answer 24

no

Question 25

Glycolysis is associated with

Answer 25

Lactic acid production - fall in muscle pH - muscle fatigue

Question 26

Skeletal muscle varies in color depending on

Answer 26

the content of myoglobin (red)

Question 27

Skeletal muscle fibers with high myoglobin vs low

Answer 27

red muscle fibers vs white mf

Question 28

Red muscle fibers have more

Answer 28

mitochondria and blood capillaries

Question 29

Skeletal muscle fibers contract and relax with different

Answer 29

velocites

Question 30

Whether a fiber is slow twitch or fast depends on

Answer 30

how rapidly it splits ATP