The Heart

Question 1

What does the term “double pump” mean?

Answer 1

Each heartbeat pumps blood to the lungs and to the body

• Pulmonary circulation: send blood to lungs
• Systemic circulation: send blood to body

Question 2

In what cavity is the heart located in the body?

Answer 2

In the Middle Mediastinum

Question 3

What is the pericardium? What does it consist of?

Answer 3

Sac containing the heart

Consists of two layers:

1. Outer Fibrous: anchor and protect heart
2. Inner Serous
   
   1. Parietal layer: outermost layer
   2. Visceral layer (epicardium): surface of heart

Question 4

What is the pericardial cavity?

Answer 4

The parietal and visceral layers of the Inner Serous pericardium have epithelial cells that produce pericardial fluid that fills the pericardial cavity

• This reduces friction

Question 5

What does the heart wall consist of?

Answer 5

1. Epicardium (visceral layer)
2. Myocardium
3. Endocardium

Question 6

What are the characteristics of the heart muscle, Myocardium, which is part of the heart wall?

Answer 6

1. Involuntary and striated muscle
2. Intercalated discs
   
   • Gap junctions to carry action potentials
3. Ventricular muscle mass larger than atrial muscle mass
   
   • Ventricular muscle mass pumps blood out of heart and needs to have a stronger contraction
4. Cardiac skeleton
   
   • collagen connective tissue separates atria and ventricle
   • no action potentials between two sides except through two openings causing millisecond delay

Question 7

What are the chambers of the heart?

Answer 7

Right and Left Aria

• Atria have appendages called auricles
• Larger space to expand and receive extra blood during exercise

Right and Left Ventricles

• Coronary Sulcus: “crown” indentation that separates Atria from Ventricle
• Intraventricular Sulci: Anterior and Posterior that separate the two ventricles

Question 8

What is the septum of the heart?

Answer 8

A Septum is a wall. There is:

• Interatrial septum: separates atria
  
  • Open as fetus for fetal gas exchange
  • Closed as adult
• Interventricular septum – always closed
  • Part membranous, part muscle.
    
    • Muscle part contracts.

Question 9

Walk through Blood Flow through the heart

Answer 9

1. Right Atrium
   
   • receives deoxygenated bloods from:
     
     • Superior vena cava
     • Inferior vena cava
     • Coronary Sinus
2. Right Ventricle
   
   • Passes through Tricuspid Valve
3. Pulmonary Trunk
   
   • Passes through Pulmonary Semilunar-Valve
4. Lungs
   
   • Gas exchange
5. Pulmonary Veins
6. Left Atrium
7. Left Ventricle
   
   • Passes through the Bicuspid Valve
8. Aorta
   
   • Passes through the Aortic Semlunar-Valve

Question 10

What are the Great Vessels?

Answer 10

1. Aorta
2. Superior/Inferior Vena Cava

Question 11

What are the Atrioventricular Valves (AV) and how do they work?

Answer 11

1. Tricuspid and bicuspid
   * right vs. left side, respectively

Chordae tendineae attach to Papillary muscles which control the opening and closing of the valves

Question 12

What are the semilunar valves?

Answer 12

The Pulmonary Semilunar Valve in trunk and Aortic Semilunar Valve

Arranged as 3 half-moon cusps (pockets)

Question 13

What arteries are involved in Coronary Circulation in the heart?

Answer 13

Left Coronary Artery

• Anterior Interventricular Artery (widowmaker)
• Circumflex Artery

Right Coronary Artery

• Posterior Interventricular Artery
• Marginal Artery

Both arteries are fused (anastomoses)

Question 14

What veins are involved in coronary circulation of the heart?

Answer 14

• Great cardiac vein
• Middle cardiac vein
• Small cardiac vein

The coronary sinus ultimately receives all cardiac venous blood and returns it to the right atrium

Question 15

What makes up the conduction system of the heart?

Answer 15

Autorhythmic cells stimulates heart, generating hearbeat by starting action potentials

The ANS can modify heart rhythm but not establish the rhythm

All cardiac muscle cells are autorhythmic but 1% lose ability to contract

• These cells form the pacemakers and conduction system

Question 16

What components make up the conduction system of the heart?

Answer 16

Sinoatrial (SA) Node

• Primary Pacemaker (fastest ap/min)

Atrioventricular (AV) Node

• Secondary Pacemaker (slower ap/min)

ORDER:

1. SA Node
2. AV Node
3. AV Bundle
4. Split into Left and Right Bundle Branches
5. Purkinje Fibers loop around

Question 17

• Where does the cardiac muscle contract first? Last?
• Why is there a 0.12 sec delay across the AV node?
• What separates the atrial muscle mass from the ventricular muscle mass?
• Why does the interventricular septum begin to contract before the apex?

Answer 17

• Atrial Cardiac muscle contract first and Upper Regions of the Ventricular Wall conduct last
• 0.12 sec delay due to the AV Node not firing as fast as SA
• Cardiac Skeleton separates the atrial and ventricular muscle masses
• Interventricular Septum contracts first b/c AP reaches there first

Question 18

What are the different Waves and intervals in the EKG?

Answer 18

1. P Wave: Atrial Depolarization
2. QRS Complex: Ventricular Depolarization
3. T Wave: Ventricular Repolarization

P-Q Interval: Atria depolarizes and contracts

P-R Interval: Atri and Ventricles Depolarize +contract

Q-T Interval:

S-T Segment: Blood Gone

Quiescent Period: Time between cycles

Question 19

What does an EKG or ECG measure?

Answer 19

Measures electrical impulses sent down each chamber

Question 20

What heart rate changes what actually changes in the conduction cycle?

Answer 20

The Quiescent period gets longer or shorter

Question 21

What phenomena control blood flow through the heart?

Answer 21

Contraction and Relaxation of the

1. Atrioventricular (AV) Valves
2. Semilunar (SL) Valves

Question 22

How does Pressure affect blood flow? What pressures are involved in the Cardiac Cycle?

Answer 22

Blood always flows from an area of high pressure to an area of low pressure

• Pressure is a result of the size of a chamber and the volume of blood within it

1. Venous Pressure
2. Atrial Pressure*
3. Ventricular Pressure
4. Aterial Pressure*

Question 23

How do the chambers behave during a normal cardiac cycle?

Answer 23

Two Atria will contract while the Two Ventricles relax, then, Two Ventricles contract while the two Atria relax

• Systole: Contraction
• Diastole: Relaxation

Question 24

What are the phases of the cardiac cycle?

Answer 24

1. Ventricular Filling
2. Isovolumetric Contraction
3. Ventricular ejection
4. Isovolumetric relaxation

Question 25

What occurs during Ventricular Filling?

Answer 25

**In diastole, ventricles expand and pressure decreases** * AV valves open when atrial pr. \> ventricular pr. **3 Phases of Ventricular Filling:** 1. Rapid ventricular filling 2. Diastisis 3. Atrial systole 70% of Ventricle fills w/ Phases 1 & 2 due to pressure difference 30% of Ventricle fills w/ Phase 3 due to Atrial Contraction **END DIASTOLIC VOLUME = 130 mL**

Question 26

What is Isovolumetric Contraction?

Answer 26

Same Volume Contraction: * Brief moment during contraction when **Ventricle Pr\>Atria Pr** but **Vent Pr** 1. Atrial Diastole Begins 2. Ventricular Systole Begins 3. AV Valves close when Ventricular Pr\>Atrial Pr 4. No blood ejected because Arterial Pr\>Ventricular Pr

Question 27

What occurs during Ventricular Ejection?

Answer 27

Ventricular Pr\>Arterial Pr * SL Valves open when Ventricular Pr\>Arterial Pr * Rapid ejection then reduced ejection Stroke Volume = 70 mL End-Systolic Volume = 60 mL

Question 28

What occurs during Isovolumetric Relaxation?

Answer 28

Brief period of time where the volume remains the same but the blood has been ejected so pressure goes down * SL Valves are closed and AV Valves are still closed **Early Ventricular Diastole** * Ventricles expand = pr decreases * SL Valves close when arterial pr\>ventricular pr **Quiescent Period** * ​Begins whe atrial pr\>ventricular pr * AV valves will open and ventricular filling occurs to begin next cycle

Question 29

What are the volume changes that occur during the cardiac cycle?

Answer 29

**End-systolic volume****=****_60 ml_** * left from previous heart beat **Passively added during atrial diastole** **(70%)** * rapid ventricular filling + diastasis **= _70 ml_** **Atrial systole** **(30%)** \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **Total end-diastolic volume = _130 ml_** **Stroke volume** minus _- **70 ml**_ (ejected by ventricular systole) \_\_\_\_\_\_\_\_\_\_\_ **Leaves the end-systolic volume =** **_60 ml_**

Question 30

What are the chamber volume and pressure changes listed in the diagram below?

Answer 30

Question 31

What is cardiac output?

Answer 31

amount of blood ejected from the left ventricle into the aorta per minute

Question 32

What is cardiac ouput determined by?

Answer 32

Stroke volume (SV) and Heart Rate (HR) SV x HR = Cardiac Ouput Example: (70 ml/beat)(75 beats/minute) = 5,250 ml/min or 5.25L/min In 1 min all of the blood within the body cycles through once

Question 33

What is cardiac reserve?

Answer 33

difference between maximum cardiac output and resting cardiac output * Resting cardiac output = 5 L/min * Max (exercise) cardiac ouput = 20 L/min * The max is 300% higher, so cardiac reserve = 300% Exercise increases Cardiac Reserve

Question 34

How do we compensate for congestive heart failure and pump more blood?

Answer 34

We tap into the cardiac reserve when ventricle not pumping all of the 70mL that it should

Question 35

How is Stroke volume regulated?

Answer 35

1. Preload 2. Contractility 3. Afterload

Question 36

What is Preload?

Answer 36

More stretch in the sarcomere = more forceful contraction * Increased venous return + Increased length of the Diastole = Increased ventricular filling = Increased Preload = Increased Ventricular stretch * This results in a more forceful contraction = increased stroke volume = increased cardiac output

Question 37

What is contractility?

Answer 37

External factors such as epinephrine increase the contractility of the muscle resulting in increased stroke volume = increased cardiac output

Question 38

What is Afterload?

Answer 38

Pressure in the artery right after ventricle is higher then ventricular pressure and decreases cardiac output * blood pools in ventricle =\> leading to hypertrophy of ventricle =\> leads to congestive heart failure

Question 39

What will affect cardiac output?

Answer 39

Heartrate (HR) or Stroke Volume (SV)

Question 40

What is the difference between Stroke Volume (SV) and Cardiac Output (CO)?

Answer 40

**Stroke Volume (SV):** amount of blood that moves out of heart w/ each Cardiac Cycle **Cardiac Output (CO):** amount of blood that leaves the heart per minute

Question 41

How does the automic nervous system regulate heart rate?

Answer 41

Sensory Input received from: * Baroreceptors: Blood Pressure * Chemoreceptors: Chemical concentration Sensory Input sent to medulla oblongata. Motor output sent to: * Cardioacceleratory neurons - via sympathetic NS * release epinephrine at SA node * increase heart rate * Cardioinhibitory neurons - via parasympathetic NS * release acetylcholine at SA node * decrease heart rate

Question 42

What kinds of chemicals can be used to regulate heart rate?

Answer 42

Hormones * epinephrine, norepinephrine, thyroxine, glucagon Ions