Unit 2: Circulation Pt3 Flashcards
What is the Vasomotor center? What are the four major regions?
collection of neurons in the medulla and pons
What are the four major regions of the Vasomotor Center?
- Pressor Center (“C1”)
- Depressor Center (“A1”)
- Sensory Area (“A2”)
- Cardioinhibitory area
What does the Pressor Center region of the Vasomotor Center do?
increases BP by stimulating SNS in mass
What does the Depressor Center of the Vasomotor Center do?
decrease BP by inhibiting SNS
What does the Sensory Area of the Vasomotor Center do?
mediates baroreceptor reflex by inhibiting SNS –> therefore inhibiting pressor center and lowering BP
What does the Cardioinhibitory Area of the Vasomotor Center do?
stimulates CN X (Vagus)
What does the Sensory Area of the Vasomotor Center primarily receive input from?
CN IX and X
A decrease in pressure with cause ___ in Barorectpor feedback, therefore causing ___ in SNS
decrease in feedback; therefore increase SNS
therefore an increase in P causes an increase in Baroreceptor feedback, and therefore a decrease in SNS
What does the short term control of BP involve?
NS effect on vascular smooth muscle –> SNS
What does the long term control of BP involve?
control is dominated by kidneys–> the Renal-Body fluid balance
What two things effect BP?
How is control of BP accomplished?
blood volume (contents) and blood vessels (container)
affect vascular tone or blood volume
Where are baroreceptors abundent?
- Carotid sinus (info to CN IX)
- Arch of Aorta (info to CN X)
Barorectpors are stimulated when stretched, what will this then inhibit in the Vasomotor center?
inhibits “Pressor Center” via CN IX and X and NTs
What are the Net Effects of Baroreceptors being stimulated?
- vasodilation
- decreased cardiac output
T/F. Baroreceptors are more sensitive to static P than changing P.
False– they are more sensitive to changing pressure than static P
What is the Carotid sinus reflex?
When baroreceptors are stimulated and a quick change in pressure and could cause you to pass out
T/F. Baroreceptors lack long term control due to adaptation
True; they reset w/in 1-2 days
Where are Low Pressure baroreceptors located?
- arterial walls and pulmonary arteries
- augment arterial baroreceptors
- minimize aterial pressure changes in response to blood volume changes
T/F. Blood volume changes mainly sensed on the low pressure side.
True
If there is stretch on the atrial wall and the heart rate decreases, what reflex is in dominant effect? What occurs?
Baroreceptor Reflex
- decreases HR (inhibit SNS)
- increasing urine production (decrease SNS in renal nerves and decreased secretion of ADH)
If there is stretch on the atrial wall and heart rate is increased, what is the dominant reflex?
Brainbridge reflex
Once there is stretch on the atrial wall, what will the release of Atrial Natriuretic Peptide (ANP) tell the body to do?
- dirurectic (get ride of water)
- natriuretic (get ride of Na+)
- vasodilator
What will an increase in ECF have on arterial pressure? What occurs in response?
will cause arterial pressure to rise and in response the kidneys excrete excess ECF
What will shift for long term arterial pressure control?
- shift the renal output curve for water and salt
- shift level of water and salt intake line
T/F. Increased total peripheral resistance will not create a long term elevation of BP if fluid intake and renal function do not change.
True
What type of arterioles supply the glomerular capillaries and what takes place here?
afferent arterioles supply the glomerular capillaries–where filtration takes place here
What type of arterioles drain the glomerular capillaries? What do these give rise to? What occurs here?
efferent arterioles drain the glomerular capillaries and give rise to peritubular capillaries–where reabsorption takes place
Where does filtration take place in the kidneys?
glomerular capillaries
Where does reabsorption take place in the kidneys?
peritubular capillaries
List in order the path through the kidneys starting with afferent arterioles.
Afferent arterioles—> glomerular capillaries (filtration takes place) –> efferent arterioles –> peritubular capillaries (reabsorption takes place)
What are specialized peritubular capillaries assoicted with juxtamedullary nephrons?
vasa recti
How does renal control of blood pressure work, as in when ECF levels rise?
the arterial pressure rises–> kidney excretes more fluid –> this brings pressure back to normal
What is the quickest mechanism for volume pressure control?
Baroreceptors
What is the better mechanism for volume pressure control, as in it has the most “gain”?
Renal Fluid Volume
How do we express the degree of effectiveness with which a control system (i.e. NS) maintains constancy of a controlled variable (i.e. BP)?
can be expressed as the “gain of a feedback system”
What is Gain equal to?
Gain = compensation / remaining error
The higher the gain the (more/less) effective the control system.*
more!!
Ex: Gain = 9; then 90/10
if Gain = 100/0; that equals infinity
For an acute renal output curve was is the effect?
effect of arterial pressure alone
For a chronic renal output curve, what is the effect?
effect of arterial pressure plus:
- SNS stimulation
- Renin-angiotensin system
- Aldosterone
- ADH
- ANP** inhibit–makes diff than others
If we want to incrase arterial pressure, we will stimulate all of the following except:**
- SNS
- Renin-angiotensin system
- Aldosterone
- ADH
- ANP
ANP will be inhibited in order to aid in promoting an increase in pressure
What three hormones will decrease renal blood flow (RBF)?
- NE
- Epinephrine
- angiotensin II
What hormones will increase renal blood flow (RBF)?
prostaglandins (E and I)`
What monitors NaCl in the Macula densa of the distal tubule in the kidney?
Tubuloglomerular feedback
If the Tubuloglomerular feedback detects a decrease in NaCl in Macula densa, what occurs?
stimulates renin release from JG (juxtaglomerular) cells
- increase in renin –> increases angiotensin II levels —> increase efferent arteriole resistance
also causes dilation of afferent arteriole
collectively increases filtration (GFR)
Where is the primary source of renin?
smooth muscle cells in afferent arteriole (synthesis, storage, and release takes place here)
What will stimulate renin to be released?
- decrease perfusion pressure
- stimulate SNS
- decrease NaCl delivery to macula densa (distal tubule)–> Tubuloglomerular feedback
- Hormonal stimulation (Thyroid hormone, GH)
What is an ezyme that catalyses the formation of Angiotension I from angiotensinogen? Where does this occur?
Renin; in the liver
Where does the conversion of angiotension I –> angioensin II occur?
primarily in lung via angiotensin converting enzyme ass. with pulmonary endothelium
What are the functions of Angiotensin II?
Stimulate:
- adrenal cortex to release aldosterone
- release of ADH/vasopressin
- kidney
- thirst/drinking behavior at level of hypothalamus
What is the net effect of the function of Angiotensin II?
decrease Na+ and H2O secretion and therefore increase BP
Experimentally what occurs if:
- tie off one renal artery
- tie of one renal artery and remove kidney
- tie off and remove both kidneys
- develop systemic hypertension (increase in renin and angiotensin II); but NO development of uremia
- NO development of hypertension or uremia
- develop BOTH hypertension and uremia
What will slow breathing (6/min) do to the arterial baroreflex?
increase the arterial baroreflex sensitivity
What are some beneficial effects of slow breathing in Congestive Heart Failure patients?
- increase resting oxygen saturation
- improve ventilation/prefusion mismatching
- improves exercise tolerance by decreasing sensation of dyspnea
- decrease chemoreflex activation
- decrease sympathetic activity
- decrease SBP and DBP
What effect does nitric oxide have on endothelium?
How is NO inactivated?
How can we prevent this?
relaxes smooth muscle
inactivated by superoxide radical
increase antioxidants to reduce free radicals and all NO effects to last longer–> lowering BP
What are some antioxidants?
- Glutathione
- Melatonin
- Superoxide dismutase
- Beta-carotene
- Lutein
- Lycopene
- Selenium
- Vit A C E
What effect does serotonin have on CNS? What about NO?
What may this promote?
serotonin–>to inhibit reflex SNS activation
NO–> inhibit sympathetic nerve activity
–this may promote bradycardia and hypotension
How does blood flow get to the placenta? How does it return to the fetus?
gets to placenta–> via umbilical arteries, branch of anterior iliac arteries
returns to fetus–> via umbilical vein
What are the three fetal shunts and what are they b/w?
- Ductus arteriosis (pulmonic trunk–> aorta)
- Foramen ovale (b/w R and L atrium)
- Ductus venosus (umbilical vein/portal vein —> IVC)
How many fetal shunts are there to bypass the lungs? What are they?
Ductus arteriosis AND Foramen ovale
What fetal shunt allows umbilical and portal blood to bypass the liver?
ductus venosus
Describe pattern of blood flow with the Ductus arteriosis in the fetus? Start with Superior vena cava.
SVC –> RA –> RV –> Pulmonic trunk –> DUCTUS ARTERIOSIS –> aorta
Describe the pattern of blood flow with the Foramen ovale in the fetus, starting with inf. vena cava.
IVC –> RA –> FORAMEN OVALE –> LA –> LV –> aorta
Most blood in the fetus coming from the superior vena cava will go through what fetal shunt?
ductus arteriosis
Most blood in the fetus coming from the inferior vena cava will go through what fetal shunt?
foramen ovale
In fetal blood, where is the highest amount of oxygen saturation?*
umbilical vein– 80%
What are these fetal shunts b/w:
- Dustuc arteriosis
- Foramen ovale
- Ductus venosus
- pulmonary trunk and aorta
- RA and LA
- Portal vein to IVC and Umbilical vein to IVC
At birth, what are the circulatory readjustments?
- increase blood through lungs and liver
- loss of blood flow through placenta
- closure of FO, DA, and DV
At birth, what doubles the systemic vascular resistance in the baby?*
loss of blood flow through the placenta
- increased LA pressure, LV pressure, and aortic BP
T/F. In the fetus the R and L ventricles pump in series into the aorta.
False—-they pump in parallel
in us they pump in series
What is the low pressure in the aorta due to in the fetus?
due to low Total Peripheral Resistance (TPR) b/c of placenta-umbilical arteries
In the fetus:
The ______ shunts most blood returning to the heart from the inferior vena cava to the left atrium.
The _____ shunts most blood returning to the heart from the superior vena cava to the aorta.
- foramen ovale
2. ductus arteriosus
What has the greatest stress on the cardiovascular system?*
exercise
How much is cardiac output increased during exercise? How is blood flow shifted?
5-6 fold; primarily from organs to active skeletal muscles
What three things occur from cerebral cortical activation of the SNS during exercise?
- vasoconstriction of arterioles to decrease flow to non active tissues (viscera)
- vasoconstriction of veins to increase MCFP with increases VR
- stimulation of heart to increase HR and SV and therefore increase CO
During exercise, what will decrease due to vasodilation in active muscle?
TPR (total peripheral resistance)
During exercise there is an increase O2 uptake by active tissues, what effect does this have on VO2?
decrease VO2 and therefore increases A-VO2 difference
T/F. AO2 stays relatively the same during exercise.
True
b/c pushing blood to lungs, but also ventilating more to get the adequate O2
During exercise, SNS stimulation could be due to, what?
- cerebral cortex stimulation
- reflex signals from active joint proprioceptors and muscle spindles
- local chemoreceptor signals from active muscle
During exercise, how does the SNS effect the heart?
targets heart to increase HR and SV = CO
During exercise, what will the increase in CO (HR and SV) by SNS induce?*
induces LOCAL metabolic vasodilation at the heart
–> increase flow directly to muscle by LOCAL override *
During exercise what is the SNS effects on:
- pre-capillaries
- veins
- vascular smooth muscle in walls of arteries
- stimulates pre-capillary resistance vessels and decreases blood flow (organs and inactive muscle)
- vein constriction–mobilizes blood out of veins, increasing VR
- stimulates it to help maintain slightly increased BP
What tissues escape the effects of SNS vasoconstriction?
- Heart
- Brain
- lungs
What are the changes in arterial pressure during exercise? (SBP, DBP, PP)
- increase SBP due to increase CO and decrease TPR
- increase DBP only slightly
- increase Pulse Pressure (PP = SBP - DBP)
What is the pulse pressure for 120/80?
PP = SBP -DBP PP = 120-80 PP = 40
What are three ways we increase venous return during exercise?
- SNS constriction of veins
- “Venous Pump”
- Increase frequency and depth of respiration
How does the “Venous Pump” work?
intermittent skeletal muscle activity coupled with one way valves in veins
- primarily in lower extremities
How does the increase in frequency and depth of respiration help increase VR during exercise?
increased cyclic negative thoracic pressure (helps pull blood up from thorax and increase VR)
How is increased flow to active muscles mediated?
NOT by SNS; but by LOCAL release of tissue metabolites in response to increase in metabolism “Local vasodilators” (adenosine, CO2, K+, histamine, lactic acid)
What is the average resting CO?
What about when exercising?
5.9 L/min
24 L/min
During rest, what gets most blood flow?* Then least most to least.
- Organs
- Brain
- tie b/w active and inactive muscles
- skin
- coronary vessels
During exercise what gets most blood flow?*
active muscle (~87%) due to local override
During exercise how is blood flow affected at:
- coronary vessels
- Brain
- Organs
- Inactive muscle
- Active muscle
- skin
- coronary vessels–> increase 4 fold
- Brain–> CONSTANT
- Organs –> decreases
- Inactive muscle–> decreases
- Active muscle–> increases
- skin –> initially decreases, then increases as body temp increases
The effects of exercise on cardiovascular endpoints increases in all, except what?*
decrease in Total Peripheral Resistance
What causes the arteriovenous oxygen difference to increase when we exercise?*
due to decrease in VO2 (venous oxygen)
T/F. we can improve our Stroke Volume by constant exercise.
True
What is the maximum volume of oxygen that one can take up from the lungs and deliver to the tissues per minute?
VO2 maximum
What can VO2 maximum range from?
cardiac patient–> 1.5 L/min
Sedentary man–> 3.0 L/min
Endurance athlete–> 6.0 L/min
What is proportional to increases in SV as exercising training occurs?
function of CO and AV O2 difference
What occurs if energy (E) demands of exercise cannot be met by oxidative phosphorylation?
Oxygen Debt occurs
If Oxygen Debt occurs, what occurs after completion of exercise?
respiration remains elevated to repay the oxygen debt of about 11.5 L
What is extra Oxygen used for?
- restore metabolite levels (i.e. creatine phosphate and ATP)
- metabolize lactate generated by glycolysis
What is the equation of Oxygen Debt?
= E consumed during exercise - the E supplied by oxidative metabolism
When is the phosphocreatine-creatine system used during exercise?
8-10 secs (if sprint)
Uses ATP and creatine phosphate
When is the glycogen-lactic acid system used during exercise?
1.3-1.6 minutes
Uses glycolysis
When is the aerobic system used during exercise?
unlimited with oxygen and nutrients
- Uses oxidation of glucose, FA, aa –> Energy
- occurs in mitochondria with sufficient O2
