Anatomy of the hypothalamus Flashcards
(27 cards)
What is the hypothalamus, and what are its primary functions?
The hypothalamus is the ventral-most part of the diencephalon, making up about 4 cm³ of neural tissue. It controls:
Fluid/electrolyte balance
Food ingestion/energy balance
Reproduction
Thermoregulation
Affect/emotional responses
Endocrine and autonomic effector systems
What are the anteroposterior and mediolateral divisions of the hypothalamus?
Anteroposterior:
Chiasmatic (supraoptic/anterior)
Tuberal (infundibulo-tuberal)
Mammillary (posterior)
Mediolateral:
Periventricular
Intermediate (medial)
Lateral
Describe the location and boundaries of the hypothalamus.
Anterior: Lamina terminalis
Posterior: Vertical plane posterior to mammillary bodies
Superior: Hypothalamic sulcus
Inferior: Optic chiasma, tuber cinereum, infundibular stalk, mammillary bodies
Lateral: Subthalamus, internal capsule, optic tract
What are the effects of lesions in:
Ventromedial nucleus
Lateral hypothalamic area?
Ventromedial nucleus: Hyperphagia and obesity (Fröhlich syndrome).
Lateral hypothalamic area: Anorexia (lack of appetite).
Name the four major bidirectional fiber tracts of the hypothalamus.
Fornix (hippocampus → mammillary nuclei)
Mammillothalamic tract (mammillary nuclei → thalamus)
Stria terminalis (amygdala → hypothalamus)
Medial forebrain bundle (olfaction, autonomic regulation)v
Match these nuclei to their functions:
Supraoptic/Paraventricular
Ventromedial
Lateral hypothalamic area (LHA)
Arcuate nucleus
Supraoptic/Paraventricular: Secrete oxytocin, vasopressin (ADH), and CRH(corticotropin releasing hormone).
Ventromedial: Satiety center (lesions → hyperphagia/obesity).
LHA: Feeding center (lesions → anorexia).
Arcuate nucleus: Controls adenohypophysis via releasing/inhibitory hormones.
How does the hypothalamus communicate with the pituitary gland?
Neurohypophysis (posterior pituitary): Axons from supraoptic/paraventricular nuclei secrete oxytocin/ADH directly into blood.
Adenohypophysis (anterior pituitary): Hypothalamic releasing/inhibitory hormones travel via the hypothalamo-hypophyseal portal system (e.g., CRH, GnRH).\q
List 6 hormones regulated by the hypothalamus via the adenohypophysis.
Growth hormone (GH)
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Prolactin
Luteinizing hormone (LH)
Follicle-stimulating hormone (FSH)
What autonomic functions does the hypothalamus regulate?
Temperature control
Cardiovascular/respiratory rates
Feeding/digestion
Sexual behavior
Mood/emotional responses
Use the mnemonic “HOME” to remember hypothalamic functions.
Hormone regulation
Osmolarity/fluid balance
Metabolism/food intake
Emotion/autonomic control
What hypothalamic nucleus is damaged in a patient with central diabetes insipidus?
Supraoptic nucleus (produces ADH). Lesions → inability to concentrate urine → polyuria/polydipsia.
Key detail: Paraventricular nucleus also secretes ADH but is less commonly tested.
A patient with a craniopharyngioma compressing the hypothalamus presents with obesity, hypothermia, and hyposexuality. What nucleus is likely affected?
Ventromedial nucleus (satiety center). Lesions cause Fröhlich syndrome (hyperphagia + obesity + hypogonadism).
Exam trick: Lateral hypothalamic area lesions cause the opposite (anorexia).
A stroke damaging the posterior hypothalamus would cause ______ in body temperature.
Hypothermia (posterior hypothalamus generates heat; anterior dissipates heat).
Clinical pearl: Anterior lesions → hyperthermia (e.g., neuroleptic malignant syndrome).
How does CRH reach the anterior pituitary?
Via the hypothalamo-hypophyseal portal system → stimulates ACTH release.
Easy-to-miss: Direct neuronal axons only go to the posterior pituitary (oxytocin/ADH).
Bilateral mammillary body damage is seen in what vitamin deficiency?
Thiamine (B1) deficiency → Wernicke-Korsakoff syndrome (confusion, ataxia, memory loss).
Why? Mammillothalamic tract connects to memory circuits.
What nucleus receives light input from the retina to regulate circadian rhythms?
Suprachiasmatic nucleus (above optic chiasm).
Exam tip: Lesions disrupt sleep-wake cycles (e.g., jet lag-like symptoms).
A patient with a lateral hypothalamic stroke would present with ______.
A: Anorexia (lateral = hunger center; medial = satiety).
Mnemonic: “Lateral = Lack of appetite.”
What hormone is released by the paraventricular nucleus during breastfeeding?
Oxytocin (milk let-down reflex).
Clinical link: Pitocin (synthetic oxytocin) induces labor.
Shivering and vasoconstriction are triggered by the ______ hypothalamus.
Posterior (heat conservation). Anterior = sweating/vasodilation.
Classic vignette: Fever → anterior hypothalamus resets temp setpoint.
The neurohypophysis is derived from ______, while the adenohypophysis comes from ______.
Neurohypophysis = neural ectoderm (brain); adenohypophysis = oral ectoderm (Rathke’s pouch).
High-yield fact: Craniopharyngiomas arise from Rathke’s pouch remnants.
What pathway carries emotional signals from the amygdala to the hypothalamus?
Stria terminalis (damage → emotional dysregulation).(Forgotten tract)
Alternative route: Ventral amygdalofugal pathway (less tested
Use the mnemonic “FLAT PEG” to list anterior pituitary hormones.
FSH
LH
ACTH
TSH
Prolactin
Endorphins
GH
Exam hack: Hypothalamic hormones are releasing/inhibiting (e.g., GnRH, somatostatin).
A patient with hyperphagia, obesity, and rage attacks likely has a lesion where?
Ventromedial nucleus (satiety center).
Subtlety: Dorsomedial nucleus lesions may cause aggression (less distinct function).
Why can the hypothalamus sense blood osmolarity but most brain regions cannot?
Circumventricular organs (e.g., OVLT, SFO) lack a BBB.
Tie-in: Supraoptic nucleus responds to hyperosmolarity by releasing ADH.
