4 Hypothalamus I & II Flashcards
(40 cards)
Big picture: what’s the role of the hypothalamus?
- controls homeostasis
- integrates endocrine, autonomic and somatomotor systems
- also involved w/ affective behavior
define: diencephalon
the thalamus, subthalamus, hypothalamus and epithalamus
define: infudibulum
“funnel” = pituitary stalk
tuber cinerum
“Grey swelling” is region on ventral surface of brain that extends from the optic chiasm to the mammilary bodies
median eminence
part of the tuber cinerum that is raised and forms the infundibulum; contains 1° capillary network of the hypophysial portal system
True or False: The neurons of the hypothalamus are nice and neatly ordered?
False, unlike the neat rows of neurons in the hippocampus, the neuronal organization of the hypothalamus is highly heterogeneous.
Describe”the”information”integrated”and”affected”by”the”hypothalamus”(e.g.,”sensory,” affective,”motor;”control”of”temperature,”osmolarity”and”salt”balance,”circadian”rhythms,” reproduction,”stress,”arousal).
??
Describe the anatomical landmarks of the brain that demarcate the hypothalamus.
- just dorsal to pituitary
- just ventral to thalamus from which it is separated by the hypothalamic sulcus
- makes up floor and lateral walls of 3rd ventricle
- continuous with the pre-optic area anteriorly and the mammillary bodies posteriorly
- medial and rostral to the subthalamic region
Describe”the”MAJOR”afferents (5) of”the”hypothalamus”and”the”type”of”
information”these”tracts”carry.”
- mfb* (median forebrain): carry sensory, motor, limbic and autonomic info from the cortex, striatum and septum
- retinohypothalamic: carry sensory/circadian info from the retina
- dlf* (dorsal longitudinal fasiculus): carry motor, sensory and autonomic info from the brainstem and spinal cord
- stria-terminalis*: carries limbic info from amygdala
- fornix: carries info from hippocampus (memory?)
*also contain efferents from hypothalamus
Describe”the”MAJOR”efferents (6) of”the”hypothalamus”and”the”type”of”
information”these”tracts”carry.”
- mfb: carry limbic, autonomic and motor info to median forebrain
- tuberoinfundibular tract: endocrine signals to adenohypophysis
- supraopticohypophysial: endocrine signals to neurohypophysis
- dlf: motor, autonomic, etc. to brainstem and spinal cord
- mammillothalamic: limbic info
- stria terminalis: limbic info to amygdala
Describe”the”nuclei”and”hormones”that”provide”input”to”the”posterior”pituitary.
SO (supraoptic) and PVN (paraventricular) nuclei of hypothalamus project their axons to the neurohypophysis via the supraopticohypophyseal tract.
- -signal with AVP (arginine vasopressin) and oxytocin–two related nonapeptides
- -cell bodies in both the SO and PVN make both hormones; each nuclei has 50/50 breakdown of AVP- and oxytocin-producing neurons
What does AVP do?
acts on the kidney to promote water reabsorption
Lesions of the ant. hypothalamus that disrupt input to the SO and PVN nuclei lead to ?
diabetes insipidus – abnormal production of lots of dilute pee
When is oxytocin released?
released in response to: sexual stim, uterine dilation, nursing and, sometimes stress
What does oxytocin do?
-stimulates uterine contraction
-stimulates milk secretion
Along with AVP, oxytocin is also involved with:
-maternal instincts, pair bonding, love, empathy, trust, eye contact
-aggressive behaviors, too
-oxytocin deficit in autism may be?
Prairie vs. Montaine voles
Have different expression of AVP and oxytocin receptors:
- prairie voles express these receptors in their nucleus acumbens (part of the mesolimbic reward system); they are monogamous and males show aggression towards other males etc.
- montaine voles express these in other areas like the lateral septum and the amydala and do not show these parental, partner-preference, mating for life behaviors
Tuberoinfundibular tract definition
the name for the collection of axons from periventricular regions of the hypothalamus (paraventricular, arcuate and ventromedial nuclei and the preoptic area) that secrete releasing/inhibitory factors into the anterior pituitary via a vascular connection
Describe”the”HPG”axis.
[photo]
Describe how gonadal steroids and other environmental factors influence GnRH neurons.
Kisspeptin neurons integrate information from estrogen, progestins, androgens and other hormones (e.g. leptin, glucocorticoids ) (i.e. they have a high amt of receptors for these hormones) and then serve as presynaptic afferents that innervate GnRH neurons in the hypothalamus.
- -The secrete kisspeptin which then acts thru G-prot coupled receptors on the GnRH neurons.
- -It therefore serves as a master regulator of the HPG axis.
- -These kisspeptide cells are responsible for the onset of puberty and regulation of cycling in adults.
Describe the difference between activational and organizational effects of steroids.
Organizational effects: permanent effects on hormone on the structure/function of brain regions; leads to sexual dymorphism (e.g. ∆s in size of SDN-POA); will continue to have their effect in the absence of that hormone later
Activational effects: transient effects of hormones involved with normal cyclicity in females sex-specific behavior and ∆s in the HPG axis necessary for parturition
–also involves w/ PMS, PMDD, enhanced sz susceptibility in catamenial epilepsy
Name the nucleus that is the master regulator of circadian rhythms and describe how loops of transcription factor expression control the “clock”.
Peripheral clocks exists all over the body, but the SCN in the master clock.
- -In the SCN (suprachiasmatic nucleus), transcription factors (clock, BMAL1, Crypton and Period) encode proteins that regulate each other’s and other downstream proteins’ expression in such a way that you get 24hr periodicity.
- -the stability of these prots is regulated by casein kinase which is mutated in FASPS (familial advanced sleep phase syndrome)
What are two sexually dimorphic regions of the forebrain/hypothalamus?
VMN (ventromedial nucleus of the hypothalamus) and POA (pre-optic area)
What is the human equivalent of the SDN-POA?
INAH3 (the interstitial nucleus of the anterior hypothalamus 3)
Name the molecule that signals peripheral energy stores from white adipose tissue.
leptin
