Anatomy and Physiology II - Part 1

STUDY HARD

Right side of heart pumps…

• deoxygenated blood

Left side of heart pumps…

• oxygenated blood

What are the 4 chambers of the heart called?

1. Right atrium

2. Right ventricles

3. Left atrium

4. Left ventricles

Roles of Right and Left Atrium

Right: receives deoxygenated blood from vena cava

Left: receives deoxygenated blood from the lungs

Role of Right and Left Ventricle

Right: pumps deoxygenated blood into pulmonary trunk and pulmonary arteries (sends blood to the lungs)

Left: pumps oxygenated blood into the aorta and blood gets distributed throughout the body (higher pressure required then Right Ventricles)_it’s muscular wall is thicker than Right Ventricles (sends blood throughout the whole body)

Atrioventricular (AV) valves separate…

the atria from the ventricle

How does atrial contraction increases ventricular filling?

actively squeezing the final 10-30% of blood into the ventricles just before they contract

Cardiac Cycle

the repeating and continuous progression of contraction and relaxation in the heart that pumps blood through the body

Atrioventricular (AV) valves separate…

the atria from the ventricle

Semilunar valves separate…

the ventricles from the great arteries

types of atrioventricular valves are…

• tricuspid valve

• mitral (bicuspid) valve

types of semilunar valves are…

• pulmonary valve

• aortic valve

Pathway of blood through the heart

step 1

• deoxygenated blood comes into the Right atrium

step 2

• deoxygenated blood flows through the tricuspid valve into the right ventricle

step 3

• As blood fills the right ventricle, it also contracts, resulting blood to move through the pulmonary valve into the pulmonary trunk then to the pulmonary arteries, then ends up into the lungs. (CO2 inside the blood exits and oxygen enters the blood)

step 4

• oxygenated blood returns through the pulmonary veins into the left atrium

step 5

• Oxygenated blood flows through the mitral valve (AV) into the left ventricle.

step 6

• As blood fills the left ventricle, the volume of it expands leading to higher strength of contraction. This cause the blood to flow through the aortic valve (SV) into the aorta, where blood is distributed throughout the whole body. After blood delivers oxygen and nutrients throughout the body, it returns to the heart and cycle begins again.

Systole

contraction

Diastole

relaxation

atria / atrium is located on the…

upper chamber of the heart

ventricle is located on the…

lower chamber of the heart

Septa

the muscle wall that separates the right and left sides of the heart

interatrial septum

separates the 2 atria

interventricular septum

separates the two ventricles

Phases of Cardiac Cycle

1. atrial contraction

2. isovolumetric contraction

3. rapid ejection

4. reduced ejection

5. isovolumetric relaxation

6. rapid filling

7. reduced filling

Atrial contraction

last bits of blood flows into the ventricles: Due to the contraction of atria, blood flows through atrioventricular valves into the ventricles. ~10% of the ventricular filling occurs.

End-Diastolic Volume (EDV) reach it’s maximum at this phase.

• 심장이 가장 큰 부피를 가지게 됨

Isovolumetric Contraction

Ventricular contraction starts, yet there is NO movement of blood volume.

• rapid increase in ventricles pressure

Closure of AV valve results in the FIRST HEART SOUND = S1.

Rapid Ejection

Blood leaves the heart RAPIDLY.

• starts when the pressure in the ventricle EXCEED the pressure in the aorta & pulmonary artery = causes SV valves to OPEN

Reduced Ejection

Blood continues to leave the heart, yet with a DECREASED speed.

• due to decrease in the volume of blood inside the ventricle, the ventricular pressure DECREASES.

Isovolumetric Relaxation

Blood has been pumped out & ventricles begin to relax, and ventricular pressure decreases.

• When ventricular pressure falls below the pressure in the aorta, the SV valves CLOSE, which results the second heart sound S2.

• Volume inside the ventricles stays the SAME.

Rapid filling

Blood flows from the atria into the ventricles.

• As the SV valves close, due to pressure difference between ventricle and aorta, AV valves OPEN up. This causes blood to flow into the ventricles PASSIVELY. (Contraction does NOT occur during this phase.)

Atrioventricular valves OPEN when…

atrial pressure exceeds the ventricular pressure

Atrioventricular valves CLOSE when…

ventricular pressure exceeds the atrial pressure

Semilunar valves OPEN when…

ventricular pressure exceeds the arterial pressure

Semilunar valves CLOSE when…

arterial pressure exceeds the ventricular pressure

S1 heart sound occurs when…

the Atrioventricular valves closes (phase: isovolumetric contraction)

S2 heart sound occurs when…

the Semilunar valve closes (phase: Isovolumetric relaxation)

Cardiac output

the volume of blood pumped by the heart each minute (L/min)

• CO = SV (stroke volume) x HR (heart rate)

Stroke Volume

the amount of blood ejected from the heart with each beat (mL/beat)

• SV = EDV - ESV

describe the relationship between the stroke volume and heart rate in the equation of cardiac output.

Stroke volume and Heart Rate has an indirect proportion relationship; while one increases, the other decreases.

End-Diastolic Volume (EDV)

the amount of blood in the ventricles at the end of diastole just before the ventricles contract

• initial amount of blood in the ventricle before contraction

End-systolic volume (ESV)

the amount of blood in the ventricles at the end of systole after the ventricles HAVE contracted

• blood left behind after ejection

Describe how heart rate affects filling time of blood.

• slower heart rate causes more filling time because it gives the heart more time to relax, resulting a higher EDV

• faster heart rate causes less filling time because it rushes the heart to move on, resulting a lower EDV (if too fast)

Frank-Starling Law/Mechanism

describes how the heart automatically adjusts how strongly it contracts based on how much blood fills it

• explains the relationship between ventricular filling and the force of contraction

* The more the heart FILLS with blood during diastole, the more FORCEFULLY it CONTRACTS during systole.

• Stretch of ventricle => increase in volume => stronger contraction

What are the determinants of Cardiac Output?

1. Venous Return

2. Preload

3. Afterload

4. Contractility

Venous Return

the amount of blood that flows BACK to the heart through the veins; affected by blood volume (more blood in the body, more blood returns to the heart) & venous tone (when veins constrict, they gently squeeze, pushing blood BACK toward the heart)

• increase of VR => heart fills with MORE blood & cardiac output INCREASE

• decrease of VR => LESS blood fills the heart & cardiac output DECREASES