Exam I Review: Endocrine System, Blood, Heart, and Blood Vessels

Endocrine System

Hormones: Definition and General Functions

The endocrine system regulates physiological processes through the secretion of hormones, which are chemical messengers released by glands into the bloodstream.

• Hormone: A chemical substance produced by endocrine glands that regulates the activity of specific target cells.

• Target tissue: Cells or organs that respond to a particular hormone.

• General effects: Hormones influence metabolism, growth, reproduction, and homeostasis.

• Types of hormones: Steroid (lipid-based), nonsteroid (protein-based).

• Negative feedback: A regulatory mechanism in which a change in a physiological variable triggers a response that counteracts the initial change.

Example: Insulin lowers blood glucose levels, and its secretion is reduced when glucose levels normalize.

Blood

General Functions and Composition

Blood is a connective tissue responsible for transporting nutrients, gases, hormones, and waste products throughout the body.

• Functions: Transport, regulation, protection.

• Composition: Plasma (liquid matrix), formed elements (erythrocytes, leukocytes, platelets).

• Plasma: Contains water, proteins, electrolytes, nutrients, and waste products.

Erythrocytes (Red Blood Cells)

• Function: Transport oxygen and carbon dioxide.

• Hemoglobin: Protein that binds oxygen; each RBC contains millions of hemoglobin molecules.

• Shape: Biconcave disc increases surface area for gas exchange.

• Groups: Blood types (A, B, AB, O) based on antigens.

• Production: Erythropoiesis in bone marrow, regulated by erythropoietin.

• Disorders: Anemia (low RBC count), polycythemia (high RBC count).

Leukocytes (White Blood Cells)

• Function: Immune defense against pathogens.

• Types: Neutrophils, lymphocytes, monocytes, eosinophils, basophils.

• Lymphocytes: B and T cells, key roles in adaptive immunity.

• Disorders: Leukopenia (low WBC count), leukocytosis (high WBC count).

Platelets (Thrombocytes)

• Function: Blood clotting and repair of damaged blood vessels.

• Hemostasis: Process of stopping bleeding, involves vascular spasm, platelet plug formation, and coagulation.

Hemostasis and Coagulation

• Vascular spasm: Immediate constriction of blood vessel after injury.

• Platelet plug formation: Platelets adhere to exposed collagen and aggregate.

• Coagulation: Cascade of clotting factors leading to fibrin formation.

• Regulation: Anticoagulants (e.g., heparin) prevent excessive clotting.

• Disorders: Hemophilia (deficiency of clotting factors).

Heart

Structure and Blood Supply

The heart is a muscular organ that pumps blood through the circulatory system.

• Blood supply: Coronary arteries provide oxygenated blood to heart tissue.

• Myocardial infarction: Heart attack due to blocked coronary artery.

Cardiac Cycle and Conduction System

• Cardiac cycle: Sequence of events in one heartbeat, including systole (contraction) and diastole (relaxation).

• Conduction system: SA node, AV node, bundle of His, Purkinje fibers coordinate heart contractions.

• Electrocardiogram (ECG): Records electrical activity of the heart.

• Intrinsic and extrinsic regulation: Autonomic nervous system modulates heart rate and contractility.

Cardiac Output

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

• Formula: $\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}$

• Regulation: Influenced by preload, afterload, and contractility.

Blood Vessels

Types and Functions

Blood vessels transport blood throughout the body and regulate blood pressure.

• Arteries: Carry blood away from the heart; thick muscular walls.

• Veins: Return blood to the heart; contain valves to prevent backflow.

• Capillaries: Microscopic vessels for exchange of gases, nutrients, and waste.

Blood Pressure

• Definition: Force exerted by blood against vessel walls.

• Regulation: Short-term (baroreceptors, hormones), long-term (renal mechanisms).

• Key hormones: ADH, ANP, angiotensin II, aldosterone.

• Formula: $\text{Mean Arterial Pressure (MAP)} = \text{Diastolic Pressure} + \frac{1}{3}(\text{Systolic Pressure} - \text{Diastolic Pressure})$

Capillary Exchange

• Mechanisms: Diffusion, filtration, osmosis.

• Hydrostatic pressure: Pushes fluid out of capillaries.

• Osmotic pressure: Pulls fluid into capillaries.

• Net Filtration Pressure (NFP): Determines direction of fluid movement.

• Formula: $\text{NFP} = (\text{Hydrostatic Pressure}_{\text{capillary}} - \text{Hydrostatic Pressure}_{\text{interstitial}}) - (\text{Osmotic Pressure}_{\text{capillary}} - \text{Osmotic Pressure}_{\text{interstitial}})$

Disorders

• Edema: Excess fluid accumulation in tissues due to imbalance in capillary exchange.

Summary Table: Blood Cell Types

Cell Type	Main Function	Key Features
Erythrocytes	Oxygen transport	Biconcave shape, hemoglobin
Leukocytes	Immune defense	Five types: neutrophils, lymphocytes, monocytes, eosinophils, basophils
Platelets	Clotting	Cell fragments, initiate coagulation

Additional info: Academic context and definitions have been expanded for clarity and completeness. All formulas are provided in LaTeX format as required.