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Anatomy & Physiology 2 > Heart > Flashcards

Heart Flashcards

1
Q

What is the function of the pericardium?

A

mechanical protection for the heart and big vessels, and a

the same provides lubrication to reduce friction between the heart and the surrounding structures.

Pericardial sac: anchors heart within the thoracic cavity and prevents heart chambers from overfilling with blood

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2
Q

Name and describe the two main layers of the pericardium

A

Fibrous pericardium - tough CT (deep) superficial
- protects the heart
- anchors it to surrounding structures
- prevents overfilling of the heart with blood
Serous pericardium →
- parietal layer - lies the pericardial cavity and folds back as the…
- (epicardium) visceral layer which covers the heart

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3
Q

Describe the location and importance of the pericardial cavity.

A

in-between the parietal and epicardium (visceral layer)

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4
Q

Name and describe the three tissue layers of the heart wall.

A

epicardium- (serous/visceral pericardium)
Outermost layer

myocardium- middle layer
- composed of cardiac muscle is stabilized by a a network of CT called the cardiac skeleton
- contracts and is responsible for blood pressure
- arranged in bundles

endocardium- Inner layer
Composed of endothelium overlying a thin layer of CT
Lines all chambers & covers surface of valves
Epithelial layer is smooth continuous with endothelium which lines blood vessels → allow blood to move w/o lots of friction

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5
Q

What is the function of the fibrous skeleton (cardiac skeleton) of the heart?

A

allows action potentials to spread via specific pathways in the heart (because connective tissue is not excitable)

reinforces myocardium internally

anchors big cardiac muscle fibers and has ropelike rings around the big vessels coming out the heart to prevent them from swelling

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6
Q

Which layer of the heart wall is the thickest?

A

Myocardium

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7
Q

Which chamber of the heart has the thickest wall?

A

left ventricle

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8
Q

Trace the flow of blood through the heart, beginning at the right atrium.

A

deoxygenated : right atrium through tricuspid valve to right ventricle through pulmonary semilunar valve to pulmonary trunk
*is carried in two pulmonary arteries to the lungs (pulmonary circuit) to be oxygenated, enters the heart

oxygenated: to four pulmonary arteries to left atrium to left ventricle through the mitral valve to the left ventricle through the aortic semilunar valve to the aorta

LEAVING:
*oxygen-rich blood is delivered to the body tissues (systemic circuit) and oxygen-poor blood returns back to the heart

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9
Q

Name the three vessels that return blood to the right atrium. From what general body
region is the blood in each of these vessels returning?

A

superior vena cava
interior vena cava
coronary sinus

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10
Q

Name the vessels that return blood to the left atrium. From what body region is the
blood in these vessels returning?

A

four pulmonary veins

from the pulmonary circuit

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11
Q

Why is the heart referred to as a double pump?

A

its pumping blood in and out

Right side of the heart pumps blood into the pulmonary circuit
Left side of the heart pumps blood into the systemic circuit

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12
Q

What is the function of the heart valves?

A

fibrous CT flaps that prevent back flow of blood open and close in response to blood pressure differences

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13
Q

Describe the mechanism of operation of the atrioventricular (AV) valves and of the
semilunar (SL) valves.

A

Atrioventricular (AV) valves: prevent backflow of blood intro atria when ventricles contract
- TRICUSPID and MITRAL valve
mechanics: when atrial pressure is higher than ventricular, the AV valves will open, when vice versa, they’ll close.

Semilunar valves (SL) : prevent back flow of blood into ventricles from ventricles
- PULMONARY VALVE and AORTIC VALVE
mechanics: when ventricle pressure outweighs atrial pressure, it opens and atrium closes

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14
Q

Which valves are associated with the chordae tendineae and papillary muscles?

A

AV valves
Tricuspid
Chordae tendineae and papillary muscles anchors flaps when ventricles are contracting→ maintains structure and makes sure valves do not collapse; helps proper closure of AV valves

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15
Q

Compare and contrast the microscopic anatomy of cardiac muscle vs. skeletal muscle
fibers.

A

Both: striated

Cardiac: contract via sliding filament mechanism, cardiac muscles are short and fat, only has endonesium which is anchored to skeletal and multi-nucleated, muscles has one or two nuclei in the center, depends more on continual oxygen than skeletal muscle, system of calcium delivery is less elaborate than skeletal

Skeletal: cardiac muscles are long and cylindrical, can perform anaerbically (?)

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16
Q

Name and describe the special intercellular junctions present in cardiac muscle tissue.

A

adjacent fibers interconnect at junctions called intercalated discs

desmosomes - intercellular junctions, hold cardiac muscle cells together during contraction

gap junctions- allows ions to flow from one cell to the next , important because it causes depolarization

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17
Q

What is the functional significance of these junctions (#16)?

A

desmosomes - intercellular junctions, hold cardiac muscle cells together during contraction

gap junctions- allows ions to flow from one cell to the next , important because it causes depolarization

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18
Q

What is the significance of the large numbers of mitochondria and the rich blood supply
to cardiac muscle tissue?

A

they have a large amount of mitochondria so they can produce large amounts of ATP because they’re always beating. The cardiac muscles cannot perform anaerobically so there are lots of myoglobin so Oxygen can get to the mitochondria quickly.

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19
Q

What is a functional syncytium? Identify the functional syncytia of the heart.

A

When depolarization happens, the gap junctions help it spread quicky and the entire ventriculam(?) contracts at once.

The two that exist in the heart:
- atrial syncytium
- ventricular syncytium

the all or none law applies to the entire syncytium

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20
Q

Describe the three main functional differences between skeletal and cardiac muscle.

A
  1. means of stimulation

cardiac muscle fibers exhibit autorhythmicity (meaning they depolarize spontaneously & rhythmically and the entire syndication contracts as a single unit.)

skeletal muscle is activated by alpha motor neurons that activate motor units.

  1. syncytium vs motor unit
    syncytia are units that contract simultaneously
    ALL IN ONE law applies to MOTOR UNITS
    does all or none law apply to syncytium?
  2. length of absolute refractory period
    short refractory period (1-2 milliseconds) so muscle fibers are stimulated more rapidly & wave summation would ______ up?

long refractory period (150 milliseconds) prevents tectonic contractions from happening in the heart. This allows the heart to rest for a second in between contractions so it can refill with blood

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21
Q

Identify (in order) the 5 components of the heart’s conduction system.

A

sinoatrial (SA) node -
*collection of autharhythmical cells (fastest rate of depolarization)
*right atrium to inferior vena cava and opens to the left atrium?
*Sets the pace for the heart
*sinus rhythm

atrioventricular (AV) node-
*Takes 15 seconds to go from the SA node to AV node
* Inferior part of the atrium (atrial septum. where coronary septum opens into the right atrium)
*delay in impulse tension @ the AV node, allows enough time for the atrial to finish contracting before the ventricles get excited and contract

atrioventricular (AV) bundle/ His bundle -
*only electrical college? between the atria and ventricles
*fibers are large diameter and signals pass quickly *rapid conductivity)
*after they go to the apex, they branch off
*capillary muscles contract before the ventricles so it tightened the copieodic ? before hand

R&L bundle branches -
*conduct the impulses through the interventricular septum
*branch off at the apex

Purkinje fibers (modified ventricular muscle fibers)-
*depolarizes the contractile cells of both ventricles

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22
Q

What are autorhythmic cells?

A

1% of the cells in myocardium

known as cardiac pacemaker cells, have the special ability to depolarize spontaneously and so pace the heart

part of the intrinsic conduction system

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23
Q

What is a pacemaker potential? Why are pacemaker potentials important?

A

pacemaker cells have an unstable resting potential that continuously depolarizes, drifting slowly towards threshold. these spontaneously changing membrane potentials are known as pacemaker potentials and initiate the action poentenials that spread throughout the heart to trigger its rhythmic contractions

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24
Q

How is a pacemaker potential generated (i.e., what ion channels are involved and at
what point do the channels open/close)?

A

voltage gated ion channels

1) First channel to open is the “fun voltage gated Na+ channel
- opens when the membrane depolarizes to -60mV
- allows slow leakage of Na+ across the membrane

2) When the membrane depolarizes to -50mV, it triggers the opening of T-type Ca2+ channels (called T-type because there transient)

3) threshold is -40mV in auto rhythmic cells

4) At threshold, L-type Ca2+ channels open, producing the upshot of the AP (called L-type because they’re long lasting)

5) depolarization occurs when voltage-gated K+ channels open and L-type Ca2+ channels simultaneously close

25
Q

What part of the myocardium normally has the fastest spontaneous depolarization rate?

A

sinoatrial (SA) node

26
Q

What is the functional significance of the 0.1 second delay in impulse transmission at
the AV node?

A

It ensures that the atria have ejected their blood into the ventricles first before the ventricles contract.

27
Q

What is the function of the Purkinje fibers? [Note: Marieb calls these the subendocardial
conducting network.]

A

since the left ventricle is larger than the right, the subendocardial conducting network is more elaborate on that side of the heart

*depolarizes the contractile cells of both ventricles

28
Q

What part of the heart is excited by the left and right bundle branches?

A

intervntricular septum

29
Q

What part of the conduction system serves as the sole electrical connection between the
atria and the ventricles?

A

atrioventricular (AV) node

30
Q

What is the normal pacemaker of the heart?

A

the sinus node

31
Q

Compare and contrast the action potential of skeletal and cardiac muscle cells.

A

In skeletal muscle cells, the action potential duration is approximately 2-5 ms. In contrast, the duration of cardiac action potentials ranges from 200 to 400 ms.

32
Q

In cardiac muscle, what are the sources of Ca2+ which trigger contraction?

A

sarcoplasmic reticulum and extracellular fluid

33
Q

What produces the plateau phase of a cardiac muscle fiber’s action potential? What is
the functional significance of the plateau phase?

A

the plateau phase is due to Ca2+ influx through slow calcium channels. This keeps the cell depolarized because most potassium channels are closed

34
Q

How does the all-or-none law relate to cardiac muscle?

A

if depolarization happens anywhere, the entire heart will receive the stimulus and contract

35
Q

When does the refractory period in cardiac muscle end? What is the functional
significance of this long refractory period?

A

it ends when…

long refractory period (150 milliseconds) prevents tectonic contractions from happening in the heart. This allows the heart to rest for a second in between contractions so it can refill with blood

36
Q

Define ECG.

A

electrocardiogram

graphic record of the electrical activity of the heart

37
Q

Name the three important waves/deflections of a normal ECG tracing and describe
what each represents.

A

P wave - atrial depolarization the first, lasts about 0.08 seconds and results from the movement of the depolarization wave from the SA node through the atria. Approximately 0.1 seconds after the P wave begins, the atria contracts.

QRS complex - Results from ventricular depolarization and precedes ventricular contraction.
- The time required for each ventricle to depolarize depends on its size relative to the other ventricle.
- Avg time is 0.08 seconds

T wave - caused by ventricular repolarization
- lasts about 0.16 seconds
- repolarization is slower than depolarization so the T wave is more spread out and has a lower amplitude than the QRS complex

38
Q

What is the duration of a normal PR interval? What might a prolonged P-R interval
indicate?

A

about 0.16 seconds, a prolonged PR interval indicates a long period of time between the beginning of atrial excitation to the ventricular excitation

PR interval measures the time for the electrical signal to get from the top of your heart to the bottom of the heart. A prolonged PR interval (greater than 200 milliseconds) indicates slow conduction between the top and bottom of the heart, usually caused by a condition known as first-degree AV block.

39
Q

What is the duration of a normal QRS complex? What might a prolonged QRS
complex indicate?

A
  • Avg time is 0.08 seconds
    Prolonged QRS Duration on the Resting ECG is Associated with Sudden Death Risk in Coronary Disease, Independent of Prolonged Ventricular Repolarization - PMC.
40
Q

What cardiac event/activity is represented by the S-T segment? What is the clinical
significance of an elevated or depressed S-T segment?

A

when the APs pf the ventricular myocytes are plateau phases, the entire ventricular myocardium is depolarized

41
Q

Describe the pressure changes in the heart which cause the valves to open and close.

A

more pressure in artria than ventricles, causes AV valves to open, and vice versa for SL valves

42
Q

Identify the three main phases of the cardiac cycle.

A

1) atrial systole
- at the beginning, the ventricles are filled to about 70% of their normal capacity due to passive flow of blood through the open AV valves

  • at the end, ventricles hold about 120 ml of blood called the end diastolic volume (EDV)

2) ventricular systole
- begins as atrial systole ends
- AV valves close when ventricular pressure becomes greater than atrial pressure and marks the beginning of isovolumic contraction
-ventricular contraction continues and ultimately, ventricular pressure becomes greater than pressure in the large arteries leaving the ventricles
(SL valves open, and marks the beginning of the ejection phase)
- at the end of the ventricular contraction, the ventricles hold approx 50 ml of blood called the end systolic volume (ESV)

3) relaxation period
- as ventricles relax, ventricular pressure falls, heading to SL valve closure
- blood in the aorta rebounds against the close valve, causing the pressure to rise briefly at the dicrotic notch
- when SL valves close, the period of the isovolumic relaxation begins

43
Q

Describe the events associated with each of the above phases (#42), making note of
changes in atrial & ventricular pressure, opening/closing of valves, ventricular volume
changes, and correlation between cardiac events and the ECG.

A

1) atrial systole
- at the beginning, the ventricles are filled to about 7-% of their normal capacity due to passive flow of blood through the open AV valves

  • at the end, ventricles hold about 120 ml of blood called the end diastolic volume (EDV)

2) ventricular systole
- begins as atrial systole ends
- AV valves close when ventricular pressure becomes greater than atrial pressure and marks the beginning of isovolumic contraction
-ventricular contraction continues and ultimately, ventricular pressure becomes greater than pressure in the large arteries leaving the ventricles
(SL valves open, and marks the beginning of the ejection phase)
- at the end of the ventricular contraction, the ventricles hold approx 50 ml of blood called the end systolic volume (ESV)

3) relaxation period
- as ventricles relax, ventricular pressure falls, heading to SL valve closure
- blood in the aorta rebounds against the close valve, causing the pressure to rise briefly at the dicrotic notch
- when SL valves close, the period of the isovolumic relaxation begins

44
Q

Define and give a normal value for end diastolic volume (EDV), end systolic volume
(ESV), and stroke volume (SV).

A

EDV - 12O ml of blood

ESV- 50 ml of blood

SV- 70 ml of blood

45
Q

Which heart valves are open during isovolumic relaxation? during isovolumic
contraction?

A

isovolumic relaxation - sl valves close so when av valves open?

isovolumic contraction - av valves close so sl valves open

46
Q

Describe the first and second heart sounds (i.e., S1 and S2, respectively). Which heart
sound marks the beginning of ventricular diastole? ventricular systole?

A

S1-
- first sound
- lub
- longer
- turbulence from av closure
- ventricular systole

S2-
- short and sharp
- blood turbulence from closure of SL valve
- ventricular diastole

47
Q

What is the contribution of atrial contraction to ventricular filling?

A

pushes blood into the ventricles

48
Q

Define cardiac output and know how it is calculated.

A

the vol of blood ejected from each ventricle per minute

CO = HeartRate x StrokeVolume

49
Q

What is cardiac reserve?

A

the ratio between the maximum CO an individual can achieve and his/her resting CO

50
Q

How is stroke volume regulated?

A

preload
afterload
contractibility

51
Q

Define ejection fraction and know how it is calculated.

A

the % of end diastolic volume pumped out of the heart during systole

calculation: SV (stroke vol)/ EDV (end diastolic vol) x 100% = 60%

52
Q

Define the terms preload and afterload.

A

preload - the degree of stretch the heart muscle before it contracts within physiological limits, the more the heart is filled during systole, the greater the force of contraction during systole

the greater the preload b4 the onset contraction, the greater the contraction

afterload - the pressure that must be exceeded before ejection of blood from the ventricles can begin

53
Q

What is the relationship between stroke volume and venous return (i.e., preload)?

A
54
Q

How does afterload influence stroke volume?

A
55
Q

How does contractility influence stroke volume? How do changes in sarcoplasmic Ca2+
levels influence contractility?

A
56
Q

What effects do the sympathetic and parasympathetic divisions of the ANS have on
heart rate?

A

sympathetic - associated with cardioacceleratory center

parasympathetic- is associated with cardioinhibitory center

57
Q

What effect does the sympathetic division have on contractility?

A
58
Q

Identify other chemical and physical factors that influence heart rate.

A
59
Q

Heart failure is a condition in which the pumping ability of the heart is low and, as a
result, blood does not circulate effectively. Explain how heart failure can result in
pulmonary edema.

A

Anatomy & Physiology 2 (7 decks)

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