Heart Lecture

Question 1

Pulmonary vs Systemic Circuit

Answer 1

Pulmonary: right side of heart that carries blood to lungs for gas exchange

Systemic: left side of heart that carries oxygenated blood to all tissues and returns it to heart

Question 2

Describe the pericardial sac that encloses the heart

Answer 2

the pericardium is a double walled sac that encloses the heart in order to prevent friction

Parietal pericardium: superficial fibrous layer of connective tissue

Visceral pericardium (epicardium): serous membrane covering the heart

Question 3

Describe the three layers of the heart wall

Answer 3

Visceral pericardium (epicardium): serous membrane with some adipose in thick layers

Myocardium: layer of cardiac muscle that is spiraled around the heart in order to make a wringing motion
-fibrous skeleton of heart: framework of collagenous and elastic fibers

Endocardium: smooth innerlining of heart and blood vessels that covers the surfaces of the valves

Question 4

List the four chambers of the heart

Answer 4

1. right and left atria
   -Receive blood returning to the heart
2. Right and left ventricle
   -pumps blood into arteries
   -the interventricular septum seperates the ventricles

Question 5

List the four valves of the heart

Answer 5

Function: ensure one way blood flow

1. Tricuspid valve
2. Bicuspid Valve
3. Pulmonary semilunar valve: Opening between right ventricle and pulmonary trunk
4. Aortic semilunar valve: opening between left ventricle and aorta

Question 6

How does blood flow through the chambers?

Answer 6

1. Deoxygenated blood enters through the right atrium
2. Blood flows through the tricuspid valve and into the right ventricle
3. Heart contracts and pulmonary semilunar valve open
4. Blood flows through the pulmonary semilunar valve and enters the lungs to unload CO2
5. Oxygenated blood returns to left atrium.
6. Blood flows through the bicuspid valve and into the left ventricle
7. Heart contracts and the aortic semilunar valve opens
8. Blood flows through the aortic semilunar valve and to the body, where oxygen is unloaded.

Question 7

Describe how the heart pumps blood to itself.

Answer 7

1. Right coronary artery: supplies right atrium and sinoatrial node

For Lab:
2. Left coronary artery contains a descending artery that supplies blood to both ventricles and 2/3 of interventricular septum

3. Cicumflex branch: supplies left atrium and posterior wall of left ventricle

Venous Drainage:
-coronary blood drains directly into the right atrium

Question 8

What makes cardiac muscle unique? (Structure of cardiac muscle and metabolism)

Answer 8

-They are striated and joined together through intercalated discs, where gap junctions exist
-Huge mitochondria
-Dark in color due to excess myoglobin (excess oxygen) and glycogen(glucose) so that aerobic respiration can occur for ATP cell energy
-depends only on aerobic respiration and can use different organic fuels
-fatigue resistant; but it is most vulnerable to oxygen deficiency

Question 9

Descibe the action potential in cardiac muscle (myocardium)

Answer 9

1. Depolarization: stimulus opens Na+ gates and Na+ rush in, membrane depolarizes rapidly, and Na+ gates close quickly (similar to skeletal muscles)
2. Plateau Phase: Lasts for milliseconds, where it sustains the contraction for expulsion of the blood from heart
   -it lengthens the span of time that the action potential occupies
   -this happens due to calcium being slowly released from sarcoplasmic reticulum
   -this impacts the absolute refractory period; peak tension
3. Repolarization: cardiomyocytes begin to relax a little bit
   -relative refractory

Question 10

Describe the heart’s pacemaker and conduction system (how does the heart contract?)

Answer 10

Function: the pacemaker coordinates the heart beat and conduction pathways through the myocardium

1. Sinoatrial node: a patch of modified cardiomyocytes that is non contractile
   -determines the heart rate
   -bad at holding resting membrane potential
   -signals spread through the atria
   -tells other cells to contract with electrical potential traveling through gap junctions
2. Atrioventricular Node: the gateway to the ventricles because the heart’s fibrous skeleton makes it difficult for the electrical current to spread
3. From the AV node, the signal travels through the AV bundle and into the interventricular septum
   -Specifically, the right bundle branch and left bundle branch
   -in the left bundle branch, the signal goes to the papillary muscles and contracts the Purkinje fibers(subendothelial conducting network)

Question 11

Systole vs Diastole

Answer 11

systole: contraction

diastole: relaxation

Question 12

Describe cardiac output

Answer 12

the cardiac output is the volume ejected by the ventricles per minute.

heart rate is one of the factor:
-avg 60 bpm
-factors impacting heart rate: age, sex, activity level, and K+ or Ca+ ions may impact it

Stroke volume is the second factor:
-preload: the tension within the ventricle impacts how much blood can enter. Exercise impacts this.
-contractility: can the muscle contract? Ion imbalances can impact this
-afterload: is anything preventing the blood from leaving the ventricle? The elasticity of systemic arteries or aorta can impact this.

cardiac output = heart rate x stroke volume