Hypothalamus, Thalamus, RAS Flashcards
Explain the boundaries of the hypothalamus.
Dorsal - sulcus limitans Medial - third ventricle Rostral - lamina terminalis Ventral - infundibulum Caudal - posterior mammillary bodies Lateral - no precise lateral border
Half way between the optic chiasm and mamillary bodies and represents the median eminence.
infundibulum
Functions of the hypothalamus.
blood osmolality (chemoreceptors), blood pressure control (carotid sinus), childbirth and lactation (oxytocin and prolactin), thermoregulation, food/fluid intake and output control, emotional control (motor aspects), sex drive (sexual orientation/behaviors)
Dysfunction in hypothalamus causing uncontrollable eating.
Prader Willi syndrome
Two pathways of the infundibulum to the pituitary.
Posterior: neural - contains axons that communicate with posterior portion of pituitary gland
Anterior: vascular - “hypothalamic portal system” and carries hormones through vasculature to anterior portion pituitary
Hypothalamic nuclei in the pre-optic and supraoptic tier.
suprachiasmatic nuclei, preoptic nuclei, anterior nuclei, paraventricular nuclei
Hypothalamic nuclei in the tuberal tier.
ventral nuclei, lateral nuclei, dorsal nuclei
Hypothalamic nuclei in the mamillary tier.
posterior nuclei and mamillary bodies
What is medial to the pairs of nuclei in the hypothalamus?
third ventricle
Functions of Pre-Optic Tier/Nuclei.
bladder control, heart rate, temperature
Functions of Supraoptic Tier/Nuclei.
water conservation, oxytocin release
Functions of Tuberal Tier/Nuclei.
thirst/hunger, emotions/rage
Functions of Mamillary Tier/Nuclei.
blood pressure, feeding reflexes, shivering/sweating
Connections of hippocampus.
connected via fornix to septal nuclei (ant. commissural fornix) and to mammillary nuclei (postcommissural fornix); connected via nuclei to anterior nucleus of the thalamus and via that to cingulate gyrus (limbic system)
Anterior Lobe: Adenohypophysis (Pituitary)
Hypothalamo-hypophyseal Portal System: made of intricate channels (venous) of released hormones from various nuclei of hypothalamus trophic hormones are released from pituitary into the body for physiological responses
Which tiers are primarily connected to the anterior pituitary?
pre-optic and tuberal tier
Posterior Lobe: Neurohypophysis (Pituitary)
Hypothalamo-hypophyseal Tract: from paraventricular nucleus and supraoptic nucleus to posterior pituitary; direct neuronal synapses in posterior pituitary
Hypothalamus is major controller of our _________ system.
endocrine (homeostatic mechanisms)
Neurotransmitters released from posterior pituitary?
ADH and oxytocin
The release of trophic hormones from the anterior lobe of the pituitary is considered a fast/slow response.
slow
The release of ADH from the posterior lobe of the pituitary is considered a fast/slow response.
fast
Explain the feedback loops to the hypothalamus for endocrine function.
short feedback loops: pituitary to hypothalamus
long feedback loops: endocrine organs/visceral organs to hypothalamus (neural - visceral organs to the brain and then to hypothalamus; metabolic - electrolytes, pH, CO2 receptors then to hypothalamus
Composes the diencephalon.
hypothalamus, thalamus, epithalamus (optic nerves and tract are an extension of the diencephalon)
Epithalamus
posteriorly above the thalamus and interconnected to the hypothalamus & septum basal forebrain (stria terminalis pathway)
Boundaries of the thalamus.
medial boundary: third ventricle
dorsal boundary: epithalamus
lateral boundary: internal capsule (posterior limb)
inferior boundary: hypothalamus
True/false: All sensory systems go through the thalamus.
false - all except smell
General physiological features of the thalamus.
chief sensory and motor relay station, multimodal integration, input/output modulation, alertness
Separates the anatomical divisions of the thalamus.
Y shaped white matter band called intramedullary lamina
What is the largest division of the thalamus?
lateral (closest to posterior limb of internal capsule)
Interthalamic nuclei - (subdivisions of the lateral division of the thalamus)
1: nonspecific nuclei (archithalamus) - not associated with specific motor/sensory input, oldest portion of the thalamus
2: specific nuclei (paleothalamus) - associated with specific motor/sensory functions
3: association nuclei (neothalamus) - integration
Archithalamus (midline)
modify visceral Input (heart, gut, sweat glands), get information about state of visceral organs (midline nuclear group); modify sensory inputs from musculoskeletal system (reticular); alertness and emotional responses to pain (intralaminar)
Paleothalamus (lateral)
Ventral Anterior Nucleus (VA) - modify basal ganglia input, interconnection between basal ganglia and motor cortex
Ventral Lateral Nucleus (VL) - modifies cerebellar input from dentate nucleus
Ventral Posterior Nucleus (VPL/M) - modifies somatosensory Input from body (VPL) and head (VPM); if lesion existed, pt would present with no sensations of body or head (homunculus)
Medial Geniculate Nucleus (MGB) - modifies auditory input from cochlear to temporal lobes
Lateral Geniculate Nucleus (LGB) - modifies visual input from retina
Neothalamus
Dorsal Tier Nuclei - sensory modification to association corteses (visual, auditory, visceral, etc)
Anterior Nuclei - sensory modification to limbic area (cingulate gyrus)
Dorsomedial nucleus - sensory modification to prefrontal cortex (affects executive function)
Pulvinar - sensory modification to occipital cortex (visual)
Functional supersystems of the thalamus.
“Motor” Thalamus - VA / VL Nuclei, get information from basal ganglia and cerebellum (reentrant systems), both modify movement (DON’T cause it)
“Limbic” Thalamus - Anterior Nuclear Group
“Sensory” Thalamus - VPL/VPM, MGB, LGB
“Cognitive” Thalamus - Pulvinar, Dorsomedial nuclear group
Explain how patients with thalamic lesions would present.
Extrapyramidal Motor Problems (difficult time controlling movement); Primary Sensory Deficits with Hyperpathic Components (exaggerated sensations); Emotional Disorders (commit suicide); Disorders of Cognitive Function (pt. no longer behave in normal ways)
Where is the reticular activating system located?
neural networks through the brainstem, between medulla and midbrain
Nuclear groups of the reticular activating system.
Raphe (midline) Nuclear Groups (serotonin -sleep/wake cycle ascending to higher levels; enkephalin - pain modulation descending to lower levels of spinal cord)
Central Nuclear Groups (arousal, motor control will affect movement via the hypothalamus of the ANS)
Lateral Nuclear Groups (filter ascending/descending sensory information)
Pre-Cerebellar Groups (filter ascending/descending proprioceptive information
Cellular morphology of the reticular activating system.
diffuse projections to both higher and lower levels; contain a single large cell body, large dendritic axonal area; two axons - one to higher levels (caudal) and one to lower (rostral) with multiple collateral branches, allows for fast conduction of information over large distances (BIPOLAR neurons)
Ascending pathways of the RAS.
wakefulness/attention
Descending pathways of the RAS.
pain control (allow you to keep functioning in pain during fight/flight)
Lesions at the pons/midbrain with damage to both hemispheres.
coma
Lesions at pons/medulla.
persistent wakefulness
What occurs during synchronized (non-REM) sleep?
surge in serotonin (Raphe) and block eye movement, creates a synchronized EEG, and normal muscle tone
What occurs during paradoxical (REM) sleep?
serotonin surge stops, surge of norepinephrine (locus coeruleus) - restoring eye movement, restore normal fast cortical waves, and shutdown muscle tone
Which type of sleep is most beneficial to rejuvenate the body?
non-REM
Sleep cycles are completed in about how many minutes?
90
In which type of sleep might the vital signs fluctuate?
REM
In which type of sleep is muscle tone normal?
non-REM
