The Hypothalamus Flashcards
principle function of the hypothalamus
physiological homeostasis
drive behaviors eg rage, sleep, feeding
Coronal Zones
Lateral, Medial and Periventricular Zones
Sagittal regions
Anterior, Tuberal, Posterior
Suprachiasmatic Nuclei function
circadian rhythm
Suprachiasmatic Nuclei pathway
retina –> optic chiasm –> suprachiasmatic nuclei –> lateral horn of spinal cord –> pineal gland
Pituitary anatomy
Adenohypophysis (anterior) - innervated by arcuate nuc.
Neurohypophysis (posterior) - supraoptic and paraventricular nuc.
Arcuate Nuclei function
parvocellular neurons secrete releasing / inhibiting factors
combine signals related to feeding behaviors
Parvocellular Neurons
neurons in the Arcuate Nuclei that secrete releasing/inhibiting factors
activates autonomic pattern generators to regulate feeding
Pituitary hormones
prolactic - mammary glands
ACTH - adrenal cortex
TSH - thyroid gland
Gonadotrophins (eg FSH) - ovaries, testes
Hypophyseal portal system
fenestrated structure of capillaries that facilitates rapid exchange between hypothalamus and pituitary
Arcuate Nuclei pathway
releasing/inhibiting factors secreted to hypophyseal portal system –> enters anterior pituitary –> stimulates secretion of hormones
Paraventricular & Supraoptic Nuclei function
Magnocellular neurons release vasopressin and oxytocin
acts as antidiuretic and also stimulates lactation
Magnocellular neurons
neurons in Paraventricular and Supraoptic nuclei that release vasopressin and oxytocin
Hypopituitarism
damage to hypothalamus/pineal gland cuases decrease of hormones –> decreased growth/responses
Hyperpituitarism
increased hormones –> increased growth
Antidiuretic process
water loss triggers releasing of more vasopressin (paraventricular and supraoptic nuc) –> increases water reabsorption in kidneys
Lactation process
mechanoreceptors in nipples cause release of oxytocin –> increases contraction of myoepithelial cells in mammary glands for lactation
Circumventricular organs
sites where blood-brain barrier is highly permeable --> allows passage of chemosensory stimuli area postrema subfornical organ pineal gland OVLT
Area Postrema
(circumventricular organ) vomiting
Subfornical organ
(circumventricular organ) osmoregulation, cardiovascular regulation, energy homeostasis
OVLT
(circumventricular organ) has osmoreceptos that are sensitive to osmotic pressure in blood
fever induction
Mammillothalamic Tract pathway
mammillary bodies –> mammillothalamic tract –> anterior nucleus of thalamus and midbrain reticular formation
Medial Forebrain Bundle pathway
autonomic/somatic info
septal nucleus –> medial forebrain bundle –> lateral nucleus
Fornix pathway
autonomic/somatic info
Hippocampus –> fornix –> mammillary bodies
Stria Terminalis pathway
autonomic/somatic info
amygdala –> stria terminalis –> preoptic & tuberal nuclei
Hypothalamic Tract pathway
retina –> hypothalamic tract –> suprachiasmatic nuc
Brainstem and Spinal cord inputs
visceral and somatic info
from: reticular formation, periaqueductal gray, solitary and parabrachial nuc.
through: Dorsal Longitudinal Funiculus and Medial Forebrain Bundle
Autonomic circuits (4 nuclei)
4 brainstem areas that network tgt w/ hypothalamus to regulate Solitary Nucleus Parabrachial Nuclei Reticular Formation Periaqueductal Gray
Solitary Nucelus (function)
principle visceral sensory nuclei w/ info regarding tase (IX) and internal organ status
Parabrachial Nuclei (function and pathway)
carries generalised visceral sensory info
solitary –> parabrachial –> Hypothalamus, thalamus, amygdala
Reticular Formation (function)
Central pattern generator centers
cardio/respiratory functions, urination
Periaqueductal Gray (function)
origin of descending pain control pathway
central pattern generator for responses to threats
Detrusor Muscles
bladder muscles taht contract to expel urine/ relax to collect
Vesicovesical reflex
stretching of bladder wall causes detrusor muscles to contract
(only active in children)
Urine collection process
sympathetic input from T11-L2 inhibit detrusor muscles from contracting –> onuf’s nucleus in S2 innervates external urethral sphincter, keeps it contracted
Urine elimination process
tension receptors in bladder wall convey info to periaqueductal gray, preoptic hypothalamus and thalamus
- -> visceral sensory cortex in insula for conscious awareness
- -> periaqueductal gray assesses social appropriateness
- -> approval signal sent to pontine micturition center
- -> inhibits sympathetic and lower motor neurons, allow detrusor muscles to contract
Medial Preoptic nucleus (function)
regulates body temperature - receives signal when temp too HIGH
(20% of neurons are warm sensitive and fire faster as temp increases)
–> stimulates blood vessel dilation, panting/sweating
Posterior Nucleus (function)
regulates body temperature - receives signal when temp too LOW
stimulates blood vessel constriction, shivering
Dorsomedial Nuclei (function)
lesions affecting the dorsomedial nuclei produce rage
Lateral Nucleus (function)
regulate food intake
lesions of lateral hypothalamus –> starvation
Ventromedial Nucleus (function)
regulate food intake
lesions of ventromedial hypothalamus –> obesity
Gherlin
chemical that encourages eating secreted by the stomach
Leptin
chemical that stops feeding, released by fat cells
binds to receptors in arcuate nucleus
