Diencephalon Flashcards
the diencephalon is embedded in the lateral wall of the ___ ventricle
third ventricle
what are the four “thalamus” components of the diencephalon
thalamus (largest, aka dorsal thalamus)
hypothalamus
epithalamus (aka pineal gland)
subthalamus (smallest, aka subthalamic nucleus)
what connects the hypothalamus to the pituitary gland
infunidbulum
what part of the hypothalamus has a role in learning and memory
mammillary neurons
what part of the diencephalon plays a role in the indirect basal ganglia pathway, suppressing unwanted movement by inhibiting the motor cortex?
subthalamus (aka subthalamic nucleus)
what part of the diencephalon is particularly sensitive to lacunar strokes
subthalamus- part of indirect pathway of basal ganglia to suppress movement. lacunar stroke results in hemiballismus (violent limb flinging) contralateral
(ventral basal complex is here)
the diencephalon is located medial to the fibers of the posterior limb of the…..
internal capsule (massive bundle of axons carrying all axons into/ out of each cerebral hemisphere)
positioned directly below the hypothalamus are the axons of the ____
optic chiasm
relay thalamic nuclei vs generalized thalamic nuclei
relay- project to restricted, functionally specific regions of cerebral cortex
generalized- project to multiple wide areas of less specific functional cortex (association cortex)
T/F: specific nuclei of the thalamus are usually relay nuclei
TRUE. designed for preservation of information transfer from specific motor/sensory system to specific area of cerebral cortex
what are the specific (relay) nuclei of the thalamus (5)
- lateral geniculate nucleus
- medial geniculate nucleus
- anterior nucleus
- ventral basal complex: VPL (ventral posterolateral)/ VPM (ventral posteromedial)
- VA (ventral anterior)/ VL (ventral lateral)
anterior nucleus of the thalamus receives what kind of input from where? where does it then project to?
receives afferent input from mammillary nuclei in hypothalamus
projects to cingulate gyrus (in cortex) directly above corpus callosum
which nucleus of the thalamus is part of the Papez circuit of limbic connections, which plays a role in memory processing
anterior nucleus- receives afferent input from mammillary nucleus of hypothalamus, projects to cingulate gyrus in cortex
what are the motor nuclei of the thalamus? how do they differ in the input they receive?
VA/VL- ventral anterior and ventral lateral
VA: input from substantia nigra pars reticularis (GABA) and internal segment of globus palidus (GABA)
VL: input from deep cerebellar nuclei and internal segment of globus palidus and substantia nigra
VL gets input from both motor control structures while VA gets input only from basal ganglia structures
where does the ventral lateral nucleus of the thalamus project
VL receives input from both motor control structures (basal ganglia and cerebellum). cerebral part projects to precentral gyrus (primary motor cortex). basal ganglia part projects to frontal lobe
what is the role of the ventral basal complex of the thalamus?
VPL and VPM: receive somatotopically organized input
VPL (ventral posterolateral) relays limb/ trunk body wall sensation to somatosensory cortex
VPM (ventral posteromedial) relays cranial nerve touch and pain proprioception (head and neck)
which thalamic nuclei relay input from the medial lemniscus and spinothalamic tract?
ventral basal complex:
VPL- spinal components
VPM- trigeminal components (cranial nerves)
which thalamic nuclei is the site of termination of touch, proprioception, pain, and temp sensation from cranial nerves, but also taste information from CN VII, IX, and X?
VPM of ventral basal complex
(ventral posteromedial)
carries taste input to solitary nucleus and then to somatosensory cortex
this occurs when there is a disruption of the very small blood vessels supplying the thalamus on one side (thalamoperforating arteries) that arise from proximal part of posterior cerebral artery
lacunar stroke
what are the symptoms of a lacunar stroke
stroke of thalamoperforating arteries arising from proximal part of posterior cerebral artery. affects ventral basal complex
causes pure sensory stroke- initial complete anesthesia of all sensation from contralateral side of body. May progress to central thalamic pain syndrome, in which chronic aching and burning replaces initial analgesia. Does not respond to analgesic medication (which target brainstem or spinal cord)
will central thalamic pain syndrome caused by a lacunar stroke respond to analgesic medication
no- these medications target brainstem or spinal cord, not at the level of diencephalon
(lacunar stroke affects ventral basal complex of thalamus)
contrast the embryonic origins of the anterior and posterior pituitary and the implications of this difference
anterior- dorsal outgrowth of oral cavity ectoderm called Rathke’s pouch (hypothalamus must interact indirectly via portal vein)
posterior- neural ectoderm, ventral outgrowth of hypothalamus (hypothalamus can interact directly via axons)
Rathke’s pouch
dorsal oral cavity ectoderm that anterior pituitary develops from
craniopharyngioma develops from what?
consistent remnants of Rathke’s pouch, from which anterior pituitary develops, which compresses parts of optic chiasm above
which part of the pituitary gland does NOT contain neuroendocrine cells, but rather axons and axon terminals
posterior pituitary- direct outgrowth of hypothalamus via infundibulum
paraventricular and supraoptic nuclei
the axons of the posterior pituitary are direct outgrowths of these 2 hypothalamic nuclei:
paraventricular (PARA)
supraoptic
both produce/secrete oxytocin and vasopressin (ADH)
what are the two hypothalamic nuclei that control the anterior pituitary via release of releasing/inhibiting factors into portal vein system that traverses down infundibulum?
arcuate nuclei
periventricular (PERI)
a bilateral lesion of the paraventricular nuclei or supraoptic nuclei, or destruction of the infundibulum, would have what effect?
affects posterior pituitary (oxytocin and vasopressin)
–> diabetes insipidus (excess water consumption and excess urination)
a lesion to the hypothalamic portal vein would have what effect?
affects anterior pituitary via inhibiting passage of releasing/ inhibiting factors of arcuate and periventricular nuclei. Mostly results in decrease in hormone production, except for prolactin which is increased because it is normally inhibited by dopamine
what is the function of the preoptic nuclei (telencephalic) that are situated rostral to the optic chiasm and adjacent to the lamina terminalis (which separates diencephalon from telencephalon)
preoptic nuclei produce GNRH (gonadotropin releasing hormone). released into hypophyseal portal system (tubuloinfundibular tract) and influence gonadal hormones in anterior pituitary
tubuloinfundibular tract
hypophyseal portal system from hypothalamus to anterior pituitary
surrounding the three regions of hypothalamic nuclei is the ____ zone, and on the medial wall of the 3rd ventricle is the _____ zone that is stretched throughout the length of the hypothalamus
surrounding the three regions of hypothalamic nuclei is the LATERAL HYPOTHALAMIC zone, and on the medial wall of the 3rd ventricle is the PARAVENTRICULAR zone that is stretched throughout the length of the hypothalamus
what are the three major regions of nuclei in the hypothalamus?
supraoptic nuclei tuberal nuclei (related to structure of anterior pituitary, major source of arcuate nuclei) mamillary nuclei (largest, most posterior)
these nuclei in the supraoptic zone of the hypothalamus are sexually dimorphic, in that it is large in males but cyclically changes in size in females
medial preoptic nuclei- releases GNRH
what are the three major types of nuclei in the supraoptic region of the hypothalamus?
medial preoptic nuclei (GNRH to anterior pituitary) supraoptic nuclei (oxytocin/ vasopressin to posterior pituitary) suprachiasmatic nuclei (receives retinal input, coordinates circadian rhythm)
the visceral centers of the brain controlling gastrointestinal, reproductive, heart, lung, etc- know when it is light/ dark out because they are indirectly informed by what region of the hypothalamus?
suprachiasmatic nuclei in the supraoptic zone of the hypothalamus
what are the nuclei of the tuberal zone of the hypothalamus?
arcuate (most prominent, regulate anterior pituitary hormones via portal system)
periventricular (same function as arcuate)
ventromedial (satiety center- when VMH is damaged one is very much hungry, regulated by leptin)
match:
arcuate and periventricular nucleus
with
gonadotropic releasing hormone, prolactin inhibiting hormone (dopamine)
or
growth hormone releasing hormone, growth hormone inhibiting hormone (somatostatin), thyroid releasing hormone
arcuate nucleus- gonadotropic releasing hormone, prolactin inhibiting hormone (dopamine)
periventricular nucleus- growth hormone releasing hormone, growth hormone inhibiting hormone (somatostatin), thyroid releasing hormone
where is the lateral hypothalamic zone that regulates hunger, and is partner to the ventromedial nucleus (which regulates satiety)
found in diffuse area out in whole lateral zone of the hypothalamus (surrounding the 3 zones of hypothalamus)
(when LH is damaged one lacks hunger)
the Papez circuit for memory consolidation involves which zone of the hypothalamus?
mammillary nuclei
what emotional center of the brain is the hypothalamus extensively connected to?
amygdala- major source of input to mammillary nuclei, which are part of Papez circuit of limbic connections and memory consolidation
to what zone of the hypothalamus does the fornix provide input?
mammillary nuclei (memory consolidation, limbic system). fornix is fiber bundle that is outflow pathway of hippocampus. memory consolidation- taking info from short to long memory
Korsakoff’s syndrome/ psychosis
preferential degradation of mammillary nuclei in hypothalamus, due to alcoholism or vitB1 (thiamine) deficiency
Wernick’es encephalopathy
due to alcohol- mental changes, blurry vision, gait ataxia, confusion
precedes Korsakoff’s syndrome
how does parasympathetic vs sympathetic innervation by hypothalamus differ
projection to visceral autonomic neurons is bilateral (both para/sympathetic)
sympathetic projection to preganglionic sympathetic neurons from T1 to L2 is ipsilateral (damage–> ipsilateral central Horner’ syndrome)
match: anterior and posterior part of the hypothalamus, and sympathetic/ parasympathetic
anterior - parasympathetic
posterior - sympathetic
which part of the hypothalamus, anterior or posterior, contains histaminergic neurons that project to cholinergic neurons in the brainstem to maintain arousal?
posterior zone
projecting off the posterior aspect of the diencephalon, and suspended over top of the pretectal area and the superior colliculi of the midbrain, and directly above the posterior commissure (crossing axons connecting one pretectal area to another) is what?
pineal gland (epithalamus). attached by a small stalk to the roof of the third ventricle
T/F: pineal gland does not contain neurons
TRUE; contains pinealocytes (secretory) and glial cells
produce melatonin, serotonin, CCK (cholecystokinin)
major source of input to pineal gland
light
regulating secretory activity of pineal gland?
retinal suprachiasmatic (supraoptic zone of hypothalamus) sympathetic pineal pathway (major source of input is light- regulates melatonin)
what connections allow the suprachiasmatic nucleus to influence the pineal gland?
- suprachiasmatic nucleus (supraoptic zone of hypothalamus)
- hypothalamospinal tract to intermediolateral cell column at T1-L2
- T1/T2 axons climb up sympathetic trunk to superior cervical ganglion which gives rise to plexus of axons that run on carotid system of arteries
- pineal gland
what plexus of axons regulates and controls all sympathetic innervation inside and outside the skull
plexus of axons that run on carotid system of arteries
most common site of calcification in the CNS
pineal gland- age related, leads to insomnia
a tumor in this part of the brain may compress the upper area of the midbrain, causing obstruction of CSF through cerebral aqueduct –> non-communicating hydrocephalus
pineal gland
tumor in this area of the brain may cause Parinaud syndrome, due to compression of upper part of midbrain in area of superior colliculus, pretectal area, and posterior commissure –> elevated intracranial pressure and impaired conjugate vertical gaze and Argyll Robertson pupil
pineal gland
Parinaud syndrome
compression (possibly by pineal tumor) of upper part of midbrain, affecting superior colliculus (-> impaired conjugate vertical gaze), pretectal area (–> Argyll Robertson pupil), posterior commissure
