Exam 1: Lecture 7: Skeletal Muscle Physiology 2

Question 1

T/F: skeletal muscle only contain fast twitch muscle

Answer 1

False, it contains both fast and slow twitch muscle fibers

Question 2

What type of muscle fiber:

• Very fatigue resistant
• Usually recruited first during a muscle contraction

Answer 2

Slow twitch

Question 3

What type of muscle fiber:

• Small diameter
• Higher oxidative capacity
• Lower glycolytic capacity

Answer 3

Slow twitch

Question 4

What type of muscle fiber:

• reddish in color due to high amounts of myoglobin and vascular supply

Answer 4

Slow twitch

Question 5

What type of muscle fiber:

• Larger diameter
• HIgher glycolytic capacity
• Lower oxidative capacity

Answer 5

Fast twitch

Question 6

What type of muscle fiber:

• Easily fatigued
• Recruited last during a muscle contraction

Answer 6

Fast twitch

Question 7

What type of muscle fiber:

• These tend to more white in color or pale because they do not have as much myoglobin or vascularization

Answer 7

Fast twitch

Question 8

What type of muscle fiber:

• extensive SR for rapid Ca2+ release

Answer 8

Fast twitch

Question 9

Spatial summation or recruitment can increase the force of contraction by recruiting more muscle fibers. we increase muscle fibers by recruiting more ______ ______

Answer 9

motor neurons

Question 10

What type of muscle fiber:

• more easily excited

Answer 10

Slow twitch

Question 11

What type of muscle fiber:

• recruited when more force is needed

Answer 11

Fast twitch

Question 12

Temporal summation can increase force of contraction by repeated stimulation of muscle before it can relax resulting in tetanus, how?

Answer 12

Repeated stimulation causes prolonged elevation of intracellular Ca

• Ca is elevated because it is released from the SR faster than it can be reaccumulated

Question 13

Can temporal summation happen in both skeletal and cardiac muscle?

Answer 13

Not in cardiac, because you need the blood to flow and time for blood to enter the next chamber

Question 14

What are the two pathways for sensing and responding to force in the muscle

Answer 14

• Muscle spindles
• Golgi tendon organ

Question 15

What are inside muscles and responsible for detecting changes in muscle length, responsible for stretch reflex, and compised of intrafusal muscle fibers (Proprioceptors)

Answer 15

Muscle spindles

Question 16

What is the stretch reflex

Answer 16

Too much stretch can cause damage = sensed and activated motor neurons = resist further stretch and helps the muscle spindles return to original length

Question 17

Where are muscle spindles located

Answer 17

inside the muscle

Question 18

Where is the golgi tendon organ located

Answer 18

Where the muscle connects to the tendon

Question 19

What is a proprioceptor that senses changes in muscle tension - stretch and speed

Answer 19

Golgi tendon organ

Question 20

This organ is activated when stretching of muscle deforms terminals of the afferent axons - opening cation channels

Answer 20

Golgi tendon organ

Question 21

How is the ATP pool continually replenished?

Answer 21

• Creatine phosphate pool - support conversion of ADP to ATP
• Muscle glycogen stores
• Glucose from the blood
• Fatty acids from blood and from stored fat within the muscle

Question 22

Not due to lack of energy sources, but due to metabolic byproducts this even effects muscles

Answer 22

Muscle fatigue

Question 23

Accumualtion of what will decrease pH and may inhibit mysoin and actin interactions

Answer 23

Lactic acid

Question 24

What is the optimal sarcomere length

• allows for maximal tension due to maximal overlap of thick and thin filaments = cross bridging

Answer 24

2-2.5 um

Question 25

T/F: Long or short sarcomere fibers limit the ability of the muscle to generate force of contraction

Answer 25

Both very short and very long

Question 26

At long or short sarcomere length actin filaments collide and actin-myosin interactions disrupted

Answer 26

short

Question 27

At long or short sarcomere length actin filaments pulled away from myosin and we get no cross briding

Answer 27

very long

Question 28

What determines preload on the heart

Answer 28

Length

Question 29

What eastablishes inital sarcomere length and load which is carried at both rest and during contraction

Answer 29

Preload

Question 30

What is preload in reference to the heart

Answer 30

stretching muscle by adding weight before stimualtion to contract

Question 31

define cardiac muscle preload

Answer 31

Left ventricular end-diastolic pressure - the amount of ventricular stretch at end of diastole

Question 32

What is the effect when you have no preload to the heart

Answer 32

quick contraction

Question 33

What is the effect when you add more preload to the heart

Answer 33

Less quickly the contraction occurs

Question 34

What describes velocity of muscle shortening when the force against which the muscle contracts (afterload) is varied

Answer 34

Force-velocity relationship

Question 35

Velocity of shortening reflects the speed of what

Answer 35

cross bridging

Question 36

The velocity of shortening is maximal when?

Answer 36

Force (load) is zero

Question 37

What is afterload in reference to the heart

Answer 37

force against which the heart has to contract to eject blood

Question 38

What is defined as stress imposed on left ventricular systole or arterial impendence to ejection of stroke volume

Answer 38

heart afterlaod

Question 39

What is the consequence of having more afterload on the heart

Answer 39

Velocity shortening decreases