11c: Motor Physiology II Flashcards Preview

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Flashcards in 11c: Motor Physiology II Deck (22):

Alpha-gamma co-activation experiment: What was measured?

1. Muscle tension
2. EMG (electrical activity from muscle fibers)
3. 1A afferent (discharge from muscle spindle)


Alpha-gamma co-activation experiment: key results showed that muscle tension signals were seen (before/after/in sync with) (X). What does that mean?

X = 1A discharge from muscle spindle

Alpha and gamma MN must have been activated almost simultaneously


List the two types of muscle stretch afferent fibers. What does each respond to?

1. Primary 1A (stretch AND rate of length change)
2. Group II (stretch amount only)


Of the two types of muscle stretch afferent fibers, which is more rapidly adapting?

Primary 1A fibers


List the two types of efferent (X) fibers to muscle spindle. They make the receptor more sensitive to (Y).

X = gamma;

1. Fusimotor plate (Y = rate of length change)
2. Fusimotor trail (Y = static stretch level)


Severing brainstem at intercollicular level leaves (X) intact, but (Y) innervation lost.

X = cerebellum and remaining brainstem
Y = thalamic/cortical


Severing brainstem at intercolliculuar level will produce with which condition?

Decerebrate rigidity


List the influences/inputs to facilitatory reticular formation. Put +/- to indicate if the input is excitatory/inhibitory.

1. Vestibular nuclei (+)
2. Cerebellum (-)
3. Cortex (-)
4. Ascending dorsal columns (+)


Stimulation of inhibitory reticular formation results in (flexor/extensor) (facilitation/inhibition).

1. Flexor facilitation
2. Extensor inhibition


List the means by which activity of alpha MN at level of SC can be mediated.

1. Direct excitatory activation from higher centers
2. Indirect activation via fusimotor activation of muscle spindle


In decerebrate cat, loss of rigidity can occur by sectioning (X), which has which effect?

X = dorsal root;

Interrupts gamma (indirect) pathway to muscle activation


Ablating anterior lobe of cerebellum will (increase/decrease) alpha MN output through (direct/indirect or gamma) pathway if the dorsal root is severed.

Increase; direct (severing dorsal root severs gamma loop)


The series of experiments in decerebrate cat prove that alpha rigidity is mediated largely by (X) pathway. And (Y) rigidity is mediated primarily by (Z) pathway.

X = vestibulospinal;
Y = gamma;
Z = reticulospinal


If the spindle reflex were operating alone, the (X) delay would lead to (Y). What prevents this?

X = loop (30-100 ms)
Y = tremor;

Cerebellar feedback to alpha MN predicts where muscle length will be at future time point, based on rate of length change info


T/F: Inhibitory reticular formation is typically quiescent.



List the influences/inputs to inhibitory reticular formation. Put +/- to indicate if the input is excitatory/inhibitory.

1. Cerebral cortex (and BG through cortex) (+)
2. Cerebellum (+)


What's the solution for the instability/constant movement of our body in body orienting/righting reflexes?

Redundancy of systems


The superior colliculus assists in body orienting reflexes by sending info to (X) via (Y).

X = vestibular nuclei


Neurons in superior colliculus respond to stationary stimuli with (X) characteristics and moving stimuli with (Y) characteristics.

Doesn't respond to stationary stimuli!

Y = uni-directional movement, out of visual field


A decerebrate cat (has/has not) lost its "head on body" reflex. Information from (X) that interact through pathways in (Y) are responsible for this reflex.

Has not;
X = muscle/joint receptors
Y = cervical SC


List the three groups of receptors responsible for body orienting reflexes.

1. Vestibular (labyrinthine)
2. Visual
3. Somatic proprioceptors


The supplementary motor area is located on (medial/lateral) surface of (X) fissure. Rostral-to-caudal body (homunculus) is oriented in (Y) direction.

X = longitudinal
Y = rostral-to-caudal