Chapter 18: Heart Flashcards
0
Q
Left atrium revolves blood from?
A
Returning pulmonary circuit
1
Q
Right atrium receives blood from?
A
Returning systemic circuit
2
Q
Right ventricle pumps blood through ?
A
Pulmonary circuit
3
Q
What is the pericardium?
A
Double walled sac
4
Q
What does the superfibrous pericardium do?
A
Protects ,
Anchors to surrounding structures ,
And prevents overfilling
5
Q
Serous pericardium is made up of what 3 layers?
A
- parietal layer
- visceral layer
- pericardial cavity
6
Q
Parietal layer does:
A
Lines the internal surface of fibrous pericardium
7
Q
Visceral layer does:
A
On external surface of heart
8
Q
Pericardial cavity:
A
Fluid filled cavity that separates the two layers
9
Q
What is pericarditis?
A
- inflammation of the pericardium
- roughens membrane surfaces->pericardial friction rub(creaking sound)
- cardiac tamponade : excess fluid sometimes compressed the heart–> limited pumping ability
10
Q
What are the three layers of the heart?
A
Epicardium
Myocardium
Endocardium
11
Q
Epicardium:
A
Is the visceral layer of the serous pericardium
12
Q
Myocardium:
A
- spiral bundle of contractile cardiac muscle cells
- cardiac skeleton : crisscrossing, interlacing layer of connective tissue
- anchors cardiac muscle fibers
- supports great vessels and valves
- limits spread of action potentials to specific paths
13
Q
Endocardium:
A
Is continuous with endothelial lining of blood vessels.
-it lines the heart chambers, covers cardiac skeleton valves
14
Q
What is the interatrial septum?
A
Separates the atria
15
Q
What structure separates the ventricles?
A
Interventricular septum
16
Q
Heart valves do what?
A
- Ensure unidirectional blood flow through heart
- open and close in response to pressure changes
17
Q
Which valves prevent backflow into atria when ventricles contract?
A
The atrioventricular valves
18
Q
What do the semilunar valves do?
A
-prevent backflow into ventricles when ventricles RELAX
There are two semilunar valves: aortic/pulmonary
19
Q
What two conditions seriously weaken the heart?
A
Incompetent valve
And
Valvular stenosis
20
Q
Incompetent valve:
A
Blood backflows so heart repos same blood over and over
21
Q
Valvular stenosis:
A
Stiff flaps- constrict opening ->heart muscle must exert more force to pump blood
22
Q
How are weakened heart valves replaced?
A
Mechanical, animal, or cadaver valves
23
Q
What is the pathway of blood through the heart in the pulmonary circuit?
A
Right atrium> tricuspid valve > right ventricle
- right ventricle > pulmonary semilunar valves > pulmonary trunk > pulmonary arteries > lungs
- lungs > pulmonary veins > left atrium
24
Pathway of blood in systemic circuit?
Left atrium> mitral valve > left ventricle
- left ventricle > aortic semilunar valve > aorta
- aorta > systemic circuit
25
What kind of pressure is the pulmonary circuit ?
Short , low pressure
26
What kind of pressure is the systemic circuit ?
Long , high-friction circulation
27
What does the left ventricles thicker wall have to do with pressure?
Makes the heart pump with greater pressure
28
What is the function of blood supply to the heart?
- delivers when heart is RELAXED
| - left ventricle receives most blood supply
29
The coronary circulation contains how many anastomoses ?
Many anastomoses (junctions )
30
What do the anastomoses do for the coronary circulation ?
- provide additional routes for blood delivery
| - cannot compensate for coronary artery occlusion
31
What do cardiac veins do?
Collect blood from capillary beds
32
Angina Pectoris:
- thoracic pain caused by fleeting deficiency in blood delivered to myocardium
- cells weakened
33
Myocardial infarction(heart attack):
- due to prolonged coronary blockage
| - areas of cell death are repaired with non contractile scar tissue
34
Intercalated disks:
Junctions between cells -anchor cardiac cells
Contains desmosomes and gap junctions
35
Desmosomes :
Prevent cells from separating during contraction
36
Gap junctions :
Allows ions to pass from cell to cell ; electrically couple adjacent cells
--allows heart to be functional syncytium
37
Cardiac differ from skeletal muscles in 3 ways:
- ~1% of cells have automaticity (autorhythmicity)
(Do not need nervous system stimulation and can DEPOLARIZE entire heart)
- all cardiomyocytes contract as unit or none do
- long absolute refactory period (250 ms) this prevents tetanic contractions
38
Three similarities cardiac and skeletal muscles have?
- depolarization opens few voltage-gated fast Na+ channels on sarcolemma->
- - reversal of membrane potential from -90 mV to +30 mV
- - brief Na channels close rapidly.
-depolarization wave down T tubules > SR to release Ca2+ ->
- excitation-contraction coupling occurs.
- -Ca2+ binds troponin> filaments slide
39
Muscle contraction differences between cardiac and skeletal?
- depolarization wave also opens slow Ca2+ channels in sarcolemma > SR to release Ca2+
- Ca2+ surge prolongs the depolarization phase (plateau)
- action potential and contractile phase last much longer (allow blood ejection from heart)
-repolarization result of inactivation of Ca2+ channels and opening of voltage-gated K + channels
( Ca2+ pumped back to SR and extracellulary)
40
Does cardiac muscle have many mitochondria ?
Yes
41
Why does cardiac muscle have many mitochondria?
-Great dependence on aerobic respiration
42
Cardiac cell imbalance?
Ischemic cells> anaerobic respiration > lactic acid
- -high H+ concentration > high Ca2+ concentration
- gap junction close > fatal arrhythmias
43
Coordinated heartbeat is a function of:
- presence of gap junctions
- intrinsic cardiac conduction system : (network of non contractile autorhythmic cells) and (initiate and distribute impulses > coordinated depolarization and contraction of heart
44
Pacemaker (autorhythmic cells):
✳️have unstable resting membrane potentials (pacemaker potentials or prepotentials ) due to opening of slow Na+ channels)
-continuously depolarize
✳️at threshold, Ca2+ channels open
✳️explosive Ca2+ influx produces the rising phase of the action potential
✳️repolarization results from inactivation of Ca2+ channels and opening of voltage-gated k+ channels
45
Three parts of action potential?
Pacemaker potential
Depolarization
Repolarization
46
Pacemaker potential:
Repolarization closes K+ channels and opens slow Na+ channels ➡️ ion imbalance
47
Depolarization :
Ca2+ channels open ➡️ huge influx➡️rising phase of action potential
48
Repolarization:
K+ channels open➡️efflux of K+
49
How long does it take the cardiac pacemaker cells to go across heart?
~220 ms
50
What is the sequence of excitation ?
```
▪️sinoatrial node ➡️
▪️atrioventricular node ➡️
▪️atrioventricular bundle ➡️
▪️right and left bundle branches ➡️
▪️subendocardial conducting network
(Purkinje fibers)
```
51
Sinoatrial node(sequence of excitation )?
- pacemaker of the heart in right atrial wall
- depolarizes faster than rest of myocardium
- generates impulses about 75X/minute (sinus rhythm)
- inherent rate of 100X/minute tempered by extrinsic factor)
-impulse spreads across atria and to AV node
52
Atrioventricular node(sequence of excitation)?
- in inferior interatrial septum
- delays pulses aprox. 0.1 second
- because fibers are smaller diameter= fewer gap junctions
- allows atrial contraction prior to ventricular contraction
-inherent rate of 50X/minute in absence of SA node input
53
Atrioventricular bundle(sequence of excitation)?
- in superior interventricular septum
- only electrical connection between atria and ventricles
- atria and ventricles not connected via gap junction
54
Right and left bundle branches (sequence of excitation)?
- two pathways in interventricular septum
| - carry impulses toward apex of heart
55
Subendocardial conducting network (sequence of excitation)?
-Complete pathway through interventricular septum into apex and ventricular walls
- more elaborate on left side of heart
- AV bundle and subendocardial conducting network depolarize 30X/minute in absence of AV node input
-ventricular contraction immediately follows from apex toward atria
56
Defects in intrinsic conduction system cause what?
▪️arrhythmias
| ▪️fibrillation
57
Arrhythmias :
- irregular heart rhythms
| - uncoordinated atrial and ventricular contractions
58
Fibrillation:
Rapid, irregular contractions; useless for pumping blood ➡️ circulation cease➡️ brain death ➡️ defibrillation to treat
59
Fasiculation:
Visible muscle tremors
60
What does a defective SA node cause?
▪️Ectopic focus
| ▪️extrasystole
61
Ectopic focus:
- abnormal pacemaker
| - AV node may take over ; sets junction all rhythm (40-60bpm)
62
Extrasystole:
- ectopic focus sets high rate
| - can be from excessive caffeine or nicotine
63
Defective AV node may cause what?
▪️heart block
| ▪️artificial pacemaker to treat
64
Heart block:
- Few(partial) or no (total) impulses reach ventricles
| - ventricles beat at intrinsic rate --too slow for life
65
What is the heartbeat modified by?
▪️Heartbeat modified by ANS via cardiac centers in medulla oblongata.
-sympathetic =⬆️ rate and force
-parasympathetic =⬇️rate
▪️cardioacceleratory center- sympathetic affects SA,AV, heart muscle , coronary arteries
▪️cardioinhibitory center - parasympathetic inhibits SA AV nodes via vagus nerves
66
Electrocardiogram:
Composite of all action potentials generated by nod and contractile cells at given time
67
Three waves in electrocardiograph?
P wave
QRS complex
T wave
68
P wave:
Depolarization SA node ➡️atria
69
QRS complex:
Ventricular depolarization and atrial repolarization
70
T wave:
Ventricular repolarization
71
P-R interval:
Beginning of atrial excitation to beginning of ventricular excitation
72
S-T segment:
Entire ventricular myocardium depolarizes
73
Q-T interval:
Beginning of ventricular depolarization through ventricular repolarization
74
What are the two heart sounds?
Lub-dub
75
Heart sound one:
As AV valves close, beginning of systole
76
Heart sound 2:
as semilunar valves close, beginning of ventricular diastole
77
Heart murmur:
Abnormal heart sounds ; usually indicate incompetent or stenotic valves
78
What is the cardiac cycle(mechanical events)?
- blood glow through the heart during one complete heartbeat; atrial systole and diastole followed by ventricular systole and diastole
- systole : contraction
- diastole : relaxation
- series of pressure and blood volume changes
79
1. Ventricular filling:
Takes place in mid to late diastole
▪️AV valves are open ; pressure low
▪️80% of blood passively flows into ventricles
▪️atrial systole occurs ;delivering remaining 20%
▪️end diastolic volume : volume of blood in each ventricle at end of ventricular diastole
80
2. Ventricular systole:
▪️atria relax; ventricles begin to contract
▪️rising ventricular pressure ➡️ closing of AV valves
▪️isovolumetric contraction phase(all valves are closed)
▪️in ejection phase , ventricular pressure exceeds pressure in large arteries, forcing SL valves to open
▪️end systolic volume ; volume of blood remaining in each ventricle after systole
81
3. Isovolumetric relaxation :
Early diastole
▪️ventricles relax ; atria relaxed and filling
▪️backflow of blood in aorta and pulmonary trunk closes SL valves
-causes dicrotic notch (brief rise in aortic pressure as blood rebounds off closed valve)
-ventricles totally closed chambers
▪️when atrial pressure exceeds that in ventricles ➡️ AV valves open ; cycle begins again at step 1
82
Cardiac output:
▪️volume of blood pumped by each ventricle in one minute
▪️CO= heart rate x stroke volume
-number of beats per minute
- volume of blood pumped out by one ventricle with each beat
▪️normal 5.25 L/minute
83
Cardiac output at rest:
▪️CO (ml/min) = HR (75beats/min) x SV (70ml/ beat) = 5.25 L/min
▪️CO increases if either/ both SV OR HR increased
▪️maximal CO is 4-5 times resting CO nonathletic people
▪️maximal CO May reach 35 L/min in trained athletes
▪️cardiac reserve- difference between resting and maximal CO
84
Cardiac reserve:
Difference between resting and maximal CO
85
regulation of stroke volume:
▪️SV= EDV-ESV
- EDV affected by length of ventricular diastole and venous pressure
- ESV affected by arterial BP and force of ventricular contraction
86
What 3 main factors affect SV?
Preload
Contractibility
After load
87
Preload:
Degree of stretch of cardiac muscle cells before they contract (Frank-Starling law of heart)
▪️cardiac muscle exhibits a length -tension relationship
▪️at rest, cardiac muscle cells shorter than optimal length
▪️MOST IMPORTANT factor stretching cardiac muscle is VENOUS RETURN - amount of blood returning to the heart.
-slow heartbeat and exercise increase venous return
-increased venous return distends (stretches ) ventricles and increases contraction force
88
Contractibility:
Contractile strength at given muscle length, independent of muscle stretch and EDV
▪️Increased by: sympathetic stimulation ➡️ increased Ca2+ influx➡️more cross bridges
-positive inotropic agents : thyroxine, glucagon, epinephrine, digitalis, high extracellular Ca2+
▪️decreased by negative inotropic agents
- acidosis, increased extracellular K+ , calcium channel blockers
89
After load:
Pressure ventricles must overcome to eject blood
90
What is the result of hypertension increasing after load?
Resulting in increased ESV and reduced SV
91
Positive chronotropic factors do what to heart rate?
⬆️ heart rate
92
Negative chronotropic factors do what to heart rate?
⬇️ heart rate
93
How is the sympathetic nervous system activated?
By emotional or physical stressors
94
Which hormone causes sympathetic nervous system to activate?
Norepinephrine
95
What does norepinephrine do in the sympathetic nervous system?
Causes pacemaker to fire more rapidly (increases Contractility)
- binds to B1- adrenergic receptors ➡️ increase HR
- ⬆️ Contractility ; faster relaxation
- offsets lower EDV de to decreased fill time
96
Which hormone in the parasympathetic nervous system effects the heart rate?
Acetylcholine
97
What does acetylcholine do in the parasympathetic nervous system ?
Hyperpolarizes pacemaker cells by opening the K+ channels ➡️ slower HR
- little to no effect on Contractility
- heart at rest exhibits Vaal tone
- parasympathetic dominant influence
98
What is the atrial (brain bridge ) reflex?
Sympathetic reflex initiated by increased venous return, hence increased Atrial filling
- stretch of atrial walls stimulates the SA node ➡️ increase HR
- also stimulates atrial stretch receptors, activating sympathetic reflexes
99
What two hormones affect chemical regulation of heart rate?
Epinephrine
And
Thyroxine
100
Epinephrine chemical regulation for heart rate?
From adrenal medulla increased heart rate and Contractility
101
Thyroxine for chemical regulation of heart rate?
Increases heart rate; and enhances effects of norepinephrine and epinephrine
102
Intra- and extracellular ion concentrations must be maintained for normal heart function ? True or false
True
103
Hypocalcemia:
Depresses heart
104
Hypercalcemia:
Increased HR and Contractility
105
Hyperkalemia:
Alters electrical activity ➡️heart block and cardiac arrest
106
Hypokalemia:
Feeble heartbeat arrhythmias
107
Does a fetus have a faster or slower heart rate?
Faster
108
Does a male or females heart beat faster?
Female
109
Does exercise increase heart rate?
Yes
110
Does body temperature increase heart rate?
Yes
111
Tachycardia:
Abnormally fast heart rate over 100bpm
112
Bradycardia:
Slow heart rate less than 60 bpm.
-results in inadequate blood flow
-desirable for endurance training
113
Congestive heart failure (CHF):
▪️progressive condition ; CO is so low that blood circulation is inadequate to meet tissue needs
▪️reflects weakened myocardium caused by :
-coronary atherosclerosis (clogged arteries)
- persistent HBP
-multiple myocardial infarcts
-dilated cardiomyopathy (DCM)
114
What is pulmonary congestion?
Left side fails ➡️ blood backs up in Lungs
115
Peripheral congestion :
Right side fails ➡️ blood pools in body organs ➡️ edema
116
What are the four Embryonic heart chambers?
Sinus venous
atrium
Ventricle
Bulbus cordis
117
What does the ductus arteriosus do in fetal hearts?
Connects pulmonary trunk to aorta
| -remnant- ligamentum arteriosum in adult
118
Congenital heart defects:
▪️most common heart defects treated by surgery
▪️two types: mixing of oxygen-port and oxygen-rich blood (septal , patent duct)
And
Narrowed valves or vessels ➡️ increased workload on heart (coarctation of aorta)
▪️tetralogy of fallot : both types of disorders present
119
4 age related changes that affect the heart?
▪️sclerosis and thickening of valve flaps
▪️decline in cardiac reserve
▪️fibrosis of cardiac muscle
▪️atherosclerosis
