cardiovascular 2

Question 1

What are the phases of the cardiac cycle?

Answer 1

Cardiac cycle: Time from atrial contraction → ventricular relaxation

Systole: Contraction phase (pumps blood into circulation)

Diastole: Relaxation phase (chambers fill with blood

Question 2

What does an ECG record, and what are its main waveforms?

Answer 2

ECG: Records electrical changes during each heartbeat

Main points:

P wave: Atrial depolarization

QRS complex: Ventricular depolarization (atrial repolarization hidden)

T wave: Ventricular repolarization

Question 3

What does the P wave on an ECG represent?

Answer 3

P wave: Depolarization of the atria

Atrial contraction starts ~25 ms after the beginning of the P wave

Question 4

What does the QRS complex on an ECG represent?

Answer 4

QRS complex: Depolarization of the ventricles

Stronger signal needed due to large ventricular muscle mass

Ventricles begin contracting at the peak of the R wave

Question 5

What does the T wave on an ECG represent?

Answer 5

T wave: Ventricular repolarization

Atrial repolarization also occurs, but is hidden within the QRS complex

Question 6

What is the difference between segments and intervals on an ECG, and what do the PR and QT intervals indicate?

Answer 6

Segments: Region between two waves

Intervals: One segment + one or more waves

PR interval: From start of P wave (atrial depolarization) → start of QRS (ventricular depolarization)

QT interval: Ventricular depolarization & repolarization; lengthened by myocardial damage, ischemia, or conduction impairments

Question 7

How does blood move through the heart during diastole in the cardiac cycle?

Answer 7

Fluids move from higher to lower pressure.

During diastole (relaxation), blood flows from veins → atria (higher pressure in veins).

As atria fill, atrial pressure rises.

Blood then moves passively from atria → ventricles.

Question 8

What happens during atrial systole in the cardiac cycle?

Answer 8

Action potential triggers atrial contraction.

Atrial pressure rises, pushing blood into ventricles.

Ventricles are already ~70–80% full from passive diastolic filling.

Atrial contraction adds the final 20–30% of ventricular filling.

Question 9

What occurs during atrial systole and ventricular systole in the cardiac cycle?

Answer 9

Atrial systole: lasts ~100 ms, ends before ventricular systole, atrial muscle then relaxes (diastole).

Ventricular systole: ventricular pressure rises.

Right ventricle → pumps blood into pulmonary trunk.

Left ventricle → pumps blood into aorta.

Question 10

What happens during isovolumetric contraction in the cardiac cycle?

Answer 10

entricular muscles contract → pressure rises.

Pressure not yet high enough to open semilunar valves.

Ventricular pressure > atrial pressure (atria in diastole).
→ Tricuspid & mitral valves close.

No blood ejected yet → ventricular volume stays constant.

This phase = isovolumetric contraction.

Question 11

What occurs during the ventricular ejection phase of the cardiac cycle?

Answer 11

Ventricular pressure > pressure in pulmonary trunk & aorta.

Semilunar valves (pulmonary & aortic) open.

Blood is ejected from ventricles.

Left ventricle generates much higher pressure than right:

Aorta pressure ~80 mmHg.

Pulmonary trunk pressure ~8–20 mmHg.

Question 12

What are EDV, ESV, and stroke volume in the cardiac cycle?

Answer 12

End-diastolic volume (EDV): ~130 mL (ventricular volume after atrial systole, before contraction).

End-systolic volume (ESV): ~50–60 mL (ventricular volume after systole).

Stroke volume (SV): EDV – ESV = ~70–80 mL (amount ejected per beat).

Question 13

What causes the two main heart sounds and how are they assessed?

Answer 13

S1 (“lub”): Closing of atrioventricular valves during ventricular contraction.

S2 (“dub”): Closing of semilunar valves during ventricular diastole.

Assessment: Heard via auscultation with a stethoscope in a healthy heart

Question 14

What are Korotkoff sounds and what do they indicate? exam LOOK MOE in

Answer 14

Korotkoff sounds are the sounds heard when measuring blood pressure with a stethoscope and sphygmomanometer.

They occur due to turbulent blood flow in the brachial artery as cuff pressure is released.

Phases:

First sound = systolic pressure (blood just starts to flow).

Disappearance of sounds = diastolic pressure (blood flow no longer obstructed).

calapse a little bu=it but not all the way

Question 15

LOOOOOOOOK AT THE PRESURE SLIDE

Question 16

What is cardiac output and how is it calculated?

Answer 16

Cardiac Output (CO or Q): Volume of blood ejected by the ventricles per minute.

Stroke Volume (SV): Blood pumped per beat.

Heart Rate (HR): Number of beats per minute.

Formula:

𝐶
𝑂
(
𝑚
𝐿
/
𝑚
𝑖
𝑛
)
=
𝑆
𝑉
(
𝑚
𝐿
/
𝑏
𝑒
𝑎
𝑡
)
×
𝐻
𝑅
(
𝑏
𝑒
𝑎
𝑡
𝑠
/
𝑚
𝑖
𝑛
)
CO(mL/min)=SV(mL/beat)×HR(beats/min)

Question 17

What are the three main factors that determine stroke volume?

Answer 17

Preload – Stretch of the heart before contraction (end-diastolic volume, influenced by filling time & venous return).

Basis of the Frank-Starling Law: greater stretch → stronger contraction.

Contractility – Strength/force of ventricular contraction.

Afterload – Pressure that must be overcome to eject blood.

~20 mmHg in pulmonary trunk.

~80 mmHg in aorta.

Question 18

What is the Frank-Starling Mechanism (Law of the Heart)?

Answer 18

Within physiological limits, the force of contraction is proportional to the initial length of the cardiac muscle fiber.

Greater ventricular stretch (preload) → stronger contraction → increased stroke volume (SV).

Thus, increasing preload enhances contractility and boosts cardiac output.

Question 19

What are the main factors that affect heart rate?

Answer 19

Autonomic Nervous System

Parasympathetic (Vagus, ACh): ↓ HR by lengthening repolarization.

Sympathetic (NE): ↑ HR by shortening repolarization.

Endocrine System / Hormones

Epinephrine (adrenal medulla) & thyroid hormones: ↑ HR.

↑ K⁺ levels: ↓ HR.

Question 20

How do heart rate and stroke volume respond to exercise?

Answer 20

eart Rate (HR):

Increases linearly with exercise intensity.

Plateaus at maximal effort.

Max HR ≈ 220 – age (young healthy adults).

Stroke Volume (SV):

Initially ↑ due to Frank-Starling mechanism despite shorter filling time.

Plateaus at moderate–high intensities.

May ↓ at very high HR when filling time is too short.

Question 21

How do cardiac output and oxygen consumption change with exercis

Answer 21

Cardiac Output (CO):

Increases with exercise.

Early rise from ↑ HR and ↑ SV.

At high intensity, mainly driven by HR.

Max CO: ~20–25 L/min (untrained), up to ~35 L/min (highly trained).

VO₂ (Oxygen Consumption):

Increases linearly with exercise intensity.

Plateaus at maximal effort (VO₂ max).