SM 119a - Integrative Function Flashcards
List the central and local cardiovascular responses to exercise
Central: Mediated by increased sympathetic and decreased parasympathetic outflow
- Increase cardiac output
- Splanclinc and renal constriction of arterioles
- Constriction of veins
Local: Mediated by increases in vasodilator metabolites
- Dilation of skeletal muscle arterioles
How does cardiac function change in response to exercise?
What mediates these changes?
- Increased Heart Rate
- Increased Contractility
- Increased Cardiac Output
- Increased Stroke Volume
Mediated by central command: decreased parasympathetic input (decreased vagal tone) and increased sympathetic input
What are the three mechanisms that increase stroke volume in response to exercise
- Increased preload -> Increased strength of contraction
- Due to increased venous return, due to constriction of veins and pumping of skeletal muscles
- Increased contractility
- Due to increased adrenergic tone
- Increased Ca2+ in the SR
- Increased myogenic sensitivity to Ca2_
- Treppe/Bowditch/Force-frequencey effect
- Increased HR leads to increased intracellular Ca2+
- Due to increased adrenergic tone
- Increased Lusitropy
How does venous constriction affect the strength of cardiac contraction?
Venous constriction increases venous return, which increases preload, thus increasing the strength of cardiac contraction
In splanchnic/renal beds, what kind of adrenergic receptors would you expect to find?
Why?
Alpha-1 receptors, causing arterioles supplying these areas to constrict in response to sympathetic input
These areas are non-essential to running away from predators, so they do not need blood flow during a sympathetic response
In veins, what kind of adrenergic receptors would you expect to find?
Why?
Alpha-1 receptors, causing constriction in response to sympathetic input
During a sympathetic response (ex: exercise or running away from predators), constriction of venules decreases the unstressed volume and increases venous return. This forces blood into the arteries and exercising muscles and increases the strength of cardiac contraction by increasing preload
In exercising myocytes, what mechanism increases the hemoglobin concentration in the blood?
Increased myocyte metabolism leads to…
- Increased metabolic byproducts
- -> Increased oncotic pressure in the extracellular space
- More force sucking fluid out of the capillary into the extracellular space
- -> Increased H2O in the extracellular space, from the capillary
- -> Increased concentration of hemoglobin in blood (due to decreased solvent)
- This increases the pO2 in the blood to allow for better oxygen delivery
What are the vasodilator metabolites produced by exercising myocytes?
- Lactate
- Adenosine
- K+
What are the two major short-term goals in repsonse to hemorrhage?
- Mitigate blood loss due to hemorrhage
- Maintain CO and BP to perfuse tissues and brain
What are the major changes to the cardiovascular circulation in immediate response to hemorrhage?
- Venous return decreases
- Central blood volume decreases
But short-term physiologic responses function to restore both, in order to maintain CO and BP
In immediate response to hemorrhage, venous return decreases.
What is the effect on central and peripheral chemoreceptor?
Decreased venous return -> Decreased CO ->
Decreased regional blood flow
- Peripheral chemoreceptors activate in response to
- Decreased pO2
- Increased pCO2
- Decreased pH
- Central chemoreceptors activate in response to
- Decreased pH in the brain ECF
In immediate response to hemorrhage, venous return decreases.
What is the effect on cardiac function? On MAP?
- Decreased Stroke Volume
- Decreased Cardiac Output
- Decreased MAP
- Decreased blood flow to all areas
List the 4 major inputs to the medullary cardiovascular control center in response to hemorrhage
- High pressure baroreceptors are deactivated
- Decreased cardiac function -> less stretch in the carotid and aorta -> No firing
- Peripheral chemoreceptors are activated
- Central chemoreceptors are activated
- Low pressure baroreceptors are deactivated
- Decreased blood volume -> Decreased atrial filling
- > Decreased atrial volume -> No firing
In response to hemorrhage, the medullary CV control center receives input and then sends efferent signals.
What is the effect of these signals on the kidney?
In general, the kidney responds to hemorrhage by working to conserve blood volume by conserving Na+ and H2O
- Constriction of renal vascular beds
- Decreased glomerular filration
- Decreased excretion of Na+ and H2O
- Decreased glomerular filration
- Decreased ANP secretion
- Decreased excretion of Na+ and H2O
- Increased renin secretion
- Increased angiotensin II
- Increased aldosterone
- Increased reabsorption of Na+
- Increased aldosterone
- Increased angiotensin II
- Increased ADH
- Increased reabsorption of H2O
What are the major goals of efferent signaling from the medullary CV control center in response to hemorrhage?
Mitigate blood loss, maintain CO and BP
- Increase CO via…
- Increased HR
- Increased contractility
- Increase TPR via…
- Arteriolar constriction
- Venous constriction
- Conserve H2O and Na+ via…
- Via signaling to the kidney
