Endocrine System

The endocrine system is responsible for regulating various bodily functions through hormones, which are chemicals released into the bloodstream to target specific organs and tissues. Key glands involved include:

  • Pituitary gland: Often referred to as the "master gland", it controls other endocrine glands and regulates growth and metabolism.

  • Thyroid gland: Produces hormones that regulate metabolism, energy generation, and overall growth and development.

  • Adrenal glands: Responsible for producing hormones like cortisol and adrenaline, which help the body respond to stress.

  • Pancreas: Plays a crucial role in glucose metabolism by producing insulin and glucagon.

A. Class of Hormones

    1. amines

    2. polypeptides and proteins
    3. glycoproteinsoo

  1. steroids

B. Tissue, Glands, and Organs

    1. Tissue

  a) adipose tissue (a connective tissue)

   2. Glands

    a) pineal, pituitary and hypothalamus

    b) thyroid, parathyroids (4), and thymus

    c) adrenal glands (2)

  1. organs

a) pancreas, ovaries (2), and testes (2)

C. Glands in the Human Brain

  1. pineal gland

a) size

    i. length is roughly 7.4 mm in length

    ii. width is roughly 6.9 mm in width

b) inferior to the corpus callosum

  1. pituitary gland

a) bi-lobed gland

b) located below the hypothalamus

c) controlled by the hypothalamus

d) anterior pituitary gland

    i. adenohypophysis

    ii. regions= pars tuberalis, pars intermedia, and pars distalis

e) posterior pituitary gland

    i. neurophypophysis

    ii. regions= infundibular stalk and pars nervosa

  1. Hypothalamus

    a. located below the thalamus

    b. maintains homeostasis

    c. secretes 9 hormones

    d. controls the anterior pituitary gland

    e. controls the posterior pituitary gland

        a) stores hormone that are produced by the hypothalamus

        b) releases hormones that are produced by the hypothalamus

f. infundibulum

        1) a stalk that connects the hypothalamus to the pituitary gland, facilitating communication between the two structures.

g. hypophyseal portal system

i. consists of blood vessels

ii. regulates the anterior lobe of the pituitary transporting hormones from the hypothalamus, traveling in the portal system to the anterior pituitary.

h. hypothalamo-hypopyseal tract

i. a bundle of axons

ii. carries hormones from the hypothalamus to the posterior pituitary gland

D. Hypothalamus- Hormones

    1. growth hormone releasing-hormone (GHRH)

        a) stimulates growth hormone

        b) function= regulation of growth and metabolism by promoting cell growth and division in various tissues.

h. hypothalamo-hypophyseal tract

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regulates the production of growth hormone from the anterior pituitary, promoting growth and development in various tissues of the body.

     2. thyrotropin-releasing hormone (TRH)

.     a) stimulates thyroid stimulating hormone

    b) function= regulates metabolism and affects the growth of the thyroid gland; promotes secretion of thyroid-stimulating hormone (TSH) and prolactin (PRL)

    3. melanocyte stimulating hormone (MSH)

    a) produced by the anterior pituitary gland, skin, and the hypothalamus

    b) function= induces melanocytes to produce a pigment called melanin

    4. corticotropin releasing-hormone (CRH)

    a) promotes secretion of adrenocorticotropic hormone (ACTH)

    5. gonadotropin-releasing hormone (GnRH)

    a) promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

    6. growth hormone inhibiting hormone (GHIH)/ somatostatin

    a) inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone (TSH)

    7. dopamine

      

    8.prolactin releasing hormone (PRH)

    a) stimulates the release of prolactin

    b) produces milk, supports breast development, and influences reproductive and immune function

    9. antidiuretic hormone (ADH)

    a) Is involved with regulating water in the body

    b) helps to control blood pressure and maintain fluid balance by promoting water reabsorption in the kidneys.

  10. oxytocin

    a) Is involved during labor contraction, milk release, involved in ejaculation, sperm transport, sexual affection, and mother-infant bonding

E. Anterior Pituitary Gland-Hormones

  1. Prolactin (PRL)

    a) Is secreted by pituitary cells called thyrotropic cells

    b) Stimulates milk production in the mammary glands following childbirth.

  1. Thyroid stimulating hormone (TSH)/ Thyrotropin

    a) stimulates the growth of the thyroid gland and secretion of thyroid hormones

    b) affects metabolic rate, body temperature, etc

  1. Growth hormone (GH). Somatotropin

a) secreted by somatotropic cells, the most numerous cells of the anterior pituitary gland

b) stimulates mitosis and cellular differentiation to promote tissues growth throughout body

  1. Adrenocorticotropin (ACTH)/ Cornicotropin

a) stimulates the growth of the adrenal cortex

b) stimulates the adrenal cortex to secrete glucocorticoids

  1. Lutenizing hormone(LH)

a) secreted by gonadotropic cells

b) stimulates the production of testosterone in males and triggers ovulation in females.

  1. Follicle stimulating hormone (FSH)

a) secreted by gonadotropic cells

b) promotes the growth of ovarian follicles and stimulates sperm production

F. Posterior Pituitary Gland

  1. Inferior to the hypothalamus

  2. connected to the hypothalamus

  1. hormone #1: Antidiuretic hormone (ADH)

    a) produced by the hypothalamus

    b) secreted by the posterior pituitary gland

    c) function is to increase water retention by the kidneys, reduce urine volume, and help prevent dehydration.

  1. Hormone #2: Oxytocin

    a) produced by the hypothalamus

    b) secreted by the posterior pituitary gland

    c) function is to aid in the propulsion of semen through the male reproductive tract, stimulate uterine contractions to transport sperm up female tract, functions in feelings of sexual satisfaction and emotional bonding, stimulates flow of milk in mammary gland.

G. Thyroid Gland

  1. butterfly -shaped gland

  2. located close to the larynx

  3. situated at the base of your neck

  4. structure

    a) right lateral lobe

    b) left lateral lobe

    c) pyramidal lobe

    d) isthmus

  1. hormones

    a) calcitonin

    i. function is to antagonizes parathyroid hormone and stimulates osteoblast activity, promoting bone formation.

b) thyroxine (T3)

i. derived from tyrosine

ii. structure

iii. functions are to Regulate metabolic rate, heart function, digestion. Muscle control, and brain development. Increases cellular energy production.

c. ) triiodothyronine (T4)

i. derived from tyrosine

ii. structure

iii. functions are to regulate your body’s metabolism, control energy se, brain development, and bone health. It is inactive until converted into the more potent T3.

H. Parathyroid gland

1. embedded in the thyroid gland

  1. shape

        a) 4 small-pea shaped glands

  1. structure

    a) superior parathyroid gland

        i. 2

    b) inferior parathyroid gland

    i. 2

  1. hormone(s)

    a) function/s are to secrete parathyroid hormone (PTH) to regulate blood calcium level.

I. Pineal gland

    1. a small endocrine gland

    2. located in the middle of the brain

    3. beneath the posterior end of the corpus callosum

    4. hormone(s)

    a) function/s are to synthesize melatonin at night from serotonin and regulate circadian rhythms

J. Thymus gland

    1. located deep to the sternum in the thorax

  1. structure

    a) right lobe

    b) left lobe

    c) capsule, cortex, and medulla

  1. hormone

    a) thymopoietin

        i. function/s are to stimulate the development of T lymphocytes (T cells) and to help regulate the immune system.

    b) thymosin

        i. function is to promote T-cell differentiation and help T-cells become immunocompetent.

c) thymulin

    i. function/s are to help T-cells mature and differentiate and function properly

K. Adrenal glands/ suprarenal glands

  1. located on top of both kidneys

  2. structure

        a) small, triangular-shaped glands

        b) consists of a capsule. cortex, and medulla

  1. adrenal medulla hormones

    a) epinephrine/ adrenaline

        i. functions are to increase heart rate, dilate airways, and enhance glucose metabolism, which collectively prepare the body for a "fight or flight" response.

    b) norepinephrine/ noradrenaline

        i. functions are to increase blood pressure, enhance alertness and focus for fight or flight

  1. adrenal cortex hormones

    a) aldosterone

        i. functions are to stimulate the kidneys to retain sodium, regulate electrolyte balance, raise blood volume and blood pressure

    b) cortisol

        i. functions are to stimulate fat and protein catabolism, gluconeogenesis, the release of fatty acids and glucose into blood.

L. Adipose Tissue

    1. Endocrine Tissue

    2.hormone

    a) leptin- regulates carbohydrate and fat metabolism having a long-ter effect on the appetite regulating center of the hypothalamus

M. Pancreas

    1. located in the abdomen, partially behind the stomach

    2. triangular shaped organ

    3. hormones

        a) glucagon

            i. functions are to promote glycogenolysis and other effects that raise blood glucose concentration

        b) insulin

            i. lowers blood glucose levels

            ii. stimulates glucose uptake

            iii. indirectly involved with the breakdown of blood glucose

N. Hormones Producing Cells in Other Organs

    1. ovaries

        a) estrogen

            i. function(s) are to develop female sex characteristics, regulate menstrual cycles, and prepare the uterus for pregnancy

        b) progesterone

            i. function (s) are to regulate the menstrual cycle, maintain the uterine lining, prepare uterus for pregnancy, and support pregnancy

        c. inhibin

            i. function (s) are to limit FSH secretion, regulating rate of sperm production.

  1. Testes/testacles

        a) testosterone

            i. function(s) are to stimulate fetal and adolescent reproductive development, muscoskeletal growth, sperm production, and libido

        b) inhibin

            i. function (s) are to inhibit FSH secretion

  1. cells in the kidneys

        a) promotes red blood cell formation

  1. cells in the heart

        a) atrial natriuretic peptide (ANP)

            i. lowers blood pressure by promoting Na+ and water loss

  1. cells in the skin

        a) cholecalciferol

            i. inactive form of vitamin D3

               ii. essential for the absorption of Ca+ from ingested food