Endocrine Glands - Fundametnals of Biology - Lecture Slides, Slides of Biology

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Endocrine Glands

Chemical Classification of Hormones

• Amine hormones are derived from tyrosine or tryptophan - Include NE, Epi, thyroxine, melatonin
• Polypeptide/protein hormones are chains of amino acids - Include ADH, GH, insulin, oxytocin, glucagon, ACTH, PTH - Glycoproteins include LH, FSH, TSH
• Steroids are lipids derived from cholesterol
  • Include testosterone, estrogen, progesterone & cortisol

Common Aspects of Neural & Endocrine

Regulation

• Target cells with receptor proteins that combine with the regulatory molecule
• The binding causes a specific sequence of changes in target cell (Signal transduction leads to response)
• There exists mechanisms to quickly turn off the action of the regulator - rapid removal or chemical inactivation - There is an OFF switch as well as an ON switch

Mechanisms of Hormone Action

Hormones That Bind to Nuclear Receptor Proteins

• Lipid hormones travel in blood attached to carrier proteins - They dissociate from carriers to pass thru plasma membrane of target - Receptors are located in the cytoplasm or nucleus

Polar hormones

• Water soluble hormones use cell surface receptors because cannot pass through plasma membrane - Actions are mediated by 2nd messengers - Hormone is extracellular signal; 2nd messenger carries signal from receptor to inside of cell
• Some second messengers include:
  • cAMP
  • Phospholipase C
  • Tyrosine kinase
  • Calcium ions

Hypothalamus

• Hypothalamus produces ADH and Oxytocin that are transported to the posterior pituitary for release. (more on these later)
• Controls the pituitary gland via a variety of releasing and inhibiting factors. - TRH thyrotropin releasing hormone - GHRH growth hormone releasing hormone - CRH corticotropin releasing hormone - Prolactin inhibiting hormone - Etc. etc.

Posterior Pituitary

• Stores & releases 2 hormones produced in hypothalamus: - Antidiuretic hormone (ADH/vasopressin) which promotes H 2 0 conservation by kidneys - Oxytocin which stimulates contractions of uterus during parturition & contractions of mammary gland alveoli for milk- ejection reflex

Anterior Pituitary

• Growth hormone (GH) promotes growth, protein synthesis, & movement of amino acids into cells
• Thyroid stimulating hormone (TSH) stimulates thyroid to produce & secrete T 4 & T (^3)
• Adrenocorticotrophic hormone (ACTH) stimulates adrenal cortex to secrete cortisol, aldosterone

Anterior Pituitary

• Follicle stimulating hormone (FSH) stimulates growth of ovarian follicles & sperm production
• Luteinizing hormone (LH) causes ovulation & secretion of testosterone in testes
• Prolactin (PRL) stimulates milk production by mammary glands

Pituitary Regulation

• Release of A. Pit. hormones is controlled by
  1. Hypothalamic releasing & inhibiting factors
  2. Feedback from levels of target gland hormones
  3. Higher brain centers (via the hypothalamus)

Anterior Pituitary continued

• Releasing & inhibiting hormones from hypothalamus are released from axon endings into capillary bed in median eminence - Carried by hypothalamo- hypophyseal portal system directly to another capillary bed in A. Pit. - Diffuse into A. Pit. & regulate secretion of its hormones

Adrenal Glands

• Sit on top of

kidneys

• outer cortex
• inner medulla

Adrenal Glands

• Adrenal Cortex
  • Mineralocorticoids
    • Aldosterone which stimulate kidneys to reabsorb Na +^ and secrete K
  • Glucocorticoids
    • Cortisol which inhibits glucose utilization & stimulates gluconeogenesis. Inhibits inflammation, Supresses the immune system