Ch16

Part 1: Endocrine Overview

  • Definition of Endocrine Glands

    • Secrete hormones directly into the blood. Examples include the thyroid and adrenal glands.

  • Definition of Exocrine Glands

    • Secrete substances through ducts to external surfaces or into cavities. Examples include sweat and salivary glands.

  • Endocrine Communication

    • Involves hormones, is slower, more persistent and widespread in its effects compared to synaptic communication.

  • Synaptic Communication

    • Involves neurotransmitters, is quicker but short-lived and specific to certain sites.

Part 2: Hormones in the Blood

  • Circulatory Pathway

    • Blood flows from the heart to organs through arteries, arterioles, and capillaries, exchanging nutrients and wastes.

    • Returns to the heart via venules and veins.

  • Hormone Accessibility

    • Hormones released into the blood need to be able to pass through capillary walls to exert their effects.

  • Color Significance in Blood Vessels

    • Red indicates oxygenated blood, blue indicates deoxygenated, and purple indicates mixed blood.

Hormone Classification

  • Types of Hormones

    • Peptides: Short chains of amino acids.

    • Polypeptides: Longer chains of amino acids.

    • Proteins: One or more polypeptides folded into a specific structure.

    • All are made from 20 standard amino acids.

Hormonal Interaction

  • Steroid Hormones vs Peptide Hormones

    • Steroid hormones pass through cell membranes easily; usually bind with intracellular receptors.

    • Peptide hormones are generally larger, do not pass through the cell membranes; they bind with surface receptors.

Hypothalamic-Pituitary Axis

  • Location and Function of Hypothalamus

    • Located in the brain, it controls the pituitary gland and regulates many homeostatic functions.

  • Location of Pituitary Gland

    • Located just below the hypothalamus, called the master gland due to its regulatory role over other endocrine glands.

  • Parts of the Pituitary Gland

    • Anterior Lobe: Produces hormones like ACTH, GH, FSH, LH.

    • Posterior Lobe: Stores and releases hormones produced by the hypothalamus like oxytocin and ADH.

Gallery of Glands (Examples)

  • Glands Identification

    • Various glands will be identified based on histological features, location, and types of hormones secreted.

  • Key Hormones and Functions

    • Hormones secreted from different glands (e.g., thyroid, adrenal) will be examined, highlighting main actions and physiological roles.

Summary of Hormones and Their Sources

  • Hypothalamus: CRH, GnRH, GHRH, PRH, TRH.

  • Anterior Pituitary: ACTH, FSH, GH, LH, Prolactin, TSH.

  • Posterior Pituitary: ADH, Oxytocin.

  • Thyroid: T3, T4.

  • Adrenal Cortex: Aldosterone, Cortisol.

  • Pancreas: Insulin, Glucagon.

Histological Features

  • Recognizing glands from histological images will aid in understanding hormonal production and secretion.

  • Practice identifying various glands based on unique histological characteristics (e.g., structures, hormone types).

  • Example Questions

    • Which specific structures secrete aldosterone?

    • Determine the differences between pituitary and adrenal histology.

The abbreviations related to the endocrine system mentioned in the notes include:

  • ACTH: Adrenocorticotropic hormone

  • ADH: Antidiuretic hormone

  • FSH: Follicle-stimulating hormone

  • GH: Growth hormone

  • GnRH: Gonadotropin-releasing hormone

  • LH: Luteinizing hormone

  • PRH: Prolactin-releasing hormone

  • TSH: Thyroid-stimulating hormone

  • CRH: Corticotropin-releasing hormone.

These abbreviations correspond to specific hormones produced by various glands in the endocrine system.