The endocrine system
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The endocrine system. Honors Anatomy & Physiology. Endocrine vs nervous system. act together to coordinate body’s activities both: use chemical messengers to communicate cell to cell major function: homeostasis endocrine : slower response time

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The endocrine system

The endocrinesystem

Honors Anatomy & Physiology


Endocrine vs nervous system
Endocrine vs nervoussystem

  • act together to coordinate body’s activities

  • both:

    • use chemical messengers to communicate cell to cell

    • major function: homeostasis

  • endocrine: slower response time

    • hormones transported thru circulatory system

    • target cells (any cell with hormone receptor) anywhere in body

  • nervous: quicker conduction of signals

    • neurotransmitters

    • act on cells close by


Glands
Glands

  • no ducts

  • secretions released and diffuse into blood capillaries

  • have ducts

  • secretions released onto surface

  • example: sweat glands, salivary glands

Endocrine

Exocrine


2 types of hormones
2 types of hormones

  • bind to protein receptors in cell membranes (do not enter cell)

  • receptor-hormone activate enzyme in cytoplasm  series of reactions result in cell response

  • enter cell & bind to receptor in cytoplasm or nucleus

  • Activates transcription of gene  protein produced

  • generally action slower than peptide hormone

Peptide

Steroid



Hypothalamus
hypothalamus

  • part of brain

  • secretes “releasing” hormones that act on pituitary gland

  • axons that store the 2 posterior pituitary hormones end there


Pituitary gland
Pituitary gland

  • 2 lobes: posterior & anterior


Negativefeedback inhibition
negativeFeedback Inhibition


Thyroid gland
Thyroid Gland

  • stimulated by TSH

  • secretes thyroxin (T4) and triiodothyronine (T3)

    • (-) feedback inhibition

  • both have similar effects on target cells


Hypothyroidism
hypothyroidism

  • Thyroid produces too little hormone

  • several causes: Hashimoto’s autoimmune/ lack of Iodine in diet  goiter (enlargement of thyroid due to increased TSH stimulation

  • Symptoms:

    • Adults: lethargy, weight gain, anovulatory cycles

    • Infants:cretinism: dwarfism, low IQ, failure to reach sexual maturity



Hyperthyroidism
hyperthyroidism

  • excessive secretion of thyroid hormones


Parathyroid glands
Parathyroid Glands

  • 4 small glands embedded in posterior surface of thyroid gland

  • secrete: parathyroid hormone (PTH)

    • regulated by serum Ca++ levels

  • actions:

  • stimulates removal of Ca++ from bone

  • increases kidney tubules reabsorption of Ca++

  • activates vit D which enhances Ca++ absorption from food



Adrenal cortex
Adrenal Cortex

  • outer layer

  • produces 2 kinds of steroid hormones

  • Glucocorticoids

    • major 1 – cortisol:

    • reduces swelling by inhibiting immune system/ raises serum glucose (stimulates liver to make glucose from proteins or lipids

  • Mineralocorticoids

    • major 1- aldosterone

    • acts on kidney to promote absorption of Na+ & excretion of K+


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