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1

Hypertension
- Direct relationship between hypertension and?
- Affects __ of adults in U.S.
- Additional ___% have prehypertension
- High priority health concern identified in?

- cardiovascular disease
- Affects 33% of adults in U.S.
- Additional 30% have prehypertension
- High priority health concern identified in Healthy People 2020

2

Blood pressure (BP) is the force exerted by the blood against the walls of the blood vessel. It must be adequate to maintain tissue perfusion during activity and rest. The maintenance of normal BP and tissue perfusion requires the integration of both?

systemic factors and local peripheral vascular effects. BP is primarily a function of cardiac output (CO) and systemic vascular resistance (SVR)

3

CO is?

total blood flow through the systemic or pulmonary circulation per minute. It is described as the stroke volume (SV) or the amount of blood pumped out of the left ventricle per beat (approximately 70 mL) multiplied by the heart rate (HR).

4

Factors influencing BP: Sympathetic nervous system (SNS)

- Activation increases HR and cardiac contractility
- Vasoconstriction and renin release
- Increases CO and SVR

5

Systemic vascular resistance (SVR) is the force opposing the movement of blood within the blood vessels. The radius of the small arteries and arterioles is the principal factor determining SVR. As arteries narrow, resistance to blood flow increases. As arteries dilate, resistance to blood flow decreases. A small change in the radius of the arterioles creates a major change in the SVR. If SVR is increased and CO remains constant or increases, what happens?

arterial BP will increase

6

The mechanisms that regulate BP can affect either CO or SVR, or both. Regulation of BP is a complex process involving both short-term (seconds to hours) and long-term (days to weeks) mechanisms.
1) Short-term mechanisms, including?
2) Long-term mechanisms include?

1) sympathetic nervous system (SNS) and vascular endothelium, are active within a few seconds.
2) renal and hormonal processes that regulate arteriolar resistance and blood volume.
- In a healthy person these regulatory mechanisms function in response to the body's demands.

7

Sympathetic Nervous System:
The nervous system, which reacts within seconds after a drop in BP, increases BP primarily by activating the SNS. Increased SNS activity increases?

HR and cardiac contractility, produces widespread vasoconstriction in the peripheral arterioles, and promotes the release of renin from the kidneys. The net effect of SNS activation is to increase BP by increasing both CO and SVR.

8

Sympathetic Nervous System: Specialized nerve cells called baroreceptors (pressoreceptors) are located in the carotid arteries and arch of the aorta.
1) These cells sense?
2) SNS efferent nerves innervate cardiac and vascular smooth muscle cells. Under normal conditions, a low level of continuous?

1) changes in BP and transmit this information to the vasomotor centers in the brainstem. The brainstem sends this information through complex networks of neurons that excite or inhibit efferent nerves.
2) SNS activity maintains vascular tone. BP may be reduced by withdrawal of SNS activity or by stimulation of the parasympathetic nervous system (PNS). The PNS decreases the HR (via the vagus nerve) and thereby decreases CO.

9

Sympathetic nervous system: The neurotransmitter norepinephrine (NE) is released from SNS nerve endings. 1) NE activates receptors located in the?
2) The response to NE depends on the type of receptors present. SNS receptors are classified as α1, α2, β1, and β2. The smooth muscle of the blood vessels has?
3) α-Adrenergic receptors located in the peripheral vasculature cause what when stimulated by NE?
4) β1-Adrenergic receptors in the heart respond to NE and epinephrine with?
5) β2-Adrenergic receptors are activated primarily by?

1) sinoatrial node, myocardium, and vascular smooth muscle.
2) α-adrenergic and β2-adrenergic receptors.
3) vasoconstriction when stimulated by NE.
4) increased HR (chronotropic), increased force of contraction (inotropic), and increased speed of conduction (dromotropic).
5) epinephrine released from the adrenal medulla and cause vasodilation

10

Sympathetic Nervous System Receptors Affecting BP
α1 Receptor:
-Location
-Response when activated

1)
-Location: Vascular smooth muscle
-Response when activated: Vasoconstriction
2)
-Location: Heart
-Response when activated: Increased contractility (positive inotropic effect)

11

Sympathetic Nervous System Receptors Affecting BP
α2 Receptor:
-Location
-Response when activated

1)
-Location: Presynaptic nerve terminals
-Response when activated: Inhibition of norepinephrine release
2)
-Location: Vascular smooth muscle
-Response when activated: Vasoconstriction

12

Sympathetic Nervous System Receptors Affecting BP
β1 Receptor:
-Location
-Response when activated

1)
-Location: Heart
-Response when activated:
* Increased contractility (positive inotropic effect)
* Increased heart rate (positive chronotropic effect)
* Increased conduction (positive dromotropic effect)
2)
-Location: Juxtaglomerular cells of the kidney
-Response when activated: Increased renin secretion

13

Sympathetic Nervous System Receptors Affecting BP
β2 Receptor:
-Location
-Response when activated

-Location: Smooth muscle of blood vessels in heart (e.g., coronary arteries), lungs (e.g., bronchi), and skeletal muscle
-Response when activated: Vasodilation

14

Sympathetic Nervous System Receptors Affecting BP
Dopamine Receptors:
-Location
-Response when activated

-Location: Primarily renal blood vessels
-Response when activated: Vasodilation

15

The sympathetic vasomotor center interacts with many areas of the brain to maintain normal BP under various conditions. It is activated during times of pain, stress, and exercise. The SNS response causes an appropriate increase in CO and BP to adjust to the body's increased O2 demands.
- During postural change from lying to standing, there is a transient?

decrease in BP. The vasomotor center is stimulated, and the SNS response causes peripheral vasoconstriction and increased venous return to the heart. If this response did not occur, blood flow to the brain would be inadequate, resulting in dizziness or syncope.

16

Baroreceptors have an important role in the maintenance of BP stability during normal activities.
1) They are sensitive to stretching and, when stimulated by an increase in BP, they?
2) When a fall in BP is sensed by the baroreceptors, the?

1) send inhibitory impulses to the sympathetic vasomotor center. Inhibition of the SNS results in decreased HR, decreased force of contraction, and vasodilation in peripheral arterioles.
2) SNS is activated. The result is constriction of the peripheral arterioles, increased HR, and increased contractility of the heart. In long-standing hypertension, the baroreceptors become adjusted to elevated BP levels and recognize this level as their new “normal.”

17

- Sensitive to stretching
- Send impulses to sympathetic vasomotor center

Baroreceptors

18

The vascular endothelium is a single-cell layer that lines the blood vessels.
- Functions:

- Functions: platelet adhesion, coagulation regulation, immune function, and regulation of fluid control within the vessel and extravascular space. The endothelium can also cause adhesion and aggregation of neutrophils and stimulate smooth muscle growth.
- essential to the regulation and maintenance of the vasodilating and vasoconstricting substances.9 Endothelium-derived vasoactive substances include nitric oxide (NO) and prostacyclin, which are both vasodilators. Another product of the endothelium is endothelin (ET), which is a potent vasoconstrictor (Fig. 32-1). A disruption or dysfunction of arterial tone (either through excessive constriction or dilation) is an early warning signal of CVD.

19

Produces vasoactive substances to maintain low arterial tone

Vascular endothelium

20

- Control sodium excretion and ECF volume
- RAAS system
- Prostaglandins

Renal system

21

Renal System
- Control sodium excretion and ECF volume

The kidneys contribute to BP regulation by controlling sodium excretion and extracellular fluid (ECF) volume. Sodium retention results in water retention, which causes an increase in ECF volume. This increases the venous return to the heart and stroke volume. Together these increase CO and BP.

22

Renal System
- RAAS system

plays an important role in BP regulation.
- juxtaglomerular apparatus in the kidney secretes renin in response to SNS stimulation, decreased blood flow through the kidneys, or decreased serum sodium concentration.
- Renin (enzyme that converts angiotensinogen to angiotensin I) Angiotensin I is converted to angiotensin II (A-II) by angiotensin-converting enzyme (ACE).
- A-II increases BP by two different mechanisms. First, A-II is a potent vasoconstrictor and increases SVR. This results in an immediate increase in BP. Second, over a period of hours or days, A-II increases BP indirectly by stimulating the adrenal cortex to secrete aldosterone
- A-II also acts at a local level within the heart and blood vessels. These effects include vasoconstriction and tissue growth that result in remodeling of the vessel walls, which can be due to or caused by endothelial dysfunction. These changes are linked to the development of primary hypertension and also the long-term effects of hypertension (e.g., atherosclerosis, renal disease, cardiac hypertrophy)

23

Renal system
- Prostaglandins

Prostaglandins (PGE2 and PGI2) secreted by the renal medulla have a vasodilator effect on the systemic circulation. This results in decreased SVR and lowering of BP. The natriuretic peptides (atrial natriuretic peptide [ANP] and b-type natriuretic peptide [BNP]) are secreted by heart cells. They antagonize the effects of antidiuretic hormone (ADH) and aldosterone. This results in natriuresis (excretion of sodium in urine) and diuresis, resulting in reduced blood volume and BP.

24

Factors influencing BP: Endocrine system main points

- Epinephrine and norepinephrine from adrenal medulla
- Aldosterone from adrenal cortex
- ADH from posterior pituitary

25

Endocrine System
1) Stimulation of the SNS results in release of epinephrine along with a small fraction of NE by the adrenal medulla. Epinephrine increases the?
2) Epinephrine activates β2-adrenergic receptors in?
3) In peripheral arterioles with only α1-adrenergic receptors (skin and kidneys), epinephrine causes?

1) CO by increasing the HR and myocardial contractility.
2) peripheral arterioles of skeletal muscle, causing vasodilation.
3) vasoconstriction.

26

Endocrine System
- A-II stimulates the adrenal cortex to release aldosterone. Aldosterone stimulates the?

kidneys to retain sodium and water. This increases blood volume and CO

27

Endocrine System
- An increased blood sodium and osmolarity level stimulates the release of?

ADH from the posterior pituitary gland. ADH increases the ECF volume by promoting the reabsorption of water in the distal and collecting tubules of the kidneys. The resulting increase in blood volume causes an increase in CO and BP.

28

Hypertension is defined as a persistent?

systolic BP (SBP) of 140 mm Hg or more, diastolic BP (DBP) of 90 mm Hg or more, or current use of antihypertensive medication

29

Prehypertension is defined as?

SBP of 120 to 139 mm Hg or DBP of 80 to 89 mm Hg

30

Isolated systolic hypertension (ISH) is defined as an average

SBP of 140 mm Hg or more, coupled with an average DBP of less than 90 mm Hg.
- SBP increases with aging.
- DBP rises until approximately age 55 and then declines. - Control of ISH decreases the incidence of stroke, heart failure, and death.