Key Points on the Endocrine System

Endocrine System Overview

  • Professor: Dr. Yolanda Wiersma
  • Chapter: 45

Key Concepts

  • Hormones bind to target receptors, triggering distinct response pathways.
  • Feedback regulation and coordination with the nervous system are prevalent.
  • Endocrine glands regulate homeostasis, development, and behavior by responding to diverse stimuli.

Hormones & Signaling Molecules

  • Hormones defined as signaling molecules regulating body functions.
  • Greek Origin: "Horman" means "to excite".

Types of Signaling

  • Endocrine signaling: Hormones travel via blood to distant targets.
  • Paracrine signaling: Signals to nearby cells.
  • Autocrine signaling: Targets the signaling cell itself.
  • Synaptic signaling: Involves neurotransmitters (next unit).
  • Neuroendocrine signaling: Interaction of nervous and endocrine systems.

Hormone Classification

  • Water-soluble hormones: Cannot pass through membranes; require receptors.
  • Lipid-soluble hormones: Can penetrate membranes; need transport proteins in blood.

Signal Transduction Mechanisms

  • Water-soluble hormones: Trigger responses like enzyme activation or gene transcription through membrane receptors.
  • Lipid-soluble hormones: Bind to cytoplasmic receptors, mainly altering gene expression.

Key Endocrine Glands

  • Pineal gland: Melatonin
  • Thyroid gland: Thyroid hormones (T3, T4), Calcitonin
  • Parathyroid glands: Parathyroid hormone (PTH)
  • Ovaries/Testes: Estrogens, Progestins, Androgens
  • Hypothalamus: Regulates other glands.
  • Pituitary gland: Produces various hormones like oxytocin and ADH.
  • Adrenal glands: Secretes stress hormones (e.g., epinephrine).
  • Pancreas: Insulin, Glucagon.

Feedback Mechanisms

  • Hormones are part of regulatory pathways:
    • Simple pathways directly respond to internal/external stimuli with hormone secretion.
    • Neuroendocrine pathways involve sensory neurons stimulating hormone release.

Thyroid Hormone Regulation

  • Negative feedback loop maintains thyroid hormone levels.
  • Imbalances lead to hypothyroidism (weight gain) or hyperthyroidism (Grave's disease).

Growth Hormone Effects

  • Excess leads to gigantism; deficiency causes dwarfism.

Adrenal Hormones

  • Stress response managed by
    • Short-term effects (e.g., increased glucose, blood pressure).
    • Long-term effects involve fluid retention and immune suppression.

Sex Hormones

  • Both sexes produce testosterone and estrogen/progesterone in different levels, impacting reproduction.

Endocrine Disruptors

  • Common disruptors include BPA, dioxins, and pesticides that interfere with hormonal functions.

Special Note

  • Pineal gland: Regulates melatonin based on light exposure, influencing sleep patterns.