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Anatomy & Physiology: Endocrine System Key Concepts

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Terms in this set (28)

  • Circulating hormones

    Enter the blood and act on target cells that may be far away. Examples include insulin, thyroid hormones, and cortisol.

  • Paracrine hormones

    Act on neighboring cells near the release site. Examples include histamine and many prostaglandins.

  • Autocrine hormones

    Act on the same cell that released the signal. Examples include some growth factors and cytokines.

  • Major endocrine organs in the brain

    Hypothalamus, pituitary gland, and pineal gland.

  • Chemical classes of hormones

    Peptides/proteins, steroids, amino acid-derived hormones (amines), and eicosanoids.

  • Peptide and protein hormones characteristics

    Made of amino acid chains, water-soluble, circulate freely in plasma, bind to cell-surface receptors, and activate intracellular signaling.

  • Steroid hormones characteristics

    Derived from cholesterol, lipid-soluble, travel bound to carrier proteins, bind intracellular receptors, and regulate gene transcription.

  • Amino acid-derived hormones subgroups

    Catecholamines (epinephrine, norepinephrine), thyroid hormones (T3, T4), and melatonin.

  • Eicosanoids

    Derived from 20-carbon fatty acids, act locally via paracrine or autocrine signaling, regulate inflammation and smooth muscle activity.

  • Hormone action via cell-surface receptors

    Used by water-soluble hormones; hormone binds membrane receptor, activates second messengers like cAMP, leading to rapid cellular responses.

  • Hormone action via intracellular receptors

    Used by lipid-soluble hormones; hormone enters cell, binds receptor in cytoplasm or nucleus, alters gene transcription, causing slower but longer-lasting effects.

  • Three main stimuli for hormone release

    Humoral (changes in blood ions/nutrients), neural (nerve signals), and hormonal (hormones stimulating other glands).

  • Negative feedback in hormone regulation

    The response reduces the original stimulus to limit further hormone release, maintaining homeostasis.

  • Positive feedback in hormone regulation

    The response intensifies the original stimulus, increasing hormone release until a specific event ends the cycle (e.g., childbirth).

  • Differences between neural and hormonal control

    Neural control is fast, targeted, uses electrical impulses; hormonal control is slower, widespread, uses blood-borne chemical messengers.

  • Hypothalamus endocrine functions

    Produces releasing/inhibiting hormones regulating anterior pituitary; also produces ADH and oxytocin.

  • Anterior pituitary hormones and functions

    GH (growth), TSH (thyroid stimulation), ACTH (adrenal cortex stimulation), FSH (follicle/sperm development), LH (ovulation/testosterone), prolactin (milk production).

  • Posterior pituitary hormones

    Stores and releases ADH (water conservation) and oxytocin (uterine contractions, milk ejection), both produced by hypothalamus.

  • Thyroid gland hormones

    T3 and T4 regulate metabolic rate and development; calcitonin lowers blood calcium but has minor adult role.

  • Parathyroid hormone (PTH)

    Raises blood calcium levels; secreted by parathyroid glands located on the posterior thyroid.

  • Adrenal cortex hormones and effects

    Aldosterone regulates sodium/potassium balance; cortisol regulates metabolism and stress response; adrenal androgens contribute to secondary sex characteristics.

  • Adrenal medulla hormones

    Epinephrine and norepinephrine support the fight-or-flight response.

  • Pancreatic islet hormones

    Insulin lowers blood glucose; glucagon raises blood glucose; somatostatin regulates islet hormone secretion.

  • Ovarian hormones

    Estrogens and progesterone regulate reproduction and pregnancy; inhibin regulates FSH secretion.

  • Testicular hormones

    Testosterone supports male reproduction and secondary sex characteristics; inhibin regulates FSH and sperm production.

  • Role of hypothalamus in nervous and endocrine integration

    Receives neural input and regulates pituitary hormone release; links nervous and endocrine systems.

  • Water-soluble hormone transport and receptor location

    Dissolve in plasma, bind to cell-surface receptors because they cannot cross lipid membranes.

  • Lipid-soluble hormone transport and receptor location

    Travel bound to carrier proteins, enter cells via transporters, bind intracellular receptors to regulate gene expression.