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Chapter 18 The Endocrine System Lecture Outline
Intercellular Communication
1. Direct gap junctions
2. Paracrine cytokines or local hormones
3. Endocrine hormones4. Synaptic neurotransmitters
Endocrine System
Glands
Endocrine
Exocrine
Endocrine tissues
Hypothalamus
Pineal GlandPituitary Gland
Thyroid Gland
Heart
Thymus
Adrenal Gland
Kidney
Adipose
Digestive Tract
PancreasGonads
Hormones
Structure
1. Amino acid derivatives
Catecholamines
Epinephrine
Norepinephrine
DopamineThyroid hormones (T3, T4)
Melatonin
2. Peptide hormones
A. Peptides < 200 amino acids
ADH
Oxytocin
Growth Hormone
B. Glycoproteins
Thyroid Stimulating Hormone3. Lipid derivations
A. Steroid hormones
Androgens
Estrogens
Calcitriol
4. secretion
5. mitosis
Receptors
1. Cell membrane receptoEnzyme activation
2nd messenger: cA
G protein
A. cAMP mechanism
hormone + recep
G protein
Adenylate cyclas
ATP cAMPKinases: phospho
Enzymes activate
B. PIP-Calcium mech
hormone + recep
G protein
PLC
PIP2 DAG + I
Ca2+
CalmodulinEnzymes activate
2. Intracellular receptors
Gene activation
hormone + recep
DNA
transcription, tra
Target cell activation
1. blood level2. receptor number
3. affinity
Distribution & duration
1. free
2. bound
Interactions
1. Antagonistic
2. Synergistic
3. Permissive
Control of endocrine activity
Negative feedback
Stimuli
1. Humoral
2. Neural
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2. Pituitary gland (Hypophysis)
Infundibulum
Sella turcica
A. Anterior lobe (Adenohypophysis)
7 tropic hormones: cAMP mechanism
1. Thyroid Stimulating Hormone(TSH) / Thyrotropin
Release:
Thyrotropin releasing hormone
(TRH)
Effects:
-thyroid hormone release
2. Adrenocorticotropic Hormone
(ACTH) / Corticotropin
Release:
Corticotropin Releasing Hormone
(CRH)
Effects:
-corticosteroid release
3. Follicle Stimulating Hormone
(FSH) / Follitropin
Release:
Gonadotropin releasing hormone(GnRH)
Effects:
-gamete production
4. Luteinizing Hormone (LH) / Lutropin
Release:
Gonadotropin releasing hormone
(GnRH)
Effects:
-gonadal hormone production
5. Prolactin (PRL) / Mammotropin
Release:
Prolactin inhibiting hormone (PIH)
Effects:
-mammary gland function
6. Growth Hormone (GH) / Somatotropin
Release:
Growth hormone releasinghormone (GHRH)
Growth hormone inhibiting
hormone (GHIH)
Effects:
-accelerate protein synthesis
I di t
Acromegaly
Pituitary dwa
7. Melanocyte Stimu
(MSH) / Melanotropi
Release:
DopamineEffects:
-melanin pro
B. Posterior lobe (Neurohypo
2 hormones: cAMP mech
1. Antidiuretic Horm
(ADH) / Vasopressin
Supraoptic nucle
Release:
electrolyte
Effects:
-water retent
-vasoconstric
2. Oxytocin (OT)
Paraventricular n
Effects:
-smooth mus
3. Thyroid GlandIsthmus & Lobes
Follicles
Simple cuboidal epitheliu
Thyroglobulin
Parafollicular cells
Thyroid Hormone
Release:
Thyroglobulin
Thyroid peroxidase:
Thyroxine / Tetraiod
Triiodothyronine (T3
TSH
Effects:
- metabolism
Hypothyroidism
Goiter
CretinismHyperthyroidism
Graves disease
Parafollicular cells/C cells
Calcitonin (CT)
Release:
C 2+
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-stimulate osteoclasts
-Ca2+ reabsoption
-Calcitriol formation
5. Adrenal Glands
A. Adrenal Cortex
Corticosteroids1. Zona glomerulosa
Mineralocorticoids
Aldosterone
Release:
-Na+, K+
-Angiotensin II
- BP, volume
- ACTH
Effects:
Na+ retention, K+ loss
2. Zona fasciculata
Glucocorticoids
Cortisol / Hydrocortisone
Release:
ACTH
Effects:
-gluconeogenesis-lipolysis
-protein hydrolysis
-fatty acid & amino acid
utilization
-inhibit inflammation
3. Zona reticularis
Gonadocorticoids
AndrogensAndrogenital syndrome
Cushings syndrome
Addisons disease
B. Adrenal Medulla
Sympathetic neurons: Chromaffin cells
Catecholamines
Release:
Sympathetic
Effects:Epinephrine / adrenaline
- cardiac
- metabolism
Norephinephrine / noradrenaline
-vasoconstriction
Insulin
Release:
glucose, parasymp
Effects:
-glucose uptake & ut
-glycogen formation-protein synthesis
-triglyceride formatio
Diabetes mellitus
Type I
Type II
Glucagon
Release:
glucose, sympathet
Effects:
-glycogenolysis
-lipolysis
-gluconeogenesis
7. Pineal Gland
Pinealocytes
Melatonin
Release:
diurnalEffects:
-sexual maturatio
-antioxidant
-circadian rhythm
8. Gastrointestinal tract
Enteroendocrine cells
Cholecystokinin
EnterocrininGastric Inhibitory Peptid
Gastrin
Secretin
Vasoactive Intestinal Pep
9. Kidney
A. Calcitriol
Release:
PTH
Effects:-Ca2+ , PO4
3- absorpti
-osteoclast activity
-Ca2+ retention
-inhibit PTH
B. Erythropoietin
R l
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-thirst
- BP
10. Heart
Natriuretic Peptide
Release:
atrial stretchEffects:
-Na+ &H2O loss
-inhibit Renin, ADH, Aldosterone
11. Thymus
Thymosins
Effects:
-T cell maturation
12. Gonads
A. Male: Testis
Interstitial Cells
Androgens: Testosterone
Release:
LH
Effects:
-male characteristics
-sperm production
-secretory glandsB. Female: Ovaries
Follicle Cells
Estrogens: Estradiol
Release:
LH & FSH
Effects:
-female characteristics
-oocyte maturation
-uterine growth
Corpus Luteum
Estrogens
Progestins: Progesterone
Release:
LH
Effects:
-uterus maintenance
-oocyte movement-mammary glands
13. Adipose Tissue
Leptin
Release:
glucose & lipid absorption
Eff t
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EndocrineOrgans(ororganswith
someendocrinefunction)
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Hormonesthatbindcellsurfa
cereceptorsworkthroughsecond
messengerstoopenionchann
elsoractivate/deac
tivateenzymes
cAMPMechanism:
Hormonebindsreceptor
G-protein
activated
Adenylate
cyclaseactivated
ATP-->cAMP
Kinasesac
tivated
Proteins(e
nzymes)phosphorylated
Enzymesa
ctivated/deactivated
P
IP-CalciumMechanism:
H
ormonebindsreceptor
G
-proteinactivated
P
hospholipaseC(PLC)activa
ted
P
hospholipids(PIP2)cleaved
intodiacyglycerol
(DAG)andinositoltriphosphate(IP3)
D
AGopensCa
++
channelson
membrane
I
P3relasesCa
++
fromER
C
alciumbindscalmodulin
E
nzymesactivated
Secondmessenger
mechanism(cAMPor
Ca++)resultsin
amplifi
cationofthe
horm
onesignal
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Hormones of the Pituitary Gland:
Anterior Pituitary Hormones:
Hypothalamus
control of secretion: Action:
Thyroid Stimulating Hormone
(TSH), thyrotropin
Thyrotropin Releasing
Hormone (TRH)
Promotes release of thyroid hormones by thyroid gland
Adrenocorticotropic Hormone
(ACTH), corticotropin
Corticotropin Releasing
Hormone (CRH)
Promotes release of corticosteroid hormones (glucocortico
Follicle Stimulating Hormone
(FSH), follitropin
Gonadotropin Releasing
Hormone (GnRH)
Promotes gamete production in ovaries and tes tes
Luteinizing Hormone
(LH), lutropin
Gonadotropin Releasing
Hormone (GnRH)
Promotes production of gonadal hormones (estrogens and
Prolactin
(PRL), mammotropin
Prolactin Inhibiting
Hormone (PIH)
Stimulates mammary gland development and milk product
May assist androgen production in males
Growth Hormone
(GH), somatotropin
-Growth Hormone
Releasing Hormone
(GH-RH) and
-Growth Hormone
I hibiti H
Accelerates rate of protein synthesis in most cells, especial
chondrocytes
Indirect mechanism: stimulates liver to release somatomed
factors (IGFs)) which trigger cells to absorb amino acids
ith th
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Formation and release of thyroid horm
1. Iodine ions (I-) from diet accumulate in cytoplasm of follicle cells.
2. At apical surface thyroid peroxidase converts I- to I+ (activated form) and links it to tyr
the previously formed protein thyroglobulin in the follicle. (Thyroglobulin is continuousl
follicle cells and exocytosed into the follicle lumen for storage.)
3. Iodated tyrosines in thyroglobulin are chemically bonded to create the thyroid hormone
thyroxine/tetraiodothyronine (T4) and triiodothyronine (T3).
4. Stimulated by TSH, follicle cells endocytose iodated thyroglobulin.
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Adrenal Gland
Adrenal Cortex : glandular, produces corticosteroids
1. Zona Glomerulosa: mineralcorticoids
control water and electrolyte balance
95% Aldosterone
stimulates Na+ retention and K+ loss
released in response to: low Na+ or high K+, renin-angiotensin mechanism,
pressure or volume, excessive ACTH
2. Zona Fasciculata: glucocorticoids
metabolic hormones: control glucose metabolism, most common = cortisol
secretion controlled by ACTH
effects: gluconeogenesis in liver, release of fatty acids from adipose, triggehydrolysis to release free amino acids from skeletal muscle,
to utilize fatty acids and amino acids instead of glucose
excess = anti-inflammatory, inhibit immune response and healing
3. Zona Reticularis: gonadocorticoids
mostly androgens may aid onset of puberty
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InsulinandG
lucagonEffec
ts
Amy Warenda Czura, Ph.D. 10 SCCC BIO132 Chapter 18 Handout
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