Endocrine System

Overview of Endocrine Function

The endocrine system consists of glands that secrete hormones directly into the bloodstream, regulating various physiological processes throughout the body.

• Endocrine glands: Organs that produce chemical messengers (hormones) released to the blood (e.g., pituitary, thyroid, adrenal glands).

• Hormones: Chemical signals that affect target cells with specific receptors.

• Regulation: Hypothalamus controls pituitary gland, which in turn regulates other endocrine glands.

• Classification: Hormones are classified by solubility (water or lipid soluble) and act on target cells via specific receptors.

• Hormonal response to stress: Short vs. long-term stress responses, including the General Adaptation Syndrome.

• Antagonistic hormones: Hormones that have opposing effects (e.g., insulin/glucagon, calcitonin/PTH).

Example: Insulin lowers blood glucose, while glucagon raises it.

Blood

Functions and Components of Blood

Blood is a connective tissue responsible for transport, regulation, and protection within the body.

• Functions: Transport of oxygen, nutrients, hormones, and waste; regulation of pH and temperature; protection via immune cells.

• Blood cell types: Erythrocytes (red blood cells), leukocytes (white blood cells), platelets.

• Blood typing: ABO and Rh systems; antigens and antibodies determine compatibility.

• Hemostasis: The process of blood clotting involving vascular spasm, platelet plug formation, and coagulation cascade.

• Blood plasma: The liquid component of blood containing water, proteins, electrolytes, and nutrients.

Example: Type O blood has no A or B antigens and can donate to any ABO type.

Cardiovascular System

Heart Anatomy and Physiology

The cardiovascular system circulates blood throughout the body, delivering oxygen and nutrients while removing waste products.

• Heart sounds: "Lub-dubb" indicates closure of AV and semilunar valves.

• Heart rate: Normal range is 60-100 bpm; bradycardia is below 60, tachycardia above 100.

• Heart conduction system: SA node, AV node, bundle of His, Purkinje fibers coordinate contractions.

• Blood vessels: Arteries, veins, and capillaries differ in structure and function.

• Blood pressure: Determined by cardiac output and vessel resistance; measured as systolic/diastolic.

• Cardiac output:

Example: Capillaries allow for efficient exchange of oxygen and carbon dioxide between blood and tissues.

Immune System

Functions and Components

The immune system protects the body from pathogens and maintains homeostasis through a network of cells, tissues, and organs.

• Organs: Lymph nodes, spleen, thymus, lymphatic vessels.

• Lymph: Fluid containing immune cells that circulates through lymphatic vessels.

• Immunity types: Innate (nonspecific) and adaptive (specific); humoral (antibody-mediated) and cell-mediated (T cells).

• Inflammation: A response to injury or infection characterized by redness, heat, swelling, and pain.

• Antigens and antibodies: Antigens trigger immune responses; antibodies bind to antigens for neutralization.

Example: Vaccines stimulate active artificial immunity by exposing the body to antigens.

Respiratory System

Anatomy and Physiology

The respiratory system enables gas exchange between the body and the environment, supplying oxygen and removing carbon dioxide.

• Pathway: Air travels from nose/mouth to alveoli in the lungs.

• Mucociliary escalator: Ciliated epithelium traps and moves mucus and debris out of the airways.

• Alveoli: Site of gas exchange; large surface area and thin walls facilitate diffusion.

• Dead space: Areas where air is present but no gas exchange occurs.

• Gas transport: Oxygen binds to hemoglobin; carbon dioxide is transported dissolved in plasma, as bicarbonate, or bound to hemoglobin.

• Equation for CO2 transport:

Example: During exercise, increased CO2 production leads to increased respiratory rate to expel excess CO2.

Digestive System

Structure and Function

The digestive system breaks down food, absorbs nutrients, and eliminates waste.

• Digestive tract: Mouth, pharynx, esophagus, stomach, small and large intestines, anus.

• Accessory organs: Salivary glands, liver, pancreas, gallbladder.

• Mechanical digestion: Physical breakdown of food (chewing, churning).

• Chemical digestion: Enzymatic breakdown of macromolecules.

• Enzymes: Pepsin (proteins), lipase (fats), amylase (carbohydrates).

• Bile: Produced by liver, stored in gallbladder, emulsifies fats.

Example: Lactase breaks down lactose; deficiency leads to lactose intolerance.

Metabolism

Energy Production and Utilization

Metabolism encompasses all chemical reactions in the body, including those that produce and use energy.

• Anabolism: Building complex molecules from simpler ones.

• Catabolism: Breaking down molecules to release energy.

• Glucose metabolism: Glycolysis, Krebs cycle, and electron transport chain produce ATP.

• Equation for aerobic respiration:

• Calorie: Unit of energy; amount needed to raise temperature of 1g water by 1°C.

Example: Fatty acids and glucose are primary fuel sources for ATP production.

Urinary System

Structure and Function

The urinary system removes waste products from the blood and regulates water, electrolyte, and acid-base balance.

• Organs: Kidneys, ureters, bladder, urethra.

• Nephron: Functional unit of the kidney; filters blood and forms urine.

• Processes: Filtration, reabsorption, secretion, excretion.

• Regulation: ADH and aldosterone regulate water and sodium reabsorption.

• Blood pressure effects: Changes in BP affect glomerular filtration rate (GFR).

Example: ADH increases water reabsorption in the collecting duct during dehydration.

Acid-Base Balance

Regulation and Disorders

Acid-base balance maintains the pH of body fluids within a narrow range, essential for normal cellular function.

• Blood pH: Normal range is 7.35-7.45.

• Acidosis: Blood pH below 7.35; can be respiratory or metabolic.

• Alkalosis: Blood pH above 7.45; can be respiratory or metabolic.

• Compensation: Respiratory and renal systems adjust to restore pH balance.

• Buffer systems: Bicarbonate, phosphate, and protein buffers help maintain pH.

• Electrolyte imbalances: Sodium, potassium, and chloride levels affect acid-base status.

Example: Hyperventilation causes respiratory alkalosis by decreasing CO2 levels.

Reproductive System

Male and Female Anatomy and Physiology

The reproductive system ensures the continuation of species through production of gametes and support of fetal development.

• Male anatomy: Testes, ducts, accessory glands, penis.

• Female anatomy: Ovaries, uterine tubes, uterus, vagina.

• Hormonal regulation: GnRH, FSH, LH, testosterone, estrogen, progesterone.

• Menstrual cycle: Follicular, ovulatory, luteal phases; changes in endometrium.

• Spermatogenesis: Production of sperm in testes.

• Oogenesis: Production of eggs in ovaries.

• Fertilization: Fusion of sperm and egg; implantation in uterus.

• Placenta: Organ that nourishes fetus and removes waste.

• Labor stages: Dilation, expulsion, placental.

• Lactation: Production of milk by mammary glands.

Example: Estrogen and progesterone regulate the menstrual cycle and prepare the uterus for pregnancy.

Developmental Biology

Embryology and Fetal Development

Developmental biology studies the formation and growth of organisms from fertilization to birth.

• Blastomeres: Early embryonic cells formed by cleavage of the zygote.

• Gastrulation: Formation of three germ layers (ectoderm, mesoderm, endoderm).

• Implantation: Attachment of embryo to uterine wall.

• Gestation: Period from fertilization to birth.

• Placenta: Supports fetal development by exchanging nutrients and waste.

• Labor: Three stages—dilation, expulsion, placental.

• Lactation: Milk production post-birth.

Example: The blastocyst implants in the uterine wall about 6-7 days after fertilization.

Additional info: These notes expand upon the original study guide by providing definitions, examples, and tables for key concepts, ensuring a self-contained resource for exam preparation.