Hypothalamus Flashcards
anterior-posterior regions
anterior (supraoptic), medial (tuberal), posterior (mammilary)
type of efferent info from hypothalamus
neural and humoral
Neural information from hypothalamus
doral longitudinal tract, medial forebrain bundle, mammillotegmetnal tract
How does hypothalamus regulate Autonomic Nervous system
sympathetic and parasympathethic preganglionic neurons; sypm = interomediolateral column of thoracic/upper 3 lumbar segments
parasympathetic = brainstem nuclei (CN 3, 7, 9, 10), spinal sacral spinal cord
Regulation of Somatic motor responses
hypothalamic neurons innervate UMN in brainstem reticular formation
- coordinates activity of these neurons with action so autonomic neurons to organize complex activities
2 pathways for hypothalamic control of endocrine system
Direct (Posterior Pituitary) and Indirect (anterior pituitary)
Direct Control of endocrine
2 hormones (vasopressin adn oxytocin) made by neurons in supraoptic neuron (SON) and paraventricular neuron –> transported down axons to posterior pituitary –> stored in axon vesicles until AP signal for release into general circulation –> to target tissues
Vasopressin action
acts on kidneys to conserve water and vasoconstricts blood vessels; receptors in brain for behavior modulation
oxytocin
constriction of smooth muscle in uterus and mammary glands for assistance in childbirth and lactation; receptors in brain for behavior modulation
Indirect Endocrine regulation
Hypothalamus makes/releases releasing/inhibiting hormones into hypo-pituitary portal –> travels to glandular cells of anterior pituitary
examples of hormones regulated via anterior pituitary
CRH, GnRH, PIF, DA, PRF, TRH, SOM, GHRH
types of input to hypothalamus
neuronal and humoral
input pathways for homeostasis
- neural afferents from brainstem (visceral receptors –> brainstem reticular formation –> hypothalamus)
- Humoral afferents to hypothalamus and intrinsic sensory neurons
also has neurons monitoring other physiological parameters (temp, osmolality of ECF, glucose)–> intrinsic sensory neurons
How does humoral input get to BBB
Have several areas in hypothalamus and preoptic area lacking BBB –> circumventricular organs
Theyhave fenestrated capillaries that allow peptides/polypeptides to pass form blood into brain
Circumventricular organs
organum vasculosum of lamina terminalis (OVLT), posterior pituitary, median eminence (bottom of 3rd ventricle), subfornical organ
Emotional expression neural connections
Fornix, Stria terminalis (amygdala with anterior/tuberal regions of hypothalamus), medial forebrain bundle, mammillothalamic tract
Path to integrate behavior with time
light info from retinal ganglion cells travel to suprachiasmatic nucleus (SCN) –> important for circadian rhythms to environmental light/dark cycle
sham rage
dissociation of rage response with appropriate environmental context
hypothalamus separate from higher brain areas but connected with braistem/spinal cord
Shame Rage observed–extreme aggression, even to inappropriate stimuli, short lived and poorly directed response
Disconnect hypothalamus from branstem
abolishes sham rage
Lesion of ventromedial nucleus
elicit rage/aggressive behavior
stimulate dorsomedial nucleus
rage/aggressive behavior
lesion of lateral hypothalamic area/mammilary region
placid/suppression of aggressive behavior
Set point of body
37 C
What part of body monitored/regulated in regards to set point
anterior hypothalamus
Nonshivering thermogenesis
brown fat can increase heat production; important in mammals that hibernate/infants
How does non-shivering thermogenesis work
Sympathetic nerves release NE on brown cells, causing them to release/activate UCP1 (thermogenin or uncoupling protein)–> open H+ channel leads to dissipation of proton motive force as heat with no ATP production
Uncoupling protein
H+ ion channel exclusively in brown fat cells
How does sweating change when you move to warmer place
increased capacity for sweat production that is less salty – more heat-adapted ppl will have hypertonic blood sooner during heavy sweating –> thirsty sooner
Thermoregulatory system
Preoptic anterior hypothalamus has receptor neurons that fire APs proportional to the temporature of POAH; increased temperature-> increased firing mechanisms –>stimulates cooling mechanisms
What input does th POAH receive for temperature
senses local temperature in brain adn receives inhibitory input from cutaneous cold receptors and excitatory input from cutaneous warm receptors
Posterior hypothalamus in temperature regualtion
receives strong excitatory input from cutaneous cold receptors and weak inhibitory input form warm receptors
No input for local brain temp
Excitation of these receptors –> induced heat-gain mechanisms
Interaction between POAH and posterior hypothalamus
Cells in POAH tonically active at 37 C; POAH neuronal activity inhibits cells of posterior hypothalamus
Drop in temperature reduces inhibition of posterior hypothalamus –> heat inducing mechanisms
cooling of POAH in absence of posterior hypothalamic neuronal excitation
don’t produce as much shivering, vasoconstriction –> need input from both POAH and cutaneous cold receptors
Fever
directly due to release of cytokines that reset the set point so the brain thinks it is cooler than it actually is to induce heat-producing mechanisms
Steps of fever
pyrogens cause release of cytokines (IL-1, IL-6, TNF, interneuron) that act on endothelial cells of hypothalamus in region of OVLT to produce PGE2. PGE2 acts on POAH to decrease thermoreceptor activity –> new set point to higher level. Body thinks it is too cold than it should be –> heat producing mechanisms
Water Balance
Cells in OVLT and Subfornical region (SFO) sense increase osmolarity –> change in firing of neurons so ADH is secreted
(SFO–> lat hypothalamus –> limbic system)
NOTE SON/PVN make ADH and send down axons to posterior pituitary
neurons also go to tell you to drink
Ventromedial nucleus
satiety; lesion here will cause increased eating ; stimuate –> inhibit urge to eat
Lateral hypothalamus
hunger/feeding center; lesion = anorexia. Stimulate – eat
Paraventricular nucleus
similar to ventromedial (satiety; lesion here will cause increased eating; stimuate –> inhibit urge to eat)
Arcuate nucleus
monitor peripheral hormone levels
Circadian rhythm
Suprachiasmatic nucleus acts as circadian clock and receives direct input from retina; SCN does not require exogenous input but light entrains clock to daily environmental light/dark cycles
Peripheral clocks
organs in boyd have clocks that are entrained by cenral clock and other cues (eating, exercise)
