Endocrine System Overview

Study Notes

Endocrine System Overview

Works with the nervous system to control and regulate the body's functions
Influences metabolic activities by transporting hormones via blood
Key functions include reproduction, growth/development, homeostasis maintenance, metabolism/energy regulation, and defense mobilization

Endocrine Glands

Lack ducts; release hormones directly into surrounding tissue
Examples: pituitary, thyroid, parathyroid, adrenal, pineal glands
Hypothalamus: a neuroendocrine organ with both neural and hormonal functions
Other organs with endocrine tissues include pancreas, gonads, placenta, adipose cells, thymus, stomach, kidneys, and heart

Hormone Types and Actions

Amino acid-based hormones: Peptide/protein based, water-soluble
Steroids: Derived from cholesterol, lipid-soluble
Eicosanoids: Classified as paracrines; influence nearby cells
Hormones affect target cells with specific receptors
Hormonal actions include changing plasma membrane permeability, protein/enzyme synthesis, activating/deactivating enzymes, inducing secretion, and stimulating mitosis

Hormone Regulation

Humoral stimuli: Response to blood levels of ions/nutrients
Neural stimuli: Nerve fibers stimulate hormone release
Hormonal stimuli: Hormones trigger the release of other hormones
The nervous system can override endocrine controls, like during stress

Pituitary Gland

Posterior Pituitary (Neurohypophysis):
- Oxytocin: Uterine contractions, milk ejection
- ADH (Antidiuretic Hormone): Water retention by kidneys; increases blood volume
- ADH imbalances:
  - Hyposecretion: Diabetes insipidus
  - Hypersecretion: Syndrome of Inappropriate Antidiuretic Hormone (SIADH)
Anterior Pituitary (Adenohypophysis):
- GH (Growth Hormone): Stimulates growth via IGFs
  - Hypersecretion: Gigantism (children), acromegaly (adults)
  - Hyposecretion: Pituitary dwarfism
- TSH (Thyroid-Stimulating Hormone): Stimulates thyroid hormone release
- ACTH (Adrenocorticotropic Hormone): Stimulates cortisol release
- FSH & LH: Regulate gonadal hormone production
- PRL (Prolactin): Stimulates milk production

Thyroid and Parathyroid Glands

Thyroid Hormone (TH): Increases basal metabolic rate, regulates growth/development
- Imbalances:
  - Hyposecretion: Myxedema (adults), goiter (iodine deficiency)
  - Hypersecretion: Graves' disease (autoimmune)
Parathyroid Hormone (PTH): Maintains calcium homeostasis
- Imbalances:
  - Hyperparathyroidism: Weak bones, kidney stones
  - Hypoparathyroidism: Tetany, respiratory paralysis

Adrenal Glands

Adrenal Cortex:
- Mineralocorticoids (e.g., Aldosterone): Regulates sodium and potassium balance
- Glucocorticoids (e.g., Cortisol): Increases blood glucose, stress response
  - Hypersecretion: Cushing's syndrome
  - Hyposecretion: Addison's disease
- Gonadocorticoids: Weak androgens that convert to testosterone or estrogen
  - Hypersecretion: Adrenogenital syndrome (masculinization)
Adrenal Medulla: Produces catecholamines (epinephrine & norepinephrine), short-term stress response (fight or flight)

Pineal Gland

Secretes melatonin, regulating sleep-wake cycles

Pancreas

Glucagon: Raises blood glucose levels
Insulin: Lowers blood glucose levels
Diabetes Mellitus:
- Type 1: Hyposecretion of insulin
- Type 2: Insulin resistance

Other Hormones and Organs

Gonads: Produce sex hormones (estrogen, progesterone, testosterone)
Placenta: Temporary endocrine organ during pregnancy
Other organs:
- Heart: ANP (reduces blood pressure)
- Kidneys: Erythropoietin (RBC production), Renin (blood pressure regulation)

Clinical Considerations

Hormone imbalances significantly impact metabolism, growth, and homeostasis
Environmental pollutants can disrupt hormone function

Description

Explore the fundamental aspects of the endocrine system and its interplay with the nervous system. This quiz covers key functions, types of hormones, and the role of various endocrine glands. Understand how hormones influence bodily functions and maintain homeostasis.