Lesson 1

Question 1

How big is the heart

Answer 1

Size of fist

Question 2

What is the location of the heart

Answer 2

• below 5th rib
• superior surface of diaphragm
• left of midline
• anterior to vertebral column, posterior to sternum

Question 3

What kind of pump is the heart

Answer 3

Dual pump

Question 4

What is the function of the interventricular septum of the heart?

Answer 4

Ensures blood from left (oxygenated) and right (deoxygenated) side do not mix

Question 5

In what manner do the chambers of the heart contract

Answer 5

Atria simultaneously and then ventricles simultaneously

Question 6

Explain how blood flows through the heart (pathway)

Answer 6

• O2 deficient blood returns from body via superior and inferior vena cava
• enters right atrium
• right ventricle
• pulmonary artery
• Lungs
• blood is oxygenated
• pulmonary veins
• left atrium
• left ventricle
• aorta
• circulates to the body

Question 7

What is Pericardium

Answer 7

A double-walled sac around the heart

Question 8

What is the pericardium composed of?

Answer 8

• Superficial fibrous pericardium
• Deep 2-layer serous pericardium

Question 9

What are the layers of serous pericardium?

Answer 9

• Parietal layer (outer): lines internal surface of fibrous pericardium
• Visceral layer (epicardium): lines surface of heart

Question 10

What are the functions of pericardium?

Answer 10

• Protects and anchors the heart
• Prevents overfilling of the heart with blood
• allows for the heart to work in a relatively friction-free environment

Question 11

What are the types of muscle in the heart?

Answer 11

• atrial
• ventricular
• specialized excitatory and conductive muscle fibers

Question 12

How does atrial/ventricular muscle differentiate from skeletal muscle?

Answer 12

• duration of contraction much longer
• Less sarcoplasmic reticulum and require calcium from extracellular fluid for contraction
• Bigger T-tubules

Question 13

What are muscle cells of the heart called?

Answer 13

Myocytes or myofibrils

Question 14

What is the outside membrane of muscle cells called?

Answer 14

Sarcolemma

Question 15

Describe myocytes.

Answer 15

• Centrally located nucleus
• actin + myosin + bands/zones/Z discs
• striated, short, fat, branched, interconnected

Question 16

Explain how cardiac muscle fibers are made up

Answer 16

Cardiac muscle fibers = many cells connected in series/parallel fused at intercalated discs

Question 17

What are intercalated discs

Answer 17

Cell membranes separating and anchoring individual cells from one another

Question 18

What do gap junctions allow?

Answer 18

Allow almost free diffusion of ions (AP travels easily)

Question 19

What is syncytium

Answer 19

Spread of depolarization waves across heart muscle cells, speeding up conduction (all-or-none principle)

Question 20

What are the 2 syncytia of the heart and why are there 2?

Answer 20

Atrial and ventricular: allows atria to contract slightly before ventricles for efficient blood flow

Question 21

How is the myocardium arranged for efficient pumping?

Answer 21

Spirally around heart to create a twisting effect, efficiently pumping blood upwards
(swirl creates vortex to efficiently empty the heart)

Question 22

Explain plateau in APs in ventricular muscle fiber (resting potential of abt -85mV), and length of contraction compared to skeletal muscle

Answer 22

• after initial spike, membrane remains depolarized for abt 0.2s: plateau
• repolarization
  Plateau causes contraction to last up to 15x longer than skeletal m.

Question 23

Explain the phases of APs

Answer 23

0: Fast Na+ channels open, then slow Ca++ channels open
1: K+ channels open
2: Ca++ channels open more
3: K+ channels open more
4: resting membrane potential

Question 24

ECG: what is the P wave representing?

Answer 24

Atrial depolarization

Question 25

ECG: what is the QRS complex representing?

Answer 25

Ventricular depolarization

Question 26

ECG: what is the T wave representing?

Answer 26

Ventricular repolarization

Question 27

What is diastole?

Answer 27

Period of relaxation: heart fills w/ blood and cardiomyocytes re-establish Na+/K+/Ca++ gradient

Question 28

What is systole?

Answer 28

Active phase (contraction)

Question 29

What is 1 cardiac cycle?

Answer 29

Beginning of 1 heart beat to the beginning of the next

Question 30

What is the cardiac cycle initiated by?

Answer 30

A spontaneous generation of an AP in the sinus node

Question 31

How much blood passes directly from atria to ventricles (without contraction)

Answer 31

80%

Question 32

Describe the pressure changes in the atria (3 waves)

Answer 32

a wave: atrial contraction c wave: ventricles begin contraction v wave: end of ventricular contraction

Question 33

Explain wall thickness

Answer 33

Ventricles thicker than atria Left ventricle thicker than right

Question 34

When does aortic pressure start increasing?

Answer 34

During systole after aortic valve opens

Question 35

When does aortic pressure decrease? Why?

Answer 35

End of ejection phase (during diastole due to elasticity of the aorta)

Question 36

What happens to the aortic pressure curve after the aortic valve closes?

Answer 36

An incisura develops due to a sudden back-flow towards left ventricle

Question 37

What is the Frank-Starling Mechanism?

Answer 37

- intrinsic ability of heart to adjust and adapt the volume change of blood - heart pumps all blood that returns w/o excessive damming in the veins - extra stretch on cardiac myocytes makes actin + myosin filaments have a more optimal degree for force generation

Question 38

What happens during the excitation of the heart by sympathetic nerves?

Answer 38

- increase HR - inc. force of contraction (=inc. vol of blood pumped)

Question 39

What usually happens to the heart regarding sympathetic nerves?

Answer 39

- sympathetic n. fibers to heart discharge continuously at a slow rate - usually maintained at 30% above normal HR w/ no sympathetic stimulation

Question 40

What happens during parasympathetic (vagal) stimulation of the heart?

Answer 40

- if strong: can stop heart for a few secs - heart "escapes" and beats at 20 to 40bpm as long as stimulation continues

Question 41

Where are vagal (parasympathetic) fibers distributed?

Answer 41

distributed to atria (not ventricles)