Powerlab 3 & 4 Questions

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What structures and processes that produces the QRS complex in the ECG?

The QRS complex is produced by the process of ventricular depolarization and repolarization.
Results from the Pukinje fibers exciting the ventricular wall.

What is the physiological processes that take place between the QRS complex and the arrival of the pulse wave at the finger.

Ventricular contracts --> aorta --> elastic arteries --> muscular arteries --> arteries in finger.

When you feel a pulse, what are you feeling?

Brief changes in diameter of the artery due to the pressure wave.

Anatomical sites where a pulse can be palpated often correspond to "pressure points" for stopping hemorrhage in first-aid treatment. Why?

Cuts off blood flow past the point you are applying pressure.
This happens because its a main artery and branches to other points.

Why can the ulnar pulse not usually be felt?

All the tissue around it and its small and deep.

Why did the pulse in the fingers disappear when the brachial artery was compressed?

The blood supply to the hands and fingers is cut off when the brachial artery was compressed.

Did the pulse disappear completely when the radial or ulnar artery alone was compressed?

No, the pulse did not disappear completely when the radial or ulnar artery alone was compressed because the connection of the ulnar and radial artery is a collateral supply of blood.
If one side is cut off, the other side will take over.

What is the function of arterial anastomoses?

- Connection between arteries.
- They will redirect blood flow when blockage occurs.

Why might a very fit person have a slower heart rate than someone of average fitness?

- Their heart beats are stronger and efficient, causing larger stroke volume and more blood pumped per minute (cardiac out put) with less beats.

Why does ventricular contraction (systole) and the "lub" sound occur immediately after the QRS complex.

-Ventricular contraction occurs immediately after the atrial goes into diastole (relaxation)
- The "lub" sound occurs during he early phase of ventricular contraction. This is produced by closing of the atrioventricular valves.

Why does the ventricular relaxation (distole) andthe "dup" sound occur after the T wave?

- Ventricular relaxation occurs after the T wave because he ventricles are being re-polarized, causing relaxation.
- The "dup" sound occurs after the T wave because it is caused by ventricular relaxation, drop in blood pressure below that in the artery, semi-lunar valve closing.

The falling phase of the volume pulse should have a small, transient plateau or upward deflection. This is called the dicrotic notch. Why does it exist?

The dicrotic notch exist because when the aortic valve shuts, there is pushing of blood against the wall.

Sinoatrial Node

- Located in the right atrial wall
- Most rapid conduction rate; roughly 75 timers per minute
- Sets the rhythm
- Known as heart's pacemaker
- Conduction is spread throughout the atria via gap junctions.

Atrioventricular Node

- Located in the inferior segment of the interatrial septum.
- Receives input from SA node through the internodal pathway.
- Signaling is delayed briefly here while the atria finish contracting.
- Signal slows due to fewer gap junctions as well as smaller diameter of conduction fibers.

Atrioventricular Bundle

- Located in the superior portion of the interventricular septum.
- Receives signal from the AV node
- First segment linking atrial conduction to ventricular conduction.

Bundle branches "Bundles of His"

- Located along the left and right sides of the interventricular septum.
- Receieves signal from the AV bundle and send it down to the apex of the heart.
- A splitting of the AV bundle to send electrical signal to the left and right ventricular walls.

Purkinje Fibers

- Penetrate into the apex and run superiorly into the ventricular walls.
- Receives signal from the bundle branches and completes the conduction cycle.
- Bulk of ventricular excitiation occurs via these fibers and gap junctional passage of signal between ventricular muscle cells.
- Purkinje network is more elaborate in the left chamber.

Electrocardiogram

- Is the sum of all electrical potentials generated by the cells of the heart at any given time.
- Normal electrical activity of the heart gives 3 distinct waves.

P Wave

- atrial depolarization
- results from the signal from the SA node spreading through the atria

QRS Wave

- Ventricular depolarization (artial repolarization)
- results from purkinje fibers exciting the ventricular walls

T Wave

- Ventricular repolarization
- Results from purkinje fibers repolarizing the ventricular walls

Cardiac Cycle

Electrical event (ventricular depolarization) --> Mechanical event (Ventricles contract) --> Change in valve status (AV valves close & SL valves open) --> Movement of blood (Left ventricles pushes blood into the aorta)

In quiet breathing, muscular effort is used mainly in inspiration, and expiration is largely passive, due to elastic recoil of the lung. Can you relate this fact to the pattern of expiratory and inspiratory flow? Hint: the normal pattern of breathing is efficient in that it requires muscular effort for only a short time.

- In quiet breathing muscular effort is used mainly in inspiration.
- Expiration is largely passive due to elastic recoil of the luna.
- We can relate this fact to the pattern of expiratory and inspiratory flow because in our experiment the expiration rate took longer than the inspiratory rate because expiration was passive and involves returning to the normal state.

Explain why RV cannot be determined by ordinary spirometry?

- Residual volume cannot be determined by ordinary spirometry because the volunteer is unable to exhale any further.
- The spirometry can only measure what you are breathing in and out.

In your own words describe the physiological significance of the FEV1/FVC ratio?

- The significance is that it describes the effectiveness of how well an individuals lungs can turn over its total volume in 1 second.

In your own words explain the physiological events that occurred during this simulated asthma attack. Hint: Think about what it felt like and how that would affect your general state of well-being and activity level.

Asthma is an obstructive disorder and once the airways walls are thickened with inflammatory exodate. The effect of bronchospasm is vastly magnified and can dramatically reduce airflow.
- It would affect your general state of well being and activity level by not always letting you inhale enough air.

Professional football players and Olympic cross-country skiers have measured FVCs as high as 8L. What determines the size of a person's lungs?

Genetics determines the size of a person's lungs no matter how much you workout.
- You cannot increase the size of your lungs.

The FEV1 is one of the most commonly evaluated clinical measurements of lung function. What would you use this test to diagnose?

- Important in testing for diseases dealing with airflow obstruction.
- It test the max amount of air you can move in 1 second- measures how effective you can move air out.

Can breathe be held longer during normal respiration or after hyperventilation? Why?

- Breath can be held longer after hyperventilation because you drive carbon dioxide out of blood during hyperventilation, meaning it will take longer for CO2 to build back up in blood.
- CO2 is the "breathe signal"

Under what circumstances would rapid, deep breathing be advantageous? Why?

- Rapid, deep breathing can be advantageous when you workout because you are getting rid of CO2 because it is building up during your workout.

Re-breathing from a closed bag results in arterial hypercapnia (raised partial pressure of carbon dioxide). Why?

- This happens because you are breathing your expired CO2 rather than "new" air.
- Your expired air is more concentrated with CO2.

Spirometry is the method of choice for a fast and reliable screening of patients suspected of having what disease?

Chronic Obstructive Pulmonary Disease (COPD)

Gas exchange between air and blood occurs in the?

Alveolar air sacs

The efficiency of gas exchange is dependent on?

- Ventilation
- Cyclical breathing movements alternately inflate and deflate the alveolar air sacs.

F (flow) =

dV / dt

V (Volume) =

F dt

IC ( Inspiratory Capacity) =

VT + IRV

EC (Expiratory Capacity) =

VT + ERV

VC (Vital Capacity) =

IRV + ERV + Vt

FRC (Functional Residual Capacity) =

ERV + RV

TLC (Total Lung Capacity) =

VC + RV

Henry's Law

When gas is in contact w/ a liquid, that gas will dissolve in the liquid in proportion to its partial pressure.

partial Pressure

- Pressure exerted by each gas
- Directly proportional to the % of that gas in the gas mixture.

Hypoxial

Inadequate oxygen delivery to body tissues.

Minutes Ventilation

Total amount of gas exchange in 1 min.

Forced vital capacity (FVC)

Measures amount gas expelled when deep breath followed by forceful exhales.

Forced expiratory Volume (FEV)

Determines amount of air expelled during specific time intervals of the FVC test.

Alveolar ventilation rate (AVR)

Assess respiratory efficiency

nonrespiratory air movements

results from reflex activity (cough, sneeze, laugh, cry, yawn)

Oxygen toxicity

Breathing O2 gas at 2atm for long periods

Oxyhemoglobin

Hemoglobin - Oxy combo (HbO2)

Reduced Hemoglobin (deoxyhemoglobin)

Hemoglobin that has released oxygen (HHb)

anemichypoxia

poor O2 --> too few RBC

Ischemichypoxia

Blood circulation blocked --> blocked O2 del. to distal tissues

Histotoxichypoxia

body cells unable to use O2

hypoxemiahypoxia

decrease arteriol Po2

Chemoreceptors

influence breathing rate and depth

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