Endo General Funct CS-K36

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GENERAL FUNCTIONOF ENDOCRINE SYSTEM

PHYSIOLOGY DEPARTEMENT

MEDICAL SCHOOL OF

UNIVERSITAS SUMATERA UTARA


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Location of Major Endrocrine Organs

Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 9.3


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HYPOTHALAMUS

The release of hormones from both the posterior

and anterior pituitary is directly controlled by

hypothalamus

Posterior pituitary connects to hypothalamus by

a neural pathway

Anterior pituitary connects to the hypothalamus

by unique vascular link


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Hypothalamic hormones

Thyrotropin RH (TRH) Thyrotropin, Prolactin

Gonadotropin RH (GnRH) LH, FSH

Corticotropin RH (CRH) Adrenocorticotropin

Hormone Target Pituitary Hormone

Growth hormone RH (GHRH) Growth hormone

Prolactin-inhibiting factor (PIF) Prolactin, Thyrotropin

(Dopamine)

Growth hormone IH (GHIH) Growth hormone(somatostatin)


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Complex endocrine pathways involving

pituitary and hypothalamus


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Hormones of the Pituitary Gland


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The Posterior Pituitary


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Neurohormones

Synthesized by neurons in the supraopticand paraventricular nuclei

Small peptides synthesized in the cell

bodies and transported to the posterior

pituitary by specific carrier proteins

Antidiuretic hormone (ADH) andoxytocin


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Antidiuretic Hormone (ADH)

Antidiuretic actions

Vasopressor actions

- increases permeability of the collecting

ducts to water

- V2

receptors

- constricts vascular smooth muscle cells

- V1 receptors, non-hormonal


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diabetes insipidus


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Oxytocin

Breast-feeding

Childbirth (parturition)

- contracts the myoepithelial cells of thealveoli

- classic neuroendocrine reflex

- in late pregnancy, uterine smooth

muscle (myometrium) becomessensitive to oxytocin

- positive feedback


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Growth Hormone

Does not have a target gland as other

pituitary hormones.

Promotes growth in all tissues.

Major targets: protein and lipid metabolism

Mechanisms: transcriptional and translational


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Physiologic effects of GH

Anabolic effects:

promotion of protein synthesis and amino acidtransport

decreased catabolism of proteins and aminoacids

Stimulation of bone growth and cartilageformation:

Cell division and protein synthesis Differentiation of condrocites to osteogenic

cells and deposition of bone


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PROLACTIN

Breast is main site of action. Episodic release

PRL secretion induced by high estrogen and hCG

PRH oxytocin

PRL inhibitor : PIH (dopamine)

most dominant

PRL inhibits LHRH secretion TRH can act as a PRL stimulator


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Secretion: mediated through hypothalamus-

pituitary secretions

Steroidal hormones:

Thyroxine (T4) and Triiodothyronine (T3):

both regulate production of ATP from glucose,

affects metabolic rate

Calcitonin: lowers blood calcium levels

Thyroid Gland


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PHYSIOLOGICAL EFFECTS OF THYROID

HORMONES

Increase O2 consumption of almost all

active tissues

(in part by mobilising fatty acids) Increase cardiac output

Needed for normal brain development

Needed for normal growth and skeletal

maturation


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Negative feedback homeostasis:

T3 and T4 effects on TSH and TRH


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Secretion: response to lowered bloodcalcium levels

Hormone: Parathyroid hormone (PTH),nonsteroidal

Removes calcium and phosphate from bone

Increases absorption of calcium by thedigestive tract

Increases renal retention of calcium andexcretion of phosphate

Parathyroid Glands


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Structures: islets of Langerhans

Hormones: nonsteroidal

Glucagon: made by alpha cells, raises blood

sugar

Insulin: made by beta cells, lowers blood sugar

Pancreas: Endocrine Functions


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Roles of Insulin and Glucagon inRegulating Blood Glucose


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Adrenal Gland

epinephrinenorepinephrine

cortisol

aldosterone


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Cortisol exerts

negative feedback on

ACTH and CRH

Cortisol effects

Synergizes glucagon

and epinephrine


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Secretion of Cortisol


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Cortisol Effects

Increases in blood[glucose] (gluconeogenesis and glycogenolysis)

[amino acids] (protein catabolism)

[fatty acids] (lipolysis)

Permissive for action of glucagon and

epinephrine(synergism)

Anti-inflammatory (prevents actions of cytokines)

Negative feedback

reduces CRH (hypothalamus)

reduces ACTH (anterior pituitary)


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Adrenal medulla: neuroendocrine organ

Secretion: sympathetic nervous system

Hormones: nonsteroidal

Epinephrine and Norepinephrine:

enhance function of sympathetic nervous

system

(Fight or flight)

Adrenal Glands: Medulla


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Roles of the Hypothalamus and Adrenal Glands in the

Stress Response

Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings


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LH and FSH

LH/ FSH functionOvary

ova

oestrogenprogesterone

Testes

sperm

testosterone


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TESTES

Testosterone synthesised from Leydig

cells

LH stimulates this release Sertoli cells play important role in

spermatogenesis

FSH stimulates Sertoli cells


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OVARIES

FSH stimulate follicle maturation

Granular cell secrete estrogen

LH stimulate follicle maturation in the last

periode and surge preceeds ovulation

Corpus luteum secrete progesteron

Mechanism negative feed back fromprogesteron and estrogen reduce FSH/LH


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Hormone: testosterone (steroidal)

Functions:

Regulates development and normal

functioning of sperm, male reproductive

organs, male sex drive

Development of male secondary sex

characteristics

Testes


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Hormones (steroidal) and functions:

Estrogen: initiates development of

secondary sex characteristics, regulatesmenstrual cycle

Progesterone: regulates menstrual cycle

Ovaries


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