Lecture 4: Heart Structure & Function

Question 1

Where will pressure in cardio system be the highest?

Answer 1

when ventricles contract in aorta during systole

Question 2

What are the 2 layers pericardium?

Answer 2

• parietal -> fibrous & attaches to diaphragm
• visceral -> fuses to surface of the heart

Question 3

What is the space between the visceral & parietal pericardium called?

Answer 3

pericardial cavity -> filled with fluid to lubricate

Question 4

Where does the heart lie?

Answer 4

in the pericardium

Question 5

Which pericardium forms the outer epicardium?

Answer 5

visceral pericardium

Question 6

What are the 3 layers of the heart?

Answer 6

• epicardium -> outer layer with blood vessels
• myocardium -> muscle layer in the middle
• endocardium -> thin epithelium & connective tissue on the inside

Question 7

How is the heart formed?

Answer 7

• from mesoderm as 2 cardiogenic cords
• single heart tube formed by lumen

Question 8

How does blood enter & exit the heart?

Answer 8

• enters posteriorly
• exits anteriorly

Question 9

What is the sinus venosus?

Answer 9

accepts blood into the heart

Question 10

Where does the blood go once into the heart?

Answer 10

1. accepted into heart by sinus venosus
2. sinoatrial valve to atrium
3. atrioventricular valve to ventricle
4. ventricles send blood into bulbus cordis
5. exits bulbus & enters truncus arteriosus

Question 11

The sinus venosus becomes what of the right atrium?

Answer 11

SA node

Question 12

What are the changes in structures within the heart?

Answer 12

• atrium -> left & right atria
• ventricle -> left ventricle
• bulbus cordis -> right ventricle
• truncus -> ascending aorta & pulmonary trunk

Question 13

How does deoxygenated blood enter the heart?

Answer 13

through vena cava - > right atrium -> tricuspid valve

Question 14

How is the tricuspid valve held to the ventricular wall?

Answer 14

chordae tendineae

Question 15

How is the tricuspid valve anchored?

Answer 15

by papillary muscles

Question 16

How does oxygenated blod enter the left atrium?

Answer 16

enters via pulmonary veins from lungs

Question 17

The left atrium has what cusps?

Answer 17

bicuspid/ mitral valve

Question 18

Actin & myosin are organized into what?

Answer 18

sarcomeres

Question 19

Cardiac muscle is composed of what cells?

Answer 19

uninucleate branched cells

Question 20

Intercalated discs are composed of what 2 things?

Answer 20

• gap junctions -> allow Ca2+ to pass b/w cells for contractions
• desmosomes -> keep cells tight together

Question 21

What is the heart chambers cycle?

Answer 21

1. relaxation of empty ventricles
2. opens mitral & tricuspid valves to pull blood in
3. atria contract to force blood into ventricles

Question 22

What occurs when the mitral & tricuspid valves are closed?

Answer 22

1. ventricles contract
2. aortic & pulmonary valves open & blood leaves
3. atrial relaxation allows blood to fill
4. negative pressure of pericardium
5. all 4 chambers relax

Question 23

What do the 1st & 2nd sound mean with a heartbeat?

Answer 23

• 1st sound -> mitral & tricuspid closing / ventricle contracts
• 2nd sound -> pulmonary & aortic closing / ventricle relaxation

Question 24

What node acts as a pacemaker for the heart?

Answer 24

sinoatrial node

Question 25

What occurs as electrical signals travel via intercalated discs?

Answer 25

* rhythmic contraction of chambers * depolarization sends signals through cardiac conducting tarcts

Question 26

How is the contraction of the atria triggered?

Answer 26

* Bachman's bundle sends signal to left atrium * tracts within right atrium trigger contraction

Question 27

What happens when non-conductive tissue blocks the way?

Answer 27

signals cannot pass to ventricles

Question 28

The electrical signal in the heart takes 50 milliseconds to reach where?

Answer 28

AV node

Question 29

The AV bundle is also known as what?

Answer 29

Bundle of His

Question 30

What is the path of electrical activity in the heart?

Answer 30

SA node -> right & left (Bachman's bundle ) atrium -> AV node -> AV bundle/Bundle of His -> right & left ventricle

Question 31

What does the depolarization of cardiac cells rely on?

Answer 31

Na+ & Ca2+

Question 32

How do cardiac cells become depolarized?

Answer 32

* resting membrane potential is unstable; only -60mV * K+ channels open at +5mV

Question 33

What nerves regulate the SA node?

Answer 33

vagus & sympathetic nerves

Question 34

What glands regulate the SA node?

Answer 34

thyroid (T3 & t4) & adrenal (norepeinephrine & epinephrine)

Question 35

What happens during the plateau of contractile cells?

Answer 35

1. as Na+ close, Ca2+ & K+ channels open 2. Ca2+ moves in slowly while K+ moves out 3. creates refractory period

Question 36

What does the PR interval represent?

Answer 36

* depolarization of SA node * how long it takes for impulse to reach AV node

Question 37

What does the QRS interval represent?

Answer 37

depolarization of ventricle

Question 38

What does the T wave represent?

Answer 38

repolarization of ventricle

Question 39

What does the P wave represent?

Answer 39

depolarization of atria

Question 40

What does the QRS complex represent?

Answer 40

depolarization of ventricles