ECG

Question 1

ECG

Answer 1

electrocardiography, activity of the heart

Question 2

Key funthion of the heart

Answer 2

pumps the blood
1. Through systemic circuit to deliver O2 and nutrients to tissues in the body and remove CO2
2. Through pulmonary circuit in order to exchange O2 and CO2 between blood and air in the alveoli of the lungs

Direction of pumping is controlled by valves
Internal rythm is made by pacemaker cells located in sinoateial node

Question 3

Spontaneous internal rhythm (respiratory sinus arrhythmia/ RSA)

Answer 3

Increased and decreased due to sympathetic and parasympathetic activation by CNS
E.g. inhalation is accompanied by light increase of sympathetic activation-> increases pace
Exhalation is increased parasympathetic activation-> decelerates the rhythm

Question 4

Prep for contraction (systole)

Answer 4

Contraction of atrial muscle is caused by electric signals from SA (sinoatrial node). Pushes blood from atria to ventricles.
Signal is transmitted to ventricular muscle via internodal fibers, atrioventricular node, bundle of his, bundle branches and purkinje fibers.

Question 5

Systole

Answer 5

Contraction starts at apex of heart after 200ms delay.
Contraction due to depolarization, depolarization leads to relaxation (diastole)
Left ventricular systole pushes blood into aorta, from there the pressure reavhes major and minor arteries

Question 6

Pulse plethysmography

Answer 6

Uses light beamed through skin, since hemoglobin reflects that light well. The amount of near infrared flight sensed by sensors can estimate changes in volume of the blood.
Used by smart watches etc but not as reliable as lab devices. Used to record HR

Question 7

Electrical activity, measured

Answer 7

Pair of electrodes on the skin.
Called electrocardiogram
- Lead II: positive electrode on left ankle, negative electrode on right wrist and ankle
- Modified lead II: negative and ground electrodes are placed on right and left collarbone, positive is placed under left ribcage

Modified preferred due to less movement of participant

Question 8

Most important components of the ECG

Answer 8

• P wave: depolarization of the atria
• QRS-complex: depolarization of two ventricles
• T-waves: depolarization of ventricles

Delay between electrical and respective mechanical events, R-peak precede the peak of blood pressure by approx 150ms

Question 9

Most important ready related variables

Answer 9

• HR: contractions per minute (bpm:typically 60-80)
• IBI: average interval between beats (typically 750 to 1000ms)
  NOT independent of each other

Question 10

What increases HR

Answer 10

• physical activity (cardiac-somatic coupling)
• psychological factors