The Motor System

Question 1

Flex

Answer 1

• Decrease Joint angle, flexor contracts and shortens
• Extensor is stretched and lenghtens

Question 2

Extend

Answer 2

• Increase joint angle, Extensor contracts and shortens,
• Flexor is stretched and lengthens

Question 3

Antigravity Muscles

Answer 3

Extensors

Question 4

Postural fixation

Answer 4

Elimination of unwanted movement at a joint (necessary for useful movement)

Question 5

Parameters of muscle action

Answer 5

1. Force
2. Speed of contraction
3. Resistance to fatigue
4. Fineness of control
   (1,2,3 result from the structure of muscle )
   (4 from the structure and pattern of innervation of muscle)

Question 6

Fast Twitch (white muscle)

Answer 6

FF fibers- fast and fatigable
FR- Fast and Resistant to fatigue

Question 7

Slow twitch (Red Muscle)

Answer 7

S fibers- least force slowest contraction time BUT MORE RESISTANT to FATIUGUE

Question 8

ALS

Answer 8

absence of trophic factors for muscle; spinal cord and cortex.

Question 9

Poliomyelitis

Answer 9

Viral infection, Motor neurons die; muscles atrophy (paralysis)

Question 10

Motor Unit:

Answer 10

Single motorneuron and all muscle fibers it innervates.
- All muscle fibers in a motor unit are of the same type.

Question 11

Large motor units

Answer 11

FF fibers

Question 12

Small motor units

Answer 12

S fibers

Question 13

Small motor unit size (Muscle Properties)

Answer 13

Fine Control

Question 14

Large motor unit size (Muscle properties)

Answer 14

Force, Speed

Question 15

Motor units are recruited in order of increasing size :

Answer 15

Smallest First, Largest Last, and drop out in reverse order.

Question 16

Feedback information
Muscle Length :

Answer 16

Receptor is the muscle spindle

Question 17

Feedback information
Muscle Force :

Answer 17

Receptor is the Golgi Tendon Organ (GTO)

Question 18

Structure of Muscle Spindle

Answer 18

• intrafusal fibers
  (Ordinary muscle fibers are extrafusal fibers)
• attached in parallel with extrafusal fibers
  Have both sensory and motor innervation

Question 19

Intrafusal Fibers

Answer 19

• Contractile poles (Motor innervation)
• Noncontractile centers (Sensory innervation)
  2 Types :
• Nuclear Bag Fibers (dynamic)
• Nuclear Chain Fibers (Static)

Question 20

2 Types of Sensory Fibers

Answer 20

Group IA 12-20 μm diameter, CV = 70 -120 m/sec.(bigger and faster)
Group II 5-12 μm diameter, CV = 30 - 70 m/sec.
(Smaller and slower)
- CV’s change in Diabetic Neuropathy

Question 21

Group IA Fibers

Answer 21

• innervate every intrafusal fiber
• Form primary or annulospiral endings
• convey both dynamic and static information

Question 22

Group II Fibers

Answer 22

• innervate only Nuclear chain fibers, secondary or flower spray endings.
  -Code static information
• When muscle stretched, endings are depolarized(stretch sensitive channels, action potentials generated with enough stretch.

Question 23

Motor innervation of the spindle : the gamma motoneuron

Answer 23

Motor innervation of contractile poles of intrafusal fibers, adjust the length of spindle in parallel with length of extrafusal fibers.
- somata in the ventral horn

Question 24

GTO and Muscle Force

Answer 24

• Attached in series with muscle at the junction of the muscle and tendon.