- Sympathetic stimulation of heart - Preload

- Sympathetic (increases) - Parasympathetic (decreases)

Lecture 15: Regulation of Arterial Pressure Flashcards by Erik Hammond

When metabolic demand is high, more blood is released through capillary beds by doing what to the arterioles?

Reducing resistance = Vasodilation

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What are the 2 general methods of control for arterial pressure?

1) Rapid, neuronally mediated

2) Slower, hormonally mediated

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The neuronally mediated mechanism for controlling arterial pressure relies on what?

Pressure sensors, a control center and pressure control mechanism influencing the heart and vasculature (baroreceptor reflex)

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What organ is most involved in the hormonally mediated mechanism for control of arterial pressure?

A large component of both the sensor and pressure influencing organs are the kidneys.

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The baroreceptor reflex utilizes?

Classical reflex arc

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What are the 2 types of receptors used by the baroreceptor reflex?

1) Mechanoreceptors - change in pressure

2) Chemoreceptors - change in PO2, PCO2, pH

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How quick can these detectors act and how long can they last?

Can act within seconds and last indefinetely

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How do the detectors sense change in pressure?

Through stretch receptors on vessel wall

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Increased stretch causes; decreases stretch casuses?

Increased stretch = increased firing rate

Decreases stretch = decreased firing rate

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The carotid sinus baroreceptors are innervated by?

Sinus nerve of Hering, a branch of the Glossopharyngeal nerve (CN IX)

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The aortic sinus baroreceptors are innervated by?

Aortic nerve, a branch of the Vagus nerve (CN X)

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The afferent neurons of the carotid and aortic sinus travel where?

Up the spinal cord, to the brain stem, and finally to the nucleus tractus solitarius (NTS)

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What is the NT used by affernet neurons the NTS?

Glutamate

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The rostral ventrolateral medulla is responsible for?

Vasculature repsonse

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The dorsal motor nucleus of the vagus and nucleus ambiguous is responsible for?

Cardiac response

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Baroreceptors send signals to the medulla, which is considered the?

Control center

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Stretch of receptors decreases firing rate of which neurons?

Afferent neurons - send the signal to the medulla

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Efferents are both?

Parasympathetic (vagus) and sympathetic

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What parts of the brain do the afferents travel to?

Cerebral cortex and hypothalamus

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Mean arterial blood pressure (MABP) =

HR x SV x TPR

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What is the baroreceptor reflex working to maintain?

MABP

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TPR is dependent on?

Sympathetic stimulation of arterioles

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SV is dependent on?

Sympathetic stimulation of heart

- Preload

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HR is dependent on?

Sympathetic (increases)

- Parasympathetic (decreases)

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Increased frequency of stimulation increases what?

Strength of AP

How is the aortic sinus different from the carotid?

- Higher threshold for activation - Continues to respond above saturation - Less sensitive to rate, less effected by decreases

The increase or decrease in firing rate of these receptor neurons is proportional to?

The change in pressure

How does the sympathetic nervous system affect the firing rate of baroreceptors?

Decreases firing rate

Sympathetic NS does what to arterioles and veins; via which receptor?

Constriction via α receptors

Sympathetic NS does what to HR and contractility; via which receptor?

Increases via β receptors

Parasympathetic NS affects the firing rate of baroreceptors how?

Increases firing rate

Which nerve is part of the parasympathetic NS and signals to the SA node, atria and ventricles; via what receptor?

Vagus nerve using muscarinic receptors

What is the affect of the parasympathetic NS on blood vessels?

Indirect vasodilation (via stimulation of NO release)

How does HTN affect baroreceptors?

Will cause them to adjust their set-point to the new condition. Makes it so that the body can still respond to changes.

How does RAAS help control BP?

Regulation blood volume

For longer term adjustments to changes in BP what kind of response is invoked?

A hormonal response

The hormonal response is invoked and begins how quick and building for how long?

Begins within minutes and can build over a period of days or longer if needed

Renin is secreted by, in response to?

Secreted by the kidney in a response to a drop in BP and by sympathetic stimulation

Stimulation of what receptor also increases the release of renin?

β1-adrenergic receptor by sympathetic NS

What does renin do in the blood?

Causes Angiotensinogen to be converted to Angiotensin I (inactive)

What must occur to angiotensin I to become active; where?

Must be converted to Angiotensin II in the lungs (and kidneys)

What part of the kidney secretes Renin?

Juxtaglomerular (JG) cells in walls of renal afferent arterioles

Angiotensin II causes the secretion of what 2 things?

1) Aldosterone from the adrenal cortex | 2) ADH (Vasopressin)

What does aldosterone do?

Leads to Na+ and H2O retention by kidney

Aldosterone causes an increase in?

Blood volume, preload/stroke volume, CO, and therefore BP

What is the affect of ADH (vasopressin)?

Reduces urine production (fluid retention) and increases TPR

How does angiotensin II affect arterioles; binds to?

Binds to AT1 receptors and causes global vasoconstriction of arterioles

Angiotensin II affect on the hypothalamus?

Increases thirst

What do ACE inhibitors do?

Prevent the conversion of angiotensin I to angiotensin II in lungs

Side effect of ACE inhibitors?

Cough because of a buildup of bradykinin (Angiotensin II breaks down bradykinin)

How can arteriolar angiotensin II receptors be blocked pharmacologically?

Using angiotensin receptor blockers (ARBs)

BP =

BP = CO x TPR *CO = SV x HR

Vasopressin (ADH) acts via which receptors, found where?

V1 receptors (smooth muscle) - increase TPR V2 receptors (collecting ducts) - fluid retention

Vasopressin (ADH) is secreted in response to what 3 things?

1) Angiotensin II 2) Increased osmolarity of blood 3) Atrial receptors in presence of low preload

What are the 3 forms of natriuretic peptides?

1) Atrial (ANP) 2) Brain (BNP) 3) C-type (CNP)

When are natriuretic peptides secreted?

During excessive preload of atria and ventricles

What 3 things do natriuretic peptides cause?

1) Arteriolar dilation - decreases TPR 2) Increase fluid loss - decreases preload 3) Inhibits renin - decreases both TPR and preload

Natriuretic peptides protect against?

Overdilation and overstretching of cardiac chambers

Cerebral ischemia causes?

Increased sympathetic outflow from vasomotor center

Why would you want increased sympathetic outflow during cerebral ischemia?

Sympathetic outflow = vasoconstriction = protective if BP is dropping and there will not be enough to adequately perfuse the brain

Cushing reflex is in response to?

Increased intracranial pressure - compresses cerebral arteries and reduces perfusion

What is the triad for the Cushing Reflex; cause for each?

1) HTN (sympathetic drive to increase blood flow to brain) 2) Bradycardia (baroreceptors sensing increased BP) 3) Irregular respiration (impaired brain stem function)

In response to increased blood volume - increased preload, what 4 things occur?

1) Increases secretion of ANP 2) Decrease ADH secretion 3) Renal vasodilation 4) Increased HR

Anticipation at what part of the brain causes the changes before exercise?

Cerebral cortex - central command response

What is the central command response to the anticipation of exercise?

1) Increased sympathetic output/decreased parasympathetic 2) Increased HR/contractility/stroke volume 3) Increased venous return (preload) 4) Vasoconstriction (slight increase in MAP)

What orchestrates the peripheral response (local) in exercising skeletal muscle; importance?

- Active hyperemia due to an increase in local metabolites (K+, lactate, and adenosine) - Most important mechanism of control during exercise

The central command during exercise causes vasoconstriction of?

Splanchnic (gut) and renal arterioles

What 2 things causes an increase in venous return during exercise?

1) Contraction of skeletal muscle around the veins has a mechanical (squeezing) action 2) Activation of the sympathetic nervous system produces venoconstriction.

What triggers the anticipatory affect produced by the central command before exercise?

Triggered by muscle mechanoreceptors

Vasoconstriction will not occur where during exercise?

Skeletal muscle, coronary and cerebral circulation

What happens to TPR during exercise?

An overall decrease in TPR due to vasodilation of skeletal muscle