Endocrine System

Hormones of the Adrenal Gland and Their Functions

The adrenal gland produces several hormones essential for stress response, metabolism, and electrolyte balance.

• Cortisol: Regulates metabolism, immune response, and stress adaptation.

• Aldosterone: Controls sodium and potassium balance, affecting blood pressure.

• Epinephrine & Norepinephrine: Mediate the 'fight or flight' response, increasing heart rate and blood flow to muscles.

Anatomical and Physiological Connections of the Hypothalamus and Pituitary Glands

The hypothalamus and pituitary glands form a central regulatory axis for hormone secretion.

• Anatomical: The hypothalamus is connected to the pituitary via the infundibulum.

• Physiological: The hypothalamus releases hormones that stimulate or inhibit pituitary hormone release.

Functional Classifications of Hormones

Hormones are classified based on their chemical structure and mechanism of action.

• Peptide hormones: Water-soluble, act via membrane receptors (e.g., insulin).

• Steroid hormones: Lipid-soluble, act via intracellular receptors (e.g., cortisol).

• Amino acid-derived hormones: Include thyroid hormones and catecholamines.

Hormones of Calcium Homeostasis

Calcium levels are regulated by three main hormones:

• Parathyroid hormone (PTH): Increases blood calcium by stimulating bone resorption.

• Calcitonin: Lowers blood calcium by inhibiting bone resorption.

• Vitamin D (Calcitriol): Enhances calcium absorption in the gut.

Thymus Gland

The thymus is involved in immune system development, particularly T-cell maturation.

• Location: Superior mediastinum.

• Function: Secretes thymosin, which promotes T-cell development.

Homeostasis of Blood Sugar

Blood glucose is regulated by hormones from the pancreas.

• Insulin: Lowers blood glucose by promoting uptake into cells.

• Glucagon: Raises blood glucose by stimulating glycogen breakdown.

Cardiovascular System: The Heart

The Heart Anatomy and Conduction System

The heart is a muscular organ with four chambers and a specialized conduction system for coordinated contraction.

• Chambers: Right atrium, right ventricle, left atrium, left ventricle.

• Conduction system: Includes the SA node, AV node, bundle of His, bundle branches, and Purkinje fibers.

Blood Flow in the Chambers of the Heart

Blood flows through the heart in a specific sequence, ensuring oxygenation and circulation.

• Right atrium → right ventricle → pulmonary artery → lungs → left atrium → left ventricle → aorta → body.

Anatomy of the Walls of the Heart

The heart wall consists of three layers:

• Epicardium: Outer layer.

• Myocardium: Muscular middle layer responsible for contraction.

• Endocardium: Inner lining.

Coronary Cardiac Circuit Anatomy

The coronary arteries supply oxygenated blood to the heart muscle.

• Left and right coronary arteries: Branch from the aorta.

• Cardiac veins: Drain deoxygenated blood into the coronary sinus.

Cardiac Cycle Events – 4 Phases

The cardiac cycle consists of four main phases, each corresponding to specific electrical and mechanical events.

• Atrial systole: Atria contract, forcing blood into ventricles.

• Ventricular systole (first phase): Ventricles contract, AV valves close.

• Ventricular systole (second phase): Semilunar valves open, blood is ejected.

• Ventricular diastole: Ventricles relax, semilunar valves close, blood flows into atria and ventricles passively.

Pulmonary and Systemic Blood Circulation

The heart pumps blood through two main circuits:

• Pulmonary circuit: Right side of heart → lungs → left side of heart (oxygenates blood).

• Systemic circuit: Left side of heart → body tissues → right side of heart (delivers oxygen).

Cardiac Output Law

Cardiac output is the volume of blood pumped by the heart per minute.

• Formula:

Stroke Volume Laws

Stroke volume is influenced by preload, afterload, and contractility.

• Preload: Degree of stretch of cardiac muscle before contraction.

• Afterload: Resistance the heart must overcome to eject blood.

• Contractility: Strength of contraction independent of preload.

ECG: All Peaks, Segments, and Intervals

An electrocardiogram (ECG) records the electrical activity of the heart.

• P-wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T-wave: Ventricular repolarization.

• PR interval: Time from atrial to ventricular depolarization.

• ST segment: Time between ventricular depolarization and repolarization.

Sinus Rhythm

Sinus rhythm is the normal rhythm of the heart, initiated by the SA node.

• Normal rate: 60-100 beats per minute.

Sounds of the Heart

Heart sounds are produced by valve closures.

• S1: Closure of AV valves (beginning of systole).

• S2: Closure of semilunar valves (beginning of diastole).

Athlete ESV, EDV

End-systolic volume (ESV) and end-diastolic volume (EDV) are often altered in athletes due to increased cardiac efficiency.

• ESV: Volume of blood remaining in ventricle after contraction.

• EDV: Volume of blood in ventricle before contraction.

• Athletes: Typically have higher EDV and lower ESV, resulting in greater stroke volume.

Blood Vessels and Circulation

Anatomy of the Blood Vessels

Blood vessels include arteries, veins, and capillaries, each with distinct structural features.

• Arteries: Thick-walled, carry blood away from the heart.

• Veins: Thin-walled, carry blood toward the heart.

• Capillaries: Smallest vessels, site of exchange between blood and tissues.

Blood Pressure Forces Components

Blood pressure is determined by cardiac output, blood volume, and resistance.

• Systolic pressure: Pressure during ventricular contraction.

• Diastolic pressure: Pressure during ventricular relaxation.

Blood Pressure Modifying Factors

Several factors influence blood pressure:

• Blood volume

• Vessel diameter

• Heart rate

• Hormones

Blood Pressure Variation Throughout the Body

Blood pressure is highest in arteries and decreases through capillaries and veins.

• Arteries: Highest pressure.

• Capillaries: Moderate pressure.

• Veins: Lowest pressure.

Role of SNS and PSNS in BP Regulation

The sympathetic (SNS) and parasympathetic (PSNS) nervous systems regulate blood pressure.

• SNS: Increases heart rate and vasoconstriction, raising BP.

• PSNS: Decreases heart rate, lowering BP.

Mean Arterial Pressure

Mean arterial pressure (MAP) is the average pressure in arteries during one cardiac cycle.

• Formula:

Types of Capillaries

Capillaries are classified based on permeability:

• Continuous: Least permeable, most common.

• Fenestrated: Have pores, allow more exchange.

• Sinusoidal: Most permeable, found in liver and spleen.

Mechanisms of Blood Pressure Regulation

Blood pressure is regulated by neural, hormonal, and renal mechanisms.

• Baroreceptors: Detect changes in pressure.

• Renin-angiotensin system: Hormonal regulation.

• Antidiuretic hormone: Increases water retention.

Capillaries Net Filtration Factors

Net filtration in capillaries depends on hydrostatic and osmotic pressures.

• Formula:

Upper Limb Arteries

Major arteries of the upper limb include:

• Brachial artery

• Radial artery

• Ulnar artery

Major Veins

Major veins include:

• Superior and inferior vena cava

• Brachiocephalic vein

• Jugular vein

Case Studies

Case Study 1: Thyroid Gland Disorders

Thyroid disorders involve abnormal hormone levels and feedback mechanisms.

• Hormones: T3, T4, and TSH.

• Feedback: High T3/T4 suppress TSH; low T3/T4 increase TSH.

Case Study 2: Heart Interventricular Defect

An interventricular wall defect affects stroke volume and EKG readings.

• Stroke volume: May decrease due to inefficient pumping.

• EKG: May show abnormal QRS complex.i

Additional info: Academic context was added to expand brief points and ensure completeness.