short term control of blood pressure Flashcards
(59 cards)
1
Q
Mechanisms For Controlling Blood Pressure: Aldosterone
A
hormonal. activation time:hours activation strength: medium
2
Q
Mechanisms For Controlling Blood Pressure: Baroreceptors
A
nervous activation time: seconds activation strength: large 7)
3
Q
Mechanisms For Controlling Blood Pressure: Capillary fluid shift
A
physiological minutes medium
4
Q
Mechanisms For Controlling Blood Pressure: Chemoreceptors
A
nervous seconds medium
5
Q
Mechanisms For Controlling Blood Pressure: CNS ischemic response
A
nervous seconds large 11
6
Q
Mechanisms For Controlling Blood Pressure: renal blood volume pressure control
A
kidneys hours infinite
7
Q
Mechanisms For Controlling Blood Pressure: renin angiotensin-vasoconstriction
A
hormonal minutes medium
8
Q
Mechanisms For Controlling Blood Pressure:stress relaxation of vasculature
A
physiologic second medium
9
Q
cns ischemic response range
A
0-75
10
Q
chemreceptors response range
A
25-115
11
Q
barreceptors response range
A
50-225 decrease prssures
12
Q
renin angiotensin vasocontriction range
A
30-120
13
Q
renal blood volume and capillary fluid shift range
A
work over all pressures.
14
Q
Parasympathetic
A
Regulation of heart rate
Small affect on contractility
Minimal regulation of
circulation
15
Q
sympathetic
A
Regulation of circulation
Regulation of contractility
16
Q
vasomotor center
A
Parasympathetic impulses via vagus nerve (heart) Sympathetic impulses via spinal cord & peripheral sympathetic nerves to all arteries, arterioles, veins
17
Q
Sympathetic Innervation of Blood Vessels
A
Arteries, arterioles, venules, veins of most tissues receive
sympathetic innervation
Some metarterioles & precapillary sphincters of mesenteric blood
vessels innervated
18
Q
Most sympathetic nerve fibers are
A
vasoconstrictor (few
vasodilator)
Vasoconstriction potent in kidneys, intestines, spleen, and skin
Vasoconstriction weaker in skeletal muscle and brai
19
Q
When sympathetic impulses sent to blood vessels
A
impulses
also go to adrenal medulla resulting in secretion of epinephrine
& norepinephrine
20
Q
Small arteries / arterioles are able
A
o change resistance / change flow through each tissue
21
Q
Veins are Able to change
A
volume held in vessels thus changing venous return
22
Q
Vasomotor Center - Location
A
bilateral.
23
Q
Reticular substance
A
Medulla
Lower third of pons
24
Q
Sympathetic impulses via spinal cord and periphereal
A
go to arteries arterioles and veins.Regulates amount of vascular
constriction AND cardiac
activity (i.e. heart rate &
contractility)
25
Vasoconstrictor area
Bilateral -Anterolateral part of upper medulla
Sends fibers to all areas of spinal cord
Fibers excite vasoconstrictor neurons of
sympathetic system
26
Vasodilator area
Bilateral -Anterolateral part of lower medulla
Sends fibers to vasoconstrictor area
Fibers inhibit activity of vasoconstrictor area
27
Sensory area
Bilateral in tractus solitarus in posterolateral
part of medulla & lower pons
Receives sensory signals from circulatory
system via vagus & glossopharynegeal nerves
Sends output to vasoconstrictor and
vasodilator areas
Allows control of vasoconstrictor / vasodilator areas
based on input from circulatory system
28
Lateral portions of vasomotor center
Sends excitatory impulses via sympathetic nerves to heart
| [increase heart rate & contractility]
29
Medial portion of vasomotor cente
Sends impulses to dorsal motor nuclei of vagus nerves which
sends parasympathetic impulses to heart [decrease heart
rate & some decrease in contractility]
30
Vasomotor Center – Cardiac Control normally
increased cardiac activity is stimulated when
vasoconstriction center is stimulated
decreased cardiac activity is stimulated when
vasoconstriction center is inhibited
31
Sympathetic Vasoconstrictor Tone
Amount of vascular constriction is proportional to
number of impulses sent out by vasoconstrictor area
Increase number of impulses per second – Increased
constriction
Decrease number of impulses per second – Decreased
constriction
32
Sympathetic Vasoconstrictor Tone under normal conditions
Vasoconstrictor center sending 1.5 to 2.0 impulses per
second
Results in partial constriction – normal vasomotor tone
33
spinal anesthesia can block
blocks transmission of
sympathetic impulses
from spine to periphery
34
Vasomotor Center – Control by CNS
Reticular substance of pons, mesencephalon,
diencephalon controls
Lateral / superior portions excite vasomotor center
| Medial / inferior portions inhibit vasomotor center
35
Vasomotor Center – Control by CNS hypothalamus
Posterolateral portions excite vasomotor center
Anterior portion produced mild excitation or inhibition
Depends on which part of anterior portion is stimulated
36
Vasomotor Center – Control by CNS cerebral cortex
Motor cortex excites vasomotor center
Multiple areas can excite or inhibit depending on specific
area stimulated
37
General Effect of Nervous Control Able to produce rapid increase in ___ which stimulates and inhibits______
vasoconstrictor area (sympathetic) increases cardiac activity (sympathetic) and inhibits parasympathetic vagal signals to heart
38
General Effect of Nervous Control physiologic response
Constriction of most arterioles of systemic circulation
Increased SVR Increased MAP
Strong constriction of veins / some constriction of larger
arteries
Transfer volume from veins to arteries Increased venous return
Increased preload Increased stroke volume Increased MAP
Increased cardiac performance
Increased HR (major effect) Increased CO Increased MAP
Increased contractility Increased stroke volume Increased MAP
39
Baroreceptors are located
```
in walls
of most large arteries of the
thorax and neck regions. Many located in wall of the
internal carotid arteries above the
bifurcation (carotid bodies in
carotid sinus) and in wall of aortic
arch
```
40
Carotid baroreceptors send
| impulses
```
via Hering’s nerves to
glossopharyngeal nerves which
carry impulses to sensory area of
vasomotor center
Aortic baroreceptors send
impulses to vasomotor center via
vagus nerves
```
41
Baroreceptors Response to Pressure
```
Carotid receptors not
stimulated until
pressure 50 to 60
mmHg
Aortic receptors not
stimulated until
pressure 80 to 90
mmHg Receptors produce
greater response when
pressure changing
(could be twice the
response)
Stimulates changes in
vascular resistance and
cardiac performance
```
42
Baroreceptors and Long Term Control
Some controversy in terms of their importance
If pressure changes and remains at new level,
baroreceptors will RESET to new level
Takes 1 to 2 days
Will produce normal rate of impulse generate at the
“new” pressure
Happens no matter which way the pressure changes
Long term, may mediate changes in sympathetic
tone to the kidneys
Increased pressure mediate decreased sympathetic
tone to kidneys promotes increases sodium and
water excretion
43
chemoreceptors sensitive to and located in
lack of oxygen and excess carbon dioxide and
hydrogen ions
Location
Carotid bodies (2) in bifurcation of each common carotid artery
Aortic bodies (1 to 3) adjacent to aorta
44
chemoreceptors excite
nerve fibers that pass through Hering’s nerves and vagus
| nerves to vasomotor center
45
CHEMORECEPTORS :Nutrient artery to each body
ensures good supply of blood to
sample
Decreased flow through artery causes decrease in oxygen and an
increase in carbon dioxide and hydrogen ions.
Impulse generation increases with decreased flow through
nutrient artery which results in excitation of vasomotor center
Increased impulses from chemoreceptors EXCITE the
vasomotor center
Kick in when pressure falls below 80 mmHg
46
CNS ISCHEMIC REPSONSE
DIRECT RESPONSE OF VASOMOTOR CENTER DUE TO ISCHEMIA. VERY POWERFUL!!!!! INCREASE BP TO 250. CUTS OFF FLOW TO LESS IMPORTANT TISSUE LIKE KIDNEYS. INITIATED AT 60 RREACHES GREATEST STIMULATION AT 15-20
47
Atrial / Pulmonary Stretch Receptors
| Located
in walls of atria and pulmonary arteries
Low-pressure receptors – similar to baroreceptors of
large systemic arteries
48
Atrial / Pulmonary Stretch Receptors MINIMIZE
changes in arterial pressure due to sudden
| changes in blood volume
49
Atrial Reflexes and the Kidney (A) PATHWAY
Increased atrial stretch Reflex dilation afferent
arterioles of kidney
Reflex dilation afferent arterioles Increased glomerular
capillary pressure
Increased glomerular capillary pressure Increased
glomerular filtration
Increased glomerular filtration Increased urine output
Increased urine output Decreased circulating blood
volume
Decreased circulating blood volume Decreased venous
return and decreased cardiac output
50
Atrial Reflexes and the Kidney (B PATHWAY
Increased atrial stretch Signals hypothalamus to
produce less antidiuretic hormone (ADH)
Decreased concentration of ADH Decreased
reabsorption of water from renal tubules
Decreased reabsorption of water Increased urine
output
Increased urine output Decreased circulating blood
volume
Decreased circulating blood volume Decreased
venous return and decreased cardiac output
51
Bainbridge Reflex
Increase in atrial pressure causes an increase in heart
rate
Part of the response due to direct stretch of the sinus
node (can increase heart rate up to 15%)
An additional 40 to 60% increase caused by
Bainbridge reflex
52
BAINBRIDGE REFLEX
Increased atrial stretch Increased impulses via vagus
nerves to medulla
Increased impulses to medulla Increased sympathetic
impulses to heart increasing heart rate and contractility
53
Respiratory Waves
| Change in arterial pressure
of 4 to 6 mmHg during each
| inspiration/expiration cycle
54
Change in arterial pressure INSPIRATION
Pressure in thoracic cavity becomes more negative
Blood vessels in chest expand
Expansion of blood vessels decreases venous return which decreases
cardiac output and arterial pressure
55
CHANGE IN ARTERIAL PRESSURE EXPIRATION
Pressure in thoracic cavity becomes positive
Blood vessels in chest constrict
Constriction of blood vessels increases venous return which increases
cardiac output and arterial pressure
56
Signals from respiratory center spill over
into vasomotor center
57
Pressure changes in thoracic vessels due to inspiration/expiration can
stimulate the vascular and atrial stretch receptors
58
Vasomotor Waves
Possible to see slow oscillation in arterial pressure
waveform of 10 to 40 mmHg
Cycle duration is approximately 7 to 10 seconds
59
Oscillation Baroreceptor / Chemoreceptor reflexes:
Increased pressure produces increased baroreceptor
response which produces vasodilation (etc.) which
causes the pressure to fall. The decreased pressure
causes a decrease in baroreceptor response which
produced vasoconstriction (etc.) which causes the
pressure to rise. Creates a cycle of pressure oscillations
