endocrine system and nervous system

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endocrine system and nervous system
2012-03-03 16:50:46

chapt 18
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  1. Endocrine system and nervous system function together to maintain homeostasis of the internal environment
    Communication, Integration and Control
  2. Hormones
    –Chemical messengers

    •Some function as both neurotransmitters and hormones

    –Secreted into the bloodstream from the endocrine glands and hormone-secreting cells

    –Bind to target cells

    •Appropriate receptors have to be present in order to initiate signal transduction

    –Most of the responses of the endocrine system are slower than responses of the nervous system
  3. Endocrine hormones
    –Made in gland(s) or cells

    –Transported by blood to distant target cells

    –Local hormones


    –Act locally by diffusing from its source to target cells in the neighbourhood.


    –Acts on the same cell that produced it
  4. Hormones
    •Hormone alters cell activity

    •Hormone can influence the following:

    –Permeability of the plasma membrane

    –Protein synthesis

    –Enzymatic activity

    –Ion channel activity

    •Electrical state of a cell

    –Secretory activity

    –Mitotic division
  5. Classification of Hormones
    • •General
    • function:

    –Tropic hormones

    –Sex hormones

    –Anabolic hormones

    •Chemical classification:

    –Lipid soluble hormones

    •Steroid hormones

    •Thyroid hormones

    •Nitric oxide

    –Water-soluble hormones

    •Amine hormones

    –Catecholamines: epinephrine, norepinephrine and dopamine


    –Serotonin and melatonin

    •Peptide hormones and protein hormones

    –Oxytocin and antiduretic hormone

    •Eicosanoid hormones

    –Prostoglandins and leukotrienes
  6. Steroid Hormones
    –Synthesized from cholesterol

    –Lipid soluble (lipophylic/hydrophopbic)

    –Mechanism of steroid hormone action:

    •Easily cross plasma membrane

    •Bind to receptors located in cytosol or nucleus

    –Form a hormone-receptor complex

    –Alters transcription of certain genes, and changes protein synthesis
  7. Water-Soluble Hormones
    –Primary synthesized from amino acids


    –Synthesized from a single amino acid

    »Melanin from tryptophan

    »Thyroid hormone from tyrosine

    •Peptides (dipeptides, polypeptides, proteins)

    –Consist of specific amino acids

    –Synthesized as a large precursor proteins

    •Eicosanoid hormones

    Prostoglandins and leukotriens
  8. Mechanism of water-soluble hormone action
    •Binds to the receptor located at the plasma membrane

    –Hormone acts as a first messanger

    •G protein activation

    • •Stimulation of the second
    • messenger system (e.g. cAMP, IP3, GMP, calcium-calmodulin mechanism)

    –Change in metabolic reactions of the cell

    •The effects of hormone are amplified by a cascade reaction
  9. Hormone Interaction


  10. Regulation of Hormone Secretion
    •Hormone secretion is usually regulated by negative feedback mechanism

    –Positive feedback mechanism is not as common

    •Secretion from endocrine gland can be influenced by another endocrine gland

    •Secretion from endocrine gland is regulated by the nervous system
  11. Negative Feedback System
    •Most common control mechanism

    •Level of hormone in the blood is adjusted

    •Homeostasis is reestablished
  12. Hypothalamus
    •Connected to the pituitary gland

    –Neuronal to posterior pituitary

    –Endocrine to anterior pituitary

    –Secretes regulatory hormones
  13. Pituitary Gland
    •Located within the skull

    –Hypophyseal fossa of the sella turcica of the sphenoid bone

    •Also known as “master gland”

    • –Releases hormones that control other endocrine glands
    • •Infundibulum

    Stemlike projection that attaches the pituitary gland to the hypothalamus


    –Anterior pituitary


    –Posterior pituitary
  14. Pituitary Gland: Adenohypophysis
    •Anterior lobe of pituitary

    •Two portions:

    –Pars Anterior

    –Pars Intermedia

    •Anterior pituitary cells:


    •Secrete Human Growth Hormone (or somatotropin)


    •Secrete Adrenocorticotropic Hormone (ACTH)

    –Stimulates secretion of glucocorticoids


    •Secrete Thyroid Stimulating Hormone (TSH)


    •Secrete Prolactin (PRL)


    •Secrete Luteinizing Hormone (LH)

    •Secrete Follicle Stimulating Hormone (FSH)
  15. Growth Hormone (GH)
    •Promotes the synthesis and secretion of insulinlike growth factors (IGFs)

    •Functions of IGFs:

    –Stimulates protein anabolism


    •Tissue repair

    –Promotes lipid mobilization and catabolism

    –Has an indirect effect on increase in glucose levels
  16. Prolactin
    –During pregnancy stimulates the development of breast in anticipation of milk production

    –At birth of a baby stimulates the mammary glands to secrete milk
  17. Gonadotrophs and Luteinizing Hormone (LH)

    –Essential for reproduction

    –Stimulate gonads

    –Luteinizing Hormone (LH)

    •Targets the interstitial cells of the testes

    –Secretion of testosterone

    •Targets the mature follicle of the ovary

    –Stimulates ovulation

    –Stimulate the development of corpus luteum

    –Stimulates secretion of estrogen and progesterone
  18. Follicle Stimulating Hormone
    •Stimulate secretion of sex steroids from gonads


    »Stimulates follicular development


    Stimulates the increase production of sperm
  19. Adrenocorticotrophic Hormone (ACTH)
    –Stimulates secretion of glucocorticoids by the adrenal cortex

    –Promotes growth of adrenal cortex
  20. Neurohypophysis
    •Cell bodies located in either the supraoptic or the paraventricular nuclei of the hypothalamus

    •Axons pass from the hypothalamus to the posterior pituitary via the hypothalamohypophysial tract

    •Store and Releases two hormones:

    –Antiduretic hormone (ADH)

    •Targets kidney

    •Important for water reabsorbtion

    –Oxytocin (OT)

    •Targets smooth muscles of uterus and breast

    •Important during the labor and delivery, and for milk ejection

    –Release of both hormones controlled by nervous stimulation
  21. Thyroid Gland and hormones
    •Thyroid gland

    •Located in the neck on the anterior and lateral surfaces of the trachea

    •Composed of two lateral lobe and connecting isthmus

    •Composed of follicles

    •Thyroid hormones:

    –Tetraiodothyronine (T4, Thyroxine)

    •20 times more abundant than T3

    •Major precursor to T3

    –Triiodothyronine (T3)

    •Principle thyroid hormone

    Several times more potent than T4
  22. Calcitonin
    –Produced by parafollicular cells of thyroid gland

    –Decrease blood calcium level
  23. Parathyroid Gland
    •Located at the posterior surface of the thyroid’s lateral lobes

    •Parathyroid hormone (PTH)

    –Responsible for maintaining calcium homeostasis

    –Produce action opposite to that of calcitonin

    –Acts on bone and kidney

    •Increases Ca levels in the blood by stimulation of bone resorption by osteoclast

    •Stimulates the production of active vitamin D by kidney, which increases calcium absorption in gut
  24. Adrenal Glands
    •Located on top of kidneys

    •Consists of two portions:

    •Adrenal cortex

    –Made up of endocrine tissue

    •Adrenal medulla

    –Made up of neurosecretory cells
  25. Adrenal Cortex
    –Secrete corticosteroid hormones

    –Composed of three layers of secreting cells:

    •Zona Glomerulosa

    –Outermost layer

    –Secretes mineralocorticoids

    •Zona Fasciculata

    –Middle layer

    –Secretes glucocorticoids

    •Zona Reticularis

    –Inner layer

    –Secretes gonadocorticoids
  26. Hormones of Adrenal Glands

    –Regulate sodium levels in the body


    •Increases sodium resorption in the kidney

    •Increases water retention

    •Promotes the loss of potassium and hydrogen ions

    •Controlled by renin-angiotensin-aldosterone system (RAAS)
  27. Hormones of Adrenal Glands cont'd -Glucocorticoids

    –Secreted by the zona fasciculata




    –Secretion regulated by negative feedback system involving ACTH

    –Affects every cell in the body:

    •Gluconeogenic and hyperglycemic effects

    •Secretion increases in response to stress
  28. Gonadocorticoids
    –Estrogen and Androgens

    –Influence secondary sex characteristics
  29. Ovaries and Testes (ovaries)

    –Located in the female pelvic cavity

    –Estrogens (estriadtol and estrone)

    •Steroid hormone

    •Secreted by ovarian follicle

    •Important for development and maintenance of female sexual characteristics


    •Secrete by corpus luteum

    •Maintains the lining of uterus


    •Inhibits secretion of follicle stimulating hormone


    •Produced by ovaries and placenta during pregnancy

    •Important for the enlargement of the birth canal during the childbirth
  30. Testes
    –Paired, oval glands within the scrotum of the male


    •Responsible for growth and maintenance of male sexual characteristics
  31. Pancreatic Islets
    •Pancreatic Islets = Islets of Langerhans

    •Contains four primary cell types

    –Alpha cells

    •Secrete glucagon

    –Beta cells

    •Secrete insulin

    –Delta cells

    •Secrete somatostatin

    –Pancreatic polypeptide cells

    •Secrete pancreatic polypeptides
  32. Pancreatic Hormones

    –Increases blood glucose levels

    –Stimulates glucogenesis in liver cells


    –Decreases concentrations of glucose, amino acids, and fatty acids in blood


    –Regulates the other endocrine cells of the pancreatic islets

    •Pancreatic polypeptide

    –Digestion and distribution of food molecules
  33. Pineal Gland
    •Small pine cone-shaped gland


    –Involved in a regulation of the body’s biological clock

    –Promotes sleepiness
  34. Thymus
    •Located in the mediastinum, just below the sternum

    –Divided into small lobules

    •Outer cortex

    •Inner medulla

    •Production of thymic hormone (thymosin)

    –Stimulate development of T-cells (lymphocytes)
  35. Eicosanoids
    •Local in their actions

    •Include prostoglandins and leukotrienes

    •Prostoglandin E

    –Unsaturated fatty acids


    –Capillary permeability

    –Platelet aggregation

    –Smooth muscle contraction