11c: Motor Physiology II

Question 1

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

Answer 1

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

Question 2

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

Answer 2

Before;
X = 1A discharge from muscle spindle

Alpha and gamma MN must have been activated almost simultaneously

Question 3

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

Answer 3

1. Primary 1A (stretch AND rate of length change)

2. Group II (stretch amount only)

Question 4

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

Answer 4

Primary 1A fibers

Question 5

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

Answer 5

X = gamma;

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

Question 6

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

Answer 6

X = cerebellum and remaining brainstem
Y = thalamic/cortical

Question 7

Severing brainstem at intercolliculuar level will produce with which condition?

Answer 7

Decerebrate rigidity

Question 8

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

Answer 8

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

Question 9

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

Answer 9

1. Flexor facilitation

2. Extensor inhibition

Question 10

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

Answer 10

1. Direct excitatory activation from higher centers

2. Indirect activation via fusimotor activation of muscle spindle

Question 11

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

Answer 11

X = dorsal root;

Interrupts gamma (indirect) pathway to muscle activation

Question 12

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

Answer 12

Increase; direct (severing dorsal root severs gamma loop)

Question 13

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.

Answer 13

X = vestibulospinal;
Y = gamma;
Z = reticulospinal

Question 14

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

Answer 14

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

Question 15

T/F: Inhibitory reticular formation is typically quiescent.

Answer 15

True

Question 16

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

Answer 16

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

2. Cerebellum (+)

Question 17

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

Answer 17

Redundancy of systems

Question 18

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

Answer 18

X = vestibular nuclei
Y = MLF

Question 19

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

Answer 19

Doesn’t respond to stationary stimuli!

Y = uni-directional movement, out of visual field

Question 20

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.

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

Medial;
X = longitudinal
Y = rostral-to-caudal