Cardiac Cycle

Question 1

Cardiac cycle

Answer 1

Consists of a series of mechanical events, pressures & volume changes in the hearty during a heartbeat

Question 2

Systole

Answer 2

Contraction phase of the cardiac cycle
When the heart muscle is squeezing

Question 3

Diastole

Answer 3

Relaxation phase of the cardiac cycle
When the chambers of the heart open like they’re dilating

Question 4

Ventricular filling

Answer 4

Occurs during mid-to-late ventricular diastole
- atrioventricular valves open
- semi lunar valves are closed
- Atria contract during the end of ventricular diastole, propelling final blood volume into the ventricles

Question 5

End diastolic volume

Answer 5

The volume of blood in each ventricle at the end of ventricular diastole

Question 6

Ventricular systole

Answer 6

Atria relax and ventricles contract.
atrioventricular valves close and semilunar valves open
- Isovolumetric contraction (all valves are closed)
- ventricular ejection (semilunar valves open due to high ventricular pressure)
- End systolic volume (volume remaining in each ventricle after systole)

Question 7

Isovolumetric relaxation

Answer 7

Occurs during early diastole, ventricular pressure drops, semilunar valves close then atrioventricular valves open.
- Dicrotic notch: a brief rise in blood pressure due to back flow of blood in the aorta and pulmonary trunk

Question 8

Heart sounds

Answer 8

First lub: closure of the atrioventricular valves during ventricular systole
S1: sound of the tri/bicuspid valves closing
Second dub: closure of the aortic and pulmonary semilunar valves during ventricular diastole
S2: sound of the pulmonary and aortic semilunar valves closing

Question 9

Heart murmurs

Answer 9

Extraneous heart sounds due to turbulent back flow of blood through a valve that doesn’t fully close (an incompetent valve) or doesn’t fully open (stenotic valve)

Question 10

Cardiac output

Answer 10

The amount of blood pumped out of a ventricle per minute
- Product of strocke volume and heart rate
** CO = HR x SV **
HR - number of heart per minute
Normal resting cardiac output = 5.25 L/min
Maximal CO in nonathletic people (20-25L/min)
in athletic people ( 35L/min)

Question 11

Stroke volume

Answer 11

Volume of blood pumped out by one ventricle in each heart beat, roughly = 70mL
- Represents the difference between the end diastolic volume and the end systolic volume

Question 12

Cardiac reserve

Answer 12

Difference between the resting & maximal cardiac output
Average adult heart rate = 75 BPM

Question 13

Frank-Starling law of the heart

Answer 13

The critical factor controlling stroke volume is preload - the degree of stretch of cardiac muscle cells immediately before they contract
- venous return to the heart ios the most important facto determining the degree of cardiac muscles stretch

Question 14

End diastolic volume

Answer 14

The amount of blood in the ventricle during diastole
- Affected by the length of ventricular diastole & venous blood pressure (120mL/ beat)

Question 15

End systolic volume

Answer 15

The volume of blood remains in in the ventricle after contraction is complete
- Is affected bu arterial blood pressure & the force of ventricular contraction (50mL/ beat)
Normal SV = 120mL (EDV) - 50mL (ESV) = 70mL/beat

Question 16

Contractility

Answer 16

The contractile strength of a muscle
Increasing cytoplasmic [Ca2+] leads to more myosin-actin cross-bridge formations & increases muscle contractility

Question 17

After load

Answer 17

The ventricular pressure that must be overcome before blood can be ejected from the heart.
Doesn’t become a signification factor for stroke volume except in hypertensive individuals

Question 18

What does increased contractility do?

Answer 18

This lowers end systolic volume
- Positive inotropic agents (thyroxine, epinephrine, digitalis etc) increase heart contractility

Question 19

Heart rate regulation

Answer 19

• Sympathetic stimulation of pacemaker cells increased heart rate & contractility by increasing Ca2+ movement into the cell
• Parasympartheticinhibition of cardiac pacemaker cells decreases heart rate by increasing membrane permeability to K+

Question 20

Congestive heart failure

Answer 20

Occurs when the pumping efficiency of the heart is so low that blood circulation cora not meet tissue needs

Question 21

Pulmonary congestion

Answer 21

• Occurs when the left side of the heart fails but the right side continues to pump blood into the lungs.
• Blood isn’t taken back into the left side of the hear and accumulated int he lungs = pulmonary edema & can lead to suffocation

Question 22

Pulmonary edema

Answer 22

Excess fluid in body cavities/tissues
also called dropsy short for hydropsy