Hypothalamus and Temp Regulation Flashcards
Hypothalamus
Bridge structure that sits in brain and modulates visceral motor, somatic motor, neuroendocrine, and behavioral responses
Homeostasis and emotional expression for survival of individual and species
Between optic chiasm and mamillary bodies
How does the hypothalamus regulate the autonomic and somatic motor systems?
Efferent projections to:
•autonomic centers and preganglionic neurons
•motor nuclei in brainstem
How does the hypothalamus regulate the endocrine system?
2 ways:
Direct (oxytocin and vasopressin): via the paraventricular nucleus and supraoptic nucleus
Indirect (releasing and inhibiting factors): Control release of anterior pituitary hormones from glandular cells (LH, GH, ACTH, PRL,TSH, FSH)
Neural inputs to hypothalamus
direct input from retina
processed sensory information from limbic areas (hippocampus and amygdala)
visceral sensation via nucleus of the solitary tract
Humoral inputs to hypothalamus
temperature
osmolality
glucose
peripheral hormones
Regions with fenestrated capillaries (no Blood Brain Barrier):
OVLT (organum vasculosum lamina terminalis)
subfornical organ
posterior pituitary
median eminence
OVLT
No blood brain barrier
Near lamina terminalis
Sensitive to osmolarity of blood
Subfornical organ
No blood brain barrier
Responsive to chemical composition of blood
Milk letdown
Lag in time from baby rat suckling for milk and actual change in pressure (milk letdown)
Because neural input but humoral output
How does the hypothalamus recruit motivated behavior pathways?
projections to the limbic system:
amygdala, hippocampus, etc.
Sham rage
Experiments doing transsections of the brain reomving cerebrum, but leaving hypothalamus intect:
Normal cat-like sham rage response (also get rage response more easily)
If remove hypothalamus in addition to cerebral cortex: no sham rage response
Pair bonding in prairie voles
Hypothalamus regulates posterior pituitary with regulates this pair bonding
Control of body temperature
Hypothalamus
Anterior hypothalamus: “I’m too hot area” Lesion - hyperthermia
Posterior hypothalamus: Heat generating mechanisms Lesion - hypothermia
Preoptic Anterior Hypothalamus (POAH)
“I’m too hot area”
Depends on temp of blood running through brain (directly senses blood temp); also gets input from skin
Hypothalamic warm sensors
Causes heat loss through vasodilating skin and sweating
Fever
Still regulated by hypothalamus but higher “set point” for body temp
Pyrogens
Cause fever
Exogenous (bacteria or virus) and Endogenous (Cytokines, IL1 for ex)
Posterior hypothalamus
Doesn’t directly sense temp of brain; gets input from skin receptors
How is fever generated?
Cytokines are released and then sensed by the OVLT which then stimulates the POAH thermoreceptors through prostaglandins to increase their tempertaure setpoint, causing vasoconstriction, shivering, and fever.
Brown adipose tissue
Heat generation in infants and baby mammals
Usually not much in adult mammals
UCP1
Increased in most humans in winter
Increased in response to NE signaling from hypothalamus
Water regulation
Hypothalamus
pOsm=295mosm/kg H2O
Regulate intake through thirst
Regulate output through vasopressin (ADH)
Body weight homeostasis
Hypothalamus
Lesions can make people lose appetite or have too much appetite
Short-term regulation of feeding behavior
Circadian Rhythms
Suprachiasmatic nucleus in hypothalamus regulates endogenous circadian rhythm
Light/dark can influence cycle
Also input from peripheral clocks and transcriptional autoregulatory feedback loops
Tumor in pituitary could do what
Endocrine problems: reproduction (pregnancy lactation), regulation of body temp, regulation of body weight, water balance and BP
Vision problems
