ch. 10 a&p

Chapter 10: Endocrine System Lecture Outline

Overview

• The endocrine system comprises glands and specialized cells that secrete hormones into the bloodstream to regulate various bodily functions.

Characteristics of the Endocrine System

• Composition: Endocrine glands and cells dispersed throughout the body.

• Hormone Secretion:

  • Hormones are released directly into the bloodstream instead of through ducts.

  • They travel through circulation to designated target tissues.

• Target Tissues: Each target tissue has specific receptors for its hormone, initiating responses upon binding.

Endocrine System Functions

• Main Functions:

  1. Regulation of metabolism

  2. Control of food intake and digestion

  3. Modulation of tissue development

  4. Regulation of ion levels

  5. Control of water balance

  6. Regulation of cardiovascular function

  7. Control of blood glucose and other nutrients

  8. Control of reproductive functions

  9. Stimulation of uterine contractions and milk release

  10. Modulation of immune system function

Types of Hormones

• Water-Soluble Hormones:

  • Include proteins, peptides, and amino acids (e.g., growth hormone, insulin).

• Lipid-Soluble Hormones:

  • Include steroids and eicosanoids (e.g., estrogen, testosterone, cortisol).

Classes of Chemical Messengers

• Neurotransmitters and Neuromodulators: Secreted by nerve cells, affecting nervous system function.

• Hormones and Neurohormones: Secreted into the blood to bind with receptors on target tissues.

Control of Hormone Secretion

• Hormonal control can be influenced by:

  • Humoral Stimuli: Blood-borne chemicals stimulate hormone release.

    • Example: low blood calcium triggering secretion of parathyroid hormone (PTH).

  • Neural Control: Neurons release neurotransmitters that trigger hormone secretion.

  • Hormonal Stimuli: Hormones can stimulate the release of other hormones.

Feedback Mechanisms in Hormone Regulation

• Negative Feedback: Most common mechanism where high hormone levels inhibit further secretion (e.g., T3 and T4 regulating TSH levels).

• Positive Feedback: Less common; hormone secretion is amplified by its own action (e.g., oxytocin during childbirth).

Hormone Action Mechanisms

• Receptors: Hormones bind to specific receptors to exert effects.

  • Lipid-Soluble Hormones: Typically bind to nuclear receptors, influencing gene transcription.

  • Water-Soluble Hormones: Bind to membrane-bound receptors, activating intracellular pathways through second messengers like cAMP.

Major Endocrine Glands and Their Hormones

Pituitary Gland

• Types: Anterior and Posterior Pituitary.

• Anatomy: Controlled by the hypothalamus, involved in producing and regulating multiple hormones.

• Hormones: Growth Hormone (GH), Thyroid-Stimulating Hormone (TSH), Luteinizing Hormone (LH), Prolactin, etc.

Thyroid Gland

• Function: Secretes thyroid hormones (T3, T4) for metabolism regulation, requires iodine.

• Calcitonin: Regulates calcium levels in the blood.

Parathyroid Glands

• Hormone: Parathyroid Hormone (PTH) regulates blood calcium levels by acting on bones and kidneys.

Adrenal Glands

• Regions: Medulla and Cortex.

• Medulla: Releases epinephrine and norepinephrine for fight-or-flight responses.

• Cortex: Produces corticosteroids like cortisol (metabolism, immune response) and aldosterone (ion balance).

Pancreas

• Functions: Exocrine (digestion) and Endocrine (regulating blood glucose levels).

• Hormones: Insulin (lowers blood glucose), Glucagon (raises blood glucose).

Reproductive Glands

• Testes: Produce testosterone, influencing male reproductive traits.

• Ovaries: Secrete estrogen and progesterone, affecting female reproductive cycles and traits.

Pineal Gland

• Hormone: Melatonin; regulates sleep/timing of puberty.

Disorders

• Diabetes Mellitus: Results from inadequate insulin action.

  • Type 1: insulin-dependent.

  • Type 2: often related to obesity, insulin resistance.

Summary

• The endocrine system plays a crucial role in maintaining physiological balance through hormones and feedback mechanisms, affecting numerous bodily functions.