Lecture 21: Regulation of Arterial Pressure

Question 1

What are the equations for calculating Mean Arterial Pressure?

Answer 1

• Mean Arterial Pressure = Cardiac Output x Total Peripheral Resistance
• Mean Arterial Pressure = Heart Rate x Stroke Volume x Total Peripheral Resistance
• Mean Arterial Pressure = 2/3 (Diastolic BP) + 1/3 (Systolic BP)

Question 2

What regulates mean arterial pressure?

Answer 2

• Baroreceptor Reflex
• RAAS System
• ADH
• ANP

Question 3

Where are baroreceptors located?

Answer 3

• Carotid sinus
• Aortic sinus

Question 4

What nerves are involved in the carotid sinus?

Where do they send their information?

Answer 4

• CN IX
• Sinus nerve of Hering

Question 5

What nerves are involved in the aortic sinus?

Answer 5

• CN X
• Aortic Nerve

Question 6

Where do nerves from the aortic and carotid sinus send their information?

Answer 6

Nucleus Tractus Solitatrius

Question 7

What neurotransmitter do afferent signals from baroreceptors use when sending information to the nucleus tractus soliatrius?

Answer 7

Glutamate

Question 8

What do chemoreceptors respond to?

Answer 8

• PO₂
• PCO₂
• pH

Question 9

What do mechanoreceptors respond to?

Answer 9

• Changes in arterial pressure

Question 10

What causes increased firing in a baroreceptor?

Answer 10

Increased pressure/stretch

Question 11

What causes decreased firing in a baroreceptor?

Answer 11

Decreases in pressure/stretch

Question 12

Where do baroreceptors send their signals to?

Answer 12

Medulla: Vasomotor center

Question 13

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

Answer 13

• Dorsal motor nucleus of the vagus
• Nucleus ambiguus

Question 14

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

Answer 14

Rostral ventrolateral medulla

Question 15

What is stroke volume is dependent on?

Answer 15

• Sympathetic stimulation of the heart
• Preload (EDV)

Question 16

Heart rate is dependent on?

Answer 16

• Sympathetic stimulation
• Parasympathetic stimulation

Question 17

Total peripheral resistance (TPR) is dependent on?

Answer 17

Sympathetic stimulation of arterioles

Question 18

What is the difference between aortic and carotid baroreceptors?

Answer 18

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

Question 19

Sympathetic nervous system causes _ baroreceptor firing rate

Answer 19

Decreased

Question 20

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

Answer 20

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

Question 21

Parasympathetic nervous system causes _ baroreceptor firing rate

Answer 21

Increased

Question 22

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

Answer 22

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

Question 23

How does hypertension saffect baroreceptors?

Answer 23

Changes “normal” set point to something higher, which becomes the new “normal”

Question 24

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

Answer 24

Juxtaglomerular cells produces renin.

Question 25

What stimulates the release of renin?

Answer 25

* Sympathetic Nervous System * \*Specifically beta 1 adrenergic receptor activation\*

Question 26

What does renin do as an enzyme?

Answer 26

Converts _angiotensinogen to angiotensin I_

Question 27

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

Answer 27

Converted by ACE in lungs

Question 28

What does angiotensin II do in its active form?

Answer 28

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

Question 29

What does aldosterone do?

Answer 29

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

Question 30

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

Answer 30

* 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 31

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

Answer 31

* 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 32

What happens when you have a hemorrhage?

Answer 32

* 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 33

What happens when you have too much blood?

Answer 33

* 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 34

What happens during exercise?

Answer 34

* 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 35

What happens during orthostatic hypotension? What happens in response?

Answer 35

* 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