Ch. 15/16: Thalamus & Hypothalamus (2/2) Flashcards
Function of Dorsal Thalamus
Largest of 4 subdivisions and neurons project to all areas of the cortex (sensory). Some nuclei receive info from subcortical and cortical motor areas and send to cortex.
Hypothalamus
Connected to forebrain, brainstem, and spinal cord, controls autonomic function
Ventral Thalamus
subthalamic nuclei; connected to basal ganglia and functions in motor circuitry
Epithalamus
Limbic system- habenula and pineal gland
Association Nuclei
Anterior Thalamic Nuclei, Dorsomedial nucleus, lateral dorsal, Pulvinar, Lateral posterior.
Generally medial/anterior, memory and decision making
Relay Nuclei
VPL, VMP, Lateral geniculate, medial geniculate, ventral anterior, ventral lateral
Sensory and motor information
What myelinated axons surround the thalamus laterally (fibers that enter/leave subcortical white matter, associated with thalami reticular nucleus)
External medullary lamina
What divides the thalamus into cell groups?
Internal Medullary Lamina, divides dorsal medial nucleus and anterior from the rest of the thalamus
Thalamus processes _______ info and relays it to _____
sensory-motor info
nucleus
Pulvinar processes ____ info
visual
Ventral part of thalamus: the medial and lateral geniculate bodies
Medial Geniculate Body (auditory info)
Lateral Geniculate (sensory, gets ganglion inputs)
3 generalizations about dorsal thalamus
- All nuclei project to cortex
- Projections are ipsilateral
- No known projections between nuclei, expect TRN
White matter that communicates between thalamus and cortex
Internal Capsule
Subthalamus (ventral thalamus)
motor functions
Subthalamic nuclei: inputs from motor cortex and projects to substantia nigra and globus pallidus.
Subthalamus is below the dorsal thalamus. Has to do with motor functions. Connects with globus palladus
Epithalamus
Pineal gland, habenular nuclei, stria medullaris thalami (which is fiber tract)
Pineal Gland
receives info about visual stimuli (rhythmically produces melatonin (circadian over 24 hour period)
Habenula
medial and lateral nuclei - part of limibic system. Role in processing rewards and addiction
Hypothalamus: Functions
Homeostasis, Metabolism, Temperature, food intake, glucose, blood flow (blood volume, pressure, salinity, O2, glucose), reproductive activity, menstruation, stress, child birth, autonomic reflexes of brainstem and spinal cord, functions of various nuclei, periventricular zone has more specific nuclei, neuroendocrine function, Leptin in feeding around the arcuate/lateral hypothalamus.
Olfactory info to hypothalamus —>
amygdala in median forebrain bundle involved in reproduction defense, feeding
visual inputs
suprachiasmatic nucleus, circadian rhythems
Visceral Sensations: Sensory info arises from nucleus of the ___ ___. Sensory info from cranial nerves ___ & ___.
solitary tract
cranial nerves 9 & 10
Hypothalamus has 3 broad zones:
Periventricular zone: neurosecretory, Automatic nervous system (ANS)
Lateral/medial zones: motivation, sex, stress
Hypothalamus EFFERENTS (output)
Endocrine system: neuroendocrine cells via pituitary
ANS: preautonomic cells via brain/spinal cord. Projections via medial forebrain bundle and dorsal longitudinal fasciculus.
Hypothalamic AFFERENTS (inputs)
Ascending sensory signals from brainstem/spinal cord
Descending afferents from cortex/limbic system
Hippocampus via fornix and amygdala via stria terminalis
Supraoptic nucleus and paraventricular nucleus
Hypothalamus
water/electrolyte balance, vasopressin lactation, and partuition, oxytocin
Paraventricular
Hypothalamus
Stress
Arcuate and paraventricular nuclei
Hypothalamus
hypothalamic releasing factors, arcuate-leptin-regulator of body fat and food intake
Ventromedial and dorsomedial
Hypothalamus
Growth hormone, hunger
Suprachiasmatic
Circadian clock
Anterior and preoptic areas
Regulation of sexual behavior, sleep regulation, temperature regulation
Anterior and posterior nuclei
Temperature regulation
Dorsal and posterior nuclei
Activation of sympathetic nervous system/adrenal medulla
Lateral hypothalamus
Thirst
Hypothalamus connections, in anterior/posterior pituitary where they release ______ into circulation that control various homeostatic functions.
Hormones
Hypothalamus connects to limbic system via ____
Fornix
Hypothalamus connects to what two areas of the brainstem and what do they do?
Reticular formation and medullary centers
Cardiovascular, respitory, and gastrointestinal processes
Vasopressin
Water/electrolyte balance
Oxytocin
lactation, physical contact (positive), possible treatment for autism
Circumventricular Organ Functions
Vasopressin release
Response to hypovolemia (decrease blood volume, hemorrhage)
Kidney secretion of Renin
Activation of vasopressin neurons (SON & PVN, asynchronous burst generation)
Water retention in kidney
Circumventricular Organ: specific process. Adaptive behaviors for water conservation (excrete NaCl)
Blood pressure down, Kidney secretes renin
Renin breaks down angiotensinogen produced by liver into angiotensin 2.
Also activates cells in lateral hypothalamus, produces thirst and motivates drinking behavior (AV3V, OVLT)
Angiotensin 2 effects
Kidney/blood vessel–> increase blood pressure
Subfornical Organ –> Activates vasopressin neurons
Lateral Hypothalamus –> Produces thirst and motivates drinking behavior (AV3V, OVLT)
Once water intake increases, vasopressin levels decrease and dilute urine is excreted.
Posterior pituitary: Neuropophysis
Hypothalamus outcropping (part of the brain) Hormone secretion into general blood stream
Cells in superoptic/paraventricular nuclei project down and release O/V into general circulation (Magnacellular cells)
Anterior Lobe: Adenohypophysis
Controlled by releasing hormone cells in hypothalamic terminals in median eminence, portable blood vessels, pituitary hormone release into general circulation.
Follicle stimulating Hormone
ovulation and spermatogenesis
Luteinizing hormone
sperm and ovarian maturation
Thyroid stimulating hormone
Thyroxin secretion (metabolism)
ACTH
cortisol secretion
Growth hormone
protein synthesis
Prolactin
growth and milk secretion
Regulation of adrenal glands under stress
Parvocellular neurons release corticotropin, releasing hormone into the portal circulation, travels to anterior pituitary to release ACTH travels to the adrenal cortex to release cortisol.
