Regulation of Arterial Pressure

Question 1

• What is the equation for calculating MAP?

Answer 1

MAP=CO x TPR

or

MAP=HR x SV x TPR

or

MAP=2/3(DBP) + 1/3 (SBP)

Question 2

• Where are baroreceptors located?
• What nerves are involved in each baroreceptor?
• Where do they send their information?

Answer 2

• Carotid sinus
  
  • CN 9 and Sinus nerve of Hering
• Aortic sinus
  
  • Vagus (CN x) and Aortic nerve
• BOTH send their information to NTS

Question 3

• What NTX do afferent signals from baroreceptors use when sending information to the NTS?

Answer 3

Glutamate

Question 4

• What are the mechanoreceptors most responsive to?

Answer 4

• Rate of change in pressure rather than just the magnitude of change

Question 5

• What causes increased firing in a baroreceptor?

Answer 5

• Increased stretch

Question 6

• What causes decreased firing in a baroreceptor?

Answer 6

• Decreases in pressure/stretch

Question 7

• What area of the brainstem is involved in parasympathetic activity in CV function?

Answer 7

• Dorsal motor nucleus of the vagus and nucleus ambiguus

Question 8

• What area of the brainstem is involved in sympathetic activity in CV function?

Answer 8

• Rostral ventrolateral medulla

Question 9

• Stroke volume is dependent on ?

Answer 9

• Sympathetic stimulation of the heart
• Preload (EDV)

Question 10

• HR is dependent on?

Answer 10

• Sympathetic stimulation
• Parasympathetic stimulation

Question 11

• Total peripheral resistance (TPR) is dependent on?

Answer 11

• Sympathetic stimulation of arterioles

Question 12

• What is the difference between aortic and carotid baroreceptors?

Answer 12

• Aortic has higher threshold for activation
  
  • ​Continues to respond above saturation
  • Less sensitive to rate

Question 13

• Recruitment occurs up to _ mm Hg in carotid bodies

Answer 13

200

Question 14

• Low frequency of APs almost vanishes at _ mm Hg

Answer 14

40-60

Question 15

• Sympathetic nervous system causes _ baroreceptor firing rate

Answer 15

Decreased

Question 16

• What are the effects of the sympathetic nervous system on HR, contractility, vein and arteriolar radius, fluid retention?

Answer 16

• Constriction of arterioles and veins (alpha receptors)
• Increases HR and contractility (beta 1)
• Renin secretion and increased fluid retention

Question 17

• Parasympathetic nervous system causes _ baroreceptor firing rate

Answer 17

• Increased

Question 18

What are the effects of the parasympathetic NS on arterial pressure?

Answer 18

• We want to decrease MAP
• Decrease HR
  
  • Vacus n signal to SA node
  • Muscarinic receptors
• Also indirect vasodilation on blood vessels via NO

Question 19

• What enzyme is secreted by the kidney in response to drops in BP? What type of cell secretes this?

Answer 19

• Renin
• Juxtaglomerular cells

Question 20

• What stimulates the release of renin?

Answer 20

• Sympathetic NS
• *Specifically beta 1 adrenergic receptor activation*

Question 21

• What does renin do as an enzyme?

Answer 21

Converts angiotensinogen to angiotensin I

Question 22

• Angiotensin I is converted to Angiotensin II via which enzyme?
• Where is this occurring?

Answer 22

• ACE
• Lungs

Question 23

• What does angiotensin II do in its active form?

Answer 23

• Causes secretion of aldosterone from the adrenal cortex
• Stimulates secretion of ADH/Vasopressin
• Causes global constriction of arterioles by binding to AT1 receptors

Question 24

• What does aldosterone do?

Answer 24

• Increases Na+ and H2O retention
• Increases blood volume, preload, SV, CO, and MAP

Question 25

• What does ADH/Vasopressin do?
• It is not only secreted in response to angiotensin II, but what other factors?

Answer 25

• Acts on V1 and V2 receptors of smooth muscle, and collecting ducts, respectively and increases TPR and water retention
• Atrial receptors during low preload, increased osmolarity of blood

Question 26

• What are the three natriuretic peptides that affect arterial pressure?
• When are they secreted?
• What are their effects?

Answer 26

• ANP, BNP, CNP
• Excessive preload of atria and ventricles
• Effects
  
  • Arteriolar dilation-decrease TPR
  • Increases fluid loss-decreases preload
  • Inhibits renin-decreases TPR and preload

Question 27

• What happens when you have a hemorrhage?

Answer 27

• Decrease in blood volume and MAP
• Decreased firing of mechanoreceptors
• Increase sympathetic activation to bring MAP back up
• Sympathetics will
  
  • Increase HR, CO and contractility via alpha ine adrenergic receptors
  • Constrict arterioles to increase TPR
  • Constrict the veins to decrease unstressed volume and increase venous return
  • Increased RAAS activation

Question 28

• What happens when you have too much blood?

Answer 28

• Increase in blood volume and increase in MAP
• Activate parasympathetics to bring MAP back down
  
  • Increased ANP secretion
  • Decreased ADH secretion
  • Renal vasodilation
  • Increased HR? (d/t increased preload?)*

Question 29

• What happens during exercise?

Answer 29

• Most important thing is getting blood to heart and skeletal muscle-increased sympathetic activation and decreased parasymp activation
• Central command
  
  • Increase HR/contractility via Beta 1 adrenergic receptors
  • Increase venous return
  • Alpha one receptor activation leads to SELECTIVE vasoconstriction in skin, kidney, splanchnic regions, and inactive muscle
  • Vasodilation in active muscles due to metabolites such as K+, adenosine and lactate
• Effects:
  
  • ​Increase in pulse pressure
  • SBP increases
  • DBP should not change much
  • Overall TPR will decrease (d/t dilation of skeletal muscle arterioles

Question 30

• What happens during orthostatic hypotension?
• What happens in response?

Answer 30

• Decreased MAP; no change in HR and TPR, CO goes down from decreased venous return, central venous pressure decreases d/t pooling of blood in lower extremities
• Increase sympathetic activation
  
  • Increase HR, contractility and CO via beta 1 adrenergic receptors
  • Want to increase TPR via constriction of arterioles
  • Want to decrease unstressed volume and increase venous return so we constrict the veins