Exam #3: Hypothalamus Flashcards
What is the general function of the hypothalamus?
Hypothalamus= general function is “homeostasis” via
1) Neural mechanism 2) Humoral (pituitary gland)
Where is the hypothalamus? What are the boundaries?
- Superior= hypothalamic sulcus i.e. the sulcus that separates the hypothalamus from the thalamus above
- Inferior= optic chiasma, tuber cinereum, & mamillary bodies
- Anterior= Lamina terminalis
- Posterior= midbrain/ interpeduncular fossa
**Note that the tuber cinereum is a hollow eminence of gray matter (part of the hypothalamus) situated between the mammillary bodies and the optic chiasm
What structure separates the hypothalamus into medial and lateral portions?
Fornix
What is the major blood supply to the hypothalamus?
Perforating branches from the Circle of Willis
What are the functions of the hypothalamus?
Homeostasis including:
- Sleep-wake cycle
- Integration of emotional responses & behavior
- ANS control center
- Temp. regulation
- Food intake
- Water balance/ thirst
- Endocrine system
What are the major inputs into the hypothalamus?
1) Limbic structures–emotions
2) Cerebral cortex–thoughts & decisions
3) Retina–light information
4) Brainstem & spinal cord–input from viscera
5) Intrinsic neurons i.e. osmoreceptors, chemoreceptors, & baroreceptors that monitor BP, osmolarity, glucose…etc.
How does the cerebral cortex effect they hypothalamus?
- You can’t “will” your heart rate to increase
- However, thinking about exciting things e.g. naked woman can increase HR
What are the major outputs of the hypothalamus?
1) Pituitary gland= hormones & hormone releasing factors
2) Brainstem & spinal cord= influences on the viscera
How are most of the nuclei of the hypothalamus named? What are the two exceptions to the general rule that the hypothalamic nuclei are named relative to their position?
Position in the hypothalamus
*****Note: arcuate & mammillary bodies are naked off of their shape, not position
What is the general function of the suprachiasmatic nucleus?
Circadian rhythm i.e. the suprachiasmatic nucleus is the “master clock” of the body
What is the general function of the mammillary bodies?
Processing emotional information
What is the general function of the anterior & posterior nuclei of the hypothalamus? What is the difference?
Regulation of body temperature
- Anterior= heat loss
- Posterior= heat conservation/ production
*****Remember, posterior= preservation
What are the general functions of the ventromedial & lateral nuclei of the hypothalamus? What is the difference between the two
Both the lateral & ventromedial nuclei control satiety and feeding
- Lateral= feeding or hunger center
- Ventromedial= satiety center
What is the general function of the supraoptic & paraventricular nuclei of the hypothalamus?
These two nuclei are associated with the posterior hypothesis/ “neurohypophysis”
- Synthesize & release hormones of the posterior pituitary
What is the general function of the preoptic, medial preoptic, arcuate, & paraventricular nuclei of the hypothalamus?
These four nuclei are associated with the anterior pituitary
- Produce & release factors that stimulate or inhibit the anterior pituitary
What does a lesion to the hypothalamus usually result in?
“Hypothalamic Syndrome”
- Manifestation damage to many hypothalamic nuclei
What tract sends light information to the suprachiasmatic nucleus?
Retinosuprachiasmatic tract i.e. from the retina
What type of receptors are in the suprachiasmatic nucleus?
Malatonin
What is the function of melatonin?
Synchronization of the “master clock” in the hypothalamus
What structure secretes melatonin?
Pineal gland
What is the output of the suprachiastmatic nucleus?
Reticular formation in the brainstem
**Note that the reticularformation feedback to the suprachiasmatic nucleus via the dorsal longitudinal fasciculus
What is the result of a tumor in the pineal gland?
Delayed or precocious onset of puberty
What are the primary inputs to the mammillary bodies? What is the function of the mammillary bodies?
Hippocampus & amygdala–processing of emotional information
**Note that hippocampal input is via the fornix
What are the two major output pathways from the mamillary bodies?
- Mammillothalamic
- Mammillotegmental
How do the mamillary bodies trigger appropriate visceral responses?
Output on brainstem PNS nuclei: VII, IX, X & SNS
What are the fibers that connect the hippocampus to the hypothalamus (mamillary bodies)? What tract connects the amygdala to the hypothalamus?
Fornix & stria terminalis, respectively
What is the shape of the fornix? How is this reflected on coronal section?
C-shaped; will see two parts of the fornix on cross-section
Why is memory important to hypothalamic function?
- Locating food & water
- Locations to avoid predators & tactics to increase survival
What are the inputs to the ANS control of the hypothalamus?
- Ascending visceral information from internal organs
- Limbic system with information about the emotional state of the organism
What hypothalamic nuclei are associated with the PNS?
Preoptic & anterior nuclei
Function= pupillary constriction, salivation, decreased HR & BP, & increased peristalsis
What hypothalamic nuclei are associated with the SNS?
Posterior & lateral nuclei
Function= pupillary dilation, decreased salivation, increased HR & BP, decreased peristalsis, and vasoconstriction
What nuclei initiate heat loss? How?
Preoptic
Anterior
**I.e. the PNS nuclei that lead to sweating, vasodilation, and decreased motor activity
What hypothalamic nuclei activate heat production? How?
Posterior
*****I.e. one of the SNS nuclei that functions in vasoconstriction, increased muscular activity, and TH
What is the lateral nucleus of the hypothalamus associated with?
Eating– this is a potential “feeding center”
What is the ventromedial nucleus of the hypothalamus associated with?
Potential satiety center
Where are the osmoreceptors located that monitor the concentration/ hydration of the blood?
Lateral zone of the hypothalamus
What nuclei are associated with control of the posterior pituitary? What tract are these nuclei associated with?
Supraoptic & paraventricular nuclei that are associated with the hypothalamohypophyseal tract
What are the two hormones associated with the posterior pituitary?
ADH
Oxytocin
What is the function of ADH?
Water conservation & increase blood pressure
What are the functions of Oxytocin?
Uterine contraction
Milk letdown
What are the two major nuclei that control the anterior pituitary?
Arcuate
Periventricular
What are the releasing factors associated with the anterior pituitary gland?
SRH
CRH
GnRH
TRH
What are the inhibitory factors associated with the anterior pituitary gland?
Somatostatin
PIF
What connects the hypothalamus to the anterior pituitary gland?
Tuberohypophysial tract
What does the medial forebrain bundle connect?
Lateral hypothalamus with septal nuceli & brainstem/ reticular formation
How does consciousness alter the hypothalamus?
Conscious thoughts influence the hypothalamus
What tract is going to be responsible for the “conscious” alteration of the hypothalamus?
Cortex–>hypothalamus called the “corticohypothalamic pathway”
