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.