OpenStax - Ch17 Endocrine Part 1 - Student handout

Chapter Overview

• Theme: Anatomy and Physiology focused on the endocrine system.

• Content Format: PowerPoint slideshow by OpenStax.

Hormones and Function

• Key Functions:

  • Hormones regulate:

    • Growth

    • Metabolism

    • Temperature regulation

    • Stress response

    • Reproduction

• Image Reference: Child catching a falling leaf, illustrating endocrine functions (Figure 17.1).

Overview of Cell Communications

• Mechanisms of Communication:

  • Gap Junctions: Direct connections between cells.

  • Paracrine Signaling: Signals act on nearby cells.

  • Neurotransmitters: Chemical messengers released by neurons.

  • Hormones: Peptides and steroids traveling in bloodstream influencing target cells.

Nervous vs. Endocrine Systems

• Communication Methods:

  • Nervous system: Electrical signals.

  • Endocrine system: Chemical signals.

• Speed of Response:

  • Nervous: Quick reaction and cessation.

  • Endocrine: Slower reaction.

• Adaptation:

  • Nervous: Declines over time.

  • Endocrine: Persists over time.

• Area of Effect:

  • Nervous: Targeted and specific actions.

  • Endocrine: General, widespread effects.

Endocrine Glands

• Major Glands:

  • Pineal gland

  • Hypothalamus

  • Pituitary gland

  • Thyroid gland

  • Thymus

  • Adrenal glands

  • Pancreas

  • Parathyroid glands

  • Gonads (Ovary and Testis)

Endocrine vs. Exocrine Glands

• Exocrine Glands:

  • Utilize ducts to carry secretions to surface/organs.

  • Produce extracellular effects.

• Endocrine Glands:

  • No ducts; secrete hormones directly into bloodstream.

  • Produce intracellular effects.

Binding of Lipid-Soluble Hormones

• Mechanism:

  • Steroid hormones readily diffuse through the cell membrane.

  • Bind to receptors in the cytosol, forming a receptor-hormone complex.

  • Complex enters the nucleus, binds to DNA, initiating protein production.

• Intracellular Effects:

  • Alters activity of specific genes.

Binding of Water-Soluble Hormones

• Mechanism:

  • Cannot diffuse through the cell membrane; bind to cell membrane receptors.

  • Activate a signaling pathway involving G proteins and cyclic AMP.

  • Protein kinases phosphorylate proteins to effect changes.

• Intracellular Effects:

  • Alters enzyme activity.

Feedback Loops

• Negative Feedback Loop:

  • Resists deviations from a set point to maintain homeostasis (Figure 1.10).

  • Example: Body temperature regulation.

• Positive Feedback Loop:

  • Leads to changes in physiological state, not a return to homeostasis (Figure 1.11).

  • Example: Normal childbirth.

• Pathway Analysis:

  • Glucocorticoids feedback inhibits further hormone release (Figure 17.6).

Hypothalamus and Pituitary Gland

• Location & Structure:

  • Hypothalamus lies inferior/anterior to thalamus, connects to pituitary via infundibulum.

  • Contains anterior and posterior lobes, each with distinct hormone functions.

• Posterior Pituitary:

  • Neurosecretory cells release oxytocin (OT) and ADH into blood.

• Anterior Pituitary:

  • Produces seven hormones, regulated by hypothalamic hormones through hypophyseal portal system.

Hormonal Regulation of Growth

• Growth Hormone (GH):

  • Promotes protein synthesis in muscle/bone.

  • Activates Insulin-like growth factor 1 (IGF-1) for cellular growth support.

• Effects Over Life Stages:

  • Childhood/adolescence: Stimulates growth plates.

  • Adulthood: Increases osteoblastic activity.

  • GH levels vary with sleep, exercise, and diet.

Pineal Gland

• Functionality:

  • Peak secretion in ages 1-5, decreased by puberty.

  • Produces serotonin by day, converts to melatonin at night.

  • May regulate puberty timing and affected by phototherapy.

Thymus

• Role:

  • Regulates development and activation of T-lymphocytes.

  • Secretes thymopoietin and thymosins.