Motor System Flashcards
What proteins create contraction of muscles?
Actin, myosin, troponin, tropomyosin
What is the functional unit of muscles?
Sarcomere
What are the three structural proteins?
M-line, Titian, Z-line (ends)
T/F myosin heads bind with actin filaments
True
What is the name of the model that shortens (contracts) muscles?
Sliding filament model
What is the sliding filament model?
Muscle shortens/lengthens by actin and myosin filaments sliding past each other without changing length
The attachment, rotation, and detachment of filaments utilize energy from what source?
ATP hydrolysis
Which bands get narrower as shortening continues?
I and H bands
What is another name for muscle membrane?
Sarcolemma
What are the projections that extend into the muscles that allow for depolarization within the muscle?
T-tubules
Depolarization within the muscles release Ca2+ from what?
Sarcoplasmic reticulum (Ca2+ sacs)
What is the inhibition complex that covers the binding site on actin filaments?
Troponin-tropomyosin complex
What causes the movement of the troponin-tropomyosin complex to expose the binding site?
Ca2+
To where do UMN tracts deliver signals to?
Spinal interneurons and LMNs
Where are the cell bodies of LMNs located?
In brainstem and ventral horn of spinal cord
What is called the “final common path” by Sir Charles Sherrington?
LMNs
Which motor neuron tract is essential for INITIATING movement?
UMNs
T/F UMNs rarely synapse with interneurons before synapsing with LMNs
False (most of them do)
What does a motor unit consist of?
LMN and the specific muscle fiber it innervates
T/F a single motor unit will innervate only one specific muscle fiber TYPE
True
What are the three classifications of motor unit characteristics?
- Twitch (speed)
- Tension (force)
- Fatigability (endurance)`
Which type of twitch is very fatigue resistant?
Slow twitch (Type 1)
Which type of exercise uses Type IIb motor units?
Plyometric exercises (fast twitch and v high force)
What generates force gradation and changes in tension?
Motor unit RECRUITMENT strategies
What are the two mechanisms that determine gradation of force?
- Increased # (recruitment, more motor units)
2. Increased frequency of motor unit discharge (repetitive stimuli = temporal summation)
What principle states that orderly recruitment produces smooth muscle actions (fine tuning)
Henneman’s Size Principle
T/F motor units fire all at once
False (different times, different intensities)
What are the three types of temporal summation in motor units?
- Wave summation (2nd stimulus occurs before complete relaxation)
- Unfused tetanus
- fused tetanus
What term refers to motor unit firing rate?
Rate coding
What does “recruitment strategy varies by size” mean?
Smaller muscles rely on rate coding / larger muscles rely on recruitment
What is the brief contraction of all muscle fibers in a motor unit in response to a single nerve impulse?
Twitch contraction
What is the record of muscle contraction called?
A Morgan
What is a recording of electrical muscle activity?
Electromyography (EMG)
Which type of motor neurons convey signals to extra/intrafusal skeletal muscle?
LMNs
What are the two types of LMNs?
Alpha motor neurons (large, extrafusal) and gamma motor neurons (medium, intrafusal)
What are groups of muscles innervated by a single spinal nerve?
Myotomes
What are groups of cell bodies whose axons project to a single muscle?
LMN pool
LMN pools are correlated to what four anatomical positions?
Medial (axial and proximal muscles)
Lateral (distal muscles)
Anterior (extensors)
Posterior (flexors)
What spinal cord function inhibits antagonist muscles during agonist contraction?
Reciprocal inhibition (prevents stretch reflex)
What do you call the spinal cord’s creation of a complete proprioceptive model of the body in real time?
Proprioceptive body schema
Which stretch reflex responds to quick stretch?
Phasic stretch reflex (deep tendon reflex)
T/F the phasic stretch reflex arc is di-synaptic
False (monosynaptic)
During stretch reflexes, what detects the quick muscle stretch?
Muscle spindles
What reflex involves a painful stimulus detected by a nociceptor?
Withdrawal reflex (flexion reflex)
What does a withdrawal reflex result in?
- Activation of flexor and inhibition of extensor
2. Movement of body away from painful stimulus
T/F the withdrawal reflex arc is polysnaptic
True
What reflex is activated simultaneously with a withdrawal reflex?
Crossed extension reflex
What does a crossed extension reflex result in?
- Contralateral activation of extensor and inhibition of flexor
- Weight support for contralateral limb
