CH. 13 - The Heart Flashcards
(77 cards)
1
Q
Flow
A
constant motion of a fluid
2
Q
Pressure
A
physical force required to create flow through any tube
3
Q
Boyle’s Law
A
pressure and volume have an inverse relationship
if chamber size ↓, then pressure ↑ and vice versa
*think lungs
4
Q
Resistance
A
force which opposes flow
5
Q
Pressure Gradient
A
difference in area of high pressure and area of low pressure
6
Q
Valves
A
prevent backflow and ensure one-directional flow of blood
7
Q
Blood Flow Equation
A
▵P/R
P = pressure
R = resistance
8
Q
What happens when cardiac muscle goes through relaxation process?
A
volume of chambers increases and pressure decreases; therefore, blood flows into the chambers from regions of higher pressure
inward flow will continue until there is no more pressure gradient
9
Q
What are the 2 major divisions of the circulatory system?
A
- Pulmonary Circulation
- Systemic Circulation
10
Q
Pulmonary Circulation
A
sends blood to lungs for oxygenation and returns oxygenated blood to heart
Pump 1
11
Q
Systemic Circulation
A
sends oxygenated blood to tissues and returns deoxygenated blood to heart
Pump 2
12
Q
Where in the thoracic cavity is the heart located?
A
Mediastinum
13
Q
What is the inferior tip of the heart called?
A
Apex
14
Q
Pericardial sac
A
protective membrane that surrounds and stabilizes the heart
15
Q
What happens when cardiac muscle goes through contraction process?
A
Decreases chamber volume; therefore, the champer pressure in increased
16
Q
Fibrous Pericardium
A
outer layer, composed of dense regular connective tissue like collagen
17
Q
Serous Pericardium
A
deep to fibrous layer; continuous, double-layered, fluid-filled membrane
Contains parietal and visceral layers
18
Q
Parietal Pericardium Layer
A
outermost layer of the serous pericardium and is in contact w/ fibrous pericardium
19
Q
Visceral Pericardium Layer
A
layer surrounding surface of the heart muscle and is continuous w/ outermost layer of the heart
20
Q
Cardiac Tamponade
A
when the heart’s pressure-volume relationships become messed up and interfere w/ blood flow
21
Q
What are the 3 layers of the heart muscle?
A
- Epicardium
- Myocardium
- Endocardium
22
Q
Epicardium
A
- bound together by loose areolar connective tissue
- adipose tissue (increases w/ age or cardiovascular disease)
synonymous w/ visceral pericardium
23
Q
Myocardium
A
- thickest layer of the heart muscle
- cardiac myocytes (non-mitotic and cannot self-regenerate)
- pacemaker cells (stimulate electrical rhythm of heart)
- cardiac skeleton: formed from dense, irregular connective tissue (not excitable, electricle insulator, maintains architecture of organ)
24
Q
Endocardium
A
- formed from endothelial (simiple squamous) tissue
- lines inner chambers of heart
- continuous w/ valves/blood vessels
- cardiac progenitor cells (can differentiate into other cardiac cell types)
25
What separates the left and right sides of the heart?
cardiac septum
26
Systemic Pump
Left atrium + Left Ventricle
| Pumps Oxygenated Blood
27
Pulmonary Pump
Right Atrium + Right ventricle
| Pumps Deoxygenated Blood
28
What is special about the Left Pulmonary Artery?
it is the only artery in the body that pumps deoxygenated blood
29
Anterior/Posterior Interventricular Sulcus
separates left and right ventricles
30
Coronary Sulcus
separates atria from ventricles
31
The blood flow in valves is:
one-directional
32
How many sets of valves does the heart possess?
Two: the atrioventricular (AV) valves and the semilunar (SL) valves
33
Atrioventricular (AV) Valves
- atria → ventricles blood flow
- formed by **cusps** that are anchored to the cardiac skeleton
- AV valve between right atrium and right ventricle has 3 cusps (**tricuspid valve**)
- AV valve between left atrium and left ventricle has 2 cusps (**bicuspid/mitral valve**)
- center-facing region of each cusp is bound by **chordae tendinae**
| Chordae Tendinae: anchor cusps to papillary muscles; prevent eversion
34
Semilunar (SL) Valves
- aorta → pulmonary trunk into ventricles blood flow
- found at bases of major vessels
- do NOT require chordae tendinae for stabilization
- **aortic valve**: located between left ventricle and aortic arch
- **pulmonary valve**: located between right ventricle and pulmonary trunk
35
What is the one exception to the normal pattern of blood flow?
- occurs during fetal stages of life when O2 is obtained from maternal circulation instead of lungs
- small hole in interarterial septum known as **foramen ovule** which allows blood to bypass the right ventricle and go directly btwn right and left atriums
- **ductus arteriosus**
- **fetal shunts**
36
What are the two major cell types in the myocardium?
1. Pacemaker cells (autorhythmic)
2. Contractile Myocytes (generate force)
| both required for heart function, but are not present in equal quant.
37
Phase 0 in Contractile Cardiomyocytes Action Potential
- **Resting Membrane Potential**
- between -80 mV and -90 mV
- continous efflux of **(+) charged potassium ions** through voltage gated inward rectifier potassium channels **K (IR))**
- small amount of calcium and sodium permeability
- NA/K/ATPase pump also maintains concentration gradient
38
Phase 1 in Contractile Cardiomyocytes Action Potential
- **Depolarization**
- fast voltage-gated **fast sodium channels** brought to threshold by adj. cells through gap junctions
- once threshold is reached, **Na+ permeability increaes and Na+ ions enter cell** causing rapid depolarization
39
Phase 2 in Contractile Cardiomyocytes Action Potential
- **Transient Repolarization**
- voltage gated **sodium channels rapidly inactivate** at the peak of the action potential
- sodium permeability decreases
- cardiomyocytes go into a **refractory period**
- membrane potential begins to hyperpolarize due to transient outward current from potassium channels
40
Phase 3 in Contractile Cardiomyocytes Action Potential
- **Plateau Phase** (equilibrium)
- voltage-gated **L-type calcium channels (CaL) **open bringing in (+) charged Ca2+ ions into cell
- opposed by the **efflux of K+ ions** through delayed rectifier potassium channels (KDR)
- two opposite electrical forces = plateau
- period when heart is making contraction and atrium is emptying
41
Phase 4 in Contractile Cardiomyocytes Action Potential
- **Rapid Repolarization**
- L-type calcium channels close
- **Efflux of K+ continues** through voltage-gated potassium channels
- Membrane potential repolarizes to resting state
42
Is the resting membrane potential in pacemaker cells stable or unstable?
Unstable
43
Subthreshold currents of Pacemaker Cells
## Footnote
fast or slow? what does the current look like?
Slow; funny current Ir inward Ca2+
44
Rising Depolarization of Pacemaker Cells
## Footnote
What is being taken into the cell?
Inward Ca2+
45
Refractory Period of Pacemaker Cells
NO REFRACTORY PERIOD
46
Repolarization of Pacemaker Cells
Rapid; outward K+
47
Action Potential Time of Pacemaker Cells
variable
48
List all the steps of the cardiac myocyte action potential in order
1. inward rectifier potassium channels are open, creating a high potassium permeability
2. depolarization from resting membrane potential occurs
3. fast sodium channels increase sodium permeability
4. refractory period begins
5. calcium permeability increases
6. delayed rectifier potassium channels are open
7. L-type calcium channels close
49
Funny Current
| Pacemaker Cell
- a mixed sodium and potassium current
- begins the pacemaker potential phase
50
HCN channels
| Pacemaker Cell
a channel that opens at very negative potentials
51
T-type calcium channels
| Pacemaker Cells
first calcium channel to open
52
L-type calcium channel
| Pacemaker Cell
- second calcium channel to open
- create rapid depolarization
53
inward rectifier potassium channels
| Pacemaker Cells
create rapid repolarization
54
Describe the Cardiac Excitation Sequence
1. **SA Node** (pacemaker cells; generate action potentials faster than any other heart cell)
2. **Internodal Pathways** (conducts action potential to myocytes in the atria throug gap junction)
3. **AV Node** (slower pacemaker cells; slows action potential conduction to allow time for an atrial refractory period)
4. **Bundle of HIS** (conducts actiona potential to interventricular septum where it splits into left and right bundle branches)
5. **Right and Left Bundle Branches** (propogate action potential through interventricular septum to heart apex)
6. **Purkinje Fibers** (spread action potentials from apex to left and right ventricles rapidly due to their high proportion of intercalated discs)
55
Sinoatrial (SA) node
- autorhythmic pacemakers
- sets rate of depolarization for the entire heart
- can fire action potentials up to 100 times per minute
- spreads through gap junctions in intercalated discs
56
Internodal Pathways
- carry depolarizing current from SA node through left/right atria
- initiates the depolarization of contractile cells in the atrial myocardium along the way
- connects SA node to AV node
57
Atrioventricular (AV) node
- **fewer gap junctions** causing a **short delay** in conduction which helps to ensure atrial contractions occur prior to excitation of ventricles
- pacemaker cells generate action potentials 40-60 times per minute, though their **pacemaker activity is usually masked by the SA node**
58
Bundle of HIS
- conducts action potential from AV node to the interventricular septum, where it splits to become left/right bundle branches
- pacemaker cells here generate action potentials ~20 times per minute, but are **masked by SA Node**
59
Left & Right Bundle Branches
- propogate the action potential through interventricular septum of the heart all the way to the apex
- necessary to allow the action potential to **circumvent the fibrous cardiac skeleton** which electrically insulates the ventricles from the aorta
60
Purkinje fibers
- large diameter cardiac muscle fibers
- travel superiorly from apex
- high density of **intercalated discs** causing increased conduction velocity through ventricles **simultaneously** and **rapidly**
- action potentials are generated ~20 times per minutes but are masked by SA Node
- **more gap junctions = ↑ speed**
61
Cardiac Arrhythmias
- family of disorders characterized by electrical activity within the heart that often lead to changes in pumping activity
- caused by breakdown of coordination of electrical conduction system
- **fibrillation:** fast, spastic depolarization of myocardium, typically localized to the atria (atrial fibrillation) or ventricles (ventricular fibrillation)
62
Electrocardiograms (ECG)
- provides a summary of the electrical changes that are taking place within the entire heart
- does NOT provide a direct measure of action potentials
- **bipolar leads:** polarized leads that have positive and neg. electrodes (placed in triangular arrangement (Einthoven's triangle) in order to assess electrical activity from multiple perspectives
63
P-Q interval
time required for **atrial depolarization** and the action potential to reach the ventricles
64
P-R interval
time required for **atrial depolarization** to propogate through the ventricles (internal conduction system)
65
S-T segment
corresponds to time course of **ventricular depolarization**
66
Q-T interval
combined time required for **ventricle depolarization and repolarization**
67
P wave
formed by depolarization of the atria
68
Q wave
depolarization of the septal region of the ventricle
69
R wave
depolarization of anterior portion of ventricle
70
S wave
depolarization of Purkinje fibers and inferior portions of the ventricles
71
T wave
ventricular repolarization
72
(+) Positive end of a lead produces:
- **depolarizing current** traveling toward this end produces **upward** deflection
- **repolarizing current** traveling toward this end produces **downward** deflection
73
(-) Negative end of a lead produces:
- **depolarizing current** traveling to this end produces **downward** deflection
- **repolarizing current** traveling to this end produces **upward** deflection
74
EKG waves correlate with `discrete electricle changes` in the heart
An EKG/ECG is a **summary**; no specifics
75
List and Describe the steps of the Cardiac Cycle:
A: atrioventricular valve opens because atrial pressure exceeds ventricular pressure
B: blood enters from atria and fills ventricular chamber until end diastolic volume is reached
C: Atrioventricular valve closes because ventricular pressure exceeds atrial pressure
D: the ventricle begins contraction phase and pressure builds within the chamber
E: semilunar valve opens because ventricular pressure exceeds aortic presure
F: blood is ejected from the ventricle into the aorta until the end systole volume is reached
G: semilunar valves close because aortic pressure exceeds ventricular pressure
H: pressure decreases inside the ventricular chamber
76
Cardiac Output
amount of blood pumped by a ventricle in period of time
C.O. = stroke volume (sv) x Heart Rate (HR)
77
Cardiac Reserve
change in cardiac output at rest and during exercise
