NIXON EXAM 4

Blood Flow Equation

Flow(F) = \Delta P / R

Driving Force ($\Delta P$)

The pressure gradient that pushes liquid through a vessel from high to low pressure.

Resistance (R)

A measure of factors that hinder or increase the effort needed for blood to flow.

Flow-Pressure Relationship

Directly proportionate (higher gradient = higher flow).

Flow-Resistance Relationship

Inversely or indirectly proportionate (higher resistance = lower flow).

Closed Loop

A term describing the circulatory system as a continuous circuit.

Pulmonary vs. Systemic Flow Volume

The flow through both circuits is identical.

Systemic vs. Pulmonary Resistance

Systemic resistance is higher due to much longer blood vessels needed to reach all organs.

Mean Arterial Pressure (MAP)

The starting pressure of the systemic circuit in the aorta; approx. 85 mmHg.

Central Venous Pressure (CVP)

The ending pressure of the systemic circuit in the right atrium; 0 mmHg.

Pressure Gradient ($\Delta P$) Calculation

$MAP - CVP$; because CVP is zero the driving pressure effectively equals MAP.

Vessel Radius

A factor of resistance determined by whether a vessel is vasoconstricted or vasodilated.

Blood Viscosity

Resistance factor related to the concentration of red blood cells and proteins (e.g. polycythemia).

Vessel Length

Resistance factor where longer vessels create higher total resistance.

Total Peripheral Resistance (TPR)

The combined resistance of every blood vessel within the systemic circuit.

Vasoconstriction Effect

Increases resistance and decreases blood flow.

Vasodilation Effect

Decreases resistance and increases blood flow.

Cardiac Output (CO)

The volume of blood flowing through the systemic circuit each minute.

MAP Calculation (CO/TPR)

$MAP = Cardiac Output X TPR$.

Elastic Arteries

Large diameter vessels with less smooth muscle that act as a pressure reservoir.

Muscular Arteries

Smaller diameter vessels with more smooth muscle that can highly constrict or dilate.

Pressure Reservoir

The function of elastic arteries to stretch and recoil maintaining flow during diastole.

Arterioles

Small vessels with the highest resistance; regulate local flow via rings of smooth muscle.

Pre-capillary Sphincters

Smooth muscle rings in arterioles that control entry into capillary beds.

Capillary Anatomy

Walls are 0.5 micrometers thick (one endothelial cell layer) and 5 to 10 micrometers in diameter.

Capillary Surface Area

These vessels have the largest total cross-sectional area in the body.

Capillary Blood Velocity

These vessels have the slowest flow to allow time for nutrient/gas exchange.

Venules

Small vessels that collect blood from capillaries; have very little smooth muscle.

Veins

Vessels returning blood to the heart; capable of increasing tone to move blood faster.

Vein Tone

Increasing this increases venous pressure to boost end-diastolic volume.

Microcirculation

The collective group of arterioles capillaries and venules.

Low Compliance

Exhibited by arteries; they do not expand easily and recoil forcefully.

High Compliance

Exhibited by veins; they expand easily and require large volume changes to increase pressure.

Systolic Blood Pressure

The highest aortic pressure during ventricular contraction and ejection.

Diastolic Blood Pressure

The lowest arterial pressure during heart relaxation and filling.

Sphygmomanometer

The technical name for a blood pressure cuff.

Korotkoff Sounds

Audible vibrations caused by turbulence in a partially compressed artery.

First Korotkoff Sound

The sound recorded as the systolic pressure.

Laminar Flow

Smooth blood flow that produces no sound.

Pulse Pressure

The calculated difference between systolic and diastolic pressure.

Weighted MAP

A mean that factors in two diastolic pressures for every one systolic because more time is spent in diastole.

Continuous Capillaries

Most common type; use narrow intercellular clefts (pores) for small water-soluble molecules.

Fenestrated Capillaries

Have large pores (fenestrations) for proteins; found in kidneys intestines and glands.

Discontinuous (Sinusoidal) Capillaries

Have very large gaps (sinusoids) for large proteins and whole cells; found in liver and bone marrow.

Transcytosis

Mechanism of exchange for proteins using endocytosis and exocytosis.

Metarterioles

Structural shunts that allow blood to bypass a capillary bed entirely.

Vasomotion

The alternating contraction and relaxation of sphincters in response to local metabolites.

Diffusion

The most common mechanism of exchange across capillary walls.

Lipophilic Molecule Transport

These substances travel directly across the capillary membrane.

Lipophobic Molecule Transport

These substances travel through pores or channels.

Filtration

The movement of fluid out of the capillary and into the interstitial space.

Absorption (Reabsorption)

The movement of fluid from the interstitial space back into the capillary.

Edema

Abnormal fluid collection in the interstitial space when filtration exceeds reabsorption/lymphatic clearance.

Hydrostatic Pressure (P)

The "pushing" force created by fluid.

Osmotic (Oncotic) Pressure ($\pi$)

The "pulling" force created by proteins.

Capillary Hydrostatic Pressure ($P_{CAP}$)

Pushing force of blood inside the capillary that favors filtration.

Interstitial Fluid Hydrostatic Pressure ($P_{IF}$)

Pushing force outside the capillary that favors absorption.

Capillary Osmotic Pressure ($\pi_{CAP}$)

Pulling force of blood proteins that favors absorption.

Interstitial Fluid Osmotic Pressure ($\pi_{IF}$)

Pulling force of leaked proteins outside the capillary that favors filtration.

Fluid Balance Totals

20 liters filtered out daily; 17 liters reabsorbed; 3 liters picked up by lymphatics.

Ankle Edema (Standing)

Caused by gravity increasing $P_{CAP}$ (hydrostatic pushing) in lower limbs.

Injury Swelling

Caused by leaked proteins increasing $\pi_{IF}$ (osmotic pulling) at the damage site.

Liver Disease (Cirrhosis) Edema

Caused by a lack of albumin which decreases $\pi_{CAP}$ (osmotic pulling) in the blood.

Heart Failure Edema

Caused by blood backing up and increasing $P_{CAP}$ (hydrostatic pushing).

Factors Determining MAP

Heart Rate Stroke Volume and Total Peripheral Resistance (TPR).

Hypotension

MAP lower than normal resulting in less blood reaching tissues.

Short-term MAP Regulation

Neural control of Heart and Vessels to adjust Cardiac Output and TPR.

Long-term MAP Regulation

Hormonal control of the Kidneys to adjust Blood Volume.

Baroreceptors

Stretch receptors in the aorta and carotid sinus that monitor pressure changes.

High BP Baroreceptor Response

Detects increased stretch increases AP frequency and decreases Heart Rate.

Low BP Baroreceptor Response

Detects decreased stretch decreases AP frequency and increases Heart Rate.

Cranial Nerves in BP

CN 9 (Glossopharyngeal) sends sensory input; CN 10 (Vagus) provides parasympathetic output.

Cardiovascular Control Center

Located in the Medulla of the brain.

Parasympathetic Innervation

Affects the SA node AV node and atrial muscle; has NO control over blood vessels.

Sympathetic Innervation

Affects the SA node AV node ventricular myocardium arterioles and veins.

Hemorrhage Reflex

Decreased volume triggers sympathetic activity to increase HR and TPR diverting blood to the brain.

Vasopressin (ADH)

Hypothalamic hormone that increases water reabsorption and causes vasoconstriction to raise MAP.

Angiotensin II

A vasoconstrictor that stimulates thirst and triggers aldosterone release.

Aldosterone

Adrenal cortex hormone that reabsorbs sodium (and water) to increase blood volume.

Epinephrine

Increases HR and SV constricts arterioles and increases vein tone to raise MAP.

Inhalation/Heart Rate

Thoracic pressure decreases sympathetic activity increases and Heart Rate increases.

Exhalation/Heart Rate

Thoracic pressure increases parasympathetic activity increases and Heart Rate decreases.

High $CO_{2}$ Systemic Response

Acts as an acid to cause systemic vasoconstriction increasing TPR and MAP.

Body Temp Rise

Hypothalamus decreases skin vascular resistance (vasodilation) to lose heat.

Body Temp Drop

Hypothalamus increases skin vascular resistance (vasoconstriction) to retain heat.

Hematocrit Layers

Plasma (top) Buffy coat (middle) Packed Erythrocytes (bottom).

Buffy Coat Components

Leukocytes (white blood cells) and Platelets.

Polycythemia

High RBC count that increases blood viscosity resistance and MAP.

Albumin

The main plasma protein responsible for the oncotic pulling pressure of blood.

Hemoglobin Affinities

Heme (iron) binds Oxygen or Carbon Monoxide; Globin binds Carbon Dioxide.

Carbonic Anhydrase Equation

$CO_{2} + H_{2}O \rightleftharpoons H_{2}CO_{3} \rightleftharpoons H^{+} + HCO_{3}^{-}$.

Bicarbonate ($HCO_{3}^{-}$)

The basic/alkaline component of the carbonic anhydrase system.

Hydrogen ($H^{+}$)

The acidic component of the carbonic anhydrase system.

Erythropoiesis

RBC production in the red bone marrow from hematopoietic stem cells.

RBC Lifespan

Approximately 120 days due to the lack of a nucleus or organelles.

Erythropoietin (EPO)

Kidney hormone secreted during hypoxemia to trigger RBC production.

RBC Graveyard

The Spleen.

Transferrin

The protein that binds and transports T-iron in the blood.

Ferritin

The storage form of F-iron in the liver and spleen.

Spectrin

Flexible protein in RBCs that allows 8-micrometer cells to fold through 5-micrometer capillaries.