Integrated Control of the CVS Flashcards
what does mean arterial pressure depend on?
cardiac output and total peripheral resistance
what does regulation of the entire cardiovascular system depend on?
the integrated action of multiple subsystem controls as well as non-cardiovascular controls
what is preload?
how much of the blood comes back from the periphery to the heart
what is afterload?
volume, work wise, in front of the heart
what decreases preload?
anything pulling the blood in the periphery
what increases preload?
anytime we have a higher peripheral resistance, it pushes blood toward the heart so that we can have a higher cardiac output so we can have a higher incoming stroke volume in the next cycle
what are the subsystems of the cardiovascular system? what monitors them?
cardiac output mean arterial pressure total peripheral resistance blood volume systemic circulatory reflexes local vasomotor control
ANS Respiratory system hematopoietic organs and liver urinary and GI systems endocrine system temperature control system
How is part of the autonomic nervous system involved in cardiovascular control?
high-pressure baroreceptor response, also fight or flight response can affect the circulation
how does the respiratory system affect the cardiovascular system?
- monitors pH changes which affect breathing
- the action of the respiratory muscles during inspiration causes intrathoracic pressure to become more negative, thereby increasing venous return
- a third example is that the evaporative loss of water during breathing reduces total body water and, ultimately, blood volume.
how does the hematopoietic organs and liver affect the cardiovascular system?
control blood composition in terms of cell constituents and plasma proteins, which plasma proteins determine colloid osmotic pressure, therefore a major component of the starling forces affecting blood volume
hematocrit and large proteins are major determinants of blood viscosity and blood flow
how does the GI system affect the cardiovascular system?
they determine the input and output of electrolytes and water and are responsible for controlling the volume and electrolyte composition of the ECF playing a role in blood pressure
how does the endocrine system affect the cardiovascular system?
epinephrine release by the adrenal medulla and necessary in a function against norepinephrine in the act of maintaining homeostasis
how does the temperature control system affect the cardiovascular system?
carrying blood from the body core to the skin where heat loss then occurs
Heat loss occurs as sweat glands secrete fluid that then evaporates
Loss of ECF volume reduces the effective circulating volume
what does the overall fight or flight response involve?
Skeletal muscle blood flow Cutaneous blood flow Adrenal medulla Renal and splanchnic blood flow Veins The heart Mean arterial pressure
how is skeletal muscle blood flow affected by the overall fight or flight response involve?
activation of sympathetic cholinergic vasodilator fibers directly causes a rapid and massive increase in blood flow to skeletal muscle.
how is cutaneous blood flow affected by the overall fight or flight response involve?
The sympathetic response causes little change in blood flow to skin unless it stimulates sweating. The neural pathway involves sympathetic cholinergic neurons, which release acetylcholine and vasodilatory neurotransmitters (e.g., calcitonin gene - related peptide [CGRP], vasoactive intestinal peptide [VIP]).
how is the adrenal medulla affected by the overall fight or flight response involve?
Preganglionic sympathetic neurons stimulate the chromaffin cells to release epinephrine, which causes vasodilation in muscle (via β2 adrenoceptors) and vasoconstriction in the kidney and splanchnic beds (via α1 adrenoceptors).
how is the renal and splanchnic blood flow affected by the overall fight or flight response involve?
increased sympathetic output causes vaso-constriction and thereby decreases blood flow. The systemic release of epinephrine also vasoconstricts these vascular beds rich in α1 adrenoceptors.
how are veins affected by the overall fight or flight response involve?
Most veins constrict in response to sympathetic output.
how is the heart affected by the overall fight or flight response involve?
Increased sympathetic output and decreased vagal output cause a rise in heart rate and contractility, so that cardiac output increases.
how is the mean arterial pressure affected by the overall fight or flight response involve?
cardiac output increases, the net result of an increased cardiac output and a resistance change is an increase in arterial pressure.
what is vagovasal syncope?
- Fainting episode
- Response to emotional stress, phlebotomy, sight of blood, acute pain
- Loss of consciousness is due to a transient fall in perfusion pressure to brain
how does the vasovagal response affect Total peripheral resistance?
massive vasodilation occurs, fall in BP is not corrected by a baroreceptor response, which decreases cardiac output
how does the vasovagal response affect Cardiac output?
intense vagal output to heart causes bradycardia and decreased stroke volume= decrease in cardiac output.
Atropine (muscarinic receptor blocker) does not reliably prevent syncope, decreased sympathetic tone to the heart may also play a role in the bradycardia
how does the vasovagal response affect arterial pressure?
fall in mean arterial pressure due to decrease in total peripheral resistance and decreased cardiac output
how does the vasovagal response affect cerebral blood flow?
global cerebral ischemia develops, which results in dizziness and faintness
- If lasts for 10 seconds results in loss of consciousness
- Stress may also provoke hyperventilation= lowers arterial PCO2
- Cerebral blood flow is impaired due to constriction of cerebral blood vessels
Other manifestations of altered ANS activity due to vasovagal syncope?
pallor of skin and sweating
○ Intense vagal stimulation of the GI causing epigastric pain/ nausea
○ Miosis (pupil constriction) and visual blurring from parasympathetic stimulation
what happens following hemorrhage?
Fall in arterial pressure
Four major receptors: high-pressure baroreceptors, low-pressure baroreceptors, peripheral chemoreceptors, and central chemoreceptors
what are the four major receptors affected following hemorrhage?
high-pressure baroreceptors
low-pressure baroreceptors
peripheral chemoreceptors
central chemoreceptors
how are the high pressure baroreceptors affected following hemorrhage?
decrease in the firing rate of afferents from the carotid and aortic baroreceptors
○ Enhanced sympathetic output and diminished vagal output
○ Increase HR and cardiac contractility
○ Produce venoconstriction and selective arteriolar constriction
○ Cooperate to re-establish the arterial pressure
how are the low pressure baroreceptors affected following hemorrhage?
○ Decreases effective circulating volume
○ Lessens the activity of low-pressure stretch receptors
○ Increased sympathetic outflow causes vasoconstriction in a number of vascular beds, particularly the kidney, reducing glomerular filtration rate and urine output
○ Divergent effects on HR
○ Atrial stretch receptors also project to the hypothalamus, enhancing release of AVP, which reduces water excretion by the kidneys
how are the peripheral chemoreceptors affected following hemorrhage?
○ BP drops causing perfusion of the carotid and aortic bodies decline
○ Hypoxia near the glomus cells and increase in firing rate of the chemoreceptor afferents
○ Increased chemoreceptor discharge leads to increased firing of the sympathetic vasoconstrictor fibers and ventilatory chances that indirectly increase HR
how are the central receptors affected following hemorrhage?
○ Severe hypotension results in brain ischemia
○ Fall in the PO2 of brain ECF
○ Rise in PCO2 and fall in pH
○ Acidosis has a profound effect on the central chemoreceptors in the medullar= greatly enhanced sympathetic vasoconstrictor output
