Ch 10.6 -- Blood Pressure -- VTPP 435

Ch 10.6 -- Blood Pressure -- VTPP 435

Baroreceptors

-pressure receptors in circulatory system that monitor blood pressure (MAP) to adjust it
-short term - alter CO or TPR
-long-term - adjust blood volume and control salt and water balance

Baroreceptor Reflex

-automatically mediated reflex response that influences heart and blood vessels to oppose a change in MAP
-adjusts CO and TPR
-has full reflex arc

Carotid Sinus Baroreceptor

-mechanoreceptor
-senses MAP changes
-near brain
-sends info to cardiovascular control center
-increases firing rate in its afferent neurons

Aortic Arch Baroreceptor

-mechanoreceptor
-senses MAP changes
-in Aorta
-sends info to cardiovascular control center
-increases firing rate in its afferent neurons

If blood pressure falls below normal

-baroreceptor activity decreases
-cardiovascular control center increases sympathetic cardiac and vasoconstrictor nerve action

Factors that Influence Cardiovascular System and Blood Pressure

1) Left atrial volume receptors and hypothalamic osmoreceptors
2) Chemoreceptors in carotid and aortic arteries sensitive to O2 or acid levels
3) Cardiovascular responses associated with behavior and emotion
4) Hypothalamic control over cutaneous arterioles
5) Cardiovascular changes in response to exercise or anticipation

Hypertension

-sustained above-normal MAP
-above 140/90 mmHg

Hypotension

-sustained, below-normal MAP
-below 90/60 mmHg
-if extreme is circulatory shock

Primary (Essential) Hypertension

-hypertension that is elevated for an unknown causes or a single disease
-can be genetic

Secondary Hypertension

-hypertension that occurs secondary to another primary problem
-like kidney disease with excess salt

Complications of Hypertension

1) Left Ventricular Hypertrophy
2) Stroke
3) Heart Attacks
4) Kidney Failure
5) Progressive Loss of Vision

Prehypertension

-blood pressure in range between 120/80 and 140/90

Orthostatic (Postural) Hypotension

-results from insufficient compensatory responses to gravitational shifts in blood when person moves from horizontal to vertical position
-transient

Circulatory Shock

-when MAP falls so low that adequate blood flow to tissues can no longer be maintained

4 Causes of Circulator Shcok

1) Hypovolemic Shock
2) Cardiogenic Shock -- weak HF
3) Vasogenic Shock -- widespread arteriolar vasodilation
4) Neurogenic Shock -- neurally defective vasoconstrictor tone