Main Objectives of the Circulation
1. To fulfill tissue metabolic demands at all times ▪ Cardiac output is linked to total metabolic needs
2. To fulfill non-metabolic blood flow demands, e.g., for
thermoregulation; for filtration
▪ Cardiac output also linked to non-metabolic needs
Give ex of non metabolic blood flow demands
thermoregulation // filtration
T or F
Cardiac output linked to non-metabolic needs
T
Define Arterial Blood Pressure
lateral pressure exerted by
circulating blood on the walls of
systemic arteries.
What is the normal range of Arterial Blood Pressure in Systolic and depend on what
100 -139 mmHg
Depend on C O
What is the normal range of Arterial Blood Pressure in diastolic and depend on what
60 – 89 mmHg
Depend on venous return
What is the formula of Pulse Pressure
Pulse pressure = Systolic pressure – Diastolic pressure
To what Volume and strength of arterial
pressure depend on
pulse pressure.
Define Mean Blood Pressure
▪ It is the average pressure in systemic arteries present through out
cardiac cycle.
What is the formula of mean blood pressure
Mean B.P = Diastolic B.P + 1/3 Pulse pressure
What is the normal range of mean blood pressure
Normal range = 70 – 110 mmHg
What Usually Tends to Reduce Arterial Pressure?
Too much outflow
Too little inflow
Basic filling is low
What is the effect of each following in reducing arterial pressure
Too much outflow – Peripheral arteriolar dilatation (generalized)
▪ Metabolism-associated
▪ Non-metabolic arteriolar dilatation
▪ e.g., To lose body heat during thermoregulation
Too little inflow – Reduced cardiac output
▪ Standing upright from the supine position
Basic filling is low - Reduced Blood Volume
▪ Blood loss
▪ Dehydration
What is the formula of arterial pressure
BP = CO X TPR
C.O. affect systolic pressure less than diastolic pressure
F
C O. affect systolic pressure more than diastolic pressure
Dose the TPR affect diastolic or systolic blood pressure
diastolic
What is the Physiological variation in B.P
1. Age
2. Diurnal variations ( less in morning and more in evening )
3. Sex ( less in females)
4. Intake of meals (increase)
5. Posture (decrease when standing due to gravity)
6. Emotional state (increase)
7. Sleep(decrease)
8. Obesity (inc
9. Exercise (inc
10. Effect of Race(American negros B.P. increased than white)
What is the factors that regulate mean arterial p in short term
Total peripheral resistance
Cardiac output ( HR X SV)
arteriolar radius is controlled by What
BP regulatory systems (and also by tissue metabolism)
Hence stroke output is controlled by ———-
▪ Hence heart rate is also controlled by ———-
Hence stroke output is controlled by BP regulatory systems (& by local Frank-Starling mechanism)
▪ Hence heart rate is also controlled by BP regulatory systems (and by intrinsic behavior of pacemaker & local stretch)
What is the factors that regulate mean arterial p in long term
Blood volume
How automatic nerves system control blood pressure
What is the type of regulation in short term regulation
1. Nervous Regulation
2. Hormonal Regulation
3. Miscellaneous/Intermediate
Give ex of Nervous Regulation
▪ Baroreceptor reflex
▪ CNS ischemic response
▪ Cushing reaction
▪ Chemoreceptor reflex mechanism
Give ex about Hormonal Regulation
▪ Catecholamines
▪ Angiotensin II
▪ ADH
Give ex of Miscellaneous/Intermediate
▪ Capillary fluid shift
▪ Stress relaxation & Reverse stress relaxation
Through what long term regulat Arterial Blood Pressure
through renal body fluid pressure
control systems
Involves kidney & body fluids
What is the four factors tha associated with long term care regulation
1. Sympathetic impulses to kidney
2. Rennin angiotensin mechanism
3. ADH mechanism
4. Aldosterone mechanism
In which case short term regulation control Arterial Blood Pressure
In case of postural changes and
Sudden blood loss
In which case Baroreceptor Reflex Mechanism maintain B.P
during postural changes
What is the role of Baroreceptor Reflex Mechanism
▪ Maintain B.P during postural changes
▪ Minimize diurnal variation in B.P.
What is the other name of Baroreceptor Reflex Mechanism
Pressure Buffer system
What is the 2 nerve that work as barorecepter in Baroreceptor Reflex Mechanism
Hering’s nerve + vagi
Where Mechanoreceptors located
in the walls of carotid arteries &
arch of aorta
Mechanoreceptors Sensitive to what
sensitive to pressure or
stretch.
What is the function of Mechanoreceptors
Keep arterial pressure constant via changes in the output of the sympathetic and parasympathetic nervous systems to the heart and blood vessels.
In what rang of blood pressure Baroreceptor remain functional
B/w 60-180 or 210 for carotid
Why baroreceptors are not suitable for long term regulation
Undergo adaptation in 24 - 48 hrs
that’s why only short acting.
Explain the Baroreceptor Reflex Mechanism
when there is an increase in blood pressure
When B.P increases → more stretch of Baroreceptors →
more impulses go to V.M.C → Sympathetic inhibition &
Parasympathetic stimulation → decrease C.O & decrease
peripheral resistance
And at the end blood pressure back to normal
What happen to the heart and blood sympathetic tone when there is increase in blood pressure
Reduced sympathetic tone to heart
▪ SA Node: Decreased rate (also by increase parasympathetic tone)
▪ Myocardium: Decreased contractility (dec SV) ▪ Reduced sympathetic tone to blood vessels
▪ Decreased arteriolar tone
▪ Overall effect – bring down arterial pressure
▪ Decreases total peripheral resistance ▪ Decreased peripheral venous tone
▪ Higher peripheral venous capacity – less venous return and less cardiac filling
What is the response of the barorecepter reflex to Postural Hypotension
What is the Response of the baroreceptor reflex to acute hemorrhage
In what range CNS Ischemic activated
It is activated when
MAP < 60 mmHg.
What is the other name for CNS Ischemic Response
ditch response
Define Cushing Reaction
A specialized CNS ischemic response activated when intra
cranial pressure (ICP) is ˃ 45 cm of H2O
What is the normal range of intra cranial pressure
Normal ICP = 8 -15 cm of H2O
Explain the mechanism of Cushing Reaction when intra cranial pressure is high
When ICP become so high → cerebral vessels compressed → ischemia of brain → Ischemic neurons causing stimulation of CNS ischemic response → increased B.P. → increases cerebral blood flow although ICP is high.
Chemoreceptor Reflex Mechanism Sense change in what factors
Ions
Po2 decreased,
PCO2increased
H+ increased
The chemoreceptors helps to maintain B.P. At what range
< 80 mmHg
Explain chemoreceptors reflex mechanism
What is the difference between barorecepter and chemoreceptors reflex
Intermediate Mechanisms
Explain the mechanism of Capillary fluid shift when there is an increase in blood pressure
When B.P. increases → capillary Capillary Exchange pressure inc. → inc. in the filtration of fluid from blood to interstitial spaces → blood vol dec → dec. VR → dec B.P. (back to normal)
What happen to the vessel wall when blood pressure change
When B.P. changes due to changes in blood volume, the vessel wall changes in size to accommodate the blood vol so that B.P is regulated.
Define stress relaxation
When B.P. Increase due to increase in blood vol (e.g blood transfusion), the
smooth muscle in vessel wall undergo stress relaxation → inc blood
vol. can be accommodated
Define Reverse Stress Relaxation
When B.P falls due to blood loss → the smooth muscle in
vessels wall contracts around the decreasing blood vol.
What is the benefit of Reverse Stress Relaxation
prevents development of
circulatory shock.
What is the Other Reflex Changes in MAP
Temperature regulation reflex
Flight-or-fight” defense response
Vasovagal fainting response
How can Temperature regulat MAP
Increased body heat leads to cutaneous vasodilation – tends to reduce
MAP
explain Flight-or-fight” defense response
increase HR,increase contractility, and increase adrenal medullary secretion
How can Vasovagal fainting response ,,change MAP
Vasovagal fainting response to pain or strong emotion (vasovagal
syncope)
▪ Due to large increase in vagal efferent activity and simultaneous cessation
of sympathetic tonic
Hormonal mechanism
Catecholamines
Renin Angiotensin Mechanism
Vasopressin or ADH mechanism
in which case Catecholamines released
When B.P decreased → sympathetic stimulation → large amount of
catecholamines are released from adrenal medulla.
From where Catecholamines release
from adrenal medulla.
Complete
Catecholamines Produces same effects as the……
Produces same effects as the direct effects produced by sympathetic
stimulation → increased peripheral resistance → inc. HR.
Why Catecholamines release when there decrease in blood pressure
Cus it increased peripheral resistance → inc. HR.
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