Physiology Exam 4 Study Guide: Cardiovascular, Respiratory, and Renal Systems

Cardiovascular Physiology

Blood Vessel Anatomy and Function

The circulatory system consists of various types of blood vessels, each with distinct structural and functional properties. Understanding these differences is essential for grasping how blood flows and is regulated throughout the body.

• Arteries: Thick-walled vessels that carry blood away from the heart under high pressure.

• Arterioles: Smaller branches of arteries; major site of vascular resistance and regulation of blood flow.

• Capillaries: Thin-walled vessels where exchange of gases, nutrients, and waste occurs.

• Venules: Collect blood from capillaries and channel it into veins.

• Veins: Vessels that return blood to the heart; have valves to prevent backflow.

Layers of Blood Vessels: Tunica intima (inner), tunica media (middle, smooth muscle), tunica externa/adventitia (outer, connective tissue).

Endothelium: The innermost lining of blood vessels, crucial for vascular health and function.

Control of Vessel Diameter

Vessel diameter is regulated by neural, hormonal, and local factors, affecting blood pressure and flow.

• Vasoconstriction: Narrowing of blood vessels, increases resistance and blood pressure.

• Vasodilation: Widening of blood vessels, decreases resistance and blood pressure.

• Key Regulators: Norepinephrine (vasoconstrictor), nitric oxide (vasodilator), local metabolites (e.g., CO2, H+).

Systemic vs. Pulmonary Circulation

The cardiovascular system is divided into two main circuits:

• Systemic Circulation: Delivers oxygenated blood from the heart to the body and returns deoxygenated blood.

• Pulmonary Circulation: Transports deoxygenated blood from the heart to the lungs for oxygenation and returns it to the heart.

Blood Pressure and Flow

Blood pressure is the force exerted by circulating blood on vessel walls. Blood flow depends on pressure gradients and vessel resistance.

• Mean Arterial Pressure (MAP): Average pressure in arteries during one cardiac cycle.

• Equation:

$MAP = CO \times TPR$

• CO: Cardiac Output (volume of blood pumped per minute)

• TPR: Total Peripheral Resistance (sum of resistance in systemic circulation)

Factors Affecting Blood Pressure: Blood volume, vessel diameter, heart rate, and contractility.

Capillary Exchange Mechanisms

Capillaries allow for the exchange of substances between blood and tissues via several mechanisms:

• Diffusion: Movement of small molecules down their concentration gradient.

• Vesicular Transport: Endocytosis and exocytosis of larger molecules.

• Bulk Flow: Movement of fluid driven by hydrostatic and osmotic pressures.

Starling Forces: Govern fluid movement across capillary walls.

$Net\ Filtration\ Pressure = (P_c - P_i) - (\pi_c - \pi_i)$

• $P_c$ = Capillary hydrostatic pressure

• $P_i$ = Interstitial hydrostatic pressure

• $\pi_c$ = Capillary oncotic pressure

• $\pi_i$ = Interstitial oncotic pressure

Respiratory Physiology

Anatomy of the Respiratory System

The respiratory system is responsible for gas exchange and consists of conducting and respiratory zones.

• Conducting Zone: Nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles (no gas exchange).

• Respiratory Zone: Respiratory bronchioles, alveolar ducts, alveoli (site of gas exchange).

• Pleura: Visceral and parietal pleura surround the lungs, creating a pleural cavity.

Mechanics of Breathing

Breathing involves changes in thoracic volume and pressure, allowing air to flow in and out of the lungs.

• Inspiration: Diaphragm contracts, thoracic volume increases, intrapulmonary pressure decreases.

• Expiration: Diaphragm relaxes, thoracic volume decreases, intrapulmonary pressure increases.

Boyle's Law: Pressure and volume are inversely related for a given amount of gas.

$P_1V_1 = P_2V_2$

Gas Exchange and Transport

Oxygen and carbon dioxide are exchanged between alveoli and blood by diffusion.

• Partial Pressure: The pressure exerted by a single gas in a mixture; drives diffusion.

• Oxygen Transport: Mostly bound to hemoglobin; small amount dissolved in plasma.

• Carbon Dioxide Transport: Dissolved in plasma, bound to hemoglobin, or as bicarbonate ($HCO_3^-$).

Relevant Equations:

• Alveolar Ventilation: $AV = (TV - DS) \times RR$

• $TV$ = Tidal Volume, $DS$ = Dead Space, $RR$ = Respiratory Rate

Pulmonary Volumes and Capacities

Lung volumes and capacities are measured to assess respiratory function.

• Tidal Volume (TV): Volume of air inhaled or exhaled in a normal breath.

• Inspiratory Reserve Volume (IRV): Additional air inhaled after a normal inspiration.

• Expiratory Reserve Volume (ERV): Additional air exhaled after a normal expiration.

• Residual Volume (RV): Air remaining in lungs after maximal exhalation.

• Vital Capacity (VC): $VC = TV + IRV + ERV$

Renal Physiology

Nephron Structure and Function

The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine.

• Glomerulus: Capillary network where filtration occurs.

• Bowman's Capsule: Surrounds the glomerulus and collects filtrate.

• Proximal Tubule, Loop of Henle, Distal Tubule, Collecting Duct: Sites of reabsorption and secretion.

Filtration, Reabsorption, and Secretion

Three main processes determine urine composition:

• Filtration: Movement of water and solutes from blood into Bowman's capsule.

• Reabsorption: Return of filtered substances to blood (e.g., glucose, ions, water).

• Secretion: Active transport of substances from blood into nephron for excretion.

Glomerular Filtration Rate (GFR): Volume of filtrate produced per minute; affected by blood pressure and nephron permeability.

Relevant Equation:

$GFR = K_f \times (P_{GC} - P_{BS} - \pi_{GC})$

• $K_f$ = Filtration coefficient

• $P_{GC}$ = Glomerular capillary hydrostatic pressure

• $P_{BS}$ = Bowman's space hydrostatic pressure

• $\pi_{GC}$ = Glomerular capillary oncotic pressure

Regulation of Renal Function

Renal function is regulated by neural, hormonal, and local mechanisms to maintain fluid and electrolyte balance.

• Renin-Angiotensin-Aldosterone System (RAAS): Regulates blood pressure and sodium balance.

• Antidiuretic Hormone (ADH): Increases water reabsorption in the collecting duct.

• Atrial Natriuretic Factor (ANF): Promotes sodium excretion.

Summary Table: Key Features of Major Systems

System	Main Function	Key Structures	Regulatory Mechanisms
Cardiovascular	Transport of nutrients, gases, wastes	Heart, arteries, veins, capillaries	Neural, hormonal, local factors
Respiratory	Gas exchange (O2/CO2)	Lungs, bronchi, alveoli	Neural control, chemical feedback
Renal	Filtration, reabsorption, secretion	Kidneys, nephrons	Hormonal (RAAS, ADH), neural

Additional info: Some details, such as specific equations and regulatory mechanisms, were expanded for clarity and completeness based on standard academic knowledge in physiology.