Chapter 9 Part 2 (Lecture)

Question 1

List the Events that Occur at the Neuromuscular Junction

Answer 1

1. Arrival of action potential at synaptic terminal
2. AP causes Ca2+ to enter axon synaptic terminal
3. Ca2+ stimulates exocytosis of ACh vesicles
4. ACh enters synaptic cleft
5. ACh binds at motor and plate
6. Appearance of an action potential in the sarcolemma
7. Return to intial state

Question 2

List the Step of the Contraction Cycle

Answer 2

1. Energized myosin head is “cocked”
2. Exposure of myosin binding site on actin, forms the cross bridge
3. Pivoting of myosin heads (Power Stroke)
4. Detachment of cross bridge

Question 3

2 Ways to Stop the Contraction Cycle

Answer 3

1. Run out of Ca2+
2. Run out of ATP

Question 4

Why is Ca2+ important in the Contraction Cycle?

Answer 4

Ca2+ is used to bind to the troponin which changes shape and moves tropomyosin exposing myosin binding sites.

Question 5

Why is ATP important in the Contraction Cycle?

Answer 5

ATP is the energy source.

Question 6

Answer 6

Treppe Graph

Question 7

Answer 7

Wave Summation

Question 8

Answer 8

Incomplete Tetanus

Question 9

Answer 9

Complete Tetanus

Question 10

3 Types of Skeletal Muscle Fibers

Answer 10

• Slow Oxidative (SO) Fibers
• Fast Oxidative Glycolytic (FOG; Intermediate) Fibers
• Fast Glycolytic (FG) Fibers

Question 11

Slow Oxidative (SO) Fibers

Answer 11

• Least powerful
• Fatigue resistant, red, myoglobin, many mitochondria, small fiber diameter
• Suited for endurance-type activity
• Marathon or triathalon

Question 12

Fast Oxidative Glycolytic (FOG; Intermediate) Fibers

Answer 12

• Moderately fatigue resistant, red to pink, intermediate diameter
• Suited for sprinting and walking

Question 13

Fast Glycolytic (FG) Fibers

Answer 13

• Fatigable
• Suited for short term intense or powerful movements, white, few mitochondria, large fiber diameter
• Weight lifting

Question 14

Sliding Mechanism of Muscle Contraction

Answer 14

Thin slides over thick to cause a contraction

Question 15

Motor Unit

Answer 15

One motor neuron and many skeletal muscle fibers

• One motor neuron to multiple muscles
• One muscle to only one motor neuron

Question 16

Motor-End Plate

Answer 16

The specific part of a skeletal muscle fiber’s sarcolemma directly beneath the NMJ

Question 17

Neurotransmitter

Answer 17

Chemical substance released from a motor end fiber; causes stimulation of the sarcolemma of muscle fiber

Question 18

Achetylcholine

Answer 18

Triggers action potential that releases Ca2+

Question 19

Achetylcholinesterase

Answer 19

Removes ACh from synaptic cleft ending muscle stimulation

Question 20

Events involved in skeletal muscle fibers contraction beginning with the necessary motor impulse initiated by the brain.

Answer 20

1. NMJ
2. Contraction Cycle

Question 21

Explain why and how a contracted skeleta muscle relaxes.

Answer 21

Ca2+ is pumped out of the sarcoplasm, actin is covered up so myosin can’t bind with actin.

Question 22

Name the 3 pathways that regenerate energy/ATP in muscle cells

Answer 22

1. Aerobics
2. Anaerobics
3. Creatine-Phosphate

Question 23

How is Lactic Acid produced in muscle cells and what its accumulation causes.

Answer 23

Produced by anaerobic respiration.

Muscles shut down until Lactic Acid is removed.

Question 24

O₂ Debt

Answer 24

Demand for O₂ outstripes O₂ supply

Question 25

Muscle Fatigue

Answer 25

Muscle runs out of ATP

Question 26

Twitch

Answer 26

Single contraction followed by an imediate relaxation

Question 27

What is meant by the "all or nothing" response in skeletal muscle fibers.

Answer 27

The threshold must be reached

Question 28

Explain how smooth and graded contractions of a skeletal muscle are produced.

Answer 28

Based on strength and frequency of stimuli

Question 29

Define the term used to describe a myogram that shows a series of twitches with increasing strength.

Answer 29

Wave summation

Question 30

Name the term when a myogram illustrates a sustained contraction that lacks even slight relaxation between twitches.

Answer 30

Complete Tetanus

Question 31

Muscle Recruitment

Answer 31

Beacuse a whole muscle is composed of many motor units, controlled by many different motor neurons, simultaneous contraction of all units does not necessarily occur.

Question 32

Isometric

Answer 32

Contraction but not shortening

Question 33

Isotonic

Answer 33

Contraction with shortening

Question 34

Force (Factors)

Answer 34

Size and Fiber Type

Question 35

Velocity (Factors)

Answer 35

Fiber Type

Question 36

Duration (Factors)

Answer 36

Fiber type