1. Introduction to the Endocrine System

    1. Endocrine glands secrete into the blood stream

    2. The major glands of the endocrine system include:

    Gland

    Adrenal cortex


    Adrenal medulla

    Hypothalamus


    Intestine


    Pancreatic islets


    Ovaries



    Parathyroids


    Pineal


    Adeno Hypophysis


    Neuro Hypophysis


    Stomach

    Testes

    Thymus

    Thyroid

    Hormone

    cortisol
    aldosterone

    epinephrine

    releasing hor.
    inhibiting hor.

    secretin
    cholecystokinin

    insulin
    glucagon

    estradiol 17 B
    progesterone


    PTH


    melatonin


    trophic hormones


    ADH
    Oxytocin

    Gastrin

    Testosterone

    thymosin

    T4 and T3

    Effect

    various
    Na and electrolyte

    stimulation

    release from pit.
    inhibit release

    inhib. gastric activity
    stimulate bile release

    gulcose uptake
    hydrolysis of glucose

    maintain repo. tract
    secondary sex
    characteristics

    Increase Ca++
    concentration

    affects
    gonadotropins

    trophic affect on
    target cells

    retention H2O
    uterine cont.

    Stimul. acid sec.

    Stim. sec. sexual

    Stim. WBC prod.

    Growth dev.

  2. Classes of Hormones

    Type

    Steroid


    Protein


    Amine

    Composition

    Lipid and chol
    like nucleus

    Amino acids with
    peptide bonds

    amino acids
    with no bonds

    Examples

    Sex hormones, Hormones
    adrenal Cortex.

    pituitary hor. PTH,
    calcitonin Pancreatic hor.

    T4,T3, adrenalin,
    melatonin

  3. Hormonal Action :

    Water soluable ( protein, amines )

    First messenger : Plasma membrane; cyclic AMP "second mess."

    AMP produced from ATP by the enzyme adenylate cyclase

    AMP activates protein kineases - add phosphate from ATP to

    Protein which allows the protein to catalyze a reaction.

    These include : regulate enzymes, alter plasma membrane.

    Cyclic AMP broken down by phosphodiesterase

    Other substances may become second messenger :

    Ca++ ions
    Guanosine mono phosphate (GMP)

    Lipid Soluable ( steroids )

    Alter cell functions by activating genes

    Pass through the plasma membrane

    Bind with receptors in the nucleus

    Genes produce specialized proteins ( usually enzymes )

    These catalyze the effect indicated by the hormone

  4. Endocrine Activities

    1. Pituitary ( Hypophysis )

      Adeno Hypophysis ( anterior lobe )
      True gland
      Produces protein type hormones
      Regulated by the hypothalamus

      1. hormones secreted by the pars distalis of anterior pit.

        1. Growth hormone

          regulated by GRF and GH-IH) from hypothalamus
          GH promotes movement of amino acids
          controls the rate of protein synthesis

        2. Thyroid Stimulating Hormone

          regulates hormone activity of thyroid
          partially regulated by the hypothalamus

        3. Adrenocorticotropic Hormone (ACTH)

          Promotes normal function of adrenal cortex
          assists in the breakdown of fats
          regulated by CRF from the hypothalamus

        4. Follicle Stimulating Hormone

          Stimulates producy=tion of sperm in male
          regulates monthly dev. of follicle in female
          stimulates secretion of female hormone
          estradiol

        5. Luteinizing Hormone (LH, ICSH)

          LH stimulates ovulation in female
          stimulates formation of corpus luteum
          stimulates production of progesterone
          in male called ICSH
          stimulates interstitial - testosterone

        6. Prolactin

          Secreted in both males and females
          major function only in females
          initiating milk production after birth

      2. Hormone of the Pars intermedia

        1. Melanocyte Releasing Hormone

          Increases melanocyte activity
          causes increased skin pigmentation
          regulated by MRF and MIF from hypothalamus

      3. Hormones of the Neuro Hypophysis

        • hormones produced in the hypothalamus neuron cell bodies
        • transported along axons to the posterior pituitary
        • posterior pituitary not a true gland

        1. Oxytocin

          Produced by nerve cell bodies in the
          hypothalamus
          Influences female physiological activities
          Produces uterine contractions at parturition
          Acts on mammary tissue to contract- let down
          No known effect in males

        2. Antidiuretic Hormone ( ADH )

          Reduces the amount of water lost in kidney
          Causes collecting tube to become permeable
          Also is a vaso constrictor (vasopressin)
          Effects will increase blood pressure

          • Hormones produced in the Supra optic and Paraventricular nuclei of the hypothalamus.

          • Oxytocin and ADH are secreted by a mechanism known as the neuro - endocrine reflex.

          • Oxytocin stimulated by sucking

          • ADH stimulated by osmoreceptors neurons in hypothalamus

        3. Interaction of pituitary and the hypothalamus

          1. Releasing and inhibiting hormone travel via the hypothalamo - hypophyseal portal system

          2. Neurons secrete hormones into the a series of capallaries

          3. . Hormones are transmitted to a secondary capillary system in the anterior pituitary.

        4. Thyroid and Parathyroid

          1. Anatomy of the thyroid

            Located below the larynx
            Consists of two lobes
            The thyroid is the largest of the endocrine glands
            Recieves a large blood supply

          2. functions of the thyroid

            Production of two major hormones ( T3, T4 )
            Production of calcitonin
            Release controlled by the hypothalamus
            Also stimulated by TSH from the adenohypophysis
            T3 and T4 function in the following manner :

            1. Increase rate of protein synthesis
            2. Increase rate of energy release from carbo.
            3. Regulates rate of growth
            4. Stimulates maturity of nervous system

              Calcitonin functions include :

              1. Increased osteoblast activity
              2. Retains calcium in the bones
              3. Prevents loss of phosphorus and calcium

                • Iodine is an important component of T3 and T4
                • TSH stimulates thyroid production of T3 and T4
                • This trophic wikll effect persons with low iodine
                • T4,T3 cont be produced
                • No feed back action
                • TSH continues to stimulate trophic effect on thyroid
                • Result is a GOITER

            5. Functions of the Para Thyroid

              Embedded in the posterior surface of the thyroid
              Usually four para thyroids
              Primary hormone produced is para thyroid hormone (PTH)
              The actions of PTH include:

              1. Increased octeoclast activity
              2. Increased Ca++ uptake from intestine
              3. Kidney stimulated to conserveb Ca++
              4. Result is a rise in blood Ca++

      4. Pancreas

        Both an endocrine and an exocrine gland
        Endocrine portion is composed of islet cells
        Alpha cells produce glucagon
        Beta cells produce insulin
        The actions of glucagon and insulin are as follows:

        Glucagon :
        Stimulate liver to convery glycogen to glucose
        Increases blood level of glucose

        Insulin :
        Promotes movement of glucosethrough cells
        Stimulates liver to convert glucose to glucagon
        Assists in protein synthesis
        Promotes transport of amino acid into cells

      5. Adrenal Glands

        Composed of the adrenal cortex and medulla
        Each is structurally and functionally different
        The medulla secretes catecholamines
        The cortex produces corticosteriods

        Catecholamines :

        Epinephrine and norepinephrine
        Are sympathetic agents
        Function to

        1. increase blood pressure
        2. Accelerate respiratory rate
        3. Increase efficiency of muscle
        4. Increased rate of glycogen breakdown
        5. Increased rate of fatty acid release
        6. Increased ACTH and TSH release

      Hormones of the adrenal cortex
      Hormone

      Mineralocorticoids
      (aldosterone)

      Glucocorticoids



      Gonadocorticoids

      Action

      Regulate electrolytes
      espically Na and K

      Metabolism of Carbo.
      Protein, Fat, vaso
      constrict.

      Supplement sex hormones

      Regulation

      electrolyte
      in blood

      ACTH

  5. Gonads (Ovaries, Testes)

    Testes :
    Interstitial cells produce testosterone
    Testosterone promotes secondary sex characteristics

    Ovaries :
    Estrogen peoduced by ovarian follicles and corpus luteum
    Estrogen also produced by the placenta, adrenal cortex
    *Also produced in the testes of the male
    Progesterone produced by the corpus luteum

  6. Pineal Gland

    Small cone shaped gland
    Located in the roof of third venrricle near corpora
    quadrigemina
    Produces melatonin which affects the hypothalamus
    Affect the release of GRH and ACTH

  7. Thymus

    Secretes thymosin which stimulates T cells after
    production

  8. Stomach and Small Intestine :

    Hormone

    Gastrin






    Secretin






    Cholecystokinin/ Pancreozymin






    Gastric Inhib. Factor

    Secreted by

    Stomach





    All following from small intestine

    Effects

    Stimulates parietal cells HCl
    Chief cells secrete pepsinogen
    Maintain gastric mucosa

    Stimulate H2O and bicarb. in
    Pancreatic juice
    Potentiates the action of chole.
    on the pancreas

    Contraction of gall bladder
    Secretion of pancreatic juice
    Potentiates action of secretin
    on the pancreas

    Inhibits gastric emptying
    Inhibits gastric secretion
    Stimulates secretion of insulin