5/27- Hypothalamus Flashcards
Anterior boundary markers of hypothalamus?
- Lamina terminalis
- Anterior commissure
- Optic chiasm
Posterior boundary markers of hypothalamus?
- Posterior comissure
- Mammillary body
Major functions of the hypothalamus?
Integrative center (essential for survival and replication)
Maintain homeostasis (interacts w/ 4 major systems):
- Homeostatic mechs (eating, thirst, sleeping, temp reg…)
- Endocrine control (via pituitary)
- Autonomic control
- Limbic mechs (memory, emotion, motivation/drives)
4 Regions of medial hypothalamus?
(picture)
- Posterior region (mammillary)
- Middle region (tuberal)— most homeostatic
- Anterior region (suprapoptic)
- Preoptic region
The fornix divides the hypothalamus into 2 main halves (medial and lateral)
Kodachrome pic
Can see lateral and medial hypothalamus divided by the fornix on the angry birds slide
Major nuclei (8) in the hypothalamus (picture)?
Posterior region (mammillary):
- Posterior nucleus
Middle region (tuberal):
- Dorsomedial nucleus
- Ventromedial nucleus
- Arcuate nucleus
Anterior region (supraoptic):
- Supraoptic nucleus
- Suprachiasmatic nucleus
- Paraventricular nucleus
Preoptic region:
- Preoptic nucleus
Role of mammillary body?
- Connected to limbic system
- Thought to be involved in memory
Cross sectional view of anterior hypothalamus (pic)
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Cross sectional view of medial region of hypothalamus (pic)
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Cross sectional view of posterior region of hypothalamus (pic)
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Role of preoptic nucleus?
- Endocrine (releasing hormones [GnRH] in pituitary, sexual, maternal, paternal behaviors)
- Temperature regulation
- Fluid balance
Role of paraventricular nucleus?
- Endocrine regulation (stress homeostasis): Vasopressin (ADH), Oxytocin (3Ls: lactation, labor, love)
Role of anterior hypothalamus?
PS responses
- Reduced heart rate
- Enhanced GIT secretomotor activity
Role of suprachiasmatic nucleus?
Circadian rhythms and sleep/wake cycles
- Vasopressin
- Biological rhythm regulation for hormone release
Role of supraoptic nucleus
- Endocrine
- Water homeostasis:
- Vasopressin (ADH)
- Oxytocin
Role of dorsomedial nucleus?
- Feeding
- Drinking
- Body weight regulation
(Activation promotes obesity and emotional behaviors)
Role of ventromedial nucleus?
- Appetitive (hunger and satiety balance)
- Consummatory behaviors (reproduction)
- Rage
Role of arcuate nucleus?
- Endocrine regulation (releasing factors into portal system)
- Feeding (hunger and satiety)
Role of posterior nucleus?
Sympathetic responses
- Increases HR
- Reduces GIT secretomotor activity
Role of mammillary bodies
Memory (Papez Circuit)
- Integrates info from limbic system via fornix
Integrative functions of hypothalamus (5)?
- Controls BP and electrolytes (drinking/appetite)
- Regulates body temp (via ANS)
- Regulates energy metabolism (influences feeding, digestion, and metabolism)
- Regulates reproduction through hormonal control of mating, pregnancy and lactation
- Directs responses to stress/threatening conditions by influencing blood flow to specific tissues and by stimulating secretion of adrenal stress hormones and activating the ANS
What are afferent inputs into the hypothalamus (4)? and major inputs/origins (3)?
- Limbic system
- Brain stem
- Retina
- Cortex
Major:
- Fornix (from hippocampus)
- Stria terminalis (from amygdala)
- Medial forebrain bundle (from brainstem nuclei)
Fornix (afferent) carries information from where to where? (test)
From hippocampus to:
- Medial hypothalamus
- Mammillary body
(- Anterior thalamic nucleus)
(- Pre/postcommissural fornices)
(- Septal area)
Stria terminalis (afferent) carries information from where to where? (test)
From amygdala to medial hypothalamus
Medial forebrain bundle (afferent) carries information from where to where? (test)
From septal area to:
- (medial) hypothalamus
- Brain stem
What are the efferent outputs from the hypothalamus (3)?
- Limbic system
- Brainstem nuclei
- Endocrine system (via pituitary)
What are the efferent projections from the mammillary bodies (destination/tracts)?
- Anterior thalamic nucleus (mammillothalamic tract)
- Cingulate gyrus (thalamocortical fibers from anterior thalamic nucleus)
- Midbrain tegmentum and reticular formation (mammillotegmental tract)
What are the efferent projections from the medial hypothalamus?
(Like a feedback loop)
Ascending/descending fibers:
- Periaqueductal grey (PAG)
- Amygdala
- Prefrontal cortex
(- Midbrain tegmentum ?)
(- Spinal cord)
(- Hippocampus (different tract))
What are the efferent projections from the medial forebrain bundle (lateral hypothalamus)?
- Prefrontal cortex
- Septal area
- Midbrain reticular formation
- Periaqueductal grey (PAG)
Hypothalamic- Hypophyseal efferents (2 tracts)?
Hypothalamo-Hypophyseal tract Tuberoinfundibular tract
What does the hyopthalamo-hypophyseal tract connect?
From: paraventricular and supraoptic nuclei
To: posterior lobe of pituitary
What does the tuberoninfundibular tract connect?
From: medial hypothalamic and arcuate nuclei
To: anterior lobe of pituitary (portal circulation)
Anatomical location of disorder:
Feeding (obesity/emaciation)
Obesity: lesions of ventromedial hypothalamus Emaciation: lateral hypothalamus
Anatomical location of disorder:
Diabetes insipidus
Supraoptic and paraventricular nuclei (Vasopressin/ADH)
Anatomical location of disorder:
Hypertension
Paraventricular nucleus
(excess release of CRH- corticotropin releasing hormone)
Anatomical location of disorder:
Endocrine disorders
Pituitary ademonas
(prolactin releasing hormone from arcuate nucleus)
Anatomic causes of amnesia?
Damage to:
- Hippocampi
- Mammillary bodies
- Fornices
TAKE HOME:
- The hypothalamus is critical for orchestration of endocrine, autonomic, and behavioral responses
- Higher regions of the brain (in limbic forebrain) also participate in these responses
- Hypothalamus is heavily interconnected with the limbic areas
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