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The Endocrine System

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Title: The Endocrine System


1
The Endocrine System
2
Defined
  • Homeostatic system that responds to stimuli over
    time through the action of hormones secreted by
    glands throughout the body

3
Endocrine System
  • Hypothalamus
  • Pituitary Gland
  • Adrenal Glands
  • Pineal Gland
  • Thyroid Gland
  • Parathyroid Gland
  • Thymus Gland
  • Pancreatic Islets
  • Ovaries and Testes
  • Stomach Small Intestine
  • Liver
  • Kidneys
  • Heart

4
Steroid Hormones
  • Lipid soluble molecules that travel through the
    cell membrane
  • Direct Mechanism - hormone binds with a receptor
    protein and together they interact with DNA
    turning on protein synthesis

5
Peptide Hormones
  • Water soluble molecules that cant travel through
    the cell membrane
  • Second Messenger Mechanism hormone binds with a
    membrane receptor and activates internal cascade
    of events

6
Second Messenger
  • Specifically, the membrane complex activates a
    G-protein then adenylyl cyclase which converts
    ATP into cAMP
  • cAMP activates kinases which define the specific
    response

7
Control of theEndocrine System
  • The endocrine system generally functions through
    a negative feedback system involving the
    Hypothalamus and Pituitary Gland
  • The Hypothalamus and Pituitary Gland reside deep
    inside the forebrain

8
The Posterior Pituitary
  • In this relationship, neurons in the Hypothalamus
    produce and store hormones in their axon endings
    which reside in the pituitary.
  • Stimuli cause the release of these hormones into
    the capillaries in the posterior pituitary

9
Posterior Pituitary Hormones
  1. Antidiuretic Hormone (ADH) involved in kidney
    function (more later)
  2. Oxytocin (OCT) involved in birth and offspring
    nutrition (more later).

10
Hypothalmic Hormones
  • Hypothalmic hormones that arent stored in the
    posterior pituitary are releasers that stimulate
    the anterior pituitary.
  • Gonadotropic Releasing Hormone (GnRH) involved
    in stimulating the reproductive hormones (more
    later)
  • Thyroid Releasing Hormone (TRH) stimulates the
    release of thyrotropin
  • Somatostatin stimulates the release of
    somatotropin or growth hormone (GH)

11
Anterior Pituitary
  • In this relationship, neurons in the Hypothalamus
    secrete hormones into Hypothalamic capillaries
    that travel to the pituitary

12
Anterior Pituitary Hormones
  • Corticotropin (ACTH) stimulates the release of
    adrenal steroid hormones from the adrenal cortex
  • Thyrotropin (TSH) stimulates the release of
    thyroid hormones from the thyroid gland
  • Somatotropin or Growth Hormone (GH) stimulates
    most cells in promoting cellular and molecular
    growth and metabolism
  • Other anterior pituitary hormones include
    Follicle Stimulating Hormone FSH), Luteinizing
    Hormone (LH), and Prolactin involved in sexual
    maturity (more later)

13
Endocrine System
  • Hypothalamus
  • Pituitary Gland
  • Adrenal Glands
  • Pineal Gland
  • Thyroid Gland
  • Parathyroid Gland
  • Thymus Gland
  • Pancreatic Islets
  • Ovaries and Testes
  • Stomach Small Intestine
  • Liver
  • Kidneys
  • Heart

14
Adrenal Glands
  • The adrenal gland contain both the adrenal cortex
    and the adrenal medulla.
  • Adrenal Cortex
  • Glucocorticoids (later)
  • Mineralcorticoids (later)
  • Adrenal Medulla
  • Epinephrine (adrenaline) Raises blood
    metabolites, and heart rate and force of
    contraction (liver, adipose, muscle). Also
    release by sympathetic nerves in the fight or
    flight response.
  • Norepinephrine (noradrenaline) Promotes
    constriction or dilation of blood vessels (muscle)

15
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16
Thyroid Gland
  • The thyroid gland secretes multiple hormones
  • Triiodothyronine and Thyroxine target most
    cells in regulating metabolism, growth, and
    development
  • Calcitonin targets the bone and causes a
    decrease in blood calcium (more bone).
  • If iodine is lacking in the diet, over
    stimulating of the thyroid by the anterior
    pituitary can cause enlargement of the thyroid
    (goiter). Iodized salt has lessened this effect.

17
Parathyroid
  1. Parathyroid Hormone targets the bone and kidney
    in causing an increase in blood calcium (less
    bone)

18
Pineal Gland
  • The pineal gland produces the hormone melatonin
    which influences daily and seasonal biorhythms
    and sexual activity (in those species that are
    inhibited by the season)
  • In humans melatonin levels are low during the day
    and high at night, and are involved in sleep and
    controlling temperature

19
Other Endocrine Glands
  • The gonads, pancreatic islets, tymus, stomach,
    small intestine, liver, kidneys, and heart also
    secrete hormones.
  • Like androgens, estrogens, progesterone, insulin,
    glucagon, tymosins, gastrin, secretin,
    somatomedins, erythropoietin, and angiotensin
    (more later)
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