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- University of Michigan - Ann Arbor
- Molecular, Cellular And Developmental Biology
- Molecular, Cellular And Developmental Biology 418
- Denver
- Lecture 7: Neuroendocrine System-Hypothalamus & Neurohypophysis
Lecture 7: Neuroendocrine System-Hypothalamus & Neurohypophysis
Molecular, Cellular And Developmental Biology 418 with Denver at University of Michigan - Ann Arbor
About this deck
By: Kristina Brooks
Created: 2010-10-04
Size: 99 flashcards
Views: 7
Created: 2010-10-04
Size: 99 flashcards
Views: 7
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What does the neurohypophysis entail?
Posterior pituitary and the median eminence
What does neurohypophysis refer to?
Axon terminals from nerve cells terminate at blood vessels
What is neurosecretion?
Release of neural hormones into blood stream via neurosecretory neurons
What is the master gland?
The hypothalamus
What controls the anterior pituitary?
The hypothalamus
What is hypophysiotropin?
Neurohormone that regulates secretion by the hypophysis
What does dual hypothalamic control refer to?
Releasing factors (liberins)
Release inhibiting factors (statins)
Release inhibiting factors (statins)
What does CRH stimulate?
The release of beta-LPH and ACTH
What does TRH stimulate?
TSH
What do GnRH and GnIH act on?
AP-LH and FSH levels
What to GRH and somatostatin act on?
AP-Growth hormone
What do PRH and PIH act on?
AP-Prolactin
Where are magnocellular neurons found?
Supraoptic nucleus (SON) and paraventricular nucleus (PVN) in the hypothalamus
What is a nucleus?
Collection of neurons with similar function
What is the SON responsible for releasing?
ADH
What is the PVN (magnocellular) responsible for releasing?
Oxytocin and vasopressin
What are the organs affected by magnocellular neurons?
Kidney, uterus, mammary gland
Where are the parvicellular hypophysiotropic neurons found?
Paraventricular nucleus (PVN) and Arcuate nucleus
What is the PVN (parvicellular) responsible for releasing?
TRH, CRH, Somatostatin
What is the Arcuate nucleus responsible for releasing?
GHRH, GnRH, Dopamine
Where are the hypothalamic projection neurons found?
PVN, Lateral hypothalamic area (LHA), and the Arcuate nucleus
Where do the hypothalamic projection neurons project?
To spinal cord and hindbrain
What is the PVN (HPN) responsible for releasing?
AVP, Oxytocin
What is LHA responsible for releasing?
MCH, ORX (orexin)
What is the arcuate nucleus (HPN) responsible for releasing?
POMC, CART
What are the targets of the hypothalamic neuron projection?
Neuronal targets-sympathetic preganglionic neuron in spinal cord
When staining transverse sections of the rat median eminence, what was discovered?
CRH and TRH fibers are located in the external zone of the median eminence
AVP fibers are located in the internal zone of the median eminence
AVP fibers are located in the internal zone of the median eminence
From this experiment, what was determined about the location of fibers?
The location of fibers is governed by where the cell bodies are located in the hypothalamus and where the axons project to (i.e. terminate in the ME or project to the pars nervosa)
What is the suprachiasmatic nucleus (SCN) important for?
Regulating biological rhythms
What does somatostatin inhibit?
Growth hormone
How is growth hormone regulated?
GHRH-growth hormone releasing hormone (stimulates)
SRIF-somatostatin (inhibits)
SRIF-somatostatin (inhibits)
What is ghrelin?
28 AA sequence derived from the gut that stimulates GH release
-Increases before meals and decreases after meals
-Increases before meals and decreases after meals
What is ghrelin acyltransferase (GOAT) responsible for?
Enzyme expressed in stomach that is responsible for acylating 3-serine of ghrelin with octanoate
What do GHRH injections do?
Stimulate GH release
Give an overview of the regulation of GH secretion.
SRIF neuron controls/inhibits both the GHRH neuron and the pituitary gland.
GHRH neuron acts on pituitary to stimulate release of GHRH, SRIF neuron acts on pituitary to inhibit as needed
Ghrelin from the stomach feeds back positively to the GHRH neuron and the pituitary
GHRH acting on liver, liver negative feedbacks to pituitary via IGF-I
GH from pituitary positive feedback on SRIF neuron
GH on fat, free fatty acids inhibit pituitary
GHRH neuron acts on pituitary to stimulate release of GHRH, SRIF neuron acts on pituitary to inhibit as needed
Ghrelin from the stomach feeds back positively to the GHRH neuron and the pituitary
GHRH acting on liver, liver negative feedbacks to pituitary via IGF-I
GH from pituitary positive feedback on SRIF neuron
GH on fat, free fatty acids inhibit pituitary
When does GH secretion increase?
During sleep
What does pulsatility refer to?
Undergoing pulsation-cyclic increase and decrease of hormone concentrations
What hormones are involved with the regulation of prolactin secretion?
Dopamine
TRH-Thyrotropin releasing hormone
VIP-Vasoactive intestinal polypeptide
PRF-Prolactin releasing factor
TRH-Thyrotropin releasing hormone
VIP-Vasoactive intestinal polypeptide
PRF-Prolactin releasing factor
Give an overview of prolactin secretion regulation.
PRF neurons in the PVN and dopamine neurons in the Arc connect with pituitary
Dopamine inhibits prolactin release from the pituitary
TRH, Oxytocin, VIP stimulate PRL release from pituitary
PRL stimulates breast, multiple other target organs
Sucking stimulus travels up spinal afferent neuron, inhibiting dopamine neurons and stimulating PVN PRF neurons
PRL stimulates dopamine neurons and inhibits itself through the pituitary
Estrogen stimulates PRL release
Dopamine inhibits prolactin release from the pituitary
TRH, Oxytocin, VIP stimulate PRL release from pituitary
PRL stimulates breast, multiple other target organs
Sucking stimulus travels up spinal afferent neuron, inhibiting dopamine neurons and stimulating PVN PRF neurons
PRL stimulates dopamine neurons and inhibits itself through the pituitary
Estrogen stimulates PRL release
What factors stimulate PRL release?
Estrogen
TRH, oxytocin, VIP release
Sucking stimulus traveling up the afferent spinal neuron to the PVN PRF neurons (also inhibits dopamine release)
TRH, oxytocin, VIP release
Sucking stimulus traveling up the afferent spinal neuron to the PVN PRF neurons (also inhibits dopamine release)
What factors inhibit PRL release?
PRL release
-Acts on pituitary and dopamine neurons
Dopamine release
-Acts on pituitary and dopamine neurons
Dopamine release
What is the thyroid system important for?
Energy balance and metabolism
Give an overview of the hypothalamo-pituitary-thyroid axis.
Temperature inputs from brain stem catecholaminergic neurons input to the TRH neurons in the PVN and the hypothalamus
TRH release stimulates pituitary to convert T4 to T3, releases TSH which acts on thyroid
Thyriod releases T3 and T4, both inhibit the pituitary and TRH neurons in the PVN
Somatostatin inhibits TSH release
TRH release stimulates pituitary to convert T4 to T3, releases TSH which acts on thyroid
Thyriod releases T3 and T4, both inhibit the pituitary and TRH neurons in the PVN
Somatostatin inhibits TSH release
What does the TRH precursor give rise to?
6 different biologically active peptides
What does TRH stimulate?
TSH release
What blocks TRH action?
T3 and T4
Give an overview of the hypothalamo-pituitary-gonadal (HPG) axis.
Stress, nutrition, exercise, seasonal cues and neuronal mediators stimulate or inhibit GnRH neuron, which projects to the hypothalamus
Pituitary releases LH and FSH, which stimulate ovaries or testes
Ovaries and testes release inhibin, which negatively feeds back to the pituitary
Ovaries release estradiol which inhibits pituitary and GnRH neuron, and also progesterone, which inhibits neuronal mediators
Testes release testosterone, which inhibits the pituitary and neuronal mediators
Pituitary releases LH and FSH, which stimulate ovaries or testes
Ovaries and testes release inhibin, which negatively feeds back to the pituitary
Ovaries release estradiol which inhibits pituitary and GnRH neuron, and also progesterone, which inhibits neuronal mediators
Testes release testosterone, which inhibits the pituitary and neuronal mediators
What inhibits the HPG axis?
Inhibin inhibits the pituitary (released from ovaries or testes)
Estradiol inhibits pituitary and GnRH neuron
Progesterone inhibits neuronal mediators
Testosterone inhibits the pituitary and neuronal mediators
Estradiol inhibits pituitary and GnRH neuron
Progesterone inhibits neuronal mediators
Testosterone inhibits the pituitary and neuronal mediators
What do most species have in regards to GnRH?
Most species have two GnRHs that may have different functions that are expressed in different regions of the brain
How many peptides are in GnRH?
Ten
What are the other forms of GnRH that are expressed in other vertebrate species?
Midbrain GnRHII
Telencephalic GNRHIII
Telencephalic GNRHIII
What nucleus modifies GnRH output? What pattern is observed?
Suprachiasmatic nucleus (SCN)
Pulsatility
Pulsatility
What kind of generators are GnRH neurons?
Endogenous pulse generators
What other hormone pulse coordinates with GnRH?
One pulse of GnRH coincides with a pulse of LH in the systemic circulation
What was observed in a female rhesus monkey with bilateral lesions in the arcuate nuclei affecting GnRH neurons, who had GnRH infused at different pulse frequencies?
One GnRH pulse per 3 hr promotes FSH secretion (mimics early-mid follicular phase)
One GnRH pulse per 1 hr promotes LH secretion (mimics late follicular phase)
One GnRH pulse per 1 hr promotes LH secretion (mimics late follicular phase)
When given a dose of estradiol, what was observed in ovariectomized monkey treated with E2 infusion?
E2 suppresses LH secretion
-Several hours after E2 treatment is stopped the LH secretion rebounds
-Several hours after E2 treatment is stopped the LH secretion rebounds
What is E2-induced negative v. positive feedback on LH secretion determined by? Explain.
The duration of exposure to and dose of estradiol
-Longer duration E2 exposure leads to positive feedback resulting in an LH surge
-At first, E2 causes negative feedback, decreases LH secretion
-Longer duration E2 exposure leads to positive feedback resulting in an LH surge
-At first, E2 causes negative feedback, decreases LH secretion
Describe the changes in plasma E2, P4, GnRH, LH, and FSH during the menstrual cycle.
E2: negative feedback during days 0-10, positive feedback/peak through days 10-14, negative feedback during remaining cycle
P4: peaks near end of menstrual cycle
GnRH: peaks during ovulation (day 14)
LH and FSH: peak during ovulation (day 14)
P4: peaks near end of menstrual cycle
GnRH: peaks during ovulation (day 14)
LH and FSH: peak during ovulation (day 14)
What are the key hormones involved in the hypothalamo-pituitary-adrenal (HPA) axis?
CRH-corticotropin releasing hormone (or factor, CRF)
AVP-arginine vasopressin
AVP-arginine vasopressin
Give an overview of the HPA axis.
Processive (Neurogenic) stress either inhibits or stimulates neuronal mediators
Neuronal mediators input to CRH neuron
CRH neuron projects to pituitary
CRH/AVP stimulate pituitary to release ACTH
ACTH stimulates adrenal gland
Adrenal gland release cortisol
Cortisol inhibits pituitary and CNS and CRH neuron
Neuronal mediators input to CRH neuron
CRH neuron projects to pituitary
CRH/AVP stimulate pituitary to release ACTH
ACTH stimulates adrenal gland
Adrenal gland release cortisol
Cortisol inhibits pituitary and CNS and CRH neuron
What stimulates the HPA axis?
CRH/AVP stimulates release of ACTH
ACTH stimulates Adrenal glands
ACTH stimulates Adrenal glands
What inhibits the HPA axis?
Cortisol release
-Inhibits pituitary and CRH neuron
-Inhibits pituitary and CRH neuron
How many peptides are formed from the CRH prohormone?
Only one-CRH
Why is pulsatility important?
Maintains sensitivity of target cell
When does GnRH pulsate more frequently?
Closer to ovulation
What is the central regulator/integrator of stress responses?
Corticotropin-releasing factor
What are some of the key characteristics of CRH?
1. Hypophysiotropin: HP-Adrenal axis
2. Neurotransmitter/neuromodulator
3. Growth factor/cytoprotective
2. Neurotransmitter/neuromodulator
3. Growth factor/cytoprotective
What effects does CRH have on the body?
Involved with locomotion, control of appetite, behavioral responses to stress, anxiety/depression, autonomic system activation
What are the four paralogous lineages of CRF-like peptides?
CRF, Urotensin I/Urocortin I, Urocortin 2, Urocortin 3
What are the different neuroendocrine control mechanisms?
1st order neuroendocrine loop
2nd order
3rd order
2nd order
3rd order
What is involved in the 1st order neuroendocrine loop?
CNS-->target
What is involved in the 2nd order neuroendocrine loop?
CNS-->Endo gland-->target
What is involved in the 3rd order neuroendocrine loop?
CNS-->Endo gland-->Endo gland-->target
What is the posterior pituitary an extension of?
The brain
Give an example of a 1st order neuroendocrine loop.
Oxytocin release, resulting in milk letdown
Posterior pituitary (AVP) --> kidney
Posterior pituitary (AVP) --> kidney
Give an example of a 2nd order neuroendorine loop.
Growth hormone
Hypothalamus --GHRH-->Pituitary-->GH
-->Liver
-->Fat
Hypothalamus --GHRH-->Pituitary-->GH
-->Liver
-->Fat
Give an example of a 3rd order neuroendocrine loop.
Thyroid hormone signaling
Hypothalamus (GnRH)-->Anterior pituitary (LH)-->Ovaries(E2)-->target tissues
Hypothalamus (CRH)-->Anterior pituitary (ACTH)-->adrenal gland (cortisol)-->target tissues
Hypothalamus (GnRH)-->Anterior pituitary (LH)-->Ovaries(E2)-->target tissues
Hypothalamus (CRH)-->Anterior pituitary (ACTH)-->adrenal gland (cortisol)-->target tissues
What are goiters caused by?
Dietary iodine deficiency resulting in dysregulation of the thyroid axis
What does failure to produce active thyroid result in?
Loss of negative feedback, elevated production of thyroid stimulating hormone (TSH) by the pituitary gland, and growth of the thyroid
What is propressophysin?
The prohormone for AVP
What is prooxyphysin?
The prohormone for oxytocin
What is the cyclic structure of AVP caused by?
Disulfide bond between cysteine residues
How can AVP be turned into AVT?
3-Phe --> Ileu
How can AVP be turned into LVP?
8-Arg --> lys
How can AVP be turned into oxytocin?
8-Arg --> Leu
Is vasopressin the only homolog in mammals?
No, there are other homologs
What is the vasopressin homolog found in birds, fish, etc.?
Vasotocin
Where is oxytocin found?
In mammals
What is the oxytocin homolog found in birds, amphibians, and lizards?
Mesotocin
What is the oxytocin homolog found in fish?
Isotocin
What are the actions of arginine vasopressin?
Osmoregulation, vasoconstriction (increase BP when blood volume drops), ACTH release, antipyretic, behavioral effects
How does ADH affect osmoregulation?
In birds and mammals: inhibits water loss from body (diuresis) by altering ability of kidney tubules to reabsorb water
Increases water reabsorption
Increases water reabsorption
How does ADH increase water reabsorption?
Acts on the collecting duct and late distal tubules to increase permeability to water
-Increases cAMP in cells which increases water channel (aquaporin) synthesis, decreases urine volume
-Increases cAMP in cells which increases water channel (aquaporin) synthesis, decreases urine volume
How does ADH affect osmoregulation in fishes and amphibians?
Constriction of the afferent arteriole, decreases glomerular filtration rate
What is vasopressin's role in social behavior?
Increased expression in vasopressin in the ventral pallidium (VP) is associated with monogamy
What are some of the actions of oxytocin?
Labor
Milk let-down response
Behavioral effects
Milk let-down response
Behavioral effects
What is oxytocin's role in labor?
Contraction of myometrium (contraction of uterine muscle) during parturition
E2 increases responsiveness to OT while P4 decrease
Pituitin-pituitary extract used to be used to induce labor
Now use purified OT
E2 increases responsiveness to OT while P4 decrease
Pituitin-pituitary extract used to be used to induce labor
Now use purified OT
What is oxytocin's role in milk let-down?
Contraction of myoepithelium in mammary alveoli-final stage of lactation
What is oxytocin's role in behavioral effects?
May be released during orgasm
Can act on smooth muscles, and may also have central effects on sexual satiety
Promotes in-group trust and cooperation
Can act on smooth muscles, and may also have central effects on sexual satiety
Promotes in-group trust and cooperation
About this deck
By: Kristina Brooks
Created: 2010-10-04
Size: 99 flashcards
Views: 7
Created: 2010-10-04
Size: 99 flashcards
Views: 7
About StudyBlue
STUDYBLUE makes things that make you better at school.
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