Endocrine System

• Works in concert with the nervous system for body communication:
• Neuro endocrine system and circulatory system with hormones.

• * Homeostasis
• * By regulating chem composition & volume of internal environment
• * Helps cope with trauma
• * Assumes a role in the smooth integration of growth and development
• * Contributes to the basic processes of reproduction

• * Cells that are acted on by a particular hormone
• * Some hormones have very widespread targets, some are very specific

• a. They control the rates of enzymatic reactions
• b. They control transport of molecules across cell membranes
• c. They control gene expression and the synthesis of proteins

Hormones & CO₂

• hypothalamus,
• heart
• stomach
• small intestines
• kidney
• adipose besides glands whose primary function is to secrete hormones

• Negative feedback usually
• Like a thermostat

• Hormone travels in the blood & is lipophobic
• Ex: Catecholamines & Polypeptides hormones
• Hormone attaches to specific mem. receptor

c_AMP c_GMP CA++ IP3 DAg

* Released by all cells but because they are so rapidly broken down, circulating levels are very low

• * PGA
• * PGE
• * PGF

* Amines - N containing derivatives of tyrosine or tryptophan.

* Peptide Hormones - polypeptides and glycoproteins secreted from ribosomes as preprohormones which have their signal sequences removed in rER (and then converted to hormone form in the vesicles. May also be neuromodulators.

• Steroids - not stored & all are derived from cholesterol made by the liver (sER)& travel bound to plasma proteins1.
• production by gonads, adrenal cortex and placenta in sER2.
• cholesterol stored as a non membrane bound lipid droplet.
• Steroids made in mitochondria and sER

mitochondria and sER

Specific chemical stimuli usally in short bursts or pulses.

At the beginning of sleep

Down regulation

• NS to Neurotransmitters
• Another hormone or Paracrine
• (Plasma) of mineral ions or nutrients

The amount of active hormone

Target cells.

• Up-regulation
• Down-regulation
• Most target cells have only a few receptors (a few thousand) so the cell has a lowcapacity
• Permissiveness

Epinephrine -  Adipocytes

• Reproductive Hormones
• Reproductive System

Progesterone

catecholamines

• T₄  --> T₃
• or
• Prehormone -> Prohormone -> active hormone (ex insulin)

*together, two hormone's effects are more than additive or complementary

*Action of E & NE on heart is Additive

*Milk production requires snergistic action of estrogen, cortosol, prolactin, oxytocin, etc

• PRL
• Glucagon
• Insulin

Excretion or metabolic transformation

---The excretory rate is used to indicate the secretory rate

Liver & Kidneys

Longer life than do peptide or amine hormones.

Location - Sella Turcica Under Diaphragma Sellae

hypothalamus via the infundibulum

Regulated by hypothalamus

Divided into 2 parts that are developmentally different: Anterior and Posterior Pituitary Gland

* ANT Pit supplied by Hypothalamo-Pituitary Portal system

* Neural Secretions from hypothalmus travel from median eminence to the anterior pituitary controlling what hormones will be made.

* This process is called releasing hormones or inhibiting hormones

• 75%
• Pars intermedia
• Avascular
• MSH

• Acidophils
• Basophils
• Chromophobes

GH

Secrete PRL

Secrete ACTH and MSH

TSH

Secrete FSH, LH, or ICSH

• Neural Tissue
• Synthesized by neurons in 2 areas of hypothalamus:  Vasopressin & Oxytocin

Secretes Antidiuretic Hormone (ADH) and Ocytocin (OT) but does not produce it

• Target Organ ________?
• Actions:
• Promotes Body Growth

Decreases blood A.A levels

Stimulates protein anabolism, hormone production by liver, and by target cells of GH

• Hormone/Product produced =
• Somatomedins (IGF-1) - Main stimulator of fetal growth.

IGF-2 - Independent of GH, Stimulates tissue repair.

Target Organ: Breast or corpus luteum

• Actions:
• _{* Promote breast developmnt during pregnancy}
• _{*Stimulates mammary glands to secrete milk after delivery}
• _{*in both sexes, PRL appears to play a role in regulation of the immune system.}
• _{* Inhibits gonadotrophins secretions inhibiting fertility}
• _{*In male may facilitate reproductive function}

• Stimulates thyroid gland to grow/ maintains it
• Secretion from basophils stimulated by TRH

• Target Organ: ______
• F = Stimulates ovary to mature an ovum & stimulates follicle cells to secrete estrogen

M = Stimulates seminiferous tubules to develop, be maintained, and produce sprem.

Secretion from Basophils stimulated by FSH-RH

F = Stimulates ovulation, corpus luteum to form, to secrete progestins, and estrogen

M = Interstitial cells of testes to develop & secrete testosterone

secretion from Basophils stimulated by LH-RH

Stimulates adrenal cortex to grow normally, be maintained and to secrete glucocorticoids

Production from basophils and release stimulated by ___________

Increases Synthesis & dispersion of melanin granules in skin causing hyperpigmentation

MSH is a major appetite inhibitor works with leptin to control the use of lipids.

Prohormone of several endogenous opioids

• Raises the pain threshold
• Stimulates release of PRL, GH, ADH
• Inhibits TSH, LH and FSH production

Target organ ______.

Decreases water loss by decreasing urine production

Large amounts of ADH causes vasoconstriction of arterioles

Increases memory and secretion of ACTH

In the hypothalamus detect and increase in blood osmolarity (due to dehydration)

This increases water permeability of distal convoluted tubules and collecting ducts to increase water reabsorbtion.