Chapter 56

Question 1

What is the main role of the cerebellum?

Answer 1

The cerebellum allows timing of motor activities, and fluidity in movement when coordinating muscle movements. It is also involved in changing muscle intensity when required (stopping your hand from hitting your face or other objects when you slip).

Question 2

What is the flocconodular lobe?

Answer 2

The flocculonodular lobe is the oldest and is found in primitive animals, such as fish. It is named the vestibulocerebellum as well, and it tells you what it is named for – vestibular functions of balance as well as eye movement

Question 3

What are the Sx of lesions to the flocconodular lobe?

Answer 3

Lesion to here will cause nystagmus due to the vestibular function, as well as problems with visual tracking, and also balance.

Question 4

What is the fxn of the lateral zone of the cerebellum?

Answer 4

The lateral zone of the hemisphere is where cerebrocerebellum is located, and is mainly involved with planning action from the cortex.

Question 5

What is the fxn of the vermis of the cerebellum?

Answer 5

The Spinocerebellum will be located in the vermis and the intermediate zone, and that is where regulation of the body parts takes place – it takes proprioception in and then will change the course of the muscle from calculating its future trajectory

Question 6

What is the fxn of the corticopontocerebellar pathway (bacon)?

Answer 6

It carries signals from the cortex in through the middle cerebellar peduncle, and into the lateral hemisphere of the cerebellum (planning area)

Question 7

What are the inputs to the olivocerebellar tract?

Answer 7

Climbing Tracts from the Inferior Olive, that go into the cerebellum at all levels

Question 8

What are the inputs to the vestibulocerebellar tract?

Answer 8

from both the vestibule apparatus and the vestibular nucleus, and all end up in the flocculonodular lobe and the fastigial nucleus.

Question 9

What are the inputs to the reticulocerebellar tract?

Answer 9

from brainstem reticular formation and end up in the vermis.

Question 10

Trace the path of the dorsal spinocerebellar tract from the periphery

Answer 10

Dorsal tract is the posterior tract that we learned – goes up the posterior spinocerebellar tract, through the ICP, and into the cerebellum

Question 11

What is the fxn of the dorsal SC tract?

Answer 11

Responsible for mainly muscle spindles, Golgi tendon organs, large tactile receptors of skin, and joint receptors. Information carried in this tract: Muscle contraction, Tendon Tension, Rate of movement of Muscle, and Forces acting on the Body.

Question 12

Trace the path of the ventral spinocerebellar tract from the periphery

Answer 12

goes through SCP (crosses once at the level of the receptor, then most fibers cross back over

Question 13

What is the fxn of the ventral SC tract?

Answer 13

carry information of what the brain is up to via corticospinal and rubrospinal tracts, and travel upwards from the anterior horn where the motor neurons are located. Basically it is providing a copy of the order given by the cortex to the cerebellum, so it is clued in on what’s going on and if it needs to intervene possibly.

Question 14

What are the deep cerebellar nuclei from lateral –> medial?

Answer 14

dentate, interposed, and fastigial

Question 15

What is the fxn of the vestibulocerebellum tract?

Answer 15

This pathway is important for equilibrium and vestibular function, this will help you when you are falling, it will send signals to extensors to aid in bringing balance and making the body upright again.

Question 16

Which deep cerebellar nuclei are teh vestibulocerebellum tract associated with?

Answer 16

fastigial N.

Question 17

Which deep cerebellar nuclei are teh spinocerebellum tract associated with?

Answer 17

interposed nucleus (globose and emboliform nucleus)

Question 18

Trace the path of the spinocerebellum tract, starting from the intermediate cerebellar hemisphere

Answer 18

(1) the intermediate zone of the cerebellar hemisphere and then passes through (2) the interposed nucleus to (3) the ventrolateral and ventroanterior nuclei of the thalamus and then to (4) the cerebral cortex, to (5) several midline structures of the thalamus and then to (6) the basal ganglia and (7) the red nucleus and reticular formation of the upper portion of the brain stem.

Question 19

Which deep cerebellar nuclei are teh cerebrocerebellar tract associated with?

Answer 19

dentate

Question 20

Where does the cerebrocerebellar tract target from the dentate?

Answer 20

just goes to the VL or VA of the thalamus and then synapses then passes onwards to the cortex

Question 21

What types of sensations does the ventral spinocerebellar tract hold?

Answer 21

Copy of the Cortex commands being sent out

Question 22

What types of sensations does the dorsal spinocerebellar tract hold?

Answer 22

Muscle Contraction, Tendon Tension, Rate of Movement, and Forces acting on the Body

Question 23

What are inferior olivary climbing fibers?

Answer 23

come from inferior olive of medulla and will affect 5-10 Purkinje cells, and then makes around 300 synapses for each cell. It will have a single large prolonged action potential then a number of weaker ones (complex spike)

Question 24

What are mossy fibers?

Answer 24

all the other fibers coming in from the brain stem, brain, and spinal cord. These send one axon to the deep nuclear cell and then others to the granule cells (the cells with parallel fibers running around). There are a ton of granule cells for purkinje (500 to 1). Mossy fibers generally need large numbers to excite the Purkinje cell, and they will have just a simple spike for the action potential.

Question 25

Describe the excitatory and inhibitory balance between the purkinje fibers and the deep nuclei

Answer 25

Mossy and Climbing fibers excite the deep nuclei, while Purkinje fibers inhibit the deep nuclei. In most cases, there is a slight level of excitation. When there is motor movement, signals cause great excitation, but then inhibition follows very quickly right after from Purkinje fibers being a little bit slower to the action – this allows damping, or basically balancing the excitation or the muscle movement that was just sent out. This stops the muscle from going too far, and makes sure it has just the right amount of intensity.

Question 26

How does the activation of the parallel fibers turn on agonist muscles?

Answer 26

Cortex sends orders down the corticospinal tract, but parallel fibers via pontile mossy fibers go into the cerebellum. These excitatory fibers send another signal back up the thalamus to the cortex or by brain stem circuitry to support the initial contraction signal. So this turn on excitatory connection is there to help out the initial signal sent by the cortex, and makes the signal stronger.

Question 27

Where is the turn off signal for antagonist muscles?

Answer 27

The turn off inhibitory signal is from the Purkinje cells, which are the only inhibitory cells in the circuit. Mossy fibers also send out fibers to the granule layer, which then turn on the purkinje fibers, which then inhibit the deep nuclear cell, thus turning off the movement.

Question 28

What is dysmetria?

Answer 28

overshooting a mark due to cerebellum not giving dampening and giving reverse directions

Question 29

What is ataxia?

Answer 29

uncoordinated movements, can result from spinocerebellar tract lesions (feedback information not present to give cerebellum timing to stop its actions)

Question 30

What is past pointing?

Answer 30

very, very similar to dysmetria, its again when moving a limb or a hand, you go past the intended stopping location, since the cerebellum is not present to turn off the movement.

Question 31

What is dusdiadochokinesia?

Answer 31

more problematic with proprioception but it is when movement starts too early or too late, so you get jumbling and clumsy hands. An example is when you turn your hands over and under (supinate and pronate) very quickly, and the loss of perception doesn’t give your cerebellum information on what’s going on, so you get jumbled, uncoordinated, attempts at movement.

Question 32

What is dusarthria?

Answer 32

speech and sound related problems with motor, so larynx, mouth have uncoordinated movements. Vocally unclear with some syllables loud, other soft.

Question 33

What is an intention tremor?

Answer 33

oscillation of movement due to cerebellum not able to stop, so you get overshooting the mark, then going in reverse, overshooting again, and then creating a cycle of overshooting, which brings the characteristic tremor.

Question 34

What is nystagmus?

Answer 34

Tremor of the eyeballs, when you look at something at the side of the head, the eyeball will suddenly jerk back to the midline. Specifically flocculonodular lobe problems.

Question 35

What is hypotonia?

Answer 35

loss of dentate and interposed nuclei causes decreased tone of peripheral muscles, since they set tonic signaling for motor cortex and brain stem nuclei.

Question 36

What is the role of the basal ganglia in motor control?

Answer 36

Basal ganglia influence motor control via mainly inhibition, so release of this inhibition allows motor control and action. They receive input from the cerebral cortex and also output right back to the cerebral cortex. Basal ganglia are the following: caudate, putamen, globus pallidus, substantia nigra, and subthalamus. One important role of basal ganglia is doing complex patterns of motor activity, like writing letters of the alphabet.

Question 37

What is the putamen circuit for motor control?

Answer 37

When you are executing a learned pattern of movement (cutting a piece of paper with scissors) first the orders come down from supplementary motor cortex and somatosensory cortex, and go right to the putamen. From the putamen, they go into the globus pallidus, which then separates into the direct and indirect pathways (subthalamus or directly to VA/VL of thalamus), and those from the thalamus find their way back to the premotor cortex and motor cortex. So input is from adjacent locations to the primary motor cortex, and output is to the primary cortex mainly.

Question 38

What are the Sx of lesion to the globus pallidus?

Answer 38

lesion here will produce spontaneous and continuous writhing movements of the hand, arm, neck, face, called athetosis

Question 39

What are the Sx of lesion to the subnthalamus?

Answer 39

lesion will cause hemiballismus, flailing motion, when a person throws their entire body forward

Question 40

What are the Sx of lesion to the putamen?

Answer 40

flicking movements in hands, face, called chorea

Question 41

What are the Sx of lesion to the substantia nigra?

Answer 41

rigidity, akinesia, tremors, AKA Parkinson’s Disease

Question 42

What is the caudate circuit for motor control?

Answer 42

cerebral cortex sends messages to the caudate, then are sent to the internal or medial globus pallidus, which then pass onto the VA/VL of the thalamus, and finally go back to the cortex, this time though only going to premotor and accessory motor regions. So this is more of drafting a plan based on things you know about the situation: if you see a bear coming at you, you don’t think, you just start running and looking for a tree or somewhere to climb or get in between you and the bear. A lot of “instinct” type things seem to be based around this.

Question 43

What are the 2 roles of the basal ganglia for the timing and scale of movements?

Answer 43

1. Rapidity/speed of movement – needs to be aware of how fast a movement needs to be to complete it
2. How large the movement needs to be – needs to be aware of how large a movement needs to be for completion