Secretion of Hormones:
NEGATIVE Feedback

Output of a system ___ the input

Operates to maintain levels of a hormone at a given “__-__”

Secretion of Hormones

Positive feedback control:
____ the initial effect of hormone

Neuroendocrine reflexes:
Produces sudden ___ in hormone secretion

Rhythms:
->____ – about hourly
->____ – about 24 hr
->____ – about 1 year
->____ – day/night

Circadian Rhythm

->Biological clocks: Approximately __ hour cycles for body functions
(Ex: Temperature, gene expression, behavior, hormone secretion)

->Master clock = ___ ___ (__)
–Cluster of neuron cell bodies above the optic chiasm

–Clock proteins = “__-___” genes of SCN neurons -> synthesis of proteins
–Accumulate over course of day
–Eventually, ___ own transcription
–Degrade -> ___ genes from block
–Cycle slower than 1 day (~ 25 hours)
***Fluctuating levels -> ______ (Leads to ∆ in effector organs)

->Synchronization of biological clock with environment:
–If not adjusted, individuals circadian rhythms fall progressively out of ___ with day/night (free running)
–SCN is reset daily by ___ cues (∆ in light intensity, i.e. day-night cycle)

PINEAL GLAND

LIGHT PATHWAY
Different than for vision
–Specialized retinal ___ cells (1-2% of total)
•Melanopsin responds to ____ -> retino-hypothalamic tract ->SCN->->->pineal gland–Pineal Gland responds with ∆ in ____

MELATONIN
–Indoleamine
–Secreted during periods of ___
•Light/dark cycle entrains biological rhythms

Proposed ROLES of melatonin:
•Can induce natural ___
•Inhibits __ hormones
–Puberty initiated by drop in melatonin levels
•In other species -> seasonal breeding, hibernation, migration cycles
•Birth control
(High levels shut down ___)
•Antioxidant
•Slows aging process
•Enhances immunity
–Also slows regression of ___

Target Tissue Responsiveness: Receptors

1.) Absence of receptors:
___ ___ syndrome – lack of receptors for testosterone

2.) Receptor down-regulation

(Ex: Chronic ↑ insulin -> ↓ receptors -> ↑ [Glucose] blood)

Interaction of Hormones

_______ :
One hormone must be present for full effect of another hormone

Interaction of Hormones

_______ :
Several hormones are complimentary

->Combined effect greater than that of either by ___

Interaction of Hormones

_______ :
One hormone reduces the effectiveness of another

REVIEW
Control of hormone secretion:
->Negative feedback – output opposes the input
->Positive feedback – amplification of initial hormone effect
->Neuroendocrine reflexes – sudden increases
->Rhythms – of varying durations
(circadian rhythm – 24 hrs, base rhythm generated by clock proteins in the SCN, synch’d by light and pineal melatonin release)
->Hyposecreton
->Hypersecretion

Target Tissue Responsiveness:
->Absence of Receptor
->Receptor Down regulation - loss of function with chronic, elevated hormone levels

Interaction of Hormones:
->Permissiveness – little if any effect on its own, but needs to be there for another hormone to be effective (epinephrine and TH)

->Synergism – combined effect greater than either alone (FSH and T)

->Antagonism – One reduces the effect of another (P and E during pregnancy)

Endocrine: Hypothalamus and Pituitary

Objectives:

Hypothalamus

_____ center:
–Body temperature
–Thirst and urine output
–Appetite
–Anterior pituitary hormones
–Posterior pituitary hormones
–Uterine contraction and milk ejection
–ANS coordinating center
–Emotions and behaviors
–Sleep-wake cycles

Conduit to endocrine system:
–Stimulates or inhibits ____ pituitary hormone secretion via releasing - and inhibiting hormones
–Synthesizes ____ pituitary hormones

Pituitary Gland, A.K.A _____

_____– greek origin, meaning outgrowth or to grow beneath

•Two separate tissues of distinct neuroanatomical origins:

1) ____ Lobe:
•True glandular tissue – ___hypophysis (___ means “glandular")

2) ____ Lobe:
•Extension of hypothalamus–
___hypophysis

Neurohypophysis
(___ lobe of pituitary gland)

Two populations of neurosecretory neurons–1) ____ Nucleus (__)
2) ____ Nucleus (__)

Terminals in posterior lobe of pituitary
(Supported by glial _____)

Hormones:
->_____
->_____
(both structurally similar)

**SON and PVN contain neurons that produce ___ peptide hormones BUT, only ___ hormone produced per cell.

VASOPRESSIN
(a.ka. ___ Hormone)

Release triggered by:
•Hypothalamic ____ (dominant factor)
•Left atrial volume receptors (if large _ in vol./pressure)
•Pain, trauma and other stressors -> inappropriate H2O ____ in case of potential blood loss
•Physical exertion in __ environment

TARGETS:
•Kidney (nephron’s distal and collecting tubules)
–V2 receptors -> Gs -> AC -> cAMP (insertion of ____)
–↑ __ permeability -> enhance ____ of
H2O
–Normal regulator of H2O loss/balance

•Arteriolar ___ muscle
–V1 receptors -> Ca2+/PLC
*___ effect (causes contraction)
–Crucial during hemorrhage

OXYTOCIN

Release triggered by:
•Stimulation of cervical mechanoreceptors

•Stimulation of mechanoreceptors in nipple

–Actions:
•At uterus -> __ threshold potential (large dose -> prevent repolarization -> ___
–Can be used therapeutically to prevent post-partum ___

•At breast -> Effects via IP3/Ca2+/DAG ->__ myoepithelial tone

•E2 increases, catecholamines ___ actions

•Paracrine role: corpus luteum (CL) ____

–Also influences behaviors
•Maternal bonding

Adenohypophysis
(____ pituitary)

AP Hormone secretion regulation:
–Hypophysiotropic hormones:

•Hypothalamic Releasing Hormones–____ release of hormone from anterior pituitary cells

•Hypothalamic Inhibiting Hormones–____ release of hormone from anterior pituitary cells

•Secreted in ____

•Induce effects via cAMP, Ca2+, and phosphatidylinositol, JAK/STAT products: (Stimulate or inhibit transcription, modulate translation, & stimulate or inhibit secretion of target AP hormones)

Hypothalamic-Hypophyseal Portal System:
•Capillary-to-capillary link
–___ route from hypothalamus to pituitary
•Neurosecretory neurons ___ on the capillaries of portal system

Adenohypophysis
(anterior pituitary) CONT'D ...

TROPIC hormone:
•____ an endocrine tissue to:
1.) ___
2.) ___ that gland’s hormone

*originates from the ___ pouch

Multiple INPUTS regulate hypophysiotropic hormones

–Can be either ____ or ____

•Neural connections w/other portions of brain: Environmental factors & Emotions

•Chemical signals: Hypothalamic regions unprotected by ___ (Easy to measure chemical changes in blood)

–Typically, target gland hormones ___ secretion of tropic hormone that is driving it

•NEGATIVE FEEDBACK CONTROL:
–Once a hormonal system is activated, it’s secretion does NOT continue ___
–Diurnal rhythms ____

FIVE cell populations produce 6 major hormones:

1) Lactotropes = ___ (__)
(Protein, similar to GH)

2) Somatotropes = ___ ___ (_)
–Protein that acts via peptide mediators (insulin-like growth factors, IGFs)

3) Thyrotropes = ___ ___ ___ (__) (Glycoprotein w/ α and β subunits)

4) Corticotropes = ___ ____ (__)
–Peptide from precursor POMC
–Other products: melanocyte-stimulating hormone and endorphin

5) Gonadotropes = ___ ___ ___(__) & ___ ___ (__)
(Glycoproteins w/ common α, but distinctive β subunits)

REVIEW:

Anatomical arrangement of the hypothalamus and pituitary:
->Neurohypophysis is anatomically connected
->Adenohypophysis is functionally connected through a portal blood system

Neurohypophysis produces 2 hormones: 1) Vasopressin release triggered by increased plasma osmolarity or decreased ECF volume or blood pressure
-Detected by hypothalamic osmoreceptors and left atrium volume receptors
-Targets the kidney (distal and collecting tubules), causes insertion of aquaporins and enhances the retention of water
-Targets the arteriolar smooth muscle to cause pressor effect

2) Oxytocin release triggered by mechanoreceptors in cervix or nipple
-Acts at uterus (increase contractions)
-Acts at breast (milk ejection)
-Act at corpus luteum to aid in termination of CL function

Adenohypophysis:
->Controlled by hypophysiotropic hormones that can be stimulatory or inhibitory ->hormones are secreted in pulses, are hydrophilic in nature
->Generally controlled by a negative feedback loop

6 major hormones:
(PRL, LH, FSH, GH, TSH, ACTH)