Chapter 30 Flashcards
1
Q
What is hemodynamics?
A
-mechanisms that influence the changing circulation of blood to maintain the body’s internal environment
2
Q
What must the mechanisms of hemodynamics accomplish?
A
- maintain circulation
- vary the volume and distribution of blood circulated
3
Q
How does blood move?
A
-from high-pressure area to low-pressure area
4
Q
Which of Newton’s laws apply to circulation? What do they mean?
A
- 2nd laws of motion
- fluid does not flow when the pressure is the same throughout
- high to low pressure
5
Q
Where is blood pressure at its highest? Lowest?
A
- Highest: aorta
- Lowest: superior and inferior vena cava
6
Q
Why does blood pressure change in this direction?
A
- flow resistance
- resistance to flow increases away from the aorta
7
Q
Where does the biggest change in blood pressure occur?
A
-arterioles
8
Q
What influences blood pressure?
A
- cardiac output
- peripheral resistance
9
Q
What is cardiac output?
A
-the amount of blood that flows out of a ventricle of the heart per unit of time
10
Q
What is resting cardiac output?
A
- 5000 ml per min
- 5 liters per min
11
Q
What determines cardiac output?
A
- stroke volume
- heart rate
12
Q
What is stroke volume?
A
-the volume of blood pumped out by each beat
13
Q
What influences stroke volume?
A
- inotropic factors
- stretch of heart
- neural factors
- endocrine factors
- cardiac afterload
14
Q
What is contractility?
A
-strength of contraction
15
Q
What is cardiac afterload? How does it affect stroke volume?
A
- the work required to push blood into the arteries
- reduces stroke volume
16
Q
What normally controls heart rate?
A
-SA node
17
Q
What does the parasympathetic nervous system do to heart rate?
A
- decreases the heart rate
- acetylcholine
18
Q
What does sympathetic nervous system do to heart rate?
A
- increases the heart rate
- norepinephrine
19
Q
What are baroreceptors?
A
- they detect blood pressure
- detect stretch
20
Q
What are cardiac pressoreflexes?
A
-receptors sensitive to changes in pressure
21
Q
Where do you find the baroreceptors for cardiac pressoreflexes?
A
- aortic baroreceptors
- carotid baroreceptors
22
Q
How does the carotid sinus reflex work?
A
- small dilation at the beginning of the internal carotid artery
- detects an increase in blood pressure
23
Q
How does the aortic reflex work?
A
- contains baroreceptors in the wall of the aorta
- send afferent fibers to the cardiac control center via the vagus nerve
- detects an increase in blood pressure
24
Q
What other factors influence heart rate?
A
- exercise
- emotions
- hormones
- blood temperature
- pain (slows)
25
How do you calculate cardiac output?
-stroke volume x heart rate
26
What is peripheral resistance?
- resistance to blood flow due to friction between blood and the walls of the vessels
- partially due to viscosity and small diameter of arterioles and capillaries
27
How does an increase in peripheral resistance affect blood pressure?
-the more resistance, the higher the blood pressure
28
What influences peripheral resistance?
- blood viscosity: increased hematocrit and protein molecules
- diameter of capillaries and arterioles
- vasoconstriction and vasodilation
29
What is viscosity?
-blood thickness
30
How does viscosity affect peripheral resistance?
-increase in viscosity causes increase in peripheral resistance causes increase in blood pressure
31
What is the viscosity of blood in someone who is severely anemic?
-lower due to the low levels of hematocrit in their blood
32
What is the vasomotor mechanism?
- smooth muscle control over the diameter of vessels
| - changes the amount of resistance
33
What is vasoconstriction?
- reduction in vessel diameter
| - 1/2 cm
34
How does vasoconstriction affect peripheral resistance?
-increases resistance
35
How does vasoconstriction affect the blood flow to that area?
-the blood flow to that area will decrease
36
What controls vasoconstriction or vasodilation?
- vasomotor control mechanism
| - medulla
37
What is vasodilation?
- increase in vessel diameter
| - 2 cm
38
How does vasodilation affect peripheral resistance?
-decreases resistance
39
How does vasodilation affect the blood flow to that area?
-the blood flow to that area will increase
40
What are blood reservoirs?
- venous networks and sinuses in the skin and abdominal organs (liver and spleen)
- NOT in skeletal muscle, heart, or brain
41
What is the importance of blood reservoirs?
-serves as a slowly moving reserve of blood
42
What activates the vasomotor mechanism?
- change in blood pressure (vasomotor pressoreflexes)
| - blood's oxygen or carbon dioxide content (vasomotor chemoreflexes)
43
Where are vasomotor pressoreflexes found?
-in the internal carotid and aorta
44
What do vasomotor pressoreflexes detect?
-sends information about blood pressure to the medulla
45
What happens if vasomotor pressoreflexes detect high/low blood pressure?
- high bp = inhibition of sympathetic fibers = vasodilation
| - low bp = more sympathetic fibers = vasoconstriction
46
Where are vasomotor chemoreflexes found?
-located in the aortic and carotid bodies
47
What are vasomotor chemoreflexes most sensitive to?
- hypercapnia
| - excess of carbon dioxide in the blood
48
What is it called when there is a decrease of oxygen in the blood?
-hypoxia
49
What affect will these vasomotor chemoreflexes have if they detect hypercapnia?
- constrict reservoir vessels
- increase heart rate
- increase stroke volume
50
What is the medullary ischemic reflex?
-when blood flow to the brain drops below normal
51
What can manipulate the vasomotor centers in the medulla?
- cerebral cortex
- hypothalamus
- in response to fear or anger
52
What is venous return?
-the amount of blood returned to the heart by veins
53
What influences venous return?
- reservoir function of veins
- blood pressure
- gravity
54
What is the orthostatic effect?
-when blood remains in the veins of limbs due to too low of a blood pressure
55
What are venous pumps?
-promotes the return of venous blood
56
What mechanisms work as a venous pump?
- respiration
| - skeletal muscle contractions
57
How do respirations work as a venous pump?
- each time the diaphragm contracts, the thoracic cavity becomes larger
- pressure alternates between the abdominal and thoracic cavity
58
How do skeletal muscle contractions work as a venous pump?
- as each skeletal muscle contracts, it squeezes the soft veins scattered within it
- blood moves towards the heart
59
What is total blood volume?
- the total amount of blood flowing through the body
| - affected by the amount of water in your blood and osmolarity
60
What is capillary exchange?
-the exchange of materials between plasma in the capillaries and surrounding interstitial fluid of systemic tissues
61
What influences capillary exchange?
- osmotic pressure
| - hydrostatic pressure
62
What is hydrostatic pressure?
-the pressure the blood exerts against a blood vessel wall
63
How does hydrostatic pressure in arteries differ than that in veins? How does this affect capillary exchange?
- arteries have a really high blood pressure = high hydrostatic pressure
- veins have a lower blood pressure = low hydrostatic pressure but high osmotic pressure
- loses water but everything else stays; reabsorbs at end of the capillary
64
What is osmotic pressure?
- the concentration of solutes in one solution vs another solution that doesn't
- causes water to want to move to the highly concentrated area
65
How does osmotic pressure in arteries differ than that in veins?
- arteries have a low osmotic pressure
| - veins have a high osmotic pressure
66
What hormones influence changes in blood volume?
- antidiuretic hormone
- renin-angiotension-aldosterone system
- atrial natriuretic hormone
67
How does ADH affect blood volume?
- released by the posterior pituitary gland
- controls water movement
- increases water absorbed = increases blood pressure
68
How does the RAAS affect blood volume?
- kidney detects low bp and secretes renin
- renin circulates and causes angiotensinogen to become angiotensin 1
- angiotensin 1 circulates to lungs
- angiotensin-converting enzyme (ACE) converts AG1 to AG2
- angiotensin 2 causes vasoconstriction (causes increase in bp) and causes adrenal cortex to secrete aldosterone
- aldosterone causes reabsorption of sodium in kidneys (causes increase in osmotic pressure so water is also reabsorbed)
69
How does ANH affect blood volume?
- secreted by the atria of the heart
- lowers bp
- causes sodium loss which lowers osmotic pressure which lowers blood volume
70
How do you measure blood pressure?
- sphygmomanometer
| - measures arterial bp
71
What does the first sound mean? Second?
- first: heart at work (systole); amount of ventricular contraction
- second: heart at rest (diastole); resistance of blood vessels
72
What are korotkoff sounds?
-the sounds that you hear while listening to bp
73
What is a normal blood pressure reading?
-120/80
74
What is hypertension?
-high blood pressure
75
What is hypotension?
-low blood pressure
76
What is mean arterial pressure?
-average blood pressure in arteries
77
How do you calculate mean arterial pressure?
-[(2 x diastolic pressure) + systolic pressure] / 3
78
What is a normal mean arterial pressure?
-70mm - 110mm
79
What is an abnormal mean arterial pressure? What could this mean?
- below 70
| - hypotension; blood isn't circulating throughout the entire body
80
How does blood bleed differently in arteries, veins, and capillaries?
- gushing in arteries
- pooling in veins
- dripping in capillaries
81
What is velocity of blood flow?
-the rate at which blood flows in different parts of the blood vessels
82
What does velocity of blood depend on?
-the speed of blood flow depends on the cross-sectional size of one area compared to another
83
How does velocity of blood change from arteries to arterioles to capillaries to venules to veins?
- fast in arteries, slow in arterioles
- slower in capillaries than in arterioles
- venules flow faster than capillaries
- veins flow slower than venules
84
Where is blood flowing the fastest? Slowest?
- fastest: aorta or arteries
| - slowest: capillaries
85
What is pulse?
-the alternate expansion and recoil of an artery
86
What causes you to feel pulse?
- intermittent injections of blood from the heart to the aorta
- elasticity of arterial walls
87
What is being represented by the expansion of the arterial wall?
-when ventricle contracts
88
What is being represented by the recoil of the arterial wall?
-when ventricle relaxes
89
What is a pulse wave?
-ventricular systole starts a new pulse which proceeds as a wave of expansion
90
The __________ from the heart, the ________ the interval between systole and feeling a pulse.
- farther
| - longer
91
How does the elasticity of arteries affect circulation?
- conserves energy
- gives the arteries potential energy
- recoil will exert pressure on the blood to keep it moving
92
What are the common sites for finding a pulse?
- radial
- temporal
- common carotid
- facial
- brachial
- femoral
- popliteal
- posterior tibial
- dorsalis pedis
93
What are common sites for applying pressure to stop bleeding?
- temporal
- facial
- common carotid
- subclavian
- brachial
- femoral
