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60 Cards in this Set
- Front
- Back
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Where is the tegmentum located?
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Anterior to the ventricular space
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What does the tegmentum contain?
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Outer tube: cranial nerve nuclei and nerve roots, ascending pathways (medial lemniscus, ALS, spinocerebellar tracts), also some descending pathways
Inner tube: Reticular formation |
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In general, the function of the reticular formation is?
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Modulatory
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Where is the basal brainstem located?
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Appended to the anterior surface of the brainstem
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What is included in the basal brainstem?
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The pontine enlargement, corticospinal fibers, pyramids of the medulla, crus cerebri and substantia nigra of the midbrain
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Where is the tectum located?
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Posterior to the ventricular space of the midbrain only
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What does the tectum consist of?
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The superior and inferior colliculi
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What three structures are contained in the basal pons?
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Corticospinal tracts, pontine nuclei and pontocerebellar fibers
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Which two structures are contained in the basal midbrain?
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Crus cerebri and substantia nigra
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At what level of the brainstem is the decussation of the superior peduncles found?
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Midbrain, within the tegmentum
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What is the reticular formation?
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A group of diffusely organized cells arranged in ill-defined clusters and mixed with fibers coursing in longitudinal and transverse directions in the brainstem
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What is the rostral-caudal extent of the reticular formation?
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Caudal- intermediate zone of the spinal cord
Rostral- continuous withe the diencephalon |
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What type of neurons does the reticular fomation contain?
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Isodendritic- all are similar in structure and can respond to many different kinds of stimuli; axons may bifurcate and ascend or descend long distances
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What type of problems is associated with the reticular formation?
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Psychological
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What are the three functional zones of the reticular formation?
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Median zone, medial zone and lateral zone
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Where is the median zone what does it contain?
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Midline reticular formation; Raphe nuclei
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Which neurotransmitter is made and used by cells of the Raphe nuclei?
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Serotonin
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What does the medial zone contain?
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Locus ceruleus; large cells (magnocellular) whose axons project to all areas of the CNS
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Which neurotransmitter do the cells of the locus ceruleus make and use?
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Norepinephrine
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What type of cells are in the lateral zone and what are they concerned with?
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Small cells (parvocellular); concerned primarily with cranial nerve reflexes and visceral functions
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What are the four general functions of the reticular formation?
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1. Control of movements through connections with spinal cord and cerebellum
2. Descending pain modulation 3. Control of autonomic reflex circuitry 4. Control of arousal and consciousness |
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What are the mesencephalic and rostral pontine (pontomesencephalic) reticular formation concerned with?
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Modulation of forebrain activity
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What are the caudal pontine and medullary reticular formation concerend with?
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Premotor coordination of lower somatic and motor pools
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Where do ascending projections from the reticular formation terminate?
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Thalamus, subthalamus, hypothalamus, basal ganglia and cerebral cortex
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What two things are required for consciousness?
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Intact cerebral cortex and input from the ARAS of the reticular system, via the thalamus
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Bilateral damage to neurons of the midbrain reticular formation and fibers passing through it result in what?
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Prolonged coma
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Modulation of the ARAS has a basic role in what?
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Sleep-wakefulnes cycle
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What provides for a normal state of consciousness?
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Collaboration of the ARAS with the monoamine-containing, transmitter-specific diffuse systems to modulate the cortex
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What is the neurotransmitter of the pontomesencephalic neurons?
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Not known for certain
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What are the major inputs to the pontomesencephalic reticular formation?
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Sensory pathways (especially ALS spinoreticular pathway involved in pain transmission), numerous regions of association cortex and limbic cortex (provide info on cognitive processes and emotion), superior colliculi, cerebellum and thalamic reticular nucleus are all involved in alertness
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What are the two components of consciousness?
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Arousal and awareness
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What is arousal?
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Wakefulness
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What provides arousal?
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The ARAS, through projections of the thalamus, hypothalamus and basal forebrain area.
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What is awareness?
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Cognition- comprehension of self and the ability to manipulate abstract ideas
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What does awareness involve?
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Proper functioning of the cerebral hemispheres
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What are cholinergic neurons of the basal forebrain area involved in?
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Tonic cortical activation and arousal
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Where in the brain can a lesion cause coma?
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1. Dysfunction of the upper brainstem reticular formation
2. Dysfunction of extensive bilateral regions of the cerebral cortex 3. Also bilateral lesions of the thalamus, esp. involving the medial and intralaminar regions |
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What are the main excitatory and inhibitory neurotransmitters in the CNS?
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Glutamate and gamma-aminobutyric acid (GABA)
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On what do the functional effects of neuromodulation depend on?
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The region of brain being modulated
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What are some of the effects of neuromodulation?
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Effects on level of consciousness, the sleep-wake cycle, emotional states, motor behavior, and other diverse functions
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What results from lesion or blockade of ACh neurotransmitterr systems?
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Profound confusion and drowsiness, but not coma
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Where are neurons containing norepinephrine located?
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In the locus ceruleus and lateral tegmental area of the pons and medulla
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What types of modulations are noradrenergic projections involved in?
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Attention, sleep-wake states and mood
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Where in the brain is serotonin (5HT) found?
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In neurons of the raphe nuclei of the midbrain, pons and medulla
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In what types of psychiatric syndromes are serotonergic pathways believed to play a role in?
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Depression, anxiety, obsessive-compulsive disorder, aggressive behavior, and certain eating disorders
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Where in the brain is dopamine found?
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Substantia nigra, pars compacta and the ventral tegmental area
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What three dopaminergic projection systems have been described?
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The mesostriatal, mesolimbic and mesocortical systems
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What does dysfunction of the mesostriatal system produce?
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Movement disorders such as Parkinson disease
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In what is overactivity in the mesolimbic pathway thought to be important?
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the "positive" symptoms of schizophrenia, such as hallucinations
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Damage to the mesocortical dopaminergic pathway may be important for what?
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Some of the cognitive deficits and hypokinesia seen in Parkinson disease, and in the "negative" symptoms of schizophrenia; also therapeutic treatment with drugs that block dopamine receptors
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What is the mesolimbic system involved in?
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Pleasure and
addiction that accompanies abuse of certain drugs |
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Which nucleus is associated with pleasure and addiction related to the limbic system?
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Nucleus acumbens in the ventral tegmental area
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Where are brainstem Ach neurons located?
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In the laterodorsal tegmental nuclei and the pedunculopontine tegmental nuclei
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Where do brainstem Ach neurons project to?
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The thalamus which in turn projects to widespread areas of the cortex
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Where do acetylcholinergic neurons in the nucleus basalis of Meynert project to?
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Directly to almost all areas of the cortex
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Where do Ach neurons from the basal forebrain area project to?
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The hippocampus where they play a role in memory functions of this brain region
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Which type of neurons are selectively damaged in Alzheimer's Disease?
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Basal forebrain cholinergic neurons
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Memory deficits similar to the cognitive symptoms of Alzheimer's Disease can be induced by what?
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Drugs which block central muscarinic ACh receptors
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Histaminergic projections to the forebrain may be important in what?
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Maintaining an alert state
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Altered states of consciousness are incuced by?
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Focal damage to the brainstem/diencephalon or
diffuse damage to the cortex |
