09c: Motor Physiology Flashcards
The motor unit is:
Alpha motor neuron and all muscle fibers it innervates
The (X) is the final common pathway for motor activation.
X = motor unit (via alpha motor neuron)
Which characteristic of (X) determines the “delicacy” of the motor act during motor activation?
X = motor unit;
Size
Gastrocnemius has a relatively (high/low) ratio of muscle fibers to alpha motor neurons. What’s the approximate ratio?
High; 1000/1
Hand muscles have which approximate ratio of muscle fibers to alpha motor neurons?
100/1
Extraocular muscles have which ratio of muscle fibers to alpha motor neurons?
5/1
T/F: Muscle twitch is miniature mechanical event that’s larger in gastrocnemius than in lateral rectus.
False - same size in all muscles
T/F: Muscle twitch is all-or-none.
True
Muscle twitches can summate in which way(s) to produce whole-muscle contractions?
- Temporal summation
2. Spatial summation
Contraction of muscle twitch peaks in (X) amount of time. And relaxes in (Y) amount of time.
X = 80 ms Y = 200 ms
Total tension produced by stimulation of motor unit increases as (X) of motor neuron increases.
X = AP frequency
T/F: Temporal summation of individual muscle contractions is linear.
False
Muscle fiber organization, in (parallel/series), is what allows for (temporal/spatial) summation.
Parallel;
Spatial
The twitch:tetanic contraction ratio in temporal summation is about:
8/1
White muscle active in (posture/fight or flight). List an example of this muscle type.
Fight or flight; gastrocnemius
Red muscle active in (posture/fight or flight). List an example of this muscle type.
Posture; soleus
(Red/white) muscle has small muscle unit.
Red
(Red/white) muscle has low oxidative rate.
White
(Red/white) muscle has fine control.
Red
(Red/white) muscle found more in axial musculature. (Red/white) muscle found more in lateral musculature.
Red; white
(Red/white) muscle has high levels of mitochondrial ATPase.
Red
(Red/white) muscle has low resistance to fatigue.
White
(Red/white) muscle has high contraction rate and (low/high) absolute tension.
White; high
(Red/white) muscle has high glycogen content and (small/large) blood supply.
White; small
Red muscle has (phasic/tonic) nerve activity. What does that mean?
Tonic; state of continuous activity
(Red/white) muscle has lowest threshold for neural activation. This means it’s recruited (first/last) at initiation and drops out (first/last) at end of motor activity.
Red;
First;
Last
(Muscle spindle/GTO) arranged in parallel with muscle fibers, measuring muscle (length/tension).
Muscle spindles; length
(Muscle spindle/GTO) arranged in series with muscle fibers, measuring muscle (length/tension).
GTO; tension
Muscle spindles are located (adjacent to/within) muscle and considered (intra/extra)-fusal.
Within; intrafusal
Muscle spindle afferent fiber is (X) type of nerve fiber that has cell body in (Y). This afferent fiber synapses onto:
X = 1A Y = DRG
- Interneurons (in SC)
- Alpha motor neurons (back to same muscle)
Muscle spindle receives efferent innervation from (X) type of nerve fiber that has cell body in (Y). This afferent fiber synapses onto:
X = gamma; Y = ventral horn of SC
Contractile (polar) ends of muscle spindle
(Muscle spindle/GTO) responsible for stretch reflex.
Muscle spindle
(Alpha/gamma) motor neurons are larger.
Alpha
T/F: Stretch/myotatic reflex is the only monosynaptic reflex.
True
Information regarding state of muscle length is transmitted to CNS when muscle is (fully contracted/fully relaxed).
The info regarding muscle length is ALWAYS transmitted to CNS
Compensatory loading is a phenomenon that’s possible due to (X) and functions to:
X = gamma motor neurons
- Keep stretch receptors in check
- Allow 1A afferents to support alpha motor neuron discharge
GTO sends afferent innervation via (X) type of nerve fiber that has cell body in (Y). This afferent fiber synapses onto:
X = 1B Y = DRG
Inhibitory interneuron (in SC)
1B afferent fiber of (muscle spindle/GTO) synapses onto (X), which (activates/inhibits) (Y).
GTO;
X = inhibitory interneuron (in SC)
Inhibits;
Y = alpha motor neuron of same muscle
Inverse myotatic reflex via (muscle spindle/GTO) is (mono/di)-synaptic.
GTO; disynaptic
Inverse myotatic reflex tends to (increase/decrease/maintain) muscle’s (X).
Maintain;
X = tension
“Facilitation” is the term describing overlap of (X) and results in response (smaller/larger/equal) than/to algebraic sum of two rootlets stimulated alone.
X = Subliminal fringes;
Larger
“Occlusion” is the term describing overlap of (X) and results in response (smaller/larger/equal) than/to algebraic sum of two rootlets stimulated alone.
X = firing zones;
Smaller
(Smaller/larger) cells with (lower/higher) thresholds constitute the subliminal fringe.
Larger; higher
