Reticular formation and cerebellum Flashcards
1
Q
The reticular formation is important in the regulation of:
A
- posture
- some stereotypic motor behaviors
- The internal environment
- Pain regulation
- Sleep and wakefulness
- Emotional tone
2
Q
Reticular formation
A
- phylogenetically old
- Central core of the brainstem
- extends into the cerebrum as the hypothalamus
3
Q
What are the three zones of the reticular formation?
A
- ) Raphe of Median
- ) Paramedian or Medial
- ) Lateral
4
Q
What reticular formation zone is the most extensive?
A
The Lateral Zone
5
Q
Raphe nuclei (location)?
A
Immediately adjacent to sagittal plane
6
Q
Medial zone (location and charateristics)?
A
- located along side Raphe
- mixture of large and small neurons
- source of most ascending and descending projections
7
Q
Lateral zone (location and characteristics)?
A
- Prominent in rostral medulla and caudal pons
- primarily involved in cranial nerve reflexes and visceral functions
8
Q
Describe the neurons of the reticular formation (what they innervate, etc.) (add pic)
A
- Reticular formation neurons have extensive, complex connections
- may innervate multiple levels of spinal cord, brainstem, and thalamus
- Some have bifurcating axons that ascend and descend as seen above
9
Q
Describe the two reticulospinal tracts?
A
- ) Medial: pons; ipsilateral, descends near MLF and in anterior funiculus
- ) Lateral: medulla, descend bilaterally, in lateral funiculus
10
Q
Describe sleep paralysis (add to this card)
A
- Your cerebrum is active but your reticular pons is still suppressing body movement.
11
Q
The reticular formation is a major alternative to what tract?
A
It is a major alternative to the corticospinal tract in regulating spinal motor neurons
12
Q
Reticular formation and movement bullet points:
A
- ) Influences spinal motor neurons directly
- ) Regulates spinal relexes (So that only noxious stimuli evoke a reflex)
- ) Reticulospinal tract neurons receive input from many areas including cerebral cortex, basal ganglia, substantia nigra, etc.
- ) RF contains basic neural machinery for some complex patterned movements
- ) If you section brainstem-diencephalon junction in a cat and it still walks
13
Q
Name some brainstem pattern generators of the reticular formation
A
- ) Gaze centers (midbrain vertical gaze center and Pontine horizontal gaze center
- ) Mastication (Supratrigeminal nucleus (pons)
- ) Medulla “Vital Center”
- locomotion (pons)
- Heart rate
- Respiration
- Swallowing, vomiting
14
Q
Bruxism characteristics
A
- Jaw muscles are co-contracted (both opening and closing muscles are contracted at the same time)
- a stereotyped movement disorder
- tooth-grinding or tooth-clenching
15
Q
Bruxism peripheral causes theory:
A
- malocclusion results in premature and one-sided contact.
- jaw movements continue in an attempt to reach the resting position
- This theory is based on clinical observation and experience with treatment
16
Q
Bruxism central causes theory:
A
- sleep-related dysfunctions cause bruxism
- Input to supratrigeminal nucleus may be from basal ganglia, lateral hypothalamus, and central nucleus of the amygdala
17
Q
Describe how the RF can modulate transmission in Pain pathways:
A
- Nervous system can suppress or facilitate pain, depending on circumstances (wounded solders on the battlefield who continue to function)
- Periaqueductal gray is central to one well described pain suppress system
18
Q
Describe the importance of the PAG (periaqueductal gray) in the RF regulating pain: (add pic)
A
- PAG receives pain infor from the spinomesencephalic fibers
- PAG also gets input from hypothalamus, cortex, etc; may contain behavioral state info (should pain suppression be activated?)
- PAG to raphe then to posterior horn of spinal cord/ spinal V nucleus.
19
Q
Describe the role of opiates in the RF pain regulation (add pic)
A
- One way opiates work to control pain is to activate PAG-raphe at multiple levels
- Opiate receptors are abundant in PAG, raphe, posterior horn of cord
- Raphe can inhibit STT directly (7) or indirectly by activating interneurons (8) that inhibit STT (7). Can also directly inhibit pain afferents (6)
- (Opiates can inhibit and modulate pain at multiple levels)
20
Q
Where are your centers for controlling inspiration, expiration, and rhythm of breathing?
A
Pons and medulla
21
Q
Where are your centers for controlling heart rate and blood pressure?
A
Medulla
22
Q
Describe the RF and autonomic reflex circuitry
A
- A lot of visceral information reaches the RF
- Responds to environmental changes and projects to brainstem autonomic nuclei and spinal cord
- Comparable to pattern generators in motor control
23
Q
Describe RF and arousal and consciousness
A
- RF projections to thalamus and cortex
- Midbrain and pons RF get input from multiple sensory modalities (e.g. pain; spinoreticular fibers)
- Project to thalamic intralaminar nuclei, which project diffusely to cortex
- Heightens arousal in response to sensory stimuli or tasks that demand attention.
- RF-thalamic intralaminar nuclear projections to cortex and monoamine reticular projections work together to modulate cortical activity
- Maintain consciousness(1-3)
1. ) bilateral damage to midbrain RF results in prolonged coma
2. ) Known as ascending reticular activating system (ARAS)
3. ) defined functionally; not an anatomic structure - ARAS also has a role in sleep-wakefulness cycle
24
Q
Describe ARAS
A
- Ascending reticular activating system
- allows you to maintain consciousness
- also has a role in sleep-wakefulness cycle
25
Neurochemical signatures: What are the brainstem neurotransmitters?
Norepinephrine, dopamine, and serotonin
26
What are the hypothalamus neurotransmitters?
Histamine
27
What are the telencephalon neurotransmitters?
Acetylcholine
28
What are the Substantia nigra neurotransmitters?
Dopamine?
29
What are the ventral tegmental area neurotransmitters?
Dopamine?
30
What are the midbrain raphe nuclei neurotransmitters?
Serotonin
31
What are the pontine raphe nuclei neurotransmitters?
Serotonin
32
What are the Medullary raphe nuclei neurotransmitters?
Serotonin
33
What are the Locus ceruleus neurotransmitters?
Norrepinephrine
34
Name locations where you would find Norepinephrine receptors?
- Solitary nucleus (memory enhancement)
- Locus ceruleus (cortex (arousal) vigilance and attention)
* active in attentive situations
* moderate while awake
* low activity during sleep
- Ventraolateral medulla
* spinal cord- pain regulation
35
Describe the Noradrenergic projections
- They innervate practically the entire CNS; heavy projections to somatosensory cortex
- They will travel through the medial forebrain bundle on route to the thalamus, hypothalamus, and cortex?
36
Describe Locus Ceruleus neurons:
- Respond to novel environmental stimuli
- stimulation produces
* increased state of arousal
* feeling of anticipation
- blue color due to melanin granules inside neuron?
37
(Locus Ceruleus slide) What is the action of NE released in the cortex verses released in the trigeminal spinal nucleus and spinal cord
- NE released in the cortex: facilitates attention to selected stimuli
- NE released in the trigeminal spinal nucleus and spinal cord: Suppresses incoming pain signals.
38
How is Norepinephrine related to depression?
- Decreased levels of norepinephrine in depression
- Locus ceruleus neuron activity is reduced
- Parkinson's disease patients often suffer from depression
* Locus ceruleus neurons are lost in Parkinson's disease
39
How is Norepinephrine related to panic disorder?
- Increased levels of norepinephrine in panic disorders.
40
The Substantia nigra is comprised of:
Putamen and caudate
41
The Ventral tegmental area is part of what system?
Limbic system
42
Dopaminergic neurons in the midbrain are found in what areas?
Substantia nigra and the Ventral tegmental area
43
Dopaminergic neurons of the Substantia nigra in the midbrain are related to?
- The Nigrostriatal pathway (motor activity)
- Parkinsons disease
- (The Nigra-striatal tract is the one that deteriorates in parkinsons..
44
Dopaminergic projections of the ventral tegmental area (Limbic system), have what two type of fibers?
- Mesocortical fibers
* Organized thinking and planning; heavy projections to frontal cortex
- Mesolimbic fibers (Nucleus accumbens, amygdala)
* emotional reward
* drug dependency
45
Name one major source of dopamine?
The ventral tegmental area
46
Name and describe two tracts from the ventral tegmental area(VTA):
- Mesolimbic tract- to the limbic system
* Nucleus accumbens septi- sense of reward or well being
- Mesocortical tract- to frontal cortex
* Organizes and initiates behavior
47
How is the ventral tegmental area related to schizophrenia?
Implicated in schizophrenia
- disorganized thinking (frontal lobe)
- Hallucinations (limbic system/ temporal lobe)
48
Describe the components of Schizophrenia:
Social withdrawal- low levels of dopamine in the prefrontal cortex
Hallucinations- high levels of dopamine in the limbic system
*drugs that lower the level of dopamine are effective in reducing hallucinations
49
In general, where are you likely to find Serotonergic neurons?
In pretty much all brainstem levels in raphe
50
The nucleus raphe magnus is involved in______? (review this card)
Pain control
51
Where do serotonergic neurons of the midbrain raphe nuclei project to? What are their functions?
They project to all regions of the cortex
They function in:
- attention: inhibition of distracting stimuli
- day and night cycle: hypothalamus
52
Where do serotonergic neurons of the medullary raphe nuclei project to? What are their functions?
They project to the spinal cord
They function in pain suppression
*Nucleus raphe magnus????(look up relation)
53
Name one treatment of clinical depression:
Selective Serotonin Reuptake Inhibitors (SSRI)
54
What do low levels of serotonin lead to?
- High carbohydrate consumption
- binge eating
- carbohydrate preference in obese women
55
What do high levels of serotonin lead to?
Compulsive behavior and anorexia nervosa
56
What are drugs that increase the level of serotonin used to treat?
Depression and Anxiety
57
Acetylcholine (Ach) are considered what type of neurons, and where are they found?
They are considered Cholinergic neurons.
They are found in:
- Basal forebrain; basal nucleus (of Meynert)
- Part of RF; Dorsolateral pontine tegmentum
58
Where is the first area where you start to see brain tangles in Alzheimer's?
In the Nucleus basalis
59
What drug slows the breakdown of acetylcholine?
Cholinesterase inhibitors
60
What are the functions of the Cerebellum?
- Regulates equilibrium
- Controls muscle tone and posture
- Provides motor coordination for voluntary movements
* In the near future (plans motor actions in space and tie
* During execution (monitors ongoing motor activity and... Adjusts the output of the motor cortex and several motor nuclei)
61
What is another name for the lateral hemisphere of the cerebellum?
Pontocerebellum
62
What is another name for the medial hemisphere of the cerebellum?
Paravermal area or the Spinocerebellum
63
What is another name for the Nodulus of vermis of the cerebellum?
Vestibulocerebellum
64
What is the name of the fissure that separates the anterior lobe of the cerebellum from the posterior lobe of the cerebellum?
Primary fissure
65
What fissure separates the body of the cerebellum from the floculonodular lobe?
Posterolateral fissure
66
Where is the Juxtarestiform body found, and what does it do?
It is found in the Inferior cerebellar peduncle (Restiform body), and it interconnects the vestibular nuclei and cerebellum
67
What is the action and connection of the Inferior cerebellar peduncle?
It monitors muscle and limb movement.
Inputs are from the spinal cord and brainstem.
68
What is the action and connection of the middle cerebellar peduncle (brachium pontis)?
- largest and lateral to the pons
- afferents from contralateral basis pontis
- relays motor signals from cortex
69
What is the action and connection of the superior cerebellar peduncle (brachium conjunctivum)?
- Efferents to the red nucleus and thalamus
| - this is an out pathway
70
Name the Cerebellar Deep Nuclei:
Dentate- contributes most fibers in SCP
Fastigal
Interposed nucleus
- Emboliform
- Globose
(Frosch Gives Everyone D's)
71
Give and overview of the cerebellar circuitry
Inputs arrive via the ICP and the MCP (mostly). The cortex does its thing and sends info to the deep nuclei. The deep nuclei send projections (mostly SCP) to other parts of brain.
72
Name the 3 layers of the cerebellar cortex from superficial to deep:
- Molecular layer
* contains purkinje cells, dendrites, and granule neuron axons
- Purkinje cell layer
* only axons to leave cortex
- Granule layer
(white mater on very inside)
73
What is a microzone?
A group of purkinje cells all having the same somatotopic receptive field. They contain on the order of 1000 purkinje cells each, arranged in a long, narrow strip, oriented perpendicular to the cortical folds
74
What are the 3 fibers found in basic cortical circuitry of the cerebellum?
Climbing fiber
- axon from contralateral inferior olivary nucleus
* major cortical input
Mossy fiber:
- input from brainstem (pons), vetibular system, and spinal cord (sensory)
* major cortical input
Parallel fiber
- axon from granule neuron/ cell
75
Describe the synaptic pathway starting with the Mossy fibers:
Mossy fibers will synapse on granular cells, which will synapse on parallel fibers, which will synapse on purkinje fibers.
76
Describe the synaptic pathway of climbing fibers
Climbing fibers emerge medially and ascend the ICP to enter the cerebellum. They then divide into 5 to 10 branches, synapse as the only climbing biver on a purkinje cell.
They regulate purkinje cell firing
The Inferior olivary nucleus gets info from the spinal cord, the red nucleus, and the cerebral cortex
77
Describe the connectivity of cerebellar cortex and deep nuclei
Mossy and climbing fibers send collaterals to deep nuclei before axon enters cortex
Purkinje cell axons end in deep nuclei
Deep nuclei have two neuronal populations
- source of mossy fibers into cortex
- projection neurons whose axons leave cerebellum
78
Each cerebellar zone is related to a particular deep nucleus. Pair them now
Pontocerebellum (Neocerebellum)(Lateral hemisphere)= dentate nucleus
Spinocerebellum (Paravermal)(medial hemisphere)= Interposed nucleus
Vestibulocerebellum (Flocculonodular lobe)(Vermis parts)= Fastigial nucleus
79
Vestibulocerebellum Inputs, outputs, location, and function.
```
Input:
- Vestibular end organ
- Vestibular nuclei
Cerebellar location:
- Flocculonodular lobe
- Vermis (part of)
Output:
- Fastigial nucleus
*Vestibular nuclei
- Vestibular nuclei
Function:
- Control of eye movements in response to head movements
- balance
```
(this is the most ancient part of the cerebellum)
80
Spinocerebellum Inputs, outputs, location, and function.
```
Input:
- Spinal cord (spinocerebellar tracts)
- Brainstem (trigeminal afferents)
Cerebellar location
- paravermal area
- vermis (part of)
Output:
- Interposed nucleus
*Red nucleus (magnocellular portion)
+ rubrospinal and reticulospinal pathways
*VA/VL of thalamus
+ limb area of primary motor cortex
```
Function:
- Coordination of trunk and limb movements.
81
Pontoocerebellum Inputs, outputs, location, and function.
Input:
- motor cortex- basilar pons- middle cerebellar peduncle
Cerebellar location:
- lateral cerebellar hemisphere
Output:
- Dentate nucleus
* Red nucleus (paravocelllular portion)
+ inferior olivary nucleus
* VA/VL of thalamus
+ all motor cortex and parietal love
Functions:
- Planning the timing of movements especially those of the upper extremity
- coordination of speech
(Some say this is the largest pathway in the brain)
82
What are the functions of the Lateral hemisphers of the cerebellum?
Planning learned, skillful movements, those that become more precise and rapid with practice.
- Injury: Involvement of arm and speech
* intention tremor
* Dysdiadochokinesia- rapid alternating movements
* Dysmetria- finger to nose test
* Dysarthria- scanning or explosive speech
83
What are the functions of the medial hemisphers of the cerebellum?
Adjusting limb movements.
84
What are the functions of the vermis of the cerebellum?
Postural adjustments
| - injury: truncal ataxia; disturbances in balance while seated, also standing and gait ataxia
85
What are the functions of the Flocculus and vermis of the cerebellum?
Eye movements
86
What is nystagmus?
back and forth eye movements
87
What part of the cerebellum may be effected by drinking too much?
Vermis
88
The cerebellum projects to what side of the thalamus?
Contralateral
89
Thecerebellum controls what side of the limbs
Ipsilateral
