Arterial Blood Pressure Regulation

Question 1

Enumerate aims of ABP regulation

Answer 1

1. Keep ABP in an adequate value prevent excessive rise or fall.
2. To dec minute-to-minute fluctuations of ABP
3. To readjust ABP whenever it is disturbed.

Question 2

Compare short and long term regulation of ABP

Answer 2

Short: involve nervous mechanisms & rapid acting hormones. Very rapid (few seconds to one minute), does not last long and does not reach full correction of ABP. Affect capacity
Long: renal mecganisms by pressure diuresis and pressure naturesis occur by action of hormones on salt and water excretion affrct volume. Slow onset within days or weeks, prolonged action (months to years). It can reach full correction of ABP.

Question 3

Define intermediate term regulation

Answer 3

Vascular mechanisms, starts after some minutes continues to hours or days. Involve both volume (capillary fluid shift) and capacity (stress and antistress relaxation)

Question 4

Mention the range of sensitivity of each type of receptor

Answer 4

Baroreceptors, 60-200 mmHg for carotid but 80-200 for aortic
Chemoreceptors, below 80 mmHg
CNS ischemic reflex (VMC itself is the receptor), below 50 mmHg

Question 5

The only receptors acting normally all the time are ….

Answer 5

Arterial baroreceptors

Question 6

Classify baroreceptors

Answer 6

A. Arterial baroreceptors: carotid sinus & aortic arch baroreceptors
B. Cardiopulmonary baroreceptors: atrial (A & B), ventricular, pulmonary receptors

Question 7

Arterial baroreceptors are located in ….

Answer 7

Adventitia of carotid sinus & aortic arch

Question 8

Define buffer nerves

Answer 8

Sinus nerve branch from glossopharyngeal from carotid sinus
Aortic nerve branch from vagus from aortic arch
To VMC & CIC

Question 9

Mention stimuli for arterial baroreceptors

Answer 9

MAP

Pulse pressure

Question 10

GR: At any MAP, baroreceptor reflex is enhanced at high rather than low PP

Answer 10

Because they are easily adapted

Question 11

Describe function of arterial baroreceptor

Answer 11

Short term regulation only. Their primary response is to regulate ABP adequately to prevent excessive rise in ABP & minimize fluctuations to nearly third. Also responsible for vagal tone & HR maintenance.

Question 12

Describe function of arterial baro in normal ABP

Answer 12

Their discharge leads to:
Stimulated depressor area & dec vasomotor tone, thus dec TPR
Stimulated CIC, thus decrease HR by inc vagal tone

Question 13

Nmention role of baroreceptors in inc ABP

Answer 13

Baroreceptor reflex is enhanced leading to more inhibition if VM tone & more decrease in HR

Question 14

Nmention role of baroreceptors in excessive inc ABP

Answer 14

Besides maximal activation of baroreceptor reflex, the hypothalamic symoathetic dilator center is stimulated leading to active VD of skeletal muscle BV by cholinergic symp
May inhibit respiratory center (adrenaline apnea)

Question 15

Nmention role of baroreceptors in dec ABP

Answer 15

Less baroreceptor discharge leading to stimulation of pressor area and inc VM tone lesding to inc TPR, inhibition of CIC leading to inc HR

Question 16

Describe effect of hemorrhage on baroreceptors

Answer 16

SBP dec due to dec SV & DBP is inc due to inc HR. Dec in PP keeps baroreceptors less stimulated leadsing maintainance if VC & normalization of ABP. Carotid sinus baroreceptors have the major role since they respond to inc and dec if ABP, while aortic only sense inc.

Question 17

Postural changes mainly stimulate ……

Answer 17

Carotid sinus baroreceptors

Question 18

Describe effect of baroreceptor reflex on veins

Answer 18

When ABP falls, this leads to inc symp NA discharge, leading to venoconstriction, dec capatictance of veins, inc VR , inc COP & inc ABP.

Question 19

Describe effect of baroreceptors on contractility

Answer 19

Normal baroreceptor discharge leads to dec sympathetic discharge, and little stimulation of cardiac contractility
Inc b.d. leads to cessation of s.d. & no stimulation if cardiac contractility
Dec b.d. leads to more activity of s.d. & an inc in cardiac contractility, SV & COP.

Question 20

Baroreceptors have …. Effect on respiration

Answer 20

Inhibitory

Question 21

What happens to baroreceptors in case of HTN

Answer 21

They are reset & cannot correct the high ABP but help maintain the new level and decrease fluctuations from the new hyoertensive level

Question 22

Describe carotid sinus syndrome

Answer 22

The baroreceptors are hypersensitive & respond to pressure on the neck resulting in inhibition of VMC & stimulation of vasodilator sympathetic center leading to dec ABP & loss of conscienceness. It is the correct response to a wring stimulus.

Question 23

Compare type A & type B atrial receptors

Answer 23

Type A: high pressure, respond to high ABP & cause VD, Bradycardia & dec contractility. May act in pulmonary circulation, to dec ABP & HR, in sudden pulmonary HTN
Type B: low pressure, repond to inc blood volume leading to VD of peripheral arterioles, inc capillary fluid shift (intermediate reg), dec secretion of ADH, VD of afferent arterioles in kidney & inc GFR, inc urine formation & inc ANP (long-term reg)

Question 24

Chemoreceptor discharge leads to secretion of …..

Answer 24

Adrenaline

Question 25

Direct effect if chemoreceptor discharge on HR is …. | Why is this effect masked?

Answer 25

Bradycradia | Due to increased HR secondary to circularing adrenaline and due to associated increased respiration

Question 26

In Bezold-Jarisch reflex injection of …… leads to ….. This effect may be associated with

Answer 26

Veratridine & serotonin Hypotension & bradycardia MI

Question 27

CNS ischemic reflex persists for …..

Answer 27

5-7 min

Question 28

Detail the Cushing Reflex

Answer 28

In case of cranial hemorrhage or brain tumour, ICP increases leading to compression of blood vessels, brain ischemia & dec blood flow to VMC. This leads to strong vasocontrictor tone leading to severe hypertenion (which maintains blood flow to brain) and bradycardia.

Question 29

Explain the bradycardia associated with Cushing reflex

Answer 29

Increased rate of arterial baroreceptor discharge & direct stimulation of CIC

Question 30

Rapidly acting hormones act within …..

Answer 30

20 min

Question 31

GR: Adrenaline & NA are secreted in case of fall in ABP

Answer 31

Decreased barireceptor activity Increased chemosreceptor activity Increased activity of CNS ischemic reflex

Question 32

Describe effects of adrenaline

Answer 32

Act on alpha & beta receptors Adranline has more effect on heart compared to NA leads to inc HR & SV thus CO is inc Hasless effect on ABP, as it cuases VC & VD of skeletal muscle BV leading to little change in TPR, SBP is inc while DBP is slighly dec. little effect of MAP & but PP is augmented

Question 33

Describe effects of noradrenaline

Answer 33

Act on alpja receptors only, on heart ot directly inc HR & SV but this effect is counteracted by its effect on ABP. It causes generalizaed VC, leading to inc TPR & ABP, which stimulated baroreceptors dec HR & CO. So net effect is inc TPR & ABP & dec HR & CO.

Question 34

ADH is synthesized by … & stored in ….

Answer 34

Hypothalamus | Posterior pituitary

Question 35

How is ADH released?

Answer 35

It is released in inc plasma osmotic pressure or stimulation of cardiopulmonary volume receptors when atrial blood volume or pressure is dec

Question 36

Describe action of ADH

Answer 36

When released it acts on V2 receptors in distal renal & collecting tubules, leading to water retention dec urine & inc blood volume. At higher levels ct on V1 receptors in resistance vessels causing VC & inc ABP

Question 37

When is Renin secreted?

Answer 37

1. Renal hypoperfusion: decreased ABP & Renal ischemia 2. Hyponatremia 3. Sympathetic discharge to JGA

Question 38

Describe action of renin

Answer 38

Activate angiotensiogen (alpha2 globin made by liver) to angiotensin-I (a decapeptide), cleaved by ACE which is flound in vascular endothelium but esp pulmonary vasculature into an octapeotide (angiotensin II) which is the active component of the system.

Question 39

What is the function of angiotensin II

Answer 39

1. Potent VC, leads to inc TPR, SBP & DBP 2. Stimulate secretion of aldosterone inc Na & water retention by kidneys, inc circulating blood voluem & ABP 3. Stimulate subfronical areas in brain inc drive to drink water

Question 40

Describe capillary fluid shift

Answer 40

When ABP rises, filtration in arterial end is augmented, resbsorption at venous end is dec leading to shift if fluid to tissue and dec blood volume & dec ABP. Opposite occurs with dec ABP, where the whole length can become reabsorptive.

Question 41

Describe stress-relaxation mechanism

Answer 41

When ABP inc big vessel open more and more to yielding to the high ABP (stress-relaxation), thus dec ABP toward normal value. But when it dec the vessel closes on the blood leading to inc ABP towards normal value (anti-stress relaxation)

Question 42

Describe rolebof rebal control

Answer 42

In inc ABP, GFR inc leading to pressure diuresis & pressure naturesis dc blood volume , VR & COP & ABP Opposite occurs in decrease

Question 43

Mention role of slowlu acting hormones

Answer 43

RAAS & ADH have long-term regulatory effects in addition to rapid effects Cortisol & aldosterone lead to Na & water retention Atrial naturetic peptide released from stretching of atria by inc circulating blood volume & pressure, inc diuresis & naturesis dec blood volume & ABP. May have VD, anti-renin, anti-aldosterone, anti-ADH.