Chapter 14: Cardiovascular Physiology Flashcards
1
Q
- the heart
- blood vessels
- blood
A
cardiovascular system
2
Q
what does the cardiovascular system transport?
A
- oxygen & nutrients to cells
- wastes from cells
- hormones, immune cells, and clotting proteins to specific target cells
3
Q
what is the flow of blood through the cardiovascular system?
A
heart–> arteries–> arterioles—> capillaries –> venules–> veins–> heart
4
Q
large, branching vessels taking blood away from the heart
A
arteries
5
Q
small branching vessels with high resistance
A
arterioles
6
Q
site of exchange between blood and tissue
A
capillaries
7
Q
small converging vessels
A
venules
8
Q
relatively large converging vessels that conduct blood to the heart
A
veins
9
Q
is the cardiovascular system open or closed?
A
closed system
10
Q
what does the blood consist of?
A
- erthyrocytes (RBC)
- leukocytes (WBC)
- platelets
- plasma
11
Q
- red blood cells
- transport oxygen and carbon dioxide
A
erythrocytes
12
Q
- white blood cells
- defend body against pathogens
A
leukocytes
13
Q
- cell fragments
- important in blood clotting
A
platelets
14
Q
fluid and solutes
A
plasma
15
Q
- supplied by right heart
- blood vessels from heart to lungs, and from lungs to heart
- oxygen diffuses from tissues to blood
A
pulmonary circuit
16
Q
- supplied by left heart
- blood vessels from heart to systemic tissues, and from tissues to heart
- oxygen diffuses from blood to tissues
A
systemic circuit
17
Q
how is the flow of blood through systemic and pulmonary circuits?
A
its in series
18
Q
what is the path of blood in the circuits?
A
Left ventricle → aorta → systemic circuit → vena cavae → right atrium right ventricle → pulmonary artery → pulmonary circuit → pulmonary veins → left atrium → left ventricle
19
Q
- located in thoracic cavity
- weighs 250-350 grams
A
heart
20
Q
separates the abdominal cavity from the thoracic cavity
A
diaphragm
21
Q
- Membranous fluid-filled sac surrounding the heart
- Lubricates the heart and decreases friction
A
pericardium
22
Q
what are the 3 layers of the heart wall?
A
- epicadium
- myocardium
- endothelium
23
Q
external membrane of heart wall
A
epicardium
24
Q
- middle layer of heart wall
- cardiac muscle
A
myocardium
25
- inner layer of heart wall
| - layer of endothelial cells
endothelium
26
drives blood flow
pressure difference (high pressure to low pressure)
27
what is the normal direction of blood flow?
- atria to ventricles
| - ventricles to arteries
28
- prevent backward flow of blood
| - open passively based on pressure gradient
valves
29
what are the two main valves of the heart?
- Atrioventricular (AV) valves
| - semilunar valves
30
tricuspid valve
Right AV valve
31
bicuspid valve = mitral valve
Left AV valve
32
Keep AV valves from being pushed back into atrium
Papillary muscles and chordae tendineae
33
- aortic valve
| - pulmonary valve
semilunar valves
34
what happens when the ventricles are relaxed?
| AV valves
blood enters the atria, pushing the atrioventricular valve cusps down into the ventricles, opening the valves
35
what happens when the ventricles contract?
| AV valves
blood presses up against the atrioventricular valve cusps, forcing the valves closed
36
what happens when papillary muscles contract?
tightens the chordae tendineae, preventing the
| valve cusps from being pushed into the atria
37
are the AV valves open or closed during ventricular contraction?
AV valves remain closed
to prevent blood flow
backward into the atria.
38
what happens when the ventricles contract?
| semilunar valves
blood presses up against the semilunar valve cusps, forcing the valves open and allowing blood to flow into the aorta and pulmonary
artery
39
what happens when the ventricles relax?
| semilunar valves
blood in the aorta and pulmonary artery presses down against the valve cusps, forcing them to close
40
prevent blood that has entered the arteries from flowing back into the ventricles during
ventricular relaxation.
semilunar valves
41
ensured by the two sets of valves
one-way flow of blood through the heart
42
drive blood flow from high pressure to low pressure
pressure gradients
43
flow due to pressure gradients
bulk flow
44
creates a pressure gradient for bulk flow of blood
the heart
45
what must exist in the circulatory system to maintain blood flow?
a gradient
46
the force exerted by blood
pressure
47
in which direction does blood flow occur?
from high pressure to low pressure
48
the force pushing blood against the various factors resisting the flow of liquid in a pipe
ΔP
49
what is flow proportional to?
ΔP
50
- the pressure exerted on the walls of the container by the fluid within the container
- proportional to the height of the water column
hydrostatic pressure
51
- depends on the pressure gradient
| - only if there is a positive pressure gradient (ΔP)
fluid flow through a tube
52
depends on the pressure gradient (ΔP), not the absolute pressure (P)
blood/fluid flow
53
is the pressure gradient greater in the systemic circuit or the pulmonary circuit?
it is much greater in the systemic circuit
54
is the flow greater in the systemic or pulmonary circuit?
flow is equal in both circuits
55
=ΔP/R
flow
56
is resistance less in the pulmonary or systemic circuit?
resistance through the pulmonary circuit is much less than resistance through the systemic circuit
57
inversely proportional to resistance
flow through a tube
58
what happens if resistance increases?
flow decreases
59
what happens if resistance decreases?
flow increases
60
- Resistance is proportional to length (L) of the tube (blood vessel)
- Resistance is proportional to viscosity (), or thickness, of the fluid (blood)
- Resistance is inversely proportional to tube radius to the (coffee straw)
Poiseuille’s Law
61
proportional to length (L) of the tube (blood vessel)
resistance
-Resistance increases as
length increases (long
straw)
62
proportional to viscosity (), or thickness, of the fluid (blood)
resistance
-Resistance increases as
viscosity increases
(milkshake)
63
inversely proportional to tube radius to the (coffee straw)
resistance
-Resistance decreases
as radius increases
64
has a large effect on resistance to blood flow (flow rate)
small change in radius of blood vessel
65
- decrease in blood vessel diameter/radius
| - decreases blood flow
vasoconstriction
66
- increase in blood vessel diameter/radius
| - increases blood flow
vasodilation
67
the volume of blood that passes a given point in the system per unit time (how much)
flow rate
68
the distance a fixed volume of blood travels in a given period of time (how fast)
velocity of flow
69
when is velocity directly related to flow rate?
when the tube has a fixed diameter
70
when does the velocity varies inversely with diameter?
when the tube has a variable diameter
71
faster in narrow sections
velocity of blood flow
72
slower in wider sections
velocity of blood flow
73
what does cardiac muscle consist of ?
- contractile cells
| - autorhythmic cells (pacemakers)
74
Striated fibers organized into sarcomeres
contractile cells
75
- Signal for contraction
| - Do not have organized sarcomeres
Autorhythmic cells, or pacemakers
76
branched, have a single nucleus, and are attached to each other by specialized junctions known as intercalated disks.
myocardial muscle
77
contain desmosomes
| that transfer force from cell to cell, and gap junctions that allow electrical signals to pass rapidly from cell to cell
intercalated discs
78
- Spontaneously depolarizing membrane potentials generate action potentials
- Coordinate and provide rhythm to heartbeat
pacemaker cells
79
- Rapidly conduct action potentials initiated by pacemaker cells to myocardium
- Conduction velocity = 4 meters/second
conduction fibers
80
- Sinoatrial node
* Pacemaker of the heart
- Atrioventricular node
pacemaker cells of the myocardium
81
what are the conduction fibers of the myocardium?
- Internodal pathways
- Bundle of His
- Purkinje fibers
82
- Sets the pace of the heartbeat at 70 bpm
| - AV node (50 bpm) and Purkinje fibers (25–40 bpm)
sinoatrial (SA) node
83
Routes the direction of electrical signals so the heart contracts from apex to base
Internodal pathway from SA to atrioventricular (AV) node
84
- SA node → right atrium → left atrium
- rapid
- Simultaneous contraction of right and left atria
interatrial pathway
85
-SA node → AV node
internodal pathway
86
- Only pathway from atria to ventricles
- Slow conduction: AV nodal delay = 0.1 sec
- Atria contract before ventricles
AV node transmission
87
how does ventricular excitation occur?
- Down bundle of His
- Up Purkinje fibers
- Purkinje fibers contact ventricle contractile cells
- Ventricle contracts from apex up
88
what is the conduction system of the heart?
SA node-->internodal pathways--> AV node-->AV bundle--> bundle branchea-->purkinje fibers
89
how do pacemakers control the heartbeat?
- autorhythmic cells
- spontaneous depolarization
- depolarize to threshold
- repolarization
90
have pacemaker potentials
autorhythmic cells
91
**caused by closing K+ channels and opening two types of channels
-Na+ funny channels (If):
net depolarization
-Ca2+ channels (T-type):
further depolarization
spontaneous depolarizations
92
how is the heart depolarized to threshold?
Open fast Ca2+ channels(L-type): action potential
93
how is the heart repolarized?
open K+ channels
94
gradually becomes less negative until it reaches threshold, triggering an action potential
pacemaker potential
95
- Depolarization due to Na+ entry
- Repolarization due to K+ exit
- Long action potential (plateau) due to Ca2+ entry in the cell prevents tetanus
myocardial contractile cells
96
lasts almost as long as the entire muscle twitch
refractory period in cardiac muscle fiber
97
prevents tetanus
long refraction period in cardiac muscle
98
refractory period is very short compared with the amount of time required for the development of tension
skeletal muscle fast-twitch fiber
99
if they are stimulated repeatedly, it will exhibit summation and tetanus
skeletal muscles
100
how does cardiac muscle compare to skeletal muscle?
- smaller & have single nucleus per fiber
- branch & join neighboring cells through intercalated disks (desmosomes & gap junctions)
- T-tubules are larger & branch
- sarcoplasmic reticulum is smaller
- mitochondria occupy 1/3 of cell volume
101
allow force to be transferred
desmosomes
102
provide electrical connection
gap junctions
103
how is excitation-contraction coupling in cardiac muscle similar to properties of skeletal muscle?
- T-tubules
- Sarcoplasmic reticulum Ca2+
- Troponin-tropomyosin regulation
104
how is excitation-contraction coupling in cardiac muscle similar to properties of smooth muscle?
- gap junctions
| - Extracellular Ca2+
105
what are the steps of excitation-contraction coupling of the heart?
1. Depolarization of cardiac contractile cell to threshold via gap junction
2. Opening of calcium channels in plasma membrane
3. AP travels down T tubules
4. Calcium is released from sarcoplasmic reticulum
5. Calcium binds to troponin, causing a shift in tropomyosin
6. Binding sites for myosin on actin are exposed
7. Crossbridge cycle occurs
106
how is calcium released from sarcoplasmic reticulum?
- calcium-induced calcium release
| - action potentials in T tubules
107
- Provides information on heart rate and rhythm, conduction velocity, and even the condition of tissues in the heart.
- has waves and sements
electrocardiogram
108
what are the components of an electrocardiogram?
- P wave
- QRS complex
- T wave
- PR segmet
109
shows atrial depolarization
P wave
110
shows ventricular depolarization and atrial repolarization
QRS complex
111
shows ventricular repolarization
T wave
112
- shows AV nodal delay
| - conduction through AV nodes and AV bundle
PR segment
113
what does an upward deflection on an ECG mean?
means the current flow vector is toward the positive electrode
114
what does a downward deflection on an ECG mean?
the current flow vector is toward the negative electrode
115
what does no deflection on an ECG mean?
the vector is perpendicular to the axis of the electrode
116
- lag behind electrical events
| - contraction follows action potential
mechanical events
117
begins with atrial depolarization, atrial contraction at the end of P wave
ECG
118
goes through AV node and AV bundle
PR segment signal
119
ventricular contraction begins and continues through T wave
Q wave end
120
- loss of conduction through the AV node
- P wave becomes independent of QRS
- atrial and ventricular contractions are independent
third degree heart block
121
- loss of coordination of electrical activity of the heart
| - death can ensue within minutes unless corrected
ventricular fibrillation
122
-Events associated with the flow of blood through the heart during a single complete heartbeat
cardiac cycle
123
what are the two main periods of the cardiac cycle?
- systole: ventricle contraction
| - diastole: ventricle relaxation
124
open passively due to pressure gradients
valves
125
open when atrial pressure > ventricular pressure
AV valves
126
open when ventricular pressure > arterial pressure
semilunar valves
127
what are the phases of the cardiac cycle?
1. Ventricular filling
2. isovolumetric ventricular contraction
3. ventricular ejection
4. Isovolumetric ventricular relaxation
128
- Middle of ventricular diastole
- Venous return
- AV valve opens
- Blood moves from atria to ventricle
- Pulmonary and aortic valves are closed
- Passive until atrium contracts
ventricular filling
129
- start of systole
- ventricle contracts-increases pressure
- AV & semilunar valves closed
- no blood entering or exiting the ventricles
Isovolumetric ventricular contraction
130
- Remainder of systole
- Pressure in ventricles > pressure in arteries
- Semilunar valves open
- Ventricular pressure < aortic pressure
- Semilunar valves close
ventricular ejection
131
- Onset of diastole
- Ventricle relaxes—decreases pressure
- AV and semilunar valves closed
- No blood entering or exiting ventricle
Isovolumetric ventricular relaxation
132
- Atrial pressure rises slowly with filling of blood
- Ventricular pressure is low
- Small rise in VP at end due to atrial contraction
Phase 1
133
- Rapid rise in ventricular pressure
| - Atrial pressure falls
Phase 2
134
- Ventricular pressure falls
| - Atrial pressure falls further until late systole
Phase 3
135
- Aortic valve closes
- Blood is still leaving aorta, so pressure falls
- Lowest point = diastolic pressure
Diastole
136
- Aortic valve opens
- Pressure rises rapidly with ejection
- Highest point = systolic pressure
- Aortic valve closes
- Backflow of blood causes slight increase—dicrotic notch
systole
137
- maintains blood flow through the entire cardiac cycle
| - continuous blood flow during cardiac cycle
aortic pressure
138
- elastic
- pressure reservoir
- stores energy during systole as walls expand
- releases energy during diastole as walls recoil inward
aorta (and large arteries)
139
Volume of blood in ventricle at the end of diastole
EDV: end-diastolic volume
140
Volume of blood in ventricle at the end of systole
ESV: end-systolic volume
141
-Volume of blood ejected from ventricle each cycle
=EDV-ESV
=130 mL-60 mL = 70 mL
SV: stroke volume
142
-fraction of end-diastolic volume ejected during a heartbeat
=stroke volume/end diastolic volume
=70 mL/130 mL = 0.54 (i.e. 54% at rest)
ejection fraction (EF)
143
-Volume of blood pumped by each ventricle per minute
=SV x HR
cardiac ouotput
144
- average= 5liters/min at rest
| - 72 beats min x 0.07 L/beat = 5.0 L/min
cardiac output
145
average blood volume of cardiac output
5.5 liters
146
determined by SA node firing frequency
heart rate
147
SA node intrinsic firing rate
100/min
148
is there extrinsic control on the heart from the SA node?
no, HR=100
149
under control of ANS and hormones
SA node
150
- at rest
| - HR=75
parasympathetic system dominates
151
- excitement
| - HR increases
sympathetic system takes over
152
what does the Activity of sympathetic neurons projecting to SA node do to the HR?
raises HR
153
what does the Activity of parasympathetic neurons projecting to SA node do to the HR?
lowers HR
154
what do levels of circulating epinephrine do to the HR?
raises HR
155
what does stimulation by the parasympathetic nerves do to the heart rate?
decreases heart rate
156
what does stimulation by sympathetic nerves do to the heart rate?
increases heart rate
157
how does increased sympathetic activity come about?
nerves or epinephrine--> beta 1 receptors in SA node --> increase open state of I_f and Ca2+ channels--> increase rate of spontaneous depolarization--> increase heart rate
158
depolarize the autorythmic cell and speed up the pacemaker potential, increasing the heart
sympathetic stimulation
159
what does increased parasympathetic activity do?
vagus nerve-->muscarinic cholinergic receptors in SA node-->increase open state of K+ channels & closed sate of Ca2+ channels---> decrease rate of spontaneous depolarization & hyperpolarize cell ---> decrease heart rate
160
hyperpolarizes the membrane potential of the autorhythmic cell & slows depolarization, slowing down the heart rate
parasympathetic stimulation
161
what are the primary factors affecting stroke volume?
- ventricular contractility
- end-diastolic volume
- afterload
162
how does ventricular contractility affect stroke volume?
-a more forceful contraction will expel more blood
163
what is involved in the sympathetic control of ventricular contraction?
- sympathetic innervation of muscle cells
| - Norepinephrine → β1 adrenergic receptors → cAMP second-messenger system
164
what are the steps involved in norepinephrine leading to the CAMP second messenger system?
1. Augment open Ca2+ channels
2. Increase Ca2+ release from sarcoplasmic reticulum (SR)
3. Increase myosin ATPase rate
4. Enhance rate of Ca2+ -ATPase activity on SR
165
what is the influence of end-diastolic volume on stroke volume?
***starlings law
-Increased EDV
stretches muscle fibers
-Fibers closer to optimal
length
-Optimal length →
greater strength of
contraction
-Result → increased SV---
--> increase venous
return-----> increase
strength of contraction--
--> increase stroke
volume
166
what does an increase in EDV cause?
stroke volume to increase
167
what are the factors affecting end-diastolic volume?
- end diastolic pressure
- filling time
- atrial pressure
- central venous pressure
- afterload
168
preload
end-diastolic pressure
169
pressure in aorta during ejection
afterload
