Chapter 18 - Heart Flashcards
(82 cards)
1
Q
the heart
beats and pumping
A
- Beats approx 100,000 times/day
- Pumping about 8000 L of blood/day
2
Q
when you get old
A
first thing that happens is the heart
3
Q
if heart is on the right side of body
A
you will die
4
Q
the pressure near the chest is
A
the highest. the lower you get (legs), the lower it gets.
5
Q
heart is inside a sack called
A
pericardium, has fluid.
6
Q
Ligamentum arteriosum
A
keeps aorta and pulmonary artery together
7
Q
everything that is returning is a
A
vein and everything that is leaving is an artery
8
Q
Visceral layer of serous pericardium (epicardium)
A
- covers surface of the heart
- covered by pericardium
9
Q
Myocardium
A
Cardiac muscle tissue
10
Q
endocardium
A
Covers inner surfaces of heart
11
Q
atrioventricular (AV) valves
A
Tricuspid and mitral valves
12
Q
semilunar valves
A
- Pulmonary and aortic valves
- Prevent backflow of blood into ventricles
13
Q
compared to the left ventricle, the right ventricle
A
Holds and pumps the same amount of blood
Has thinner walls bc it is the systemic circulation
Develops less pressure
Is more pouch-shaped than round
14
Q
low blood pressure in old people
A
swollen feet. heart not pumping hard enough
15
Q
we are using all our brains, but
A
we are never using all our heart capacity
16
Q
if theres high blood pressure, the first place it is going to effect is the
A
is the coronary arteries
17
Q
coronary circulation
A
Supplies blood to muscle tissue of heart
18
Q
Coronary ischemia
A
blood doesn’t reach a tissue and the coronary arteries get blocked and the cells die
19
Q
when coronary arteries are blocked, what do doctors do?
A
put in a stent
bypass. take arteries from other places
20
Q
coronary artery disease
A
clot/plaque narrows pathway and reduces blood flow
- common cause of MI
- coronary thrombosis
21
Q
Myocardial infarction (MI), or heart attack
A
- Part of coronary circulation becomes blocked
- Cardiac muscle cells die from lack of oxygen
- Infarct- Death of affected tissue creates a nonfunctional area
22
Q
heart is only tissue that
A
uses anything as source of fuel
23
Q
how to not get heart problems
A
- Stop smoking
- Treat high blood pressure
- Adjust diet to lower cholesterol and promote weight loss
- Reduce stress - cortisol affects heart
- Increase physical activity - heart becomes stronger
24
Q
propranolol
A
block sympathetic stimulation
block norepinephrine
25
nitroglycerine
cause vasodilation
| reduce blood pressure
26
calcium ion channel blockers
- Block calcium ion movement into muscle cells
| - Relieve pain and help dissolve clots (in MI)
27
Pacemaker cells found in
- Sinoatrial (SA) node—in wall of right atrium
| - Atrioventricular (AV) node—at junction between atria and ventricles
28
Conducting cells found in
- Internodal pathways of atria
| - Atrioventricular (AV) bundle, bundle branches, and Purkinje fibers of ventricles
29
what do you need to depolarize a cell?
electricity. need Na channels.
30
Pacemaker potential
-Gradual depolarization of pacemaker cells
-Do not have a stable resting membrane potential
Rate of spontaneous depolarization
-SA node: 60–100 action potentials per minute
-AV node: 40–60 action potentials per minute
Parasympathetic stimulation slows heart rate
31
Purkinje fibers
pass electricity to the myocardium
32
impulse conduction through heart
1. SA node activity and atrial activation begin
2. Stimulus spreads across atria and reaches AV node
3. Impulse is delayed for 100 msec at AV node
Atrial contraction begins
33
P wave
SA node fires, atria depolarization
34
QRS complex
Ventricular depolarization
| Complex shape of spike due to different thickness and shape of the two ventricles
35
T wave
Ventricular repolarization and relaxation
36
Bradycardia—
abnormally slow heart rate
37
Tachycardia—
abnormally fast heart rate
38
Ectopic pacemaker
| wire that goes to your SA node
Abnormal cells generate high rate of APs
Bypasses conducting system
Disrupts timing of ventricular contractions
39
Q wave
beginning of ventricular depolarization
40
P-R interval
conduction through AV node and AV bundle
41
membranes of adjacent junctions are
- Held together by desmosomes
| - Linked by gap junctions
42
characteristics of cardiac contractile cells
1 central nucleus
Branching interconnections between cells
Intercalated discs
43
Action potential in cardiac contractile cells
1. Rapid depolarization
Massive influx of Na+ through fast sodium channels.
2. Plateau
Extracellular Ca2+ enters cytosol through slow calcium channels. depolarization
3. Repolarization
K+ rushes out of cell through slow potassium channels
44
ACTH will
depolarize (voltage dependent channels) in the membrane and releases ca in cytoplasm
45
```
Ca 2+
Ca 2+
Na
K
HCN channels
```
```
L type
T type
fast
slow
slow
```
46
Refractory period
Absolute refractory period (200 msec)
| Relative refractory period (50 msec)
47
Action potential in a ventricular contractile cell
- 250–300 msec
- 30x longer than that in skeletal muscle fiber
- Prevents summation and tetany
48
in the heart it is a
slow climbing of contraction and relaxation
49
energy for cardiac contractions
Aerobic energy
- From mitochondrial breakdown of fatty acids and glucose
- Cardiac contractile cells store oxygen in myoglobin
50
Cardiac cycle
- From start of one heartbeat to beginning of next
| - alternating periods of contraction and relaxation
51
systole
contraction
52
diastole
relaxation
53
blood pressure in each chamber
Rises during systole
| Falls during diastole
54
Blood flows from an area of higher pressure to lower pressure
- Controlled by timing of contractions
| - Directed by one-way valves
55
cardiac cycle and heart rate
when heart rate increases?
-Cardiac cycle lasts about 800 msec
When heart rate increases
-All phases of cardiac cycle shorten, particularly diastole
56
phases of cardiac cycle
1. start a atrial systole
blood is entering both atrials and ventricles. systemic-unoxygenated, right atria, right ventricle, enters lungs, gets oxygenated (arteries). pulmonary veins into left atria and left ventricle into systemic circulation
57
two main things that fills ventricles w blood?
- atria systole
| - passive --> vacuum
58
first its atrial systole then
```
Atrial systole ends
Atrial diastole begins
-Ventricles contain maximum blood volume (called end-diastolic volume (EDV))
Ventricles contract and build pressure
-Closing AV valves
-Producing isovolumetric contraction
```
59
ventricular systole phase
ventricular diastole-early
Ventricular systole phase
-Ventricular pressure exceeds arterial pressure and opens semilunar valves, allowing blood to exit
Ventricular diastole-early
-Semilunar valves close as ventricular pressure falls
-Ventricles contain end-systolic volume (ESV)
-About 40% of end-diastolic volume
60
when the ventricles are filling that means
they are not contracting, they are relaxing
61
3 things that affect heart conditions
1. males have bigger hearts
2. age
3. hormonal
62
after ventricular diastole-early is
| Ventricular diastole- late
Isovolumetric relaxation
-All heart valves are closed
-Ventricular pressure is higher than atrial pressure (Blood cannot flow into ventricles)
AV valves open; ventricles fill passively
-Atrial pressure is higher than ventricular pressure
63
what can lead to heart failure?
ventricular damage
| Individuals can survive severe atrial damage
64
cardiac output CO
Volume pumped by left ventricle in one minute
| CO (mL/min) = HR (beats/min) × SV (mL/beat)
65
your heart pumps how many L per min?
5 liters. during exercise, 25-35 liters.
66
factors that affect heart rate?
1. autonomic innervation
| 2. hormones (epinephrine and thyroxine)
67
factors that affect stroke volume?
1. end diastolic volume
| 2. end systolic volume
68
Autonomic innervation
- Cardioacceleratory center-controls sympathetic neurons that increase heart rate
- Cardioinhibitory center-controls parasympathetic neurons that slow heart rate
69
cardiac reflexes
Cardiac centers
- Monitor blood pressure (baroreceptors)
- Monitor arterial O and CO2 levels (chemoreceptors)
70
Autonomic tone
-Fine adjustments meet needs of body
71
Effects on pacemaker cells of SA node
ACh
NE
```
Membrane potentials of pacemaker cells
Are closer to threshold than those of cardiac contractile cells
ACh released by parasympathetic neurons
Decreases heart rate
NE released by sympathetic neurons
Increases heart rate
```
72
venous return
Amount of blood returning to heart through veins
-Stretch receptors in right atrium
Trigger increase in HR by stimulating sympathetic activity
73
HR increased by 3 factors
Epinephrine (E)
Norepinephrine (NE)
Thyroid hormone (T3)
74
Two factors affect EDV
Filling time
-Duration of ventricular diastole
Venous return
75
preload
Degree of ventricular stretching during ventricular diastole
Directly proportional to EDV
Affects ability of muscle cells to produce tension
76
frank starling
when edv increases, SV increases
77
afterload
Tension produced by ventricle to open semilunar valve and eject blood
78
increase in contractility is a
decrease in ESV
79
cardiac reserve
difference bw resting and maximal cardiac outputs
80
ejection fraction
SV/EDV
81
venous return controls
EDV, SV, CO
82
veins hold most of
blood. app. 70%
