BIO 266: Chap 16- Endocrine Communication

Visual Anatomy & Physiology - Chapter 16: The Endocrine System

• This chapter introduces the endocrine system and its role in the body
• The endocrine system includes organs and tissues whose primary function is releasing hormones and paracrines
• The endocrine system works closely with the nervous system but uses different mechanisms of communication

Learning Outcomes 16.1-16.4

• Explain the similarities between the endocrine and nervous systems and how they communicate
• Describe the chemical classification of hormones
• Identify the organs and tissues of the endocrine system and the key functions of the hormones
• Explain the general mechanisms of hormonal action

Learning Outcomes 16.5-16.10

• Describe how the hypothalamus controls endocrine organs
• Describe the location and structure of the pituitary gland, and its hormones and functions
• Describe the role of negative feedback in the relationship between the hypothalamus and pituitary gland
• Locate and describe the thyroid gland, its hormones, and their functions
• Describe the location of the parathyroid glands, and their hormone and functions
• Describe the location, structure, and functions of the adrenal glands, and their hormones and functions

Learning Outcomes 16.11-16.13

• Describe the location and structure of the pancreas, identify the hormones it produces, and specify their functions
• Describe the location of the pineal gland, and identify the functions of its hormone
• Explain diabetes mellitus: its types, clinical manifestations, and treatments

Module 16.1: The Nervous and Endocrine Systems

• Both systems release chemicals to bind to specific receptors in target cells
• Both systems share many chemical messengers (e.g., norepinephrine and epinephrine)
• Both are regulated primarily by negative feedback mechanisms
• Both are vital for maintaining homeostasis by coordinating the body's systems

Mechanisms of Intercellular Communication

• Direct Communication: Through gap junctions, typically between adjacent cells of the same type
• Paracrine Communication: Through extracellular fluid, chemicals affect nearby cells
• Autocrine Communication: Through extracellular fluid, chemicals affect the secreting cell itself
• Synaptic Communication: Across synapses, a specialized gap between neurons, where chemicals called neurotransmitters are released
• Endocrine Communication: Through the bloodstream, hormones affect distant cells throughout the body

Module 16.2: Hormones May Be Amino Acid Derivatives, Peptides, or Lipid Derivatives

• Hormones are categorized based on their chemical structure
• Amino acid derivatives: thyroid hormones, catecholamines, tryptophan derivatives (melatonin)
• Peptide hormones: most hormones in the body, synthesized as prohormones then converted to active hormones
• Lipid derivatives: eicosanoids (prostaglandins), steroid hormones

Module 16.3: The Endocrine System

• Includes organs (hypothalamus, pituitary, thyroid, adrenal, pancreas, pineal, parathyroids) with primary function of hormone production
• Other organs (heart, thymus, digestive tract, kidneys, and gonads) contain tissues that secrete hormones, but endocrine function is secondary

Module 16.4: Hormones Affect Target Cells

• Target cells must have protein receptors to respond to hormones
• Hormones can act through intracellular or extracellular receptors
• Extracellular receptors (catecholamines and peptide hormones) often use second messengers
• Intracellular receptors (steroid hormones) often affect target cell gene expression

Module 16.5: The Hypothalamus

• The hypothalamus is the primary regulator of the anterior pituitary gland

• The hypothalamus secretes regulatory hormones that either stimulate or inhibit the release of hormones from the anterior pituitary

• The hypothalamus contains autonomic centers that directly stimulate the adrenal medulla. These hormones are released in response to sympathetic activation, impacting metabolic functions and the stress response

• The hypophyseal portal system connects the hypothalamus to the anterior pituitary. Regulatory hormones are transported directly through this system

Module 16.6: The Anterior Lobe of the Pituitary Gland

• The anterior lobe produces seven tropic hormones that stimulate other endocrine glands

• The anterior lobe produces hormones that affect multiple systems like the thyroid, adrenal, and reproductive systems in the body

• The anterior lobe produces prolactin to aid in the development of mammary glands in females

• The anterior lobe produces growth hormones that supports cell growth

• The posterior lobe produces oxytocin, affecting smooth muscle contractility for processes like uterine contractions, and antidiuretic hormone (ADH), primarily affecting nephron function

Module 16.7: Negative Feedback Mechanisms

• Negative feedback loops regulate hormone secretion

• The second hormone release typically inhibits further release of the hypothalamic releasing hormone and the first pituitary hormone

• Feedback regulation of growth hormone and prolactin secretion includes both releasing and inhibiting hormones

Module 16.8: The Thyroid Gland

• The thyroid gland has follicles filled with colloid and produces hormones (thyroxine and triiodothyronine) that affect metabolism
• C cells secrete calcitonin, which plays a role in calcium homeostasis

Module 16.9: Parathyroid Hormone

• Parathyroid glands produce parathyroid hormone (PTH), which increases blood calcium levels
• PTH promotes calcium reabsorption to help maintain calcium levels within normal range

Module 16.10: Adrenal Hormones

• Adrenal glands have two regions: the cortex and medulla, with distinct functions; the adrenal cortex produces steroid hormones collectively called corticosteroids that affect metabolism, electrolyte balance, and the stress response
• Mineralocorticoids (like aldosterone) regulate mineral balance
• Glucocorticoids affect glucose metabolism; including cortisol, affecting the body's response to stress
• Adrenal gland medulla produces epinephrine and norepinephrine in response to stressful situations

Module 16.11: The Pancreas

• The pancreas has exocrine and endocrine functions; the islets of Langerhans are the endocrine portion
• Alpha cells produce glucagon, raising blood glucose
• Beta cells produce insulin, lowering blood glucose

Module 16.12: The Pineal Gland

• The pineal gland, part of the epithalamus, secretes melatonin, important in regulating circadian rhythms.
• Melatonin production is influenced by light levels

Module 16.13: Diabetes Mellitus

• Diabetes mellitus is a condition characterized by consistently high blood glucose levels

• Type 1 diabetes involves inadequate insulin production

• Type 2 diabetes involves the body's cells not responding properly to insulin

• Complications include retinopathy, nephropathy, and neuropathy stemming from abnormal blood flow and vessel changes throughout the body

Module 16.14: Hormone Interactions

• Hormones interact in various ways to achieve coordinated physiological responses. These interactions are often antagonistic, additive, or permissive
• Different hormones interacting with different receptors to alter cellular activity

Module 16.15: Regulation of Blood Pressure and Blood Volume

• Hormones from the heart and kidneys regulate blood pressure and volume.
• The heart releases natriuretic peptides to decrease blood pressure (and volume) and volume
• The kidneys release erythropoietin (EPO) to increase red blood cell production and renin to activate the renin-angiotensin-aldosterone system leading to increased fluid intake

Module 16.16: Normal Growth

• Several endocrine organs and hormones cooperatively contribute to normal growth
• Hormones affect various aspects influencing growth patterns, including bone growth, skeletal and muscle development

Module 16.17: The Stress Response

• The general adaptation syndrome (GAS) describes the body's predictable response to stress. The response typically includes three phases of initial activation, subsequent stabilization and then failure of long-term maintenance

• Initial activation is mediated by a primarily sympathetic response (epinephrine)

• The subsequent resistance phase is characterized by increased glucocorticoid, growth hormone, and thyroid hormone activity; leading to mobilization for longer-term stability

• If the stimulus continues, exhaustion phase may develop where the body's regulatory systems fail, impacting overall health

Module 16.18: Endocrine Disorders

• Endocrine disorders are caused by hormone overproduction or underproduction impacting various systems
• Imbalances that can cause disease include problems with the hormone-producing organs, with their regulation mechanisms, and with receptor activity within target cells
• Examples include goiter, Addison's disease, and Cushing's disease

Test your knowledge on the various types of endocrine communication mechanisms. This quiz covers topics such as hormone targeting, signaling processes, and the roles of receptors in target cells. Explore key concepts related to autocrine and endocrine signaling methods.