Chapter 11: The Neuromuscular System and Physical Activity

Question 1

Three important brain neurotransmitter categories

Answer 1

Monoamines(epinephrine, norepinephrine, serotonin, histamine, and dopamine), Neuropeptides (Arginine, vasopressin, angiotensin II, enkephalins, endorphines), nitric oxide

Question 2

Sympathetic nerve fibers

Answer 2

mediate excitation

Question 3

parasympathetic activation

Answer 3

inhibits excitation

Question 4

Three factors govern tension development

Answer 4

1. All-or-none principle
2. graduation of force principle
3. Level of motor unit recruitment patterns

Question 5

Three physiological and mechanical motor unit and muscle properties of innervation

Answer 5

1. Twitch (speed of contraction) characteristics
2. Tension-generating (force) characteristics
3. Neuromuscular fatiguability

Question 6

All or none Principle

Answer 6

All accompanying muscle fibers act synchronously if stimulus triggers a motoneuron’s action potential

Question 7

graduation of force principle

Answer 7

1. Increasing number of recruited motor units
2. increasing frequency of motor unit discharge

Question 8

Four factors decrease force-generating capacity

Answer 8

1. PA-induced alterations in levels of the
   neurotransmitters serotonin, dopamine,
   5-hydroxytryptamine, ACh
2. Reduced glycogen content in active muscle fibers
   occurs during prolonged PA
3. Increased levels of blood and muscle lactate
4. Fatigue occurs at the neuromuscular junction

Question 9

Muscle spindles

Answer 9

provide mechanosensory information about changes in muscle fiber length and tension

Question 10

Stretch reflex

Answer 10

1. Muscle spindle: responds to stretch
2. Afferent nerve fiber: carries sensory impulse from spindle to spinal cord
3. Efferent spinal cord motor neuron: activates stretched muscle fibers

Question 11

Golgi tendon organs (GTOs)

Answer 11

protect muscle and its connective tissue harness from injury by sudden, excessive load or stretch

Question 12

Pacinian Corpuscles

Answer 12

respond to quick movement and deep pressure

Question 13

Four major characteristics of fast-twitch muscle fibers

Answer 13

1. Rapidly transmit action potentials
2. high activity level of myosin ATPase
3. Rapid rate of Ca2+ release and uptake by sarcoplasmic reticulum
4. Generate rapid corssbridge turnover

Question 14

Type IIa fibers

Answer 14

Exhibits fast shortening speed and well-developed
capacity for energy transfer from aerobic and anaerobic sources

Represents fast-oxidative-glycolytic fibers

Question 15

Type IIx fiber

Answer 15

posses greatest anaerobic potential and rapid shortening velocity, represents fast-glycolytic fiber (fast fatiguable)

Question 16

Slow-twitch muscle fibers

Answer 16

resist fatigue and power in prolonged aerobic PA, slow-oxidative fibers