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Prohormone biosynthesis
Receptor
Transportation
in blood
Effector
Response
Endocrine System
Hyperfunction
Endocrine System
Hypofunction
Endocrine gland
Target cell
Degradation
Excretion
Storage
Inputs
Degradation
Excretion
Hyperplasia
Tumor / CancerDestruction
Over stimulationOver inhibition
Secretion
Hormone processing
Review of Endocrine System
Antagonist Agonist
Inhibition Stimulation
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Know Major Hormone Signal
Transduction Pathwaysp 674
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Learning Objectives
By the end of this lecture you will learn about:
The basic neuroanatomy and function of the hypothalamus andpituitary the central endocrine organs.
The definition of neuroendocrinology.
The hypothalamic-pituitary anatomical & functional links. Understand posterior pituitary hormones and their functions.
Know all of the hypothalamic releasing/inhibiting hormones, theircorresponding pituitary hormones, and corresponding targethormones by abbreviation and by full name(s)!
Learn more about negative feedback.
Learn about biological rhythms controlled by hypothalamus andpineal hormones.
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I. Central Endocrine Organs
Brain (hypothalamus) Releasing/inhibiting hormones
Functions include reproduction, lactation, thyroid/metabolism,growth, stress
Anterior pituitary Has corresponding hormones to each hypothalamic hormone
Posterior pituitary Water balance, milk ejection
Pineal Biological rhythms
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What is Neuroendocrinology?
Link between nervous and endocrinesystems.
Primary driving force is typically the nervous
system; the endocrine system responds tonervous system signal; the endocrine systemfeedback to nervous system.
Often a single cell can have both neuronaland endocrine qualities.
Example: The hypothalamus.
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From AC Gore,
Fundamental Neuroscience
Vol 3, Ed. Squire et al, 2008
Overview of Hypothalams Neuroendocrine System
Pay a@enon to feedbackregulaon at
hypothalamus & pituitary
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Anatomical Relationship Between
Hypothalamus & Pituitary
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Hypothalamus
Anterior Pituitary
AKA: Portal Capillary Vasculature
Fig 188, p 676Fig 185, p 671
Hypothalamus
Posterior Pituitary
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Anterior Pituitary
Cells
Capillary
Secretory
vesicles incytoplasm
Posterior Pituitary
Neuroterminals
Nucleus
Extracellularspace
Secretory
vesicles innerve terminals
Electron microscopy (TEM) images of pituitary from a female rat
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II. Hypothalamus - Anterior Pituitary -Target System
Hypothalamic hormones involved in anterior pituitary
regulation are tropic hormones
Stimulate/inhibit hormone secretion of anotherendocrine gland (Anterior pituitary)
Stimulates and maintains the target function.
Most anterior pituitary hormones are tropic hormones
Stimulate/inhibit hormone secretion of another
endocrine gland (Target organ, e.g., thyroid gland,
testis).
Stimulates and maintains their target functions.Loss of secretion of a tropic hormone results in
hypotrophy/atrophy of the target.
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Vascular Link Between Hypothalamus &
Anterior PituitaryFig 18-8, p 676
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Hypothalamic Releasing & Inhibiting Hormones
Hormone Effect on Anterior Pituitary
Thyrotropin-Releasing
hormone (TRH)
Stimulates release of TSH
and prolactin
Corticotropin-Releasing
hormone (CRH)
Stimulates release of ACTH
Gonadotropin-releasinghormone (GnRH)
Stimulates release of FSHand LH
Growth-hormone releasing
hormone (GHRH)
Stimulates release of
growth hormone
Somatostatin (Growth-
hormone inhibiting hormone;
GHIH)
Inhibits release of growth
hormone and TSH
Prolactin-releasing hormone
(PRH)
Stimulates release of
prolactin
Dopamine (Prolactin-inhibiting
hormone; PIH)
Inhibits release of prolactin
Table 18-4, p 674
Secreon of each anterior
pituitary hormone is
smulated or inhibited by
one or more hypothalamic
hypophysiotropic hormones
Not identified yet
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Anterior Pituitary Synthesizes and Secrete 6
Different Protein (Peptide) HormonesTropic:
Thyroid-stimulating hormone(TSH): Stimulates secretion of thyroid hormone
Adrenocorticotropic homone (ACTH): Stimulates secretion of cortisol by adrenal cortex
Follicle-stimulating hormone (FSH): In females, stimulate growth and development of
ovarian follicles; promotes secretion of estrogen by ovaries. In males, required for
sperm production
Luteinizing hormone (LH): In females, responsible for ovulation and luteinization;
regulates ovarian secretion of female sex hormones. In males, stimulates
testosterone secretion.
Growth hormone (GH): Primary hormone responsible for regulating overall body growth;
involved in metabolism. Stimulates IGF-1 secretion.
Not Tropic:
Prolactin (PRL): Enhances breast development and milk production in female.
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Targets of Anterior Pituitary Hormones
Fig 18-6, p 673
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Links Between
Hypothalamic - Anterior Pituitary - Target HormonesGnRH
CRH
TRH
GHRH/ss
PIH (DA)
LH/FSH
ACTH
TSH
GH
PRL
Sex steroid hormonesCorsol (glucocorcoids)
Thyroid hormones
IGFI (also growth)
Milk synthesis
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III. Hypothalamus + Posterior Pituitary -
Target System
1. The paraventricular and supraoptic
nuclei both contain neurons that
produce vasopressin and oxytocin. The
hormone, either vasopressin or oxytocin
depending on the neuron, is synthesizedin the neuronal cell body in the
hypothalamus.
2. The hormone travels down the axon to
be stored in the neuronal terminals
within the posterior pituitary.
3. When the neuron is excited, the storedhormone is released from the terminals
into the systemic blood for distribution
throughout the body.
Fig 185, p 671
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Posterior Pituitary
Along with hypothalamus forms neuroendocrine
system
Does not synthesize any hormones Store and release two small peptide hormones
Vasopressin
Conserves water during urine formation
Oxytocin
Stimulates uterine contraction during childbirth and milk
ejection during breast-feeding
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Vasopressin (VP)
Also called ADH (anti-diuretic hormone) andarginine vasopressin (AVP).
Major function: Enhances water retention by the kidneys; it is
primary regulator of water balance in the body. Result is to cause changes in drinking and salt appetite.
Works together with CRH on stress response.
Arteriolar smooth muscle contraction (bloodpressure) - minor effect
Regulated by osmoreceptors in hypothalamus,that respond to a rise in plasma osmolarity (soluteconcentration).
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Vasopressin and Oxytocin
They are synthesized off of genes located head to head in
opposite orientations.
Each is nine amino acids (nonapeptide) and they are
structurally similar.
Both are in cells that are relative large (20-40 um), known as
magnocellular neurons*.
One type of OT receptor, on breast tissue, pituitary, brain,
uterus, arterioles.
Three types of AVP receptors, on kidney, pituitary, brain.
All receptors are G-protein coupled receptors.
*Contrast this with parvicellular (small) cells of hypothalamicreleasing/inhibiting neurons
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Pineal Gland
Tiny, pinecone-shaped structure
Located in center of brain
Secretes melatonin, a tryptophan metabolite Hormone of darkness
Secretion falls to low levels during light of day
Functions Helps keep bodys circadian rhythms in synchrony with light-dark
cycle
Promotes sleep
Influences reproductive activity, including onset of puberty
Acts as antioxidant to remove free radicals
Enhances immunity
Metatonin
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Circadian Rhythms
Suprachiasmatic nucleus (SCN) Part of hypothalamus
Bodys master biological clock
Self-induced cyclic variations in clock proteinconcentrations within SCN bring about cyclic changesin neural discharge from SCN
Cycle takes about a day
Drives bodys circadian (daily) rhythms
SCN must be set daily by external cues so bodys
biological rhythms are synchronized with activity levelsdriven by surrounding environment
Fundamental Neuroscience, Vol 2 (2002)
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Circadian Rhythms
Daily changes in light intensity
Major environmental cue used to adjust SCN
master clock
Photoreceptors in retina pick up light signalsand transmit them directly to SCN
SCN relays message regarding light status to
pineal gland
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Circadian (Diurnal) Rhythms of Hormones
From: Richter et al., Biological Research 37, 2004
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Examples of Other Circadian Rhythms in Humans
FundamentalNeuroscience,
Vol 2 (2002)