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:
Regulation of metabolism
Control of food intake and digestion
Modulation of tissue development
Regulation of ion levels
Control of water balance
Regulation of cardiovascular function
Control of blood glucose and other nutrients
Control of reproductive functions
Stimulation of uterine contractions and milk release
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.