PSIO202 Exam 1 Lectures 1-3

Question 1

What are the two main branches of the “circulatory tree”?

Answer 1

Systemic circulation and pulmonary circulation

Question 2

Compare and contrast red and blue blood.

Answer 2

Red: Arterial blood, oxygen and nutrient rich
Blue: Venous blood, low in oxygen and nutrients

Question 3

Where does arterial blood enter and leave the heart?

Answer 3

Enters the heart from the pulmonary veins into the left atrium (after being oxygenated in the lungs) and leaves the heart through the aorta (left ventricle) to go to the rest of the body.

Question 4

Where does venous blood enter and leave the heart?

Answer 4

Enters right atrium from superior/inferior vena cava + coronary sinus, leaves right ventricle through pulmonary arteries

Question 5

List the flow of blood through the heart (start with entering through the vena cava)

Answer 5

Venous blood enters through inferior/superior vena cava
Right atrium
Tricuspid valve (AV)
Right ventricle
Pulmonary valve (Semilunar)
Pulmonary trunk/arteries
Lungs
Pulmonary veins
Left atrium
Bicuspid/mitral valve
Left ventricle
Aortic valve (semilunar)
Aorta
Body
Repeat

Question 6

What “side” of the heart is blue/venous and which “side” is red/arterial?

Answer 6

Right is blue/venous and left is red/arterial

Question 7

What do valves in the heart ensure?

Answer 7

That blood flows in one direction, from the heart to tissues and back to the heart

Question 8

What are the two AV valves, and are they pressure dependent or not?

Answer 8

The tricuspid and bicuspid/mitral valves, they are not pressure dependent.

Question 9

What structures control the AV valves, and what does that control look like?

Answer 9

The chorda tendinae and pappillary muscles control the AV valves.
Ventricles relaxed = chordae tendonae relaxed, atria contract, shoot blood through valves into ventricle
Ventricles contract = papillary muscles contract, chordae tendonae pull tight to prevent the valves from inverting when the ventricles push blood up through the pulmonary/aortic valve.

Question 10

Do the chorda tendinae/papillary muscles pull the AV valves open?

Answer 10

NO! They just contract to keep the valve from inverting when the ventricle contracts to shoot blood upward (preventing backflow into the atria).

Question 11

What are the two semilunar valves, and are they pressure dependent or not?

Answer 11

The aortic valve and pulmonary valve are pressure dependent.

Question 12

What does pressure dependent mean, and what is the pressure required for the aortic valve to open?

Answer 12

The semilunar valves only open when there is enough pressure in the ventricle to force it open. For the aortic valve, this amount is 100 mmHg. Less than 100 it will not open, more than 100 it will be open.

Question 13

Which ventricle has a thicker wall? Why?

Answer 13

The left ventricle, because it must force blood out to the entire body while the right ventricle only pushes blood out to the lungs.

Question 14

Where do the right and left coronary arteries originate?

Answer 14

The ascending aorta

Question 15

What does the right coronary supply? What are its two branches? What do they supply?

Answer 15

Supplies the right atrium (SA and AV nodes), the ventricles and the interventricular septum
The Marginal Branch: anterior right ventricle
The Posterior Interventricular Branch: posterior both ventricles

Question 16

What does the left coronary supply? What are the two branches, and what do they supply?

Answer 16

Supplies the SA node, left atrium, ventricles and interventricular septum.
The Circumflex Branch: left atrium and posterior left ventricle
The Anterior Interventricular Branch: anterior ventricles

Question 17

What does the great cardiac vein do?

Answer 17

drains the anterior heart

Question 18

What does the middle cardiac vein do?

Answer 18

Drain the posterior heart

Question 19

Where do the great cardiac vein and middle cardiac vein drain into? (structure and chamber)

Answer 19

Coronary sinus in the right atrium

Question 20

What are the main characteristics of cardiac muscle cells?

Answer 20

striated (actin and myosin in myoibrils), 1 central nucleus, branching, intercalated disks and gap juctions, desmosomes, large mitochondria, one T tubule per sarcomere, simple sarcoplasmic reticulum

Question 21

What are gap junctions? Where are they in a cardiac muscle cell? What is their role regarding electrical impulses and ions?

Answer 21

They are channels that allow ionic ionic continuity between the cells (basically, they are a channel for the ions to easily go from one cell to the next). Located at intercalated disks, and they allow electrical impulses to pass from one cell to another.`

Question 22

Because of gap junctions, does the myocardium contract in a coordinated or uncoordinated fashion? For this reason, it is called a ———- ———–.

Answer 22

Coordinated contrcation, Functional syncytium

Question 23

What are they key differences between cardiac muscle and skeletal muscle?

Answer 23

functional syncytium vs multinucleated syncytium, act on the fibrous skeleton of the heart instead of tendons/bones, have much larger mitochondria, and there is only 1 T-tubule instead of 2

Question 24

What is another name for the cardiac pacemaker?

Answer 24

The SA node (sinoatrial node)

Question 25

Where is the SA node located? What do both nodes do?

Answer 25

In the right atrium. They discharge action potentials SPONTANEOUSLY

Question 26

What is the very first event in the sequence of cardiac muscle excitation?

Answer 26

The SA node depolarizes (Na+ moves in)

Question 27

After the SA node is depolarized, what happens?

Answer 27

The action potential travels down the atria causing atrial muscle fiber contraction

Question 28

What structure is located at the AV border? What does it cause? Why is this important?

Answer 28

The AV bundle, or Bundle of His, is a band of poorly-conducting tissue with very few gap junctions. It slows the impulse just a little but, which allows the atria to fully empty before the ventricles contract.

Question 29

After the action potential gets through the AV bundle, where does it go next? What occurs?

Answer 29

It travels down the bundle branches to the ventricles, and they contract from the bottom up (forcing blood upwards to the semilunar valves)

Question 30

What is the difference between the rate the pacemaker cells discharge action potentials and the resting heart rate?

Answer 30

pacemaker cells discharge at 100-120 bpm resting heart rate is 70 bpm nervous system (parasympathetic) slows down the heart rate because it knows it doesn't need to be that fast

Question 31

Because pacemaker cells are auto-rhythmic (spontaneously discharge potentials), are they stable or not?

Answer 31

They are unstable.

Question 32

What does the membrane potential graph look like for the pacemaker cells? Draw it.

Answer 32

start at -60, slow rise to threshold at -40, jump up to 10, and fall back down to -60

Question 33

What events cause the characteristics of the membrane potential graph for pacemaker cells?

Answer 33

1) slow depolarization to threshold - leak current slowly increases permeability to Na+ 2) full depolarization - sudden increase of Ca++ permeability when threshold is reached 3) repolarization - permeability to K+ opens and Ca++ stops

Question 34

What does the membrane potential graph for cardiac muscle look like?

Answer 34

fast rise from -90 to a peak of 30, slight fall to a plateau around 0, then a steady fall back to resting potential of -90

Question 35

What causes the characteristics of the membrane potential graph for cardiac muscle?

Answer 35

fast depolarization to peak - Na+ fall back to resting potential (plateau) - Ca++ in but K+ out repolarization - Ca++ channels close and K+ stay open

Question 36

What is a refractory period? How long does it last for the muscle cells (time in ms and relation to the action potential)

Answer 36

This is the period where the cell will not respond to an additional action potential. It lasts about 250 ms, which is about as long as the action potential.

Question 37

Is the refractory period for cardiac muscle longer or shorter than for skeletal? Can cardiac do summation or tetanus like skeletal muscle?

Answer 37

Much longer, and it cannot do summation or tetanus from repeated stimulations (they just wont do anything)

Question 38

What is atrial diastole and ventricular diastole?

Answer 38

atrial diastole: when the atria fill passively ventricular diastole: ventricular muscles are repolarized (relaxed) and drop in pressure resulting in them passively filling

Question 39

What is atrial systole and ventricular systole?

Answer 39

Atrial systole: very brief contraction of the atria, actively filling the ventricles Ventricular systole: pressure in the ventricles rises, the muscle fibers are depolarized and then the ventricles contract

Question 40

During diastole (atrial and ventricular) are the AV valves open or closed?

Answer 40

open

Question 41

During systole (atria and ventricles) are the AV valves open or closed?

Answer 41

closed

Question 42

What does the P wave of an ECG come from?

Answer 42

depolarization of the atria just before they contract (systole) to "top off" the ventricles and make sure everything gets out of the atria

Question 43

What causes the QRS spike on an ECG?

Answer 43

ventricular contraction

Question 44

What causes the T wave on an ECG?

Answer 44

relaxation of the ventricles (atria are already relaxed) and begin filling everything up again

Question 45

Give an overview of the contraction/relaxations of the chambers in one cycle (start with everything being relaxed)

Answer 45

everything is relaxed and filling with blood (running through the atria and into the ventricles) atria give a little contraction to "top off" the ventricles Atria relax while the ventricles contract and eject blood out into circulation everything is relaxed again

Question 46

When does aortic pressure spike? (what time in the contraction/relaxation cycle)

Answer 46

When the ventricles contract

Question 47

Which is bigger, the peak pressure for the atrium or ventricles?

Answer 47

The ventricular pressure peaks much higher

Question 48

Out of the atria, ventricles, and aorta, which pressure always remains relatively high?

Answer 48

the aorta

Question 49

There is a short period where pressure in the ventricles is high but still low in the aorta. What is the term for this? Why does it happen?

Answer 49

Isovolumetric contraction. When the ventricles first start to contract they build up pressure but not enough to over come the semilunar valve and open them. Therefore, pressure is increased in the ventricle but not yet the aorta because blood hasn't been ejected into the aorta yet.

Question 50

What pressure is required for the aortic valve to open?

Answer 50

100 mmHg

Question 51

What is the equation for stroke volume?

Answer 51

EDV-ESV

Question 52

What is the equation for cardiac output?

Answer 52

CO=HRxSV

Question 53

What two main factors affect cardiac output? Draw a flow chart of what affects CO.

Answer 53

stroke volume and heart rate

Question 54

What are the determinants of stroke volume?

Answer 54

EDV/preload, aortic and pulmonary artery pressure/afterload, and contractility

Question 55

What is afterload?

Answer 55

pressure the heart must overcome to eject blood into the aorta/pulmonary artery

Question 56

What is preload/EDV?

Answer 56

volume of blood in the ventricles at the end of diastole

Question 57

What factors affect preload/EDV? Why is preload such an important factor in SV?

Answer 57

driving pressure, muscle pump, and respiratory pump The heart can only pump out what it receives, so it needs to receive more blood in each relaxation to be able to pump more out with each contraction.

Question 58

What is driving pressure?

Answer 58

heart chambers only fill when the pressure at point 1 is greater than at point 2 (travel down a pressure gradient)

Question 59

How does the respiratory pump impact preload?

Answer 59

breathing affects venous return through changes in the right atrial pressure

Question 60

What is passive/Frank-Starling mechanism contractility?

Answer 60

Changes in contractilty due to change in the length of cardiac muscle fibers. When the volume increases, the muscle fibers stretch, and then will produce a more forceful contraction.

Question 61

What is active contractility?

Answer 61

Change in contractility due to stimulation of the heart by the sympathetic nervous system

Question 62

With no nervous system input, what will happen to stroke volume if the preload increases?

Answer 62

The stroke volume will increase

Question 63

What are chronotropy and inotropy?

Answer 63

chronotropy- HR inotropy- contractility/force

Question 64

How does the nervous system increase contractility?

Answer 64

release of norepinepherine increases permeability to Ca++, which causes an increase in cross bridges that increases the strength of contraction

Question 65

After norepinephrine is released by the neurons, how does it increase contractility? (details)

Answer 65

binds to B1 adrenergic receptors, opens Ca++ channels, initiates cAMP then PKA which keeps Ca++ open longer, increases the crossbridges and therefore the force of contraction