Skeletal Muscle Physiology (Smith) Week 3

Question 1

List the steps of skeletal muscle contraction (know the ORDER)

Answer 1

1.

Question 2

List the Steps in the Cross Bridge Cycle

Answer 2

Question 3

What are the 3 main energy sources for Muscle Contraction

Answer 3

1. Creatine Phsophate (Anareobic, 1 atp, 15 sec)
2. Glycogenolysis (Anareobic respiration Lactic acid formation) (Glucose 2 ATP, 30 - 60 sec)
3. Cellular Respiration
   - Energy: glucose, pyruvic acid, free fatty acids & amino acids - 38 ATP

Question 4

Isotonic vs. Isometric Contractions

Answer 4

Isotonic: Tension generated by muscle is greater than the load (muscle shortens)

Isometric: The load exceeds the tension (muscle doesnt shorten)

Question 5

Explain the different types of muscle twitches and how they relate to Motor Unit Recruitment

Answer 5

Type I: Slow twitch (think marathons)

Type IIa: Fast twitch (think sprinting)

Type IIb: When load becomes even greater these are recruited to further supplement Type I & IIa

Question 6

What is a Reflex Arc?

Answer 6

A neural pathway that controls a reflex - Most of the time are INDEPENT of the brain and synapse in the spinal chord.

Question 7

List the 6 steps of a reflex arch

Answer 7

1. sensory receptor
2. afferent neuron
3. integration center (CNS)
4. Interneuron
5. motor neuron
6. Effector (muscle)

Question 8

List and explain the 3 examples of Reflex Arcs

Answer 8

Question 9

What do the Muscle spindle and Golgi tendon organ do in respect to a reflex

Answer 9

Muscle spindle - measure muscle length (monosynaptic)

Golgie tendon organ - Measure muscle tension (disynaptic)

Question 10

What is “fractionation”

Answer 10

All motor units in a muscle do not need to activate, however, the more units the larger the force generated by the muscle

Question 11

The muscle twitch

Answer 11

Question 12

What is wave summation

Answer 12

AKA temporal summation

• Increasing the frequency of a stimulus held at a constant intensity

Question 13

Unfused (incomplete) tetanus

Answer 13

Wave summating at a frewuency sufficient to produce periods of incomplete relaxation between contractions

AKA - Treppe or staircase effect

Question 14

Define Tetanus

Answer 14

Prolonge contraction WITHOUT relaxation resulting from repeated stiulations so fast the muscle has no ooportunity to relax

• Tetanus is due to the binding sites on actin continually staying exposed

Question 15

Define Fatigue

Answer 15

The muscle loses tension despite continuing stimuli

Question 16

What are the 2 subtypes of muscle fiber?

Answer 16

1. Extrafusal Fibers
   - make up bulk of muscle
   - innervated by Alpha motor
   - provide the FORCE
2. Intrafusal Fibers
   - innervated by gamma motor
   - Form the muscle spindle

Question 17

What are the 2 subtypes of INTRAfusal fibers

Answer 17

1. Nuclear bag fibers: Nuclei in bag like bundle, detect FAST changes in muscle length
2. Nuclear chain fibers: Nuclei in single row (chain), detect STATIC changes in length & tension