Short Term BP Control- Exam 1 Flashcards
1
Q
What does control of blood flow to local tissue depend on?
A
Maintaining a constant pressure drop across the tissue
2
Q
What two components are involved in maintaing a constant pressure drop across the tissue?
A
Constant mean arterial pressure
Constant central venous pressure
3
Q
What are some mechanisms for controlling blood pressure?
A
Aldosterone Baroreceptors Capillary fluid shift Chemoreceptors CNS ischemic response Renal-blood volume pressure control Renin-angiotensin-vasoconstriction Stress relaxation of vasculature
4
Q
What type of mechanism is aldosterone?
A
Hormonal
5
Q
What type of mechanism is baroreceptors?
A
Nervous
6
Q
What type of mechanism is capillary fluid shift?
A
Physiologic
7
Q
What type of mechanism are chemoreceptors?
A
Nervous
8
Q
What type of mechanism is CNS ischemic response?
A
Nervous
9
Q
What type of mechanism is Renal-blood volume pressure control?
A
Kidneys
10
Q
What type of mechanism is renin-angiotensin-vasoconstriction?
A
Hormonal
11
Q
What type of mechanism is stress relaxation of the vasculature?
A
Physiologic
12
Q
Which blood pressure control mechanisms are activated within seconds?
A
- Baroreceptors
- Chemoreceptors
- CNS ischemic response
- Stress relaxation
13
Q
Which blood pressure control mechanisms are activated within minutes?
A
- Capillary
6. Fluid Shift
14
Q
Which blood pressure control mechanisms are activated within hours?
A
- Aldosterone
8. Renal-blood volume pressure control
15
Q
What blood pressure control mechanisms has the greatest ability to create change?
A
Renal-blood volume pressure control
16
Q
CNS ischemic response mechanism
Range and Peak
A
0 to 75 mmHg
Peak: 0 mmHg
17
Q
Chemoreceptor response mechanism
Range and Peak
A
20- 110 mmHg
Peak: 60 mmHg
18
Q
Renin-Angiotensin vasoconstriction
Range and Peak
A
35- 115 mmHg
Peak: 75 mmHg
19
Q
Baroreceptor response mechanism
Range and Peak
A
50- 225 mmHg
Peak: 115 mmHg
20
Q
Parasympathetic Nervous Control
A
Regulation of HR
Small affect on contractility
Minimal regulation of circulation
21
Q
Sympathetic Nervous Control
A
Regulation of circulation
Regulation of contractility
22
Q
Vasomotor Center
A
Parasympathetic impulses via spinal cord & peripheral sympathetic nerves to all arteries, arterioles, veins
23
Q
Where do sympathetic nerve fibers exit spinal cord?
A
Via all thoracic spinal nerves & first two lumbar spinal nerves
24
Q
Where do sympathetic nerve fibers enter the sympathetic chains?
A
Either side of spinal cord
25
What are the two routes sympathetic nerve fibers go to circulation?
1. Specific sympathetic nerves to vasculature of internal viscera & heart
2. Peripheral portions of spinal nerves to peripheral vasculature
26
What tissue receive sympathetic innervation?
Arteries, arterioles, venules, veins of most tissues receive sympathetic innervation; some metarterioles & precapillary sphincters of mesenteric blood vessels innervated
27
Are most sympathetic nerve fibers vasconstrictor or vasodilator?
Vasoconstrictor (few vasodilator)
28
Where is vasoconstriction potent?
Kidneys, intestines, spleen, kidney
29
Where is vasoconstriction weaker?
Skeletal muscle and brain
30
When sympathetic impulses are sent to blood vessels, impulses also go where?
Adrenal medulla resulting in secretion of epinephrine and norepinephrine
31
What is able to change resistance/change flow through each tissue?
Small arteries/arterioles
32
What is able to change volume held in vessels thus changing venous return?
Veins
33
Where is the vasomotor center located?
Bilateral
| Reticular substance: medulla, lower third of pons
34
Parasympathetic impulses are via what nerve?
Vagus nerve
35
Sympathetic impulses are via what structures?
Spinal cord & peripheral sympathetic nerves to all arteries, arterioles, veins
36
What does the vasomotor center do?
Regulates amount of vascular constriction and cardiac activity (i.e. heart rate and contractility)
37
3 components of the vasomotor center
Vasoconstrictor area
Vasodilator area
Sensory area
38
Where is the vasoconstrictor area?
Bilateral; anterolateral part of upper medulla
39
What does the vasoconstrictor area of the vasomotor center do?
Sends fibers to all areas of spinal cord; fibers excite vasoconstrictor neurons of sympathetic system
40
Where is the vasodilator area?
Bilateral; anterolateral part of the lower medulla
41
What does the vasodilator area of the vasomotor center do?
Sends fibers to vasoconstrictor area; fibers inhibit activity of vasoconstrictor area
42
Where is the sensory area of the vasomotor center?
Bilateral in tractus solitarus in posterolateral part of medulla & lower pons
43
What does the sensory area of the vasomotor center do?
Sends output to vasoconstrictor and vasodilator areas; allows control of vasoconstrictor/vasodilator areas based on input from circulatory system
44
Where does the sensory area receive sensory signals from?
Circulatory system vai vagus and & glossopharyngeal nerves
45
What do lateral portions of the vasomotor center do?
Send excitatory impulses via sympathetic nerves to the heart [ increased HR and contractility ]
46
What do medial portions of the vasomotor center do?
Sends impulses to dorsal motor nuclei of vagus nerves which sends parasympathetic impulses to heart [decrease heart rate and some decrease in contractility ]
47
Normally, what happens when the vasoconstriction center is stimulated?
Increased cardiac activity
48
Normally, what happens when the vasoconstriction center is inhibited?
Decreased cardiac activity
49
Amount of vascular constriction is proportional to what?
Number of impulses set out by vasoconstrictor area
| more impulses, increased constriction
50
Normally, vasoconstrictor center sends how many impulses per second?
1.5 to 2.0 impulses per second
| Results in partial constriction (normal vasomotor tone)
51
Total spinal anesthesia blocks what?
Transmission of sympathetic impulses from spine to periphery; stops transmission of impulses from vasoconstrictor center
52
CNS Control of vasomotor center consists of what 3 areas of the brain?
pons, mesencephalon, diencephalon
53
Lateral/superior portions of CNS_________vasomotor center.
Excite
54
Medial/Inferior portions of CNS ________ vasomotor.
Inhibit
55
What part of the hypothalamus excite the vasomotor center?
Posterolateral portions
56
Stimulation of the anterior portion of the hypothalamus results in what?
Mild excitation or inhibition; depends on which part of the anterior portion is stimulated
57
What part of the cerebral cortex stimulates the vasomotor center?
Motor cortex; multiple areas can excite or inhibit depending on specific area stimulated
58
Nervous control can double blood pressure within how many seconds?
5 to 10 seconds
59
Stimulation of nervous control results in what?
Stimulation vasoconstrictor area (sympathetic)
Stimulation increases cardiac activity (sympathetic)
Inhibit parasympathetic vagal signals to heart
60
What is the physiologic response of stimulating nervous control?
Constriction of most arterioles of systemic circulation
Strong constriction of veins/larger arteries
Increased cardiac performance
61
Where are baroreceptors?
Walls of most large arteries of the thorax and neck
Many in wall of internal carotid arteries above the bifurcation (carotid bodies in carotid sinus) and in wall of aortic arch
62
How do carotid baroreceptors send impulses?
Hering's nerves to glosspharyngeal nerves which carry inpulses to sensory area of vasomotor center
63
Where do aortic baroreceptors send impulses to?
Vasomotor center via vagus nerves
64
At what pressures are carotid baroreceptors stimulated?
50 to 60 mmHg
65
At what pressures are aortic baroreceptors stimulated?
80 to 90 mmHg
66
When do receptors produce a greater response?
When pressure changing (could be twice the response)
67
Baroreceptors stimulate changes in __________ and __________.
Vascular resistance; cardiac performance
68
What would happen if the baroreceptors were denervated?
Huge variations in blood pressure moment to moment due to buffer function of the baroreceptors
69
What would happen to baroreceptors if pressure changes and remains at a new level?
Baroreceptors will reset to new level
70
How long does it take for baroreceptors to reset to a new level?
1 to 2 days; happens no matter which way the pressure changes
71
What are the function of baroreceptors, long-term?
May mediate changes in sympathetic tone to the kidneys
72
How do baroreceptors mediate changes in sympathetic tone to the kidneys?
Increased pressure
Mediate decreased sympathetic tone to kidneys
Promotes increased sodium and water excretion
73
What are chemoreceptors sensitive to?
Lack of oxygen and excess carbon dioxide and hydrogen ions
74
Where are chemoreceptor located?
```
Carotid bodies (2) in bifurcation of each common carotid artery
Artery bodies (1 to 3) adjacent to aorta
```
75
Chemoreceptors excite which nerve fibers?
Nerve fibers that pass through Hering's nerves and vagus nerves to vasomotor center
76
What ensures good supply of blood to each body?
Nutrient artery
77
Decreased flow through nutrient artery results in what?
Increased impulse generation; results in excitation of vasomotor center
78
When do chemoreceptors kick in with increased impulses? (What pressure)
excite vasomotor center, when pressure falls below 80 mmHg
79
What is the direct response of vasomotor center to ischemia?
CNS Ischemic Response
80
What is the CNS ischemic response mediated by?
Vasoconstrictor and cardioaccelerator portions in response to increasing levels of carbon dioxide (may include other substance such as lactic acid)
81
What can the CNS ischemic response increased BP to?
250 mmHg (very powerful)
82
What does the CNS ischemic response do to flow to less important tissues?
Completely cuts off flow to less important tissues (kidneys)
83
At what pressure is the CNS ischemic response initiated?
When BP falls below 60 mmHg
84
When does the CNS ischemic response reach greatest level of stimulation?
15 to 20 mmHg
85
What are atrial/pulmonary stretch receptors?
Low-pressure receptors- similar to baroreceptors of large systemic arteries; minimize changes in arterial pressure due to sudden changes in blood volume
86
Where are atrial/pulmonary stretch receptors located?
Walls of atria and pulmonary arteries
87
What happens if you infuse 300 mls of blood into dog?
Only 15 mmHg increase in BP if all receptors intact
40 mmHg increase in BP if baroreceptors deactivated
100 mmHg increase in both baroreceptors and low-pressure receptors deactivated
88
Bainbridge Reflex
Increase in atrial pressure causes an increase in heart rate; part of hte response due to direct stretch of the sinus node (can increase HR up to 15 %) an additional 40 to 60% increase caused by Bainbridge reflex
89
What does increased atrial stretch result in? (Bainbridge Reflex)
Increased impulses via vagus nerve to medulla
90
What do increased impulses to medulla result in? (Bainbridge Reflex)
Increased sympathetic impulses to heart increasing HR and contractility
91
What are respiratory waves?
Change in arterial pressure of 4 to 6 mmHg during each inspiration/expiration cycle
92
Inspiration
Expansion of blood vessels decreases venous return which decreases cardiac output and arterial pressure
93
Expiration
Constriction of blood vessels increases venous return which increases cardiac output and arterial pressure
94
Pressure changes in thoracic vessels can stimulate what?
Vascular and atrial stretch receptors
95
Vasomotor Waves
Possible to see slow oscillation in arterial pressure waveform of 10 to 40 mmHg
96
What is the cycle duration for vasomotor waves?
7 to 10 seconds
97
What causes vasomotor waves (cycle of pressure oscillations)?
Increased pressure increase baroreceptor response (dilate)
| Decrease pressure decreases baroreceptor response (constricts)
98
Increased atrial stretch has what kidney reflex?
1. Signals to hypothalamus to produce less ADH
| 2. Reflex dilation afferent arterioles of kidney
