Ch. 16: The Endocrine System

Overview of the Endocrine System

The endocrine system is a network of glands that secrete hormones to regulate various bodily functions. It works in conjunction with the nervous system but differs in its mechanisms and effects.

• Main Characteristics: The endocrine system uses chemical messengers (hormones) released into the bloodstream, resulting in slower but longer-lasting effects compared to the rapid, short-lived responses of the nervous system.

• Comparison to Nervous System: The nervous system uses electrical impulses and neurotransmitters for fast, targeted responses, while the endocrine system influences broader, longer-term physiological processes.

Key Definitions

• Hormone: A chemical messenger secreted by endocrine glands that travels through the bloodstream to target organs, influencing their function.

• Target Cell (Organ): A cell or organ that has specific receptors for a hormone and responds to its signal.

Endocrine vs. Exocrine Glands

• Endocrine Glands: Ductless glands that secrete hormones directly into the bloodstream (e.g., pituitary, thyroid).

• Exocrine Glands: Glands that secrete substances through ducts to an epithelial surface (e.g., sweat, salivary glands).

Organs with Endocrine Functions

• Some organs, such as the pancreas, gonads, and hypothalamus, have both endocrine and non-endocrine functions.

• Other tissues, like adipose tissue and the heart, also secrete hormones.

Classification of Hormones

• Chemical Classes:

  • Lipid-soluble hormones: Steroid hormones (e.g., cortisol, estrogen) and thyroid hormones. They pass through cell membranes and bind to intracellular receptors.

  • Water-soluble hormones: Amino acid-based hormones (e.g., insulin, epinephrine). They bind to receptors on the cell surface and use second messengers.

• Examples of Second Messengers: cAMP, IP3, DAG.

Hormone Transport and Mechanisms

• Transport in Blood: Water-soluble hormones travel freely in plasma; lipid-soluble hormones are bound to plasma proteins.

• Mechanisms of Action:

  • Lipid-soluble hormones alter gene expression directly.

  • Water-soluble hormones activate second messenger systems.

Hormone Regulation

• Down-regulation: Decrease in receptor number in response to high hormone levels.

• Up-regulation: Increase in receptor number in response to low hormone levels.

• Antagonism: One hormone opposes the action of another (e.g., insulin vs. glucagon).

• Synergism: Combined effect of hormones is greater than the sum of their individual effects.

• Pituitary Gland: Secretes multiple hormones, including ADH, ACTH, GH, TSH, LH, FSH, and prolactin.

Major Endocrine Hormones and Functions

• ADH (Antidiuretic Hormone): Regulates water balance by increasing water reabsorption in kidneys.

• Insulin: Lowers blood glucose by promoting cellular uptake of glucose.

• Glucagon: Raises blood glucose by stimulating glycogen breakdown in the liver.

• Thyroid Hormones (T3, T4): Regulate metabolism, growth, and development.

• Calcitonin: Lowers blood calcium levels.

• Parathyroid Hormone (PTH): Increases blood calcium levels.

• Adrenal Cortex Hormones: Glucocorticoids (e.g., cortisol), mineralocorticoids (e.g., aldosterone), and androgens.

• Adrenal Medulla Hormones: Catecholamines (epinephrine, norepinephrine) for fight-or-flight response.

Table: Comparison of Diabetes Mellitus and Diabetes Insipidus

Matching and Classification

• Hormones can be classified by structure (steroid, peptide, amine), mechanism (second messenger, direct gene activation), and function (tropic, permissive, antagonistic).

• Examples:

  • Synergism: Glucagon and epinephrine both raise blood glucose.

  • Permissiveness: Thyroid hormone increases the effect of epinephrine.

Ch. 17: Cardiovascular System – Blood

Blood Composition and Functions

Blood is a connective tissue composed of plasma and formed elements. It transports gases, nutrients, wastes, and hormones, and plays a role in immunity and homeostasis.

• Main Components: Plasma (liquid matrix) and formed elements (cells and cell fragments).

• Physical Characteristics: Viscous, slightly alkaline (pH 7.35–7.45), temperature ~100.4°F.

• Functions: Transport, regulation (pH, temperature), protection (clotting, immunity).

Formed Elements of Blood

• Erythrocytes (RBCs): Transport oxygen and carbon dioxide.

• Leukocytes (WBCs): Defend against pathogens.

• Platelets: Involved in blood clotting.

Key Definitions

• Hematopoiesis: Formation of blood cells in the bone marrow.

• Erythropoiesis: Production of red blood cells, regulated by erythropoietin (EPO) from the kidneys.

• Hematocrit: Percentage of blood volume occupied by RBCs.

• Hemolysis: Destruction of red blood cells.

Blood Groups and Transfusion

• Antigens (Agglutinogens): Surface markers on RBCs that determine blood type.

• Antibodies (Agglutinins): Proteins in plasma that react with foreign antigens.

• Major Blood Groups: ABO and Rh systems.

• Universal Donor: Type O negative.

• Universal Recipient: Type AB positive.

Hemostasis

• Three Steps: Vascular spasm, platelet plug formation, coagulation.

• Key Terms:

  • Anticoagulant: Substance that prevents blood clotting.

  • Thrombus: Stationary blood clot.

  • Embolus: Traveling blood clot.

Table: Types of Anemia

Ch. 18: Cardiovascular System – The Heart

Structure and Function of the Heart

The heart is a muscular organ that pumps blood through the circulatory system. It consists of four chambers and is surrounded by protective layers.

• Layers of the Heart Wall: Epicardium (outer), myocardium (muscular middle), endocardium (inner).

• Chambers: Two atria (upper), two ventricles (lower).

• Valves: Atrioventricular (tricuspid, bicuspid/mitral) and semilunar (pulmonary, aortic) valves prevent backflow.

Blood Flow Pathways

• Systemic Circuit: Delivers oxygenated blood from the left ventricle to the body and returns deoxygenated blood to the right atrium.

• Pulmonary Circuit: Carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

Cardiac Cycle and Conduction System

• Systole: Contraction phase of the heart.

• Diastole: Relaxation phase of the heart.

• Stroke Volume: Amount of blood pumped by a ventricle per beat.

• Cardiac Output: Volume of blood pumped by the heart per minute.

  • Formula:

• Conduction System: Includes SA node (pacemaker), AV node, bundle of His, bundle branches, Purkinje fibers.

Electrocardiogram (ECG) Waves

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T wave: Ventricular repolarization.

Heart Disorders

• Tachycardia: Abnormally fast heart rate.

• Bradycardia: Abnormally slow heart rate.

• Myocardial Infarction (Heart Attack): Death of heart muscle due to blocked blood supply. Risk factors include hypertension, smoking, high cholesterol, diabetes.

Table: Major Heart Valves and Their Locations

Additional info:

• Some content was inferred and expanded for clarity and completeness, such as detailed hormone functions, blood group compatibility, and the cardiac conduction system.

• Tables were recreated to summarize key comparisons and classifications.