BPK142 final

Function of circulatory system

Transport essential materials through body to cells (oxygen, fuel, hormones)

Collects waste material products of metabolic activity (lactate/lactic acid, CO2, urea)

2 divisions of CS

Pulmonary circuit: blood going to and from lungs

Systemic circuit: blood going to and from the rest of the body tissues

Unidirectional valves

RA-RV: tricuspid valve

RV-PA: pulmonary valve

LA-LV: mitral valve

LV-A: aortic valve

Heart murmur

Valve does not close properly or is damaged

Regurgitating blood makes gargling noise

Cardiac muscle

Myocardium- specialized muscle

All fibers or cells of cardiac muscle interconnected functionally

Fibers of atria and ventricles electrically separated

SA node

sinoatrial

specialized tissue where the hearts inherent contractile rhythm originates

located in right atrium

Electrical conduction in heart

Autorhythmic cells: spontaneously fire action potentials and depolarization spreads through gap junctions to adjacent contractile tissue

Localized to the conduction areas on atria and ventricles

AV node

atrio-ventricular

focuses and routes signal that arises in SA, only pathway for electrical conduction between atria and ventricles (wave of depolarization delayed in AV for 0.10 seconds so atria can contract and empty contents into ventricles)

Atria conduction system

SA node - internodal pathways across both atria - AV node

Ventricular conduction

AV node - AV bundle (bundle of his) - L and R divisions - numerous Purkinje fibers spread through ventricles

ECG

Using electrodes on bodies surface: records wave of depolarization as it passes across heart

PQRST

P wave

Atrial depolarization

QRS complex

Atrial re-polarization and ventricular depolarization

T wave

Ventricular repolarization

Arrhythmia

Irregularity in rhythm of heart beat

Can be diagnosed w ECG by observing amplitude, wave form and time intervals of electrocardiograph

Common arrhythmias

Tachycardia: HR faster than normal

Bradycardia: HR slower than normal

Fibrillation: ECG disorganized (atrial fibrillation heart can still function as a pump, ventricular fibrillation it cannot)

Right Coronary Artery

RCA, supplies blood to right atrium, right ventricle; back of septum; bottom portion of left ventricle

Left Coronary Artery

LCA: divides into circumflex artery and left anterior descending artery

Circumflex: left atrium; side and back of left ventricle

LAD: front and bottom of left ventricle, front of septum

hearts blood and oxygen supply

Always extras ~4% of total cardiac output, relies on increased blood output instead of increased extraction

Rest: 4% of 5.8L/min

Exercise: 4% of 25.6L/min

*heart extracts approximately 70-80% oxygen compared to 30% for other tissues

Arteries and arterioles

High pressure portion of circulatory system

Elastic, systemic, maintain blood flow during ventricular relaxation

As artery size decreases elasticity does as well (replaced with smooth muscle)

Veins and venules

Low pressure portion of circulatory system

Valves especially in legs to carry blood against force of gravity

Thinner walled than arteries - also have smooth muscle to change diameter

Capillaries

Exchange between nutrients and wastes and gases between blood and tissues

Very tiny and thin walled

Pulse pressure

Difference between systolic and diastolic pressure readings in arteries

Mechanisms of venous return

Pressure difference between atrium and left ventricle

Skeletal muscle pump

Respiratory pump

Pressure difference

LV = 120 mm Hg

RA = 3 mm Hg

Difference = 117 mm Hg (driving pressure, keeps circulation going)

Skeletal muscle pump

Boosts return during movement

Muscles squeeze veins and push blood back toward heart, valves prevent backflow due to gravity

Respiratory pump

Boosts return during breathing

Inspiration decreases pressure in thoracic cavity, “pulls” blood back from lower portions

Inferior vena cava - thoracic cavity - RA

Blood

WBCs, RBCs, platelets

Plasma 50-60% of BV

Plasma: 90% water, 10% solutes (proteins, nutrients, hormones)

Blood volume

Normal adult approx 8% body mass

Greater for people who are larger, more endurance trained and heat acclimatized

RBCs

Biconcave discs 7 microns diameter

5-6m per cubic mm of blood

Lifespan 120 days

Produced: red bone marrow (ends of long bones, flat bones)

Contain hemoglobin

Hemoglobin

Protein

Each molecule contains 4 subunits (contain 1 molecule of iron)

Can bind with oxygen reversibly (carries oxygen in blood)

Normal hemoglobin levels

140-160g/1,000 mL of blood in M

120-140g/1,000 mL of blood in F

Hematocrit

Percentage of BV made up of cells (mostly RBCs)

Females: 37-47%

Males: 42-52%

Anemia

Lowered hematocrit

(Fewer RBCs = less oxygen delivery)

Fatigue, weakness

Polycythemia

Elevated hematocrit levels

Too many RBCs (blood thicker) - increased viscosity and clotting (poor flow)

Gas exchange

Alveolar-capillary diffusion in lungs (O2 into blood, CO2 into lungs/tissue)

Capillary-tissue diffusion (O2 from blood to tissue, CO2 from tissue to blood)

Factors that increase rate of diffusion

Higher concentration gradient (difference)

Shorter diffusion distance (thin membranes)

Higher temperature (molecules move faster)

Greater surface area (more space)

Henry’s law of partial pressures

Amount of gas that dissolves in a fluid is a function of:

Pressure of a gas (higher pressure = more gas dissolves)

Solubility of the gas (CO2 20.3x more soluble in liquid than O2)

Lung diffusing capacity

Volume of oxygen that crosses alveolar-capillary membrane per minute and per mm Hg

Factors that affect diffusing capacity

Partial pressure gradients (Henry’s law)

Thickness of respiratory membrane

Number of RBCs OR their hemoglobin concentration OR both

SA of respiratory membrane

Lung diffusing capacity during exercise

Can increase up to 3x resting value because:

• increased lung volumes - increased SA

• Opening up of more capillaries in lungs and greater volume of blood flowing through lung

Transport of oxygen

2% dissolved in plasma, 98% carried in hemoglobin (oxyhemoglobin - HbO2)

O2 carrying capacity of blood = 20.1mL of O2/ 100mL of blood

O2 carrying capacity of hemoglobin: 1.34mL O2/ 1g Hb

15g Hb/100mL of blood

Single RBC contains 300m Hb

%SO2

Percent saturation of Hb with oxygen (not maximum oxygen capacity of Hb - actual saturation)

Hemoglobin concentration values sea level

Arterial blood: 97.5% saturated w oxygen (97.5×20.1 = 19.5mL/100mL)

Venous blood: 75% (75×20.1 = 15.1mL/100mL)

Arteriovenous Oxygen difference (a-v): 4.4mL O2/ 100mL

Oxyhemoglobin dissociation curve

shows how much oxygen hemoglobin is carrying at different oxygen pressures

%SO2 vs PO2

Upper respiratory system

Nasal cavity

Larynx

Pharynx

Lower respiratory system

Trachea, lungs: bronchi (primary and secondary - L and R), terminal bronchioles

Respiratory bronchioles, pulmonary lobules: contain alveolar ducts and alveoli

Airway resistance

Impacted by contractions of bronchioles (smooth muscle: dilates or constricts)

Conducting airway

Leads inspired air to alveoli

Anatomical dead space/Vd; 150mL

Alveoli

Small thin walled sacs with capillary beds in their walls

Site of gas molecule exchange

Contained in lungs alongside conducting airways, elastic tissue and blood vessels

Boyle’s Law

Pressure of a gas is inversely related to volume (as volume increases, pressure decreases)

Charles’ Law

Pressure of gas varies proportional to temperature (temperature increases pressure increases)

ATPS

Ambient temperature and pressure saturated

Conditions of temperature and pressure when measuring gas volumes

Corrected to STPD

Inspiration

Active process

Sternocleidomastoids, scalenes, external intercostals, diaphragm

Diaphragm descends and external intercostals contract - increase thoracic cavity volume

Air molecules move from atmosphere to lungs following pressure gradient

Expiration

Internal intercostals and abdominal muscles

Diaphragm and internal intercostals relax - decrease volume of thoracic cavity

Pressure in TC exceeds atmosphere - molecules move out of lungs following pressure gradient

Active process during exercise, passive during rest

Lung volumes

Tidal volume (Vt)

Breathing frequency (Fr)

Minute ventilation (Ve)

Expiratory reserve volume (ERV)

Inspiratory capacity (IC)

Vital capacity (VC)

Residual volume (RV)

Functional residual capacity (FRC)

Total lung capacity (TLC)

Forced vital capacity (FCV)

Maximum breathing capacity (MBC)

Vt

Tidal volume

Volume of gas inspired or expired with each breath at rest or during any stated activity (500mL inspired or expired at rest)

Fr

Breathing frequency

12-16 breaths per minute

Ve

Minute ventilation

Volume of gas inspired or expired per minute (tidal volume x breathing frequency)

Rest: (Vt x Fr) (0.5L x 12-16) = 6-8L/min

Exercise max: (Vt x Fr) (3L x 12-16) = 180L/min

ERV

Expiratory reserve volume

Maximum volume of air that can be exhaled from the resting end-expiratory position

Approx 25% of VC at rest

IC

Inspiratory capacity

Maximum volume of gas that can be inspired from resting end-expiratory position

Approx. 75% of VC at rest

VC

Viral capacity

Greatest volume of gas that can be expelled by voluntary force after maximal inspiration (or reversed - total usable air)(IC + ERV)

RV

Residual volume

Volume of air remaining in lungs after forced expiration (keeps lungs from collapsing)

Varies with age (should not exceed 20-30%)

FRC

Functional residual capacity

Volume of gas remaining in lungs after a quiet/normal exhalation (where lungs normally sit)

ERV + RV

TLC

Total lung capacity

Volume of gas in the lungs after maximal inspiration (VC + RV)

Everything in your lungs including things you can remove (RV)

Pulmonary function tests

FVC: measures VC in a forced and timed (4 seconds) way (forced vital capacity) - measures lung capacity

FEV1: forced expiratory volume in one second (how much air you can blowout in first second of FVC) - measures airway resistance

ratio: 80% air typically comes out in 1st second

MBC: maximum breathing capacity: measures how much air you can move in and out over time (12 seconds): shows issues with airway resistance, muscle strength and chest/lung mechanics

Pulmonary function test norms issues

Based on sex age and height usually

Don’t consider size of subject (specifically chest size) - would be better to use sitting rather than standing height

Should be interpreted in relation to medical history, smoking habits, occupational history and chest X ray

Obstructive respiratory disorders

Blockage or narrowing of airways causing increased airway resistance (can be observed by FEV1 decrease, ratio of FEV1:FCV less than 80%, decreased MBC)

Asthma, bronchitis, emphysema

Causes of obstructive disorders

Blockage due to inflammation and edema, smooth muscle constrictions or bronchiolar secretion

Restrictive respiratory disorders

Loss of elasticity and compliance: limits expansion of lungs

All lung volumes reduced (VC, RV, FRC, TLC)

FEV1 and MBC reduced but FEV1/FVC ratio 90% or higher

Causes of restrictive disorders

Pulmonary fibrosis, pneumonia, damage to lung tissue

Alveolar ventilation (Va)

Volume of air that reaches alevoli per minute (contributes in gas exchange)

Obtained through Tidal volume - Anatomical dead space (Vd)

Va at rest

Va = Fr x (Vt-Vd) = 12× 500mL-150mL

= 4,200 mL/minute

Va during max exercise

Va = Fr x (Vt-Vd) = 60 × 500mL - 150mL

= 170,000 mL/m or 170L/minute

Why do volumes and capacities decrease when an individual lies down?

• abdominal contents push up against diaphragm

• Increase in intrapulmonary blood volume which decreases space available for pulmonary air

Ventilation during exercise

Ve increases linearly with exercise intensity (oxygen consumption)

Threshold; Ve increases disproportionately with oxygen consumption/exercise intensity (extra CO2 and acidity buildup means breathing must increase faster)

Ve threshold

Untrained average individual: 50-60% of vO2max

Endurance athletes 75-80%

Stroke volume

Amount of blood pumped by the right or left ventricle per beat (mL)

SV

Cardiac output

Q = HR x SV

Amount of blood pumped by either the right or left ventricle per MINUTE (L/min)

How much blood you SEND

aVO2 -diff

Arterial-venous oxygen difference (how much oxygen is extracted at capillary beds)

How much oxygen USED by muscles and the efficiency of this process

VO2

Oxygen uptake/consumption or utilization by body tissues

Fick equation

VO2 = Q (HRxSV) x a-VO2 diff

In order to increase oxygen consumption you must increase cardiac output and/or extract more oxygen from the arterial blood

Factors that determine vo2max

Ability to ventilate lungs and oxygenate blood passing through lungs

Cardiac output (ability of heart to pump blood)