Block 4 Shut the door Flashcards
homeostasis example pathway
receptors: baroreceptors (peripheral) or temperature (central) > AFF > hypothalamus > EFF > hormones/ANS
homostasis fxn
integrates info for control of ENDOCRINE, ANS, and neural systems concerned with motivation (LIMBIC SYSTEM)
fornix
major projection from hypothalamus > mammillary bodies
pituitary structure
when head trauma…
lies at base of brain in sphenoid bone: sella turcica
infundibulum/stalk to pit can be severed = severs pit from thalamus»_space;> increase in prolactin (because under inhibitory control)
adenohypophysis
neurophypophysis
median eminence
anterior pituitary (more rostral)
posterior pituitary
infundibulum (intersection between hypothalamus and pit gland = impt relay)
posterior pituitary fxn
synthesis and secretion of VASOPRESSIN OR OXYTOCIN
synthesized in MAGNOCELLULUAR hypothalamic neurons in SUPRAOPTIC (SON) and PARAVENTRICULAR (PVN) nuclei (secrete directly into systemic circulation)
>
transported via axons to nerve terminals in posterior pituitary
Supraoptic nucleus (SON) and paraventricular nucleus (PVN) are where?
activated by
in medulla
limbic structures (motivation, emotions) solitary nucleus (medulla) (requires AFF from baroreceptors and gi tract)
nerve terminals in posterior pituitary >
vasopression and oxytocin axonal transported > terminal > vesicles > released by AP activity
Vasopressin/ADH stimulus
- increased BLOOD OSMOLALITY: too much NaCl > hypothalamus > VP > kidney > INC WATER RESORPTION by kidney
- HYPOVOLEMIA: dec blood volume > receptors in heart > hypothalamus > VP > INC WATER RESORPTION
- HYPOTENSION: dec blood pressure > baroreceptor > hypothalamus > VP > VASOCONSTRICTION > inc BP
Oxytocin stimulus
WOMEN
- SUCKLING/nursing > inc OT > “milk ejection reflex” via smooth muscle contraction in breast
- UTERINE SITMULATION > inc OT > uterine contraction > delivery of newborn
* bonding idea, delivered intranasally
anterior pituitary fxn
families
secretions of “families” of hormones into system circulation
1. somatomammotropins
GH
PROLACTIN
- glycoproteins
TSH
FSH
LH - opiomelanocortin peptides
ACTH
B-EP
somatomammotropins
stimulus and effects
GH growth hormone
stimulus: EXERCISE, STRESS, SLEEP
effect: tissue growth, metabolism of fat, carbs, etc.
PROLACTIN
stimulus: SUCKING, STRESS
effect: development of mammary tissue, LACTATION (to be ejected by oxytocin)
glycoprotein
stimulus and effects
TSH thyroid-stimulating hormone
stimulus: COLD TEMPS
effects: increase TH > inc cell metabolism, inc metabolic rate, inc heat production *negative feedback
FSH follicle-stimulating hormone gonadotropin regulated by hypothalamic peptide effects: MEN inc SPERMATOGENESIS WOMEN development of ovarian FOLLICLE
LH luteinizing hormone
gonadotropin regulated by hypothalamic peptide
effects:
MEN *required for SPERATOGENESIS (with FSH), stimulates TESTOSTERONE
WOMEN initiates OVULATION “trigger,” stimulates PROGESTERONE from spent follicle
opiomelanocortin peptides
stimulus and effects
opiate receptor binding, pigment action, adrenal cortex
common precursor: pro-imc: POMC
ACTH adrenocorticotropic hormone
stimulus: STRESS
effects: secretes CORTISOL/glucocorticoid from adrenal cortex
B-EP beta-endorphin
stimulus: STRESS (fight or flight)
effects: opiate-like ANALGESIA
POMC special because
when cleaved makes two biologically active peptides: ACTH and B-EP
test used clinically to asses anterior pituitary function?
stress common stimulus, so induce insulin-induced hypoglycemia
inject small insulin: decrease blood glucose»_space;> increase in ACTH, cortisol, prolactin, b-EP, GH
hypothalamus controls anterior pituitary by _______ neurons,
which secrete _______ to median eminence
parvocellular neurons
hypothalamic releasing hormones
hypothalamic releasing hormone
function/pathway
synthesized in parvocellular neurons > transported via axons to median eminence > released from nerve terminals into hypophyseal portal vein
hypothalamic releasing hormones
excitatory
inhibitory
4 excitatory:
TRH thryotropin-releasing hormone = INC TSH
GnRH gonadotropin-releasing hormone = INC FSH and LH
CRH corticotropin-releasing hormone = INC ACTH and B-EP
GHRH growth hormone-releasing hormone = INC GH
2 inhibitory:
SOMATOSTATIN decrease GH secretion
DOPAMINE decrease PROLACTIN
only pituitary hormone controlled by excitatory and inhibitor HRHs
GH
diabetes insipidus
bitter urine
LOSS OF VASOPRESSIN SECRETION
etiology: head trauma (sever pit stalk), autoimm, idiopathic
POLYURIA excess urine
POLYDYPSIA excess drinking
Tx: desaminovasopression
galactorrhea-amenorrhea
inappropriate lactation
cessation of menstruation
HYPERPROLACTINEMIA increased blood prolactin
etiology: tumor in pituitary = MICROADENOMA that release prolactin > dec LH and FSH > cessation of menstruatio > INFERTILITY
Tx: surgically remove microadenoma, block prolactin with DOPAMINE REC AGONIST
signals from periphery that cause us to stop eating
- hormone CCK from gi tract thru vagus to brainstem
(SHORT-TERM SIGNAL) - LEPTIN from intestines from high fat content to hypothalamus
(LONG-TERM SIGNAL)
short term signals of satiety (decreased food intake)
a. oropharyngeal: TASTE
b. GASTRIC DISTENSION/STRETCH and INTENSTINAL NUTRIENT
c. POST-ABSROPTIVE SATIETY: gi > liver through portal vein; SENSORS FOR GLUCOSE AND FREE FAs in liver
satiety factors in CNS
a. gastric distention
b. CCK
c. ghrelin
a. gastric distenion: MECHANORECEPTORS on VAGAL AFFERENTS > solitary nucleus (NTS)
* add leptin, increased response to gastric stretch
b. cholecystokinin CCK: hormone released from duodenum in response to meals
-inc gallbladder contraction > inc bile release > inc fat digestion
-inc pyloric constriction
-inc gastric contractions
CCK Rec > inc VAGAL AFF response > NTS
c. ghrelin hormone: from stomach
increased by fasting
OREXIGENIC: INC APPETITE
Prader-Willi syndrome
Sx
fetal hypotonia mental retardation hypogonadotropic hypogonadism DEC FSH and LH ghrelin secretion HYPERGHRELINEMIA obesity hyperphagia EXCESSIVE EATING
long-term CNS signals of satiety
LEPTIN: adipocytes release leptin *morbid obesity: higher > normal amounts leptin site of action: 1. solitary nucleus in brainstem 2. hypothalamus
MULTIPLE HYPOTHALAMIC NUCLIE implicated in control of food intake: LHA, PVN, ARC
CNS nuclei of satiety:
LHA lateral hypothalamic area
PVN paraventricular nucleus
ARC arcuate nucleus
activation of LHA > release of “anabolic” NT = OREXIN > increase in eating
activation of PVN > release of “catabolic” NT = CRH (corticotropin releasing hormone) > decrease in eating
ARC: integrates all this info
two populations of neurons:
i. NPY (neuropeptide Y) neurons project both to PVN and LHA to INC EATING
ii. MELANOCORTIN neurons project both to PVN and LHA to DEC EATING
LHA lesion
APHAGIA cessation of eating
1. aphagia due to damage to MEDIAL FOREBRAIN BUNDLE = MESOLIMBIC SYSTEM dopeminergic system
reduced MOTIVATION to eat
reduced MOTOR FUNCTION to eat
- aphagia due to loss of neurons that synthesis “orexigenic” peptide = OREXIN
actions of leptin on ARC
i. leptin acts in ARC to inhibit NPY: DEC FOOD INTAKE
ii. leptin acts in ARC to activate melanocortin neurons: DEC FOOD INTAKE
actions of ghelin on ARC
ghrelin acts in ARC to activate NPY neurons: INC FOOD INTAKE
what type of drug could be promising candidates for treating hyperphagia-induced obesity?
activate melanocrtin receptors
___% treated for mood disorders
over 50%
limbic system related structures
amygdala hippocampus septal nuclei nucleus accumbens medial prefrontal cortex and anterior cingulate cortex ventral segmental area anterior and dorsomedial nuclei of thalamus mamillary nuclei
limbic system pathways:
FORNIX: hippocampus > mammillary body and septal nuclei
MAMMILLO-THALAMIC TRACT: mammillary body > anterior n of thalamus
anterior n of thalamus > cingulate gyrus and prefrontal cortex
STRIA TERMINAULIS: amygdala > septal nucleus
MEDIAL FOREBRAIN BUNDLE: midbrain via hypothalamus > forebrain
all limbic areas receive rich innervation by _____ and _____ axons
monoaminergic and cholinergic axons
a. NE from locus ceruleus (LC) in pons
b. 5HT from raphe nuclei (Ra) midbrain, pons
c. DA from mesolimbic system***
d. ACh from nucleus baseless and septal nucleus
= general arousal, sleep wake cycles
ventral segmental area (VTA) projects to:
DA neurons
nucleus accumbens
medial prefrontal cortex
amygdala
septal nuclei
mesolimbic system (DA)
i. self-stimulation studies: VTA > REWARDING
ii. drug addiction
COCAINE block DA repute: inc DA in synapse
lesion VTA, NAcc
decreased drug seeking behavior
DA receptors permanently blocked
***has effects on our natural reward system (endorphins, natural opioids, nicotine, opioids)
natural rewards
SEX
FOOD
ACh neurons lost in AD in
nucleus basalis**
spetal nucleus
limbic system functions
AMYGDALA and lesion
amygdala fxns
a. role in fear conditioning/type of learning
Pavlovian classical conditioning
lesions to amygdala: prevent fear conditioning