ANS regulation & (e.g. temperature, digestion, CSF condition)
Limbic system regulation (e.g. drive-related behavior, sex behavior)
Hypothalamus is just a small collection of neurons organized into dozens of nuclei and subnuclei in ventral diencephalon
involved in all unconscious and involuntary aspects of everyday survival of the individual
What are the parts of the hypothalamus?
mammillary bodies (2) ("dangle" in interpeduncal fossa)
infundibulum
tuber cinereum (floor) (central part surrounding infundibulum = median eminence)
(all of these parts are exposed to CSF within the subarachnoid space of the 3rd ventricle --> sense CSF condition)
preoptic region (anterolateral to supraoptic regions)
anterior (supraoptic) regions
middle (tuberal) regions
posterior (mammillary) regions
lateral region: medial forebrain bundle
What does the hypothalamus look like?
ventral diencephalon (i.e. between mesencephalon and telencephalon)
inferior to anterior commissure (anterior portion of hypothalamus)
surrounds anterior/inferior portion of 3rd ventricle (abuts thalamus, which covers posterior/superior portion of 3rd ventricle)
3 bumps inferior to hypothalamus: 2 posteriorly: mammillary bodies, 1 at midline: infundibulum
diamond shaped (ventral view)
Where is the hypothalamus?
ventral diencephalon
inferior to anterior commissure (anterior portion of hypothalamus)
surrounds anterior/inferior portion of 3rd ventricle (abuts thalamus, which covers posterior/superior portion of 3rd ventricle)
posterior to optic chiasm and tracts
anterior to cerebral peduncles (midbrain)
close to middle cerebral artery
medial to amygdala
basal forebrain is fluid with antero-lateral border of hypothalamus
What is considered "unique" about the hypothalamus as compared to other brain structures?
The hypothalamus has inputs and outputs with both neural and non-neural (e.g. humoral; physical stimuli) sources
inputs: neural and non-neural (e.g. humoral, physical stimuli)
outputs: neural and non-neural (e.g. neuroendocrine outputs)
Cells of hypothalamus act directly as their own sensory organs for physical stimuli arising from the internal environment (visceral information) such as temp/hormone levels
part of hypothalamus resides outside of blood brain barrier (i.e. circumventricular organ system)
some hypothalamus axons synapse directly on blood vessels (i.e. neuroendocrine outputs)
What part of the pituitary gland shares the same developmental origin as the hypothalamus?
posterior lobe of the pituitary (i.e. the neurohypophysis)
What are the borders of the hypothalamus?
-anterior border: plane through the anterior commissure and optic chiasm (approximately the same as the lamina terminalis)
-lateral border: anteriorly indistinct, blends with the basal forebrain. posteriorly distinct, the internal capsule (posterior limb)
-medial border: 3rd ventricle
-posterior border: plane drawn coronally through the posterior end of the mammillary bodies (separates the hypothalamus from the subthalamic nucleus and midbrain)
-inferior border:
-superior border: anteriorly, the anterior commissure and septal nuclei; posteriorly, the hypothalamic sulcus (which separates the hypothalamus and thalamus)
What 2 structures are located at the posterior border of the hypothalamus?
subthalamic nucleus
midbrain
What 2 structures does the hypothalamic sulcus separate?
hypothalamus
thalamus
What anatomical relation does the hypothalamus have with the basal forebrain? What disease is particularly associated with the basal forebrain and why?
the hypothalamus' anterior portion of its lateral boundary is indistinct with the basal forebrain
the basal forebrain is associated with Alzheimer's disease because it has a nucleus that contains ACH-cells, which are degenerated in Alzheimer's
What are the 7 zones/regions of the hypothalamus?
paraventricular zone
medial zone
lateral zone
preoptic
anterior/supraoptic zone
middle/tuberal zone
posterior/mammillary zone
What structure traverses the lateral zones of the hypothalamus?
medial forebrain bundle
In which zone of the hypothalamus are most of the parvocellular cells located?
A. paraventricular zone
In which hypothalamic zone(s) do most of the well-defined hypothalamic nuclei reside?
B. medial and paraventricular zones
Which of the following hypothalamic regions functions as though it is hypothalamic but does not share the same origin as the rest?
C. preoptic region
What contributes to the lateral region of the hypothalamus?
medial forebrain bundle
What contributes to the anterior/supraoptic region of the hypothalamus?
anterior hypothalamic nucleus
supraoptic nucleus
suprachiasmatic nucleus
paraventricular nucleus
What contributes to the middle/tuberal region of the hypothalamus?
What contributes to the posterior/mammillary region of the hypothalamus?
posterior hypothalamic nucleus (PMH)
mammillary bodies/nuclei (MAM)
Which statement is false?
B. the anterior hypothalamus senses heat loss and initiates heat conservation while the posterior hypothalamus senses heat increase and
starts heat loss behavior
(the anterior hypothalamus senses heat increase and initiates heat loss behavior while the posterior hypothalamus senses heat loss and
starts heat conservation)
True or false: the infundibular nuclei of the hypothalamus is the same as the arcuate nucleus
true
What are the functions of the anterior/supraoptic hypothalamic nuclei?
preoptic nucleus: water intake, sleep, have parvocellular cells
suprachiasmatic: circadian rhythms, retina input (b/c on top of optic chiasm), sexual behavior (?)
supraoptic: oxytocin, ADH production
anterior hypothalamic: temperature (heat loss), sleep-waking, have parvocellular cells
paraventricular: oxytocin, ADH production, have parvocellular cells
Which hypothalamic nuclei has connections to both the anterior and posterior pituitary thus regulating endocrine functions and also controls the ANS via "regular" neurons that send axons down to brainstem and spinal cord neuron targets?
paraventricular nucleus (in anterior/supraoptic region of hypothalamus)
What are parvocellular cells?
they are small cells within (hypothalamic) nuclei that control endocrine secretion of anterior pituitary cells by secreting releasing or inhibitory factors
e.g. growth hormone, LH, FSH, ACTH, TSH
What are magnocellular cells?
magnocellular cells are large cells in (hypothalamic) nuclei that secrete ADH and oxytocin from posterior pituitary gland
found in supraoptic and paraventricular hypothalamic nuclei
Which hypothalamic nuclei have magnocellular cells?
Supraoptic
Paraventricular
What are the functions of the middle/tuberal hypothalamic nuclei?
dorsomedial hypothalamus: feeding, rage
ventromedial hypothalamus: feeding (satiety center), rage, has parvocellular cells
infundibular/arcuate: endocrine control (e.g. senses decreased sex hormones), has parvocellular cells
(tuberomammillary nucleus: sleep/waking)
What would happen to a mouse's appetite if it had a bilateral lesion through its ventromedial hypothalamic nuclei?
the mouse would never feel satiated; it would continually eat
Where are the brain "centers" that contribute to the sensation of satiety and decrease appetite?
Which hypothalamic nuclei have cells whose axons go down through the infundibular stalk and release neurohormones into bloodstream for circulation to distant targets (e.g. smooth muscle of uterus)?
paraventricular nuclei
supraoptic nuclei
Label each circled hypothalamic nucleus. What region of the hypothalamus is this?
A = paraventricular nucleus
B = suprachiasmatic nucleus
C = supraoptic nucleus
this is the anterior/supraoptic region of the hypothalamus
Which area has magnocellular cells? Which area has retinal input and sets the Circcadian rhythms of the body?
A and C (i.e. paraventricular nucleus and supraoptic nucleus) have magnocellular cells
B (i.e. suprachiasmatic nucleus) has retinal iput and sets the Circcadian rhthms of the body
Which hypothalamic nuclei have parvocellular cells (i.e. cells that control endocrine secretion of anterior pituitary hormones by secreting releasing or inhibiting factors)?
preoptic nucleus
paraventricular nucleus
anterior hypothalamic nucleus
venteromedial hypothalamic nucleus
infundibular/arcuate nucleus
posterior hypothalamic nucleus
What happens if a person suffers a bilateral lesion through their suprachiasmatic nuclei?
sleep-waking cycles disrupted
Circadian rhythms disrupted
temperature regulation disrupted
Which factor could possibly be dysfunctional in an obese person?
B. leptin
What are some orexigenic factors of the body and what do they do? What are some anorexigenic factors of the body and what do they do?
orexigenic factors: stimulate eating/appetite (e.g. ghrelin, orexin (hypocretin) A & B, neuropeptide Y (NPY))
Which hypothalamic nuclei are thought to play a role in sexual behavior because of comparative size differences between homosexual and heterosexual men?
interstitial nuclei of anterior hypothalamic nuclei (INAH)
suprachiasmatic nucleus
Which structures give input to the hypothalamus?
F. all of the above
Through which structures does the hypothalamus receive signals from the rostral limbic system?
fornix (hippocampus)
stria terminalis (amygdala)
medial forebrain bundle (MFB) (olfactory areas and limbic structures)
ventral amygdalofugal tract (VAF)
Through which structures does the hypothalamus receive signals from the cerebral cortex?
medial forebrain bundle (MFB)
Through which structures does the hypothalamus receive signals from the retina?
optic tract to suprachiasmatic nucleus
What are the target areas of the descending tracts of the DLF from the hypothalamus?
posterior lobe/neurohypophysis origin: dragged down hypothalamus
What hormones does the anterior pituitary secrete? What structure controls their secretion?
GH
Prolactin
FSH
LH
ACTH
TSH
the hypothalamus controls their secretion
In what two ways does the hypothalamus control the pituitary gland?
hypothalamo-hypophyseal TRACT: axons of cells in the SO and PV nuclei transmit signals to blood vessels in the neurohypophysis
hypothalamo-hypophyseal PORTAL SYTEM: hypothalamic controlling factors are released onto a private venous portal system (at level of median eminance) that transmits signals to the adenohypophysis, where receptor cells are located
What factors does the posterior pituitary release into the bloodstream? What are their target organs?
oxytocin: smooth muscle of uterus (parturition), breast (lactation)
What affect does alcohol have on ADH levels and what are the consequences of this change, if any?
alcohol inhibits release of ADH (antidiuretic hormone)
the change in blood osmolarity is sensed by the hypothalamus, which triggers the kidney tubules to increase urination
a person becomes flooded with uninhibited diurectic signals --> uninhibited increased urination
What is the effects of diabetes insipidus on ADH levels and what are its associated symptoms?
diabets insipidus reflects a marked decrease in ADH levels
symptoms: increased thirst and drinking, increased urination of vast quantities of dilute urine
Describe the hypothalamus-pituitary-axis pathway that controls ACTH release.
note negative feedback on two levels
(side note: adrenal cortex is backup to ANS activated in prolonged stress response)
What are some parasympathetic innervated structures in the brainstem?
DMNX (dorsal motor nucleus of Vagus)
Edinger-Westphal nucleus
salivary nucleus
Where are some sympathetic innervated structures of the ANS in the spinal cord?
lateral horn in T1-L2
Through which two tracts does the hypothalamus regulate the autonomic nervous system?
dorsal longitudinal fasciculus: (through brainstem) parasympathetic preganglionic cells in brainstem
hypothalamo-spinal tract: (through brainstem) sympathetic preganglionic cells in lateral horn of spinal cord (T1-L2)
most of both tracts originate in the PV nucleus
In the context of acting as the "head ganglion" of the ANS, what are the inputs and outputs of the hypothalamus?
inputs:
-viscera (afferents via CN X, IX to caudal solitary nucleus)
-somatic afferents
-limbic system
outputs:
-autonomic centers in brainstem
-parasympathetic cranial nerve motor nuclei
-sympathetic spinal cord motor nuclei
Hypo controls ans for homeostasis and for emotional expression, therefore needs visceral inputs and external world inputs—and then sends outputs to ans—to parasympathetic neurons, to sympathetic neurons and to brainstem ANS coordinating centers
What are the (preganglionic) parasympathetic nuclei in the brainstem and the (preganglionic) sympathetic nuclei in the spinal cord?
Edinger-Westphal nucleus
dorsal motor nerve of vagus (DMNX)
salivary nucleus
interomedial lateral (IML) column in lateral horn in thoracic cord (T1-L2)
lateral horn in sacral cord (giving rise to pelvic splanchnic nerves)
What will damage to one side of the hypothalamus cause if the lesion is at the level where the ANS and PNS are lateralized?
a. there will be no clinical presentation, must have bilateral damage to hypothalamus to cause noticeable effects
b. unilateral, contralateral loss of ANS function
c. bilateral loss of ANS function
d. unilateral, ipsilateral loss of ANS function
True or False: On their way to the spianl cord from the hypothalamus, only branches from the dorsal longitudinal fasciculus terminate on nuclei in the brainstem (e.g. DMNX).
False
Some branches of the descending hypothalamo-spinal tract terminate on nuclei in the brainstem as well as branches from the DLF.
Choose correct word: (Descending/Ascending) fibers drive sympathetic motor nuclei in interomedial lateral (IML) horn/column.
Descending fibers drive sympathetic motor nuclei in interomedial lateral (IML) horn/column.
What are the symptoms of Horner's Syndrome? Why would a hemisection of the spinal cord at the thoracic level be a possible cause of Horner's Syndrome?
Horner's Syndrome: ("Horny PAMELa"): Ptosis, Anhydrosis, Miosis (pupil constriction), Excess mucous, Loss of ciliospinal reflex (also vasodilation)
A hemisection of the spinal cord at the thoracic level would be a possible cause of Horner's syndrome because the sympathetic fibers from the hypothalamus (hypothalamo-spinal tract) travel through the lateral funiculus of the spinal cord and synapse on the interomedial lateral horn (IML) and a hemisection through the cord would cause signal blockage to sympathetic system targets
Trick with horner’s is to remember that the block can be along the length of the pathway: centrally from hypothalamus through brainstem to cord, or peripherally from cord to chain, to superior cervical ganglion to carotid plexus to target in head.
Which of the following is regulated in some way by the hypothalamus?
E. all of the above
What 2 major cerebral arteries are in close proximity to the hypothalamus?
