Flashcards in Cerebral Cortex II Deck (23)
Label the lateral brain.
What is most of the cortex composed of?
Association areas (that will interpret and analyze the information). See slide 6.
Describe the language localization of the brain.
Broca's area (motor area of speech, produces language) and Wernicke's area are connected through arcuate fasciculus which helps the two areas communicate
L hemisphere is dominant for language (around the lateral fissure)
Describe how to clinically test for aphasic syndrome of Broca motor area.
Verbal fluency, repetition, comprehension, and naming.
Lesion site 1
Verbal fluency: nonfluent
verbal repetition: poor
verbal comprehension: good
verbal naming: poor
Describe how to clinically test for aphasic syndrome of Wernicke's area (sensory).
Verbal fluency, repetition, comprehension, and naming.
Lesion Site 2
verbal fluency- fluent
verbal repetition- poor
verbal comprehension- poor
verbal naming- poor
What is reticular formation?
coordination network for the brainstem nuclei
network within the brainstem, though it continues rostrally into the thalamus and hypothalamus and caudally into the propriospinal network of the spinal cord
a "coordinating system" (Like the limbic system) with "connections" to sensory, somatic motor and visceral motor systems
Describe what the reticular formation receives and generates. Discuss its unique cytoarchitecture.
receives specific premotor afferents
generate coordinated output to nearby motor or sensory nuclei
unique cytoarchitecture (allows convergence of somatosensory information and divergence of efferent outputs)
Discuss the range of functions of the reticular formation.
pattern generator (eye, chewing, swallowing, coughing, sneezing, locomotor)
centers for respiratory/CV/micturition control (basic autonomic function)
1. Pattern generator
- eye movements; horizontal (PPRF) and vertical (riMLF)
-rhythmical chewing movements (pons)
-posture and locomotion (midbrain and pons)
-swallowing, vomiting, coughing and sneezing (medulla)
2. Respiratory control (medulla); expiratory, inspiratory, apneustic and pneumotaxic
3. Cardiovascular control (medulla); vasomotor pressor/depressor, cardioacceleratory and inhibitory
-afferents arise from baroreceptors (carotid sinus and aortic arch), chemoreceptors (carotid sinus, lateral reticular formation chemosensitive area in the medulla) and stretch receptors (lung and respiratory muscles)
-efferents arise from RF neurons within the pons and medulla
4. Sensory modulation or "gate" control
-term "gating" refers to "modulation" of synaptic transmission from one set of neurons to the next
Describe the organization of the reticular formation. How is it subdivided? Give details.
Subdivided into three neuronal "cell columns" (medial to lateral) as well as on the basis of their neurotransmitter release
median (midline) reticular formation - Diffuse Modulatory System
-essentially a column of serotonergic neurons (series of raphe nuclei)
paramedian reticular formation (contains the largest cells) - "efferent" zone (Effector Zone)
Locations: medulla (Ventral reticular nucleus and Gigantocellular reticular nucleus
pontine (Caudal pontine nucleus and PPRF)
Lateral reticular formation "afferent" zone (sensory zone)
extends from medulla to pons
receives collaterals from all sensory pathways including special senses
projects to the paramedian zone
Describe the RF afferents.
Primarily project to the gigantocellularis, caudal and oral pontine nuclei - the medial or paramedian group
1. Corticoreticular- motor and premotor cortex onto neurons of origin of the reticulospinal tract (medial group), provides mechanism of cortical feedback
2. Tectoreticular - superior colliculi origin
3. Cranial nerves (trigeminal, vestibular, auditory and CN IX and X) - project to the lateral parvocellular area
4. Cerebelloreticular -primarily from the fastigal nucleus
5. Spinoreticular - receives collaterals from spinothalamic tract, widespread bilateral distribution, no somatotopy
Describe RF efferents.
(arise from the gigantocellularis, caudal and oral pontine nuclei - the medial group)
Spinal cord termination - pontine and medullary reticulospinal tracts
-descend bilaterally, terminate in intermediate gray of spinal cord
-effect on axial muscles of posture and locomotion
Brain stem termination - reticulobulbar tract and Central tegmental tract
- indirect to cranial nerve motor/sensory nuclei, direct to dorsal column and parasympathetic nuclei
- thalamus, hypothalamus, basal forebrain nuclei, amygdala, medial septal nuclei
Describe the Diffuse Modulatory Systems. Where do they lie? What does it play a role in?
What projects to it?
-Lie around the borders of the RF
-Cytoarchitecture is different than RF
- = Ascending Reticular Activating System (ARAS) - a role in level of alertness, sleep-wake rhythms and alerting (startle) reactions)
- Play a role in activation of the cerebral cortex, but there are other "participants" :
1. cholinergic neurons close to the locus ceruleus
2. orexin (neuropeptide) - tuberomammillary body
3. acetylcholine secreting neurons - basal nucleus of Meynert
Cerebral cortex projects to the DMS
- influences alertness (as can visual, auditory and mental imagery)
- inhibits other sensory input, allows focusing of attention
Diffuse Modulatory System
What is the function of the serotonergic and adrenergic systems?
Where do they originate from?
-sleep and arousal mechanisms
-integrative behavioral and neuroendocrine functions
-modulate actions of other neurotransmitters
-brain growth and development
Substantia nigra and ventral tegmental nucleus- dopamine
raphe nuclei- serotonin
Locus ceruleus- noradrenaline
Describe Raphe nuclei. What is it an origin of? What does it receive afferents from?
(important in the diffuse modulatory system) SEROTONIN
Largest territorial distribution of any CNS neurons
midbrain- projects to cerebral cortex
pons- ramifies in brainstem and cerebellum
medulla- projects to spinal cord
origin of serotonergic projections to widespread areas of cerebral cortex, cerebellum, brainstem and spinal cord. Afferents from cerebral cortex, hippocampus, hypothalamus and periaqueductal gray.
How are raphe nuclei different than RF?
1. the neurotransmitter they release (serotonin)
2. widespread projection throughout the brain
(can wake up whole cortex, or turn off...)
Describe locus ceruleus.
aminergic neurons in reticular formation
origin of noradrenergic (noradrenaline, norepinephrine) projections to all areas of the CNS (via the central tegmental tract, median forebrain bundle, dorsal longitudinal fasciculus and SCP)
afferents from other reticular nuclei, PAG, hypothalamus, amygdala and prefrontal cortex
What is consciousness?
What is the content/level?
(state of self-awareness in which it is possible to direct attention and manipulate abstract ideas)
Content- reflects activity/interactions of different cortical areas
Level- dependent on diffuse modulation projections
Describe in a broad sense how the diffuse modulating system maintains consciousness. Name the chemical secreted from each location and where it is projected.
Basal nucleus of Meynert
Raphe nuclei (serotonin) - cortex and thalamus
LC (norepinephrine) - cortex and thalamus
Midbrain RF (acetylcholine) - thalamus
Tuberomammillary nucleus (histamine) - cortex and thalamus
Lateral hypothalamus (orexin) - cortex and thalamus
Basal nucleus of Meynert (acetylcholine) - cortex
Describe the role of sleep.
restoration and recovery
consolidation of memory and daily experiences
brain growth and development
brain anabolism (synthesis of glycogen)
"rest" for the body and brain
strategies for prey and predator
programming of innate behavior
(lack of sleep linked to Alzheimer's - diff chemicals in our brains get washed out when we sleep)
(dendritic spines hang around - cramming for a test doesn't produce dendritic spines)
Describe the mammilian circadian system.
Diagram slide 24.
enter REM 60-90 min into sleep
can wake up quick from REM ...brain cycles rapidly between REM/nonREM
EEG - large amplitude, slow frequency, synchronized
Muscle tone- decreased
arousal level- progressively higher
mental activity- vague dreams
autonomic activity-increased parasympathetic, slow regular pulse and respiration
EEG- low amplitude, fast frequency, desynchronized
Muscle tone- almost abolished
arousal level- highest
mental activity- detailed, visual, emotional dreams
autonomic activity- increased sympathetic, irregular pulse and respiration
Discuss/diagram the regulation of sleep-wake cycles.
See slide 28.
suprachiasmatic nucleus (hypothalamus) talks to preoptic area (hypothalamus) which has feedback with medullary reticular formation...both medullary RF and preoptic area turn off wakefulness network (includes ACH, histamine, norepi, orexin, serotonin) which then has effect on REM machinery (pons) and sends input to thalamus