Endocrine System Hormones Quiz

Endocrine System Overview

• The endocrine system maintains homeostasis through hormone secretion
• Major endocrine glands include the thymus, thalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, uterus, ovaries (female), and testes (male)
• Hormones are chemicals that originate in tissues and organs and affect other tissues/organs
• Hormones vary in composition from simple amino acids to complex combinations of lipids, proteins, and carbohydrates
• Roles of hormones include metabolism, growth and development, muscle and fat distribution, fluid and electrolyte balance, and sexual development and reproduction
• The nervous system and endocrine system work together to maintain homeostasis within the human body using various communication pathways

Endocrine System Objectives

• Identify how the endocrine system maintains homeostasis
• Describe the structure and function of major endocrine glands
• Describe the function, regulation, and effects of hormones of major endocrine glands
• Describe the negative feedback mechanism in relation to hormone secretion
• Differentiate between endocrine and exocrine gland function

Types of Hormones

• Endocrine system: a collective group of tissues/organs capable of secreting hormones
  • Pancreas (insulin - controls blood glucose)
  • How do hormones work? (Emma Bryce YouTube video; 5 min suggested duration)
• Neurons: can synthesize and release neurotransmitters (hormones) which can stimulate a neural response (fast response)
  • Epinephrine: role in fight-or-flight responses
  • Dopamine: pathways are involved in motor control, learning, reward, and motivation

Inflammatory and Immune Response

• An inflammatory or immune response can trigger the release of chemical mediators acting as hormones
• Chemical mediators include cytokines, leukotrienes, and prostaglandins for defense mechanisms
• These systems work independently but ultimately aim to protect the body from injury and maintain homeostasis

Hormone Classification

• Hormones in the human body are categorized into three classes:
  • Amino acid derivatives (amines)
  • Peptides
  • Steroids

Pathways for Hormonal Receptors

• Intracellular hormone receptors: located inside the cell; hormones bind to these receptors after crossing the plasma membrane
• Membrane hormone receptors: located on the extracellular surface of the cell membrane; hormones bind to these receptors without crossing the plasma membrane

Major Pathways of Cell-to-Cell Communication

• Paracrine pathway
• Autocrine pathway
• Endocrine pathway
• Synaptic pathway
• Neuroendocrine pathways

Other Chemical Signals

• Paracrine activity: a chemical signal is released into the interstitial fluid and targets neighboring cells
• Autocrine activity: chemicals released by a cell elicit a response in the same cell

Factors Affecting Target Cell Response

• Permissive effect: the presence of one hormone enables another hormone to act (e.g., thyroid hormones and reproductive hormones)
• Synergistic effect: two hormones with similar effects produce an amplified response (e.g., FSH and estrogens in egg maturation)
• Antagonistic effect: two hormones with opposing effects (e.g., insulin and glucagon regulating blood glucose)

Feedback Loops

• Positive feedback loop: the presence of a hormone stimulates increased production until the cycle is interrupted (e.g., oxytocin in childbirth)
• Negative feedback loop: like an internal thermometer, signals the body to return to homeostasis (e.g., ADH and fluid levels)
• Negative feedback: characterized by the inhibition of further hormone secretion in response to adequate hormone levels, allowing regulation within a narrow range

Role of Endocrine Gland Stimuli

• Humoral stimuli: changes in ion or nutrient levels in the blood
• Hormonal stimuli: changes in hormone levels initiating or inhibiting secretion of another hormone
• Neural stimuli: a nerve impulse prompting hormone secretion or inhibition

Hypothalamus-Pituitary Complex

• The "command center" of the endocrine system
• Secretes hormones that directly produce responses in target tissues and regulates hormone synthesis and secretion in other glands
• Watch this 2-Minute Neuroscience video (YouTube link provided in the document).

Hypothalamic-Pituitary Axis

• Hypothalamus: located in the brain; produces hormones that act on the anterior and posterior pituitary gland
• Releasing hormones:
  • Growth hormone-releasing hormone (GHRH)
  • Thyrotropin-releasing hormone (TRH)
• Inhibitory hormones:
  • Dopamine
  • Somatostatin

Hypothalamus/Pituitary Review Chart (Detailed description of hormone functions and regulated processes)

Thyroid Gland

• Located in the neck, wrapping around the trachea
• Composed primarily of thyroid follicles
• The larger parafollicular cells often appear within the matrix of follicle cells
• Watch the provided YouTube video for detailed information on the thyroid's functions (link provided in the document).
• Thyroid hormones (T3 and T4) regulate metabolic rate

Parathyroid Glands

• Embedded in the posterior surface of the thyroid gland
• Most people have four parathyroid glands
• Secrete parathyroid hormone (PTH), regulating blood calcium levels
• The provided YouTube video describes parathyroid glands and PTH (link provided)
• Low serum calcium stimulates PTH release, leading to calcium increase in the blood

Adrenal Gland

• Situated atop the kidneys, comprised of a cortex and medulla
• The adrenal cortex produces hormones like mineralocorticoids (mineral balance), glucocorticoids (glucose metabolism), and androgens (masculinization)
• The adrenal medulla produces epinephrine and norepinephrine (stress hormones)

Reproductive Hormones

• The male and female reproductive systems are regulated by follicle-stimulating hormone (FSH), luteinizing hormone (LH), and gonadotropin-releasing hormone (GnRH) from the hypothalamus.
• FSH stimulates sperm maturation in males. In females, FSH promotes egg maturation and LH signal the release of estrogens and progesterone.
• Testosterone, a steroid hormone, is important for male secondary sex characteristics.
• The placenta produces hormones to maintain pregnancy.

Pancreas

• Pancreatic endocrine function involves insulin (beta cells) and glucagon (alpha cells) secretion, regulating glucose metabolism

Homeostatic Regulation of Blood Glucose Levels

• Blood glucose levels are tightly regulated between 70 and 110 mg/dL
• Insulin helps glucose enter cells, storing excess as glycogen in the liver.
• Glucagon stimulates glycogenolysis (the breakdown of glycogen to glucose), gluconeogenesis (the creation of new glucose), and lipolysis (the breakdown of triglycerides) to increase blood glucose.

Organs with Secondary Endocrine Functions

• Various organs have secondary endocrine functions (e.g., heart, gastrointestinal tract, kidneys, adipose tissue, skin, thymus, liver). List of secondary organs and their function

Development and Aging of the Endocrine System

• Endocrine system originates from three layers of the embryo (endoderm, ectoderm, mesoderm)
• Aging affects endocrine glands; hormone levels decrease as one ages (e.g., decreased growth hormone, cortisol, aldosterone, sex hormones, and thyroid hormones)

Knowledge Check (Questions and Answers)

• List of questions and answers pertaining to the key hormones and their roles in regulation