Flashcards in Hypothalamus II Deck (22)
What kind of input gets to the hypothalamus?
multimodal brainstem afferents
How does olfactory info get to the hypothalamus?
mdeial forebrain bundle, stria terminals, ventral amygdalofugal path and fornix
Where does visual info go in the hypothalamus?
suprachiasmatic nucleus from the retina
How does visceral info get to the hypothalamus?
ascending projections from the nucleus tractus solitarius, which relays info from CNIX and CNX
What kind of multimodal brainstem afferents go to the hypothalamus?
medial forebrain bundle: bidirection tract including monoamine (noradrenergic A6, A1, A2) and adrenergic (C1,C2) info; seratonergic info
How does limbic info get to the hypothalamus?
bidirection connections with the amygdala, hippocampus, septum via the fornix, stria terminalis, and the ventral amygdalofugal bundle
What are circumventricular organs?
regions of the brain that lack a blood brain barrier and allow blood borne signals to reach chemosensitive neurons.Also allow them to use neurohumoral/hormonal mechanisms to control peripheral function
What is the subfornical organ?
a circumventricular organ around the anterior wall of the third ventricle that contains angiotensin II receptors that induce drinking
What is the organum vasculosum of the lamina terminalis? OVLT
may have neuroendocrine function and may contain osmoreceptors for vasopressin release
What is the area postrema?
circumventricular organ in the walls of the fourth ventricle in the medulla. It is the chemoreceptor trigger zone for vomiting.
What is the median eminence?
part of the pituitary stalk. major route oc fommunication between the hypothalamic-pituitary system and target effector organs. circumventricular organ.
What is the medial forebrain bundle?
group of axons running rostrocaudally through the lateral hypothalamus. conntects the hypothalamus with the brainstem and basal forebrain. important for olfactory input and monoamine input
What is the dorsal longitudinal fasciculus?
output of hypothalamus to the autonomic cell groups in the brainstem and spinal cord.
What are the connections between the hypothalamus and the anterior and posterior pituitary? What is the embryological origin?
posterior pituitary is a true neuronal connection derived from neural ectoderm. As such, communication is very fast. called the neurohypophysis.
anterior pituitary is a hormonal connection derived from oral ectoderm/Rathke's pouch The anterior pituitary is also called the adenohypophysis. Message from the hypothalamus conveied by the portal plexus. These are slower responses.
What hormones are released by the neurohypophysis?
oxytocin and vasopressin (antidiuretic hormone)
Where are oxytocin and vassopressin synthesized?
magnocellular neurons of the supraoptic and paraventricular nucleus
How do oxytocin and vasopressin get to the posterior pituitary? How do they get to the body?
from the supraoptic and paraventricular nuclei, they are transported in the tuberohypophyseal or (more important) supraopticohypophysial tract. these are basically axons from these nuclei. the hormones are released after an AP goes down the axon.
they get to the rest of the body via release into a capillary plexus and then transport to the general circulation by the hypophyseal veins
What does ADH/vasopressin do?
binds to receptors in the collecting duct of the kidney and promotes reabsorption of water. substances that suppress ADH (like alcohol) promote diuresis. also helpful during hemorrhage as a vasoconstrictor
What is diabetes insipidus? What are the etiologies?
impaired or absent ADH secretion.
excessive drinking and urination seen. This is called central diabetes insipidis.
nephrogenic diabetes insipidus is when the kidneys don't respond to ADH
What are 3 main functions of oxytocin? Main receptors?
1. milk letdown (taget cell is smooth muscle of mammary alveoli)
2. stimulation of uterine smooth muscle contraction to promote birth (oxytocin receptors on uterine smooth muscles at the end of gestation = more irritable uterus)
3. maternal and affiliative behaviors (from praire vole research. probably controled by the nucleus accumbens, at least in animals)
What are the effects of oxytocin and social cognition in humans?
increased facial recognition memory
increased gaze specificity to the eye.