1 - Hypothalamus and Pituitary Flashcards
Key functions of hypothalamus?
HEAL
Homeostasis
Endocrine (+ pituitary)
Autonomic (sympathetics/parasympathetics)
Limbic (behavior)
Embryology development of Pituitary
Two Sources:
Anterior Pituitary - ectodermal cells of developing pharynx (Rathke’s Pouch)
Posterior Pituitary - Prosencephalon (diencephalon)
How does the mature pituitary reflect is origin?
Anterior Pituitary - Glandular cells secrete hormones into circulation through vascular portal system (via median eminence)
Posterior Pituitary - Axon terminals of hypothalamic neurons release hormoes into circulation
What marks the superior border with hypothalamus and thalamus?
What can help identify the posterior border of the hypothalamus?
What can help mark the lateral border?
Hypothalamic Sulcus (groove)
Mammillary Bodies
Internal capsule
Tuber Cinereum
Bulge between optic chiasm and mammillary bodies (marks ventral border)
Infundibulum arises from this structure
“sort of the area between the balls and the infundibulum”
Medial Forebrain Bundle
Path
Function
Path: Runs from basal forebrain to brainstem tegmentum, connects hypothalamus to forebrain and brainstem tegmentim
Functions: Carries axons from monoaminergic nuclei in brainstem to cerebrum
**runs through lateral zone**
Major Nuclei: Feeding and Satiety
Lateral Hypothalamic Area
Ventromedial Nucleus
Lateral Hypothalamic Area - Feeding Center
- Electrical simulation in animals increases feeding; lesions reduce feeding
Ventromedial Nucleus - Satiety Center
- Electrical stimulation in animals decrease feeding; lesions increase feeding
Major Nuclei: Sleep and Circadian Rhythms
Preoptic Area
- Telencephalon (all others from diencephalon)
- Ventrolateral Preoptic Area (VLPO) Regulates Sleep
Tuberomammillary Nucleus
- Projects to cerebral hemispheres; release histamine
- Helps maintain wakefullness
Suprachiasmatic Nucleus
- “Master Clock” for circadian rhythms
- Receives light input from retina
Major Nuclei: Anterior Pituitary
Arcuate Nucleus (Ar)
Paraventricular Nucleus (PV)
Medial Preoptic Area
Project to Median Eminence
***Control hormon release from Anterior Pituitary***
Major Nuclei: Posterior Pituitary
Suproptic Nucleus (SO)
Paraventricular Nucleus (PV)
Project to posterior pituitary
Release Oxytocin / Vasopressin
Hormones of Posterior Pituitary?
Ocytocin: Milk ejection, uterine contractions, maternal behavior, bonding
Vasopressin (ADH): Stimular water retention in kidney to regulate plasma osmolarity
Major Nuclei: Autonomic Control
Paraventricular (PV)
Dorsomedial (DM)
Lateral (L)
Posterior (Po)
Autonomic control by descending fivers
Medial forebrain buncle
Preganglionic parasympathetics nuclein in brainstem and sacral spinal cord
Preganglionic sympathetic in intermediolateral column of thoracolumbar spinal cord
Major Nuclei: Memory
Mammillary Bodies (MB)
Input
Output
Lesions
Input: Receive input from hippocampal formation (via Fornix)
Output: Anterior thalamus (mammillothalmamic tract); anterior thalamus projects to cingulate gyrus
Lesions: Impair memory formation; ex. Korsakoff Syndrome - Thiamine (B1) Deficiency = Chronic alcohol abuse
Major Nuclei: Thermoregulation
Divisions of nervous system?
Locations key for function?
Lesions?
Divisions
Autonomic: Sweating, altered blood flow
Somatic: Shivering, panting
Locations
Anterior - Heat dissipation
Posterior - Heat conversion
Lesions
Hypothermia, hyperthermia, fluctuation body temperature
Input to Hypothalamus: Visceral Sensory
From spinal cord, solitary nucleus, periaqueductal grey, anterolateral system; mostly via medial forebrain bundle
Input to Hypothalamus: Blood
Temperature, osmolarity, glucose/other metabolites, homrones
Circumventricular organs, anterior pituitary median eminence (circulating hormones)
***These structures MUST be outside Blood/Brain barrier to regulate this function***
Input to Hypothalamus: Retina
to Suprachiasmatic Nucleus
Input to Hypothalamus: Prefrontal and Limbic Cortex, Hippocampus, Amygdala
Integration of emotion with autonomic function and homeostatic pathways, memory function
Output from Hypothalamus: Preganglionic autonomic neurons
Through medial forebrain bundle
Direct and indirect (relays in PAG, reticular formation) control parasympathetic and sypathetic preganglionic fibers
Output from Hypothalamus: Prefrontal and Limbic Cortex, Hippocampus (indirect) and Amygdala
Intregration of emotion with autonomic function and homesostatic pathways, memory formation
Output from Hypothalamus: Anterior and Posterior Pituitary
Endocrine regulation
Hormones:
Suprotic Nucleus, Paraventricular Nucleus to posterior pituitary?
Arcuate Nucleus, Paraventricular nucleus, preoptic nucleus, Periventricular nucleus?
Oxytocin
Vasopressin
Release of regulating factors into portal system via medial eminence
Hypothalamic Pituitary Adrenal (HPA) Axis System
Hormone Release Control?
Hormon Release Location?
Downstream Effects?
Feedback
Hormone Release: Preoptic, Supraoptic, Paraventricular Nuclei release Corticotrophin Releasing Hormon (CRH)
Location: Corticotropin (ACTH) releasef from Anterior Pituitary (+ by CRH)
Downstream: ACTH stimulates release of Cortisol from Adrenal Cortex
Feedback: Negative Feedback to Ant. Pituitary and Hypothalamus regulates CRH/ATCH
How/When is the HPA Axis activated?
Chronic over activation?
Response to stress, emotion (input from amygdala)
Chronic over activation can lead to stress, depression, and neuronal atrophy in hippocampus
Clinical: Pituitary Adenomas
Benign, slow growing
Endocrine disturbance
Non-secreting may grow large, and cause symptoms
Clinical: Panhypopituitarism
Deficiency of ALL pituitary hormones
Causes: Tumors, treatment of tumors (tissue loss), infections, autoimmune disorders
**Requires hormone replacement**
