Reticular Formation and Cerebellum

Question 1

where does the brainstem travel through and extend?

Answer 1

into the cerebrum as the hypothalamus

Question 2

what does the reticular formation regulate?

Answer 2

posture, stereotypic motor behaviors, internal environment, pain regulation, sleep and wakefulness and emotional tone

Question 3

what are the 3 zones of the Reticular formation?

Answer 3

Raphe (median), medial and lateral

Question 4

Raphe Nuclei

Answer 4

immediately adjacent to the sagittal plane

Question 5

Medial zone

Answer 5

alongside raphe, mixture of large and small neurons
-source of most ascending and descending projections cell bodies originate here
(ascend to the cerebrum or descend to spinal cord for example)

Question 6

Lateral zone

Answer 6

• prominent in rostal medulla and caudal pons, but most extensive zone of the reticular formation
• cranial nerve reflexes and visceral functions (nucleus ambiguous here that is a relay for vagus nerve)

Question 7

Sleep paralysis

Answer 7

• The RF has extensive and complex connections that can innervate multiple levels of the spinal cord, brainstem and thalamus
• the RF has a descending reticulospinal tract that keeps muscles flaccid while sleeping and another that contributes to dreams (so that you dont run away from mud monster!)
• If you have a problem with this part of your RF in the pons, you cannot move but when the cerebrum “wakes up”
• “living through a dream”, tightness on chest, hallucinations

Question 8

Describe the 2 reticulospinal tracts for reticular MOVEMENT/CONTROL

Answer 8

• Medial (pontine) reticulospinal tract starts in the pons, remains ipsalateral and descends near the MLF in the anterior funiculus ((major one during sleep))
• Medullary (lateral) reticulospinal tract starts in the medulla and descends bilaterally in the lateral funiculus
• *both synapse in the anterior horn of the spinal cord

Question 9

what major tract is the reticulospinal tract an alternative for?

Answer 9

corticospinal tract, in regulating spinal motor neurons (directly)

Question 10

how does the RF regulate spinal reflexes?

Answer 10

so that only noxious stimuli evoke a reflex

Question 11

where do reticulospinal tract neurons receive input from??

Answer 11

cerebral cortex, basal ganglia, substantia nigra

**receives input from many areas

Question 12

Explain RF and walking movement

Answer 12

• RF contains basic neural machinery for complex patterned movement
• brainstem-diencephalon junction in cat cut out and the cat still walks (remnant of the rhythm in humans is walking and swinging arms)

Question 13

Motor patterns in the reticular formation

Answer 13

• gaze centers (midbrain for vertical and pons for horizontal)
• mastication in the supratrigeminal nucleus (pons)
• locomotion in the pons

Question 14

what is controlled in the Medulla “vital center”

Answer 14

heart rate, respiration, swallowing and vomiting

**cluster in the RF

Question 15

Bruxism causes

Answer 15

During sleep all mm. are supposed to be in atonia, but in bruxism, the jaw mm. are co-contracted (openers and closers both working)

• peripheral causes theory blames malocclusion and the jaw constantly trying to reach resting postions
• the central causes theory says that sleep related dysfunctions to the supratigeminal nucleus is the issue

Question 16

Explain how pain is transmitted in the RF

Answer 16

spinomesenchephalic/STT receives pain (post. horn sc) and goes to the PAG, which gets input from the hypothalamus, cortex, etc that controls whether or not pain should be suppressed (ex. wounded soldier) , the PAG then goes to the nucleus raphe magnus then to the posterior horn of the spinal cord
**the spinomesencephalic tract can also go directly to the RF or the thalamus

Question 17

opiates and pain

Answer 17

• opiates can activate the PAG-raphe at many levels (PAG, raphe or posterior horn)
• can inhibit spinothalamic tract directly , indirectly through interneurons or can inhibit pain afferents from even going through the STT

Question 18

What is comparable to pattern generators in motor control

Answer 18

visceral information that reaches the RF

• responds to environmental changes and projects to brainstem autonomic nuclei
• *inspiration, expiration, rhythm of breathing in pons and medulla, heart rate ad and blood pressure in medulla

Question 19

Explain the ARAS (ascending reticular activating system)

Answer 19

-the reticular formation projects to the thalamus which in turn projects to the cortex that work together to control consciousness
-functional, not anatomic
(PET scan from an attention demanding task)

Question 20

is there is bilateral damage to the midbrain RF what happens?

Answer 20

prolonged coma
(midbrain and pons RF are whats important for heightening arousal to sensory stimuli that demand attention)

Question 21

where are Noepinephrine neurons located?

Answer 21

solitary nucleus in medulla, locus ceruleus in the rostral pons (near the 4th ventricle) and ventrolateral medulla

Question 22

what does the locus ceruleus control?

Answer 22

vigilance and attention

• active in attentive situations, moderate while awake and low activity when asleep
• releases noepinephrine to the cortex that directs attention to the stimulus
• releases noepinephrine to the trigeminal spinal nucleus and spinal cord to suppress incoming pain signals

Question 23

where do noepinephrine neurons project?

Answer 23

practically the entire cortex, heavily in to the primary somatosensory cortex, goes through the medial forebrain bundle

Question 24

low levels of norepinephrine lead to

Answer 24

• clinical depression
• reduced locus ceruleus neuron activity
• *parkinsons disease has loss of locus ceruleus neurons

Question 25

high levels of norepinephrine lead to

Answer 25

panic disorder

Question 26

where are dopamine neurons located?

Answer 26

in the substantia nigra and ventral tegmental area in the midbrain

Question 27

where does dopamine travel?

Answer 27

from the substantia nigra to the putamen and caudate and from the ventral tegmental area to the cortex or limbic system

Question 28

what does the nigrostriatal path control?

Answer 28

motor activity (degenerates in parkinsons)

Question 29

what do mesocortical and mesolimbic fibers control?

Answer 29

- mesocortical fibers have heavy projections to the frontal cortex to stimulate organized thinking and planning - mesolimbic fibers project to nucleus accumbens and amygdala and control emotional reward (what causes drug dependency)

Question 30

Schizophrenia

Answer 30

has two parts: hallucinations and social withdraw the hallucinations are due to high levels of dopamine in the limbic system and social withdrawl is due to low levels of dopamine in the prefrontal cortex **imbalance of dopamine levels

Question 31

where are serotonin neurons located?

Answer 31

in all of the brainstem levels in the raphe | **Nucleus raphe magnus modulates pain control

Question 32

projections of the serotonergic neurons

Answer 32

midbrain raphe to the cortex * *much like Norepinephrine (but heavy in somatosensory AND limbic system) - inhibits distracting stimuli and regulates day-to-night cycle in the hypothalamus - medullary raphe project to the spinal cord to suppress pain

Question 33

Controlling serotonin levels

Answer 33

low levels of serotonin are due to high carbohydrate diets and high levels are due to compulsive behaviors and anorexia

Question 34

Where are cholinergic neurons located?

Answer 34

- basal nucleus of Meynert (main source) and in part of the RF called the dorsolateral pontine tegmentum (near the locus cerelus) * *Remember Ach is also the neurotransmitter used by motor neurons, preganglionic autonomic neurons and postganglionic parasympathetic neurons (CNIII and X)

Question 35

Alzheimers disease

Answer 35

-drug treatment inhibits Ach to slow the breakdown of Ach (in the basal nucelus)

Question 36

What part of the substantia nigra are the dopaminergic neurons coming from?

Answer 36

the compact part (black dots)

Question 37

What do SSRI's do?

Answer 37

alleviate clinical depression | selective serotonin reuptake inhibitors

Question 38

What does the dorsolateral pontine tegmentum control?

Answer 38

sleep and wakefulness

Question 39

where is the gray and white matter located respectively in the cerebellum?

Answer 39

on the outside and inside respectively

Question 40

what are the functions of the cerebellum?

Answer 40

regulates equilibrium, controls muscle tone, motor coordination prior to the event and adjustment during the movement

Question 41

inferior cerebellar peduncle function

Answer 41

IN pathway from the spinal cord and brainstem | **restiform and sometimes juxtarestiform body

Question 42

middle cerebellar peduncle function

Answer 42

IN pathway from motor signals from the cortex (brachium pontis) **largest peduncle

Question 43

superior cerebellar peduncle function

Answer 43

OUT pathway to the red nucleus and thalamus

Question 44

describe the cerebellar circuitry

Answer 44

inputs come into the ICP and MCP, the ICP and MCP project out to the cortex, which does its thing, the cortex then sends info to the deep nuclei which in turn send to the SCP which projects to other parts (other than the cerebellum) of the brain

Question 45

what are all the deep nuclei?

Answer 45

dentate, interpose (emboliform and globose) and fastigal | "Frosch Gives Everyone D's"

Question 46

what is the only cell to leave the cerebellar cortex?

Answer 46

purkinje cell

Question 47

where do the climbing fibers originate and what do they climb?

Answer 47

the inferior olivary nucleus and they climb dendrites of purkinje cells

Question 48

what are the collateral to deep nuclei and what do they do?

Answer 48

they come from the climbing fibers and mossy fibers to keep their function in check

Question 49

what are the deep nuclei neuronal populations?

Answer 49

-they are a source of mossy fibers into the cortex and a source of neurons whose axons leave the cerebellum

Question 50

vestibulocerebellum

Answer 50

- contains flocculonodular lobe and part of the vermis - gets inputs from the vestibular end organ and vestibular nuclei to control eye movement in relation to head movements (balance) - goes to to the fastigal nucleus

Question 51

spinocerebellum pathway

Answer 51

the spinocerebellar tract goes to the paravermal area then to the interposed nuclei which take the SCP to the red nucleus or VA/VL of the thalamus to the corticospinal tract (which regulates trunk and limb movements)

Question 52

pontocerebellum pathway

Answer 52

information from the primary motor, supplementary motor, premotor and parietal lobe info goes to the baislar pons, which crosses over (to form the MCP) to travel on mossy and climbing fibers to the lateral cerebellar cortex, which goes to the dentate nucleus, up the SCP to the thalamus and then ultimately back to the motor cortex etc.. ***LOOP that controls speech and coordination of arm movement

Question 53

what does cerebellar cortex injury lead to??

Answer 53

failure to coordinate multiple mm. moves | ex. intention tremor and dysmetria

Question 54

lateral vs. medial cerebellar limb movements??

Answer 54

lateral is planned, learned movements whereas the medial hemisphere is adjusting limb movements ex. a good baseball player will only use their lateral hemisphere whereas a poor baseball player will use there medial and lateral hemisphere to adjust movements that are off

Question 55

what does injury to the vermis cause?

Answer 55

disturbances in balance (even when seated), gait ataxia | ex. drunk people

Question 56

explain why the cerebral hemisphere controls contralateral muscles but the cerebellum influences ipsalateral limbs

Answer 56

the spinocerebellar pathways are all ipsalateral wheres projections from the cerebellum to the thalamus and then cortex are contralateral