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3. SWITCHING STATE OF OUTPUT SIGNALS FROM THE CEREBELLUM.

The typical function of the cerebellum is to help provide rapid
turn-on signals for the agonist muscles and simultaneous
reciprocal turn-off signals for the antagonist muscles at the
onset of a movement, while it controls the timing. Se trata de
pequeñas contracciones que ayudan a parar e iniciar el
movimiento en el momento adecuado.

3.1. Circuit for agonist muscles.

Although the exact details are not fully know, one can speculate
from the basic cerebellar circuit how this might work. Let’s
suppose that:

1. The turn-on/turn-off pattern of agonist/antagonist
contraction at the onset of movement begins in the
cerebral cortex.
2. These signals pass through the brain stem and cord
pathways directly to the agonist muscle to begin the
initial contraction.
3. Simultaneously, signals are sent by way of the pontile
mossy fibers into the cerebellum. One branch of each
mossy fiber goes directly to deep nuclear cells in the
dentate or other deep cerebellar nuclei to send an
excitatory signal back into the cerebral corticospinal motor system, either (1) by return signals
through the thalamus to the cerebral cortex or (2) by way of neuronal circuitry in the brain
stem. To support the muscle contraction signal that had already begun by the cerebral
cortex.
4. As a consequence, the turn-on signal becomes even more powerful than it was at the start
because it becomes the sum of both the cortical and the cerebellar signals.

1) This is the normal effect when the 2) This cerebellar support makes the turn-on
cerebellum is intact, but in the absence of the muscle contraction much more stronger,
cerebellum, the secondary extra supportive faster and precise than it would be if the
signal would be missing. cerebellum dindn’t work.

But, what causes the turn-off signal for the agonist muscles at the termination of the movement?

 For turn-off signal for the agonist muscles at the termination of the movement we get the
mossy fibers involved. All mossy fibers have a second branch that transmits signals by way of
the granule cells to the cerebellar cortex and eventually, by way of "parallel" fibers, to the
Purkinje cells.
 The Purkinje cells in turn inhibit the deep nuclear cells.
 This pathway to turn-off agonist muscles passes through the parallel fibers of the cerebellar
cortical molecular layer, which have diameters of only a fraction of a mm. Also, the signals from
these fibers are weak, so they require a period of time to build up enough excitation in the
dendrites of the Purkinje cell to excite it.
 Once the Purkinje cell is excited, it sends a strong inhibitory signal to the same deep nuclear cell

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