Integrated Control of the Cardiovascular System

Chapter 24

Integrated Control of the Cardiovascular System

Chapter 24

• CO = SV x HR

• SV = EDV – ESV

• EDV (Pre Load):

• Filling Pressure is determined by rate of venous return

• Muscle Pump and Thoracic pump aid venous return• Heart Rate; SA node

• SNS increases and PSN decreases, Epi of ß1 increases

• Threshold depolarized and Maximum hyperpolarized by PSN

• Slope is Decreases by PSN and Increased by SNS

• MAP = CO x TPR• Closed system so increasing CO decreases Filling Pressure and visa versa (Red line)

• TPR: Vasoconstriction will increases TPR while Vasodilatation will decreases TPR

• Baroreceptor monitors and regulates MAP

• Orthostasis, living in Gravity

• Orthostatic Hypotension (OH)

• Myogenic response minimizes OH

• Blood will pool in lower body

• SNS stimulation decreases the dispensability (compliance) of the lower body veins to minimize the pooling of blood

• Muscle Pump prevents pooling

• 1 cm of water is about 1 mmHg pressure

• Standing: capillary pressure in the feet can be at least 100 mmHg an cause fluid movement into the interstitial space, feet swell

• Fight or Flight Response

• Response from Higher Centers through the ANS

• SNS alfa1, vasoconstriction

• Dogs only

• ß2

• Vagovagal Syncope, Heart Stops Momentarily

• Increase output of PSN and decrease of SNS

Lower Pressure

• AVP (ADH) increases

• Blood levels high enough to stimulate the V1 receptor of the vascular smooth muscle to constrict

• Explains why after the syncope episode the person may be flushed and pallor, no blood flow to the shin.

• Greatest Stimulus for ADH release• Blood osmolality less of a stimulus but it is the most common regulator

• Exercise

• Higher brain levels initiate ANS

• Activated immediately on movement

• SNS initially causes constriction of the arterioles in muscle (Alfa1) but this is quickly over ridden by local metabolic control and epinephrine stimulating the ß2 adrenergic receptor

• Exercise Hyperthermia

• Reset in Hypothalamus

• Increase MAP, 120 mmHg

• Reset baroreceptor reflex

• Set point is increased to about 120 mmHg

• Exercising Muscle Effects

• During exercise TPR decreases

• Hemorrhage, Reversible• Thirst and Na+ appetite (low pressure receptors)• ADH (Low pressure baroreceptors)• ANP (right atria)• Transcapillary Refilling

• Lower Capillary Pressure

• ADH and AVP are the same

• Hemorrhage greatest stimulus for release

• V1 receptor of vascular smooth muscle, not very sensitive, need > 100 pM, vasoconstrictor

• V2 receptor in kidney, very sensitive, < 15 pM, save water

• Irreversible

• Low AVP

• High NO

• Transcapillary Refilling

• Low capillary pressure permits High capillary Colloid Osmotic Pressure (25 mmHg) to pull interstitial fluid into blood

• Interstitial fluid is replaced with cellular fluid