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Figure 7-2 (1 of 2)
Anatomy Summary: Hormones
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Figure 7-2 (2 of 2)
Anatomy Summary: Hormones
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Pituitary gland (Hypophysis)
Pituitary gland – two-lobed organ that secretes nine majorhormones
Neurohypophysis – posterior lobe (neural tissue) and theinfundibulum
Receives, stores, and releases hormones from thehypothalamus
Adenohypophysis – anterior lobe, made up of glandulartissue
Synthesizes and secretes a number of hormones
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Neurohypophysis hormones
Hormone
Target
Effect
Antidiuretic hormone(ADH)
Arginine vasopresin(AVP)
Kidneys
Reabsorption of water,
elevation of blood volume and pressure(vasoconstriction)
Oxytocin (OT)
Uterus, mammary glands(female)
Ductus deferens and prostategland (male)
Labor contractions, milk ejection
Contractions of ductus deferens andprostate gland
Hormones that are produced in the hypothalamus andstored in the neurohypophysis
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Figure 7-12, steps 1–4
HYPOTHALAMUS
Vein
POSTERIOR PITUITARY
Vesicles are transported
down the cell.
Vesicles containing
hormone are stored in
posterior pituitary.
Hormones are released
into blood.
Hormone is made and
packaged in cell body
of neuron.
1
2
3
4
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Portal system - a system of blood vessels that begins andends in capillaries. The blood, after passing through onecapillary bed, is passing through a second capillary network.
All blood entering the portal system will reach the targetcells before returning to the general circulation
Question – why is such a system important in thecommunication between the hypothalamus and thehypophysis?
Hypophyseal portal system
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Pituitary-Hypothalamic Relationships: anterior Lobe
•The hypophyseal portal system,consisting of:
•The primary capillaryplexus in the infundibulum
•The hypophyseal portalveins
•The secondary capillaryplexus
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The anterior lobe
There is no direct neural contact with the hypothalamus
Hormone production is regulated by the hypothalamus
Regulatory factors from the hypothalamus arrive directly to theadenohypophysis through the hypophyseal portal system
Releasing hormones stimulate the synthesis and release ofhormones
Inhibiting hormones shut off the synthesis and release ofhormones
The hormones of the anterior pituitary (7) are calledtropic/trophic hormones because they “turn on” other glands ororgans
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Tropic Hormones of the Anterior Pituitary
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The Pituitary Gland: Anterior
Figure 7-13
HYPOTHALAMIC
HORMONES
ANTERIOR
PITUITARY
HORMONES
NONENDOCRINE
TARGETS
ENDOCRINE TARGETS
AND THE HORMONES
THEY SECRETE
Somatostatin
GHRH*
GnRH
Portal system
Anterior pituitary
FSH
LH
Neurons in hypothalamus
secreting trophic hormones
To target
tissues
GH
Endocrine cells
of the gonads
Endocrine
cells
Many
tissues
Germ cells
of the gonads
Thyroid
gland
Thyroid
hormones
Adrenal
cortex
Cortisol
Liver
IGFs
Androgens
Estrogens,
progesterone
PRFs
TRH
CRH
TSH
ACTH
Prolactin
Breast
Dopamine*
(Gonadotropins)
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Anterior pituitary hormones
Region
Hormone
Target
Effect
Hypothalamic regulatoryhormone
Follicle-stimulatinghormone(FSH)
Follicle cells ofthe ovaries,sustentacularcells of testes
Secretion ofestrogen, follicledevelopment,stimulation ofsperm maturation
Gonadotropin-releasing hormone(GnRH)
Luteinizing-Hormone(LH)
Follicle cells ofovary
Interstitial cell oftestes
Ovulation,formation ofcorpus luteum,secretion ofprogesterone
Secretion oftestosterone
Gonadotropin-releasing hormone(GnRH)
Prolactin(PRL)
Mammary glands
Production of milk
Prolactin-releasing factor (PRF)
Prolactin-Inhibiting hormone (PIH)
Growthhormone(GH)
All cells
Growth, proteinsynthesis, lipidmobilization andcatabolism
Growth-hormone- releasinghormone (GH-RH)
Growth-hormone-inhibitinghormone (GH-IH)
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Anterior pituitary hormones
Region
Hormone
Target
Effect
Hypothalamic regulatoryhormone
Follicle-stimulatinghormone(FSH)
Follicle cells ofthe ovaries,sustentacularcells of testes
Secretion ofestrogen, follicledevelopment,stimulation ofsperm maturation
Gonadotropin-releasing hormone(GnRH)
Luteinizing-Hormone(LH)
Follicle cells ofovary
Interstitial cell oftestes
Ovulation,formation ofcorpus luteum,secretion ofprogesterone
Secretion oftestosterone
Gonadotropin-releasing hormone(GnRH)
Prolactin(PRL)
Mammary glands
Production of milk
Prolactin-releasing factor (PRF)
Prolactin-Inhibiting hormone (PIH)
Growthhormone(GH)
All cells
Growth, proteinsynthesis, lipidmobilization andcatabolism
Growth-hormone- releasinghormone (GH-RH)
Growth-hormone-inhibitinghormone (GH-IH)
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Anterior pituitary hormones
Region
Hormone
Target
Effect
Hypothalamicregulatoryhormone
Thyroid-stimulatinghormone (TSH/thyrotropin)
Thyroid gland
Secretion ofthyroidhormones (T3,T4)
Thyrotropin-releasinghormone (TRH)
Adrenocorticotropichormone (ACTH)
Adrenal cortex(zonafasciculate)
Secretion ofglucocorticoids(cortisole,corticosterone)
Corticotrophin-releasinghormone (CRH)
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Anterior pituitary hormones
Region
Hormone
Target
Effect
Hypothalamic regulatoryhormone
Follicle-stimulatinghormone(FSH)
Follicle cells ofthe ovaries,sustentacularcells of testes
Secretion ofestrogen, follicledevelopment,stimulation ofsperm maturation
Gonadotropin-releasing hormone(GnRH)
Luteinizing-Hormone(LH)
Follicle cells ofovary
Interstitial cell oftestes
Ovulation,formation ofcorpus luteum,secretion ofprogesterone
Secretion oftestosterone
Gonadotropin-releasing hormone(GnRH)
Prolactin(PRL)
Mammary glands
Production of milk
Prolactin-releasing factor (PRF)
Prolactin-Inhibiting hormone (PIH)
Growthhormone(GH)
All cells
Growth, proteinsynthesis, lipidmobilization andcatabolism
Growth-hormone- releasinghormone (GH-RH)
Growth-hormone-inhibitinghormone (GH-IH)
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The thyroid gland on the anterior side of theneck. The thyroid gland has a right lobe anda left lobe connected by a narrow isthmus
http://webanatomy.net/histology/endocrine_histology.htm
Thyroid Gland
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Thyroid hormone – major metabolic hormone
Consists of two related iodine-containing compounds
T4 – thyroxine; has two tyrosine molecules plus fourbound iodine atoms
T3 – triiodothyronine; has two tyrosines with threebound iodine atoms
Thyroid Hormone
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Functions of Thyroid Hormones
Elevates rates of oxygen consumption and energy consumption; inchildren, may cause a rise in body temperature
Increases heart rate and force of contraction; generally results in arise in blood pressure
Increases sensitivity to sympathetic stimulation
Stimulates red blood cell formation and thus enhances oxygendelivery
Activate genes that code for enzymes that are involved inglycolysis (Glucose oxidation)
increase rate of ATP production
In the nucleus – activate genes that control the synthesis ofenzymes that involve with energy production and utilization (forexample increase of production of sodium-potassim ATPase thatuses ATP)
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TSH
T4, T3
T4
T3
Hypothalamus
Anteriorpituitary
Thyroidgland
Systemicmetaboliceffects
Stimulus
Integrating center
Efferent pathway
Effector
Systemic response
TRH
Tonic release
KEY
Negative feedback
Thyroid Hormone Control Pathway
Figure 23-11
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Protein hormones that control calcium
Parathyroid gland – PTH
PTH—most important hormone in Ca2+ homeostasis
Thyroid gland – calcitonin
Liver and Kidney - Calcitriol – also known as vitamin D3
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Calcitonin targets the skeleton, where it:
Inhibits osteoclast activity (and thus bone resorption)and release of calcium from the bone matrix
Stimulates calcium uptake and incorporation into thebone matrix
Regulated by a humoral (calcium ion concentration in theblood) negative feedback mechanism
Calcitonin
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PTH release increases Ca2+ in the blood:
Stimulates osteoclasts to digest bone matrix
Enhances the reabsorption of Ca2+ and the secretion ofphosphate by the kidneys
Increases absorption of Ca2+ by intestinal mucosal
Rising Ca2+ in the blood inhibits PTH release
The antagonist is the Calcitonin secreted by the thyroidgland
Effects of Parathyroid Hormone
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Simple Endocrine Reflex: Parathyroid Hormone
Figure 7-10
Bone
and
kidney
Low plasma
[Ca2+]
Plasma
[Ca2+]
Bone
resorption
Kidney
reabsorption of
calcium
Parathyroid
cell
Parathyroid
hormone
Production of calcitriol
leads to intestinal
absorption of Ca2+
Negative feedback
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Pancreas structure
Exocrine pancreas (99% of volume)
Cells (pancreatic acini) forming glands andducts that secrete pancreatic fluid and enzymeswith digestive function
Endocrine pancreas (1%)
Small groups of cells scattered in clusters(pancreatic islets) that secrete hormones
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Structurally and functionally, they are two glands in one
Adrenal medulla – neural tissue; part of thesympathetic nervous system
Adrenal cortex - three layers of glandular tissue thatsynthesize and secrete corticosteroids
Adrenal (Suprarenal) Glands
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Adrenal Cortex
Synthesizes and releases steroid hormones calledcorticosteroids
Different corticosteroids are produced in each of the threelayers
Zona glomerulosa – glomerulus- little ball. Secretesmineralocorticoids – main one aldosterone
Zona fasciculata – glucocorticoids (chiefly cortisol)
Zona reticularis – gonadocorticoids (chiefly androgens)
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Zona glomerulosa – Mineralocorticoids
Aldosterone secretion is stimulated by:
Rising blood levels of K+
Low blood Na+
Decreasing blood volume or pressure
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Aldosterone and urine concentration
Aldosterone is a steroid secreted by the adrenal cortex
It is secreted when blood sodium falls or if blood potassiumrises or when blood pressure decreased
Aldosterone increases reabsorption of Na+ in the kidneys inexchange for secretion of K+ ions – water follow
Net effect is that the body retains NaCl and water and urinevolume reduced
The retention of salt and water help to maintain bloodpressure and volume
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Zona fasciculata - Glucocorticoids (Cortisol/hydrocortisone)
Main hormones secreted are the Cortisol/hydrocortisone and smallamounts of corticosterone
It protects against hypoglycemia by stimulating catabolism of energystores.
While adrenaline is responsible for rapid metabolic responses theglucocorticoids are responsible for long-term stress:
Glucocorticoids accelerate the rates of glucose synthesis andglycogen formation – especially in the liver
Promotes the utilization of fatty acids as source of energy -glucose-sparing effect
Clucocorticoids also have anti-inflammatory effect – inhibit theactivities of WBC (use?)