3.4 Cardiovascular Regulation Flashcards
Two levels of regulation
1) Local: occurs within the tissue
2) Non-local: maintaining body-wide MAP
Local control of blood flow through capillaries
Controlled by ARTERIOLES
What causes vascular smooth muscle relaxation (local control through capillaries)
Local increases in metabolites generated as waste products of anaerobic cellular respiration / decreases in nutrients
What happens after vascular smooth muscle dilation? (local control through capillaries)
Dilation and increased blood flow (Active hyperemia)
What does increased dilation and blood flow do?
Reduces SVR if widespread
Metabolites with vasodilatory effects
CO2, lactic acid, O2, glucose
A(n) ______ in CO2 and lactic acid (decrease in pH) would lead to vasodilation
Increase
A(n) ______ in O2 or glucose would lead to vasodilation
Decrease
Mechanism of local control though capillaries
Vasodilation follows endothelial cells release of NO (nitric oxide)
Essential sensory receptors in cardiovascular reflexes
- Baroreceptors
- Chemoreceptors
Baroreceptors
Stretch receptors monitor pressure in large arteries
Chemoreceptors
Detect pH (indirectly CO2, O2) in carotid and aortic bodies and medulla oblongata
What is the signal integrator of cardiovascular reflexes?
Cardiovascular center in medulla
Effectors of cardiovascular reflexes
1) Heart
2) Vascular smooth muscle
What does the heart control in terms of blood regulation?
Cardiac output (both HR and SV)
What does vascular smooth muscle control in terms of blood regulation?
SVR and CO Vasoconstriction / vasodilation Venous return (impacts CO)
Vessels innervated by adrenergic fibers…
Vasoconstrict (e.g. vessels to skin, abdominal organs)
Vessels innervated by cholinergic fibers…
Vasodilate (e.g. vessels to skeletal muscles, coronary muscles)
Vessels innervated by cholinergic fibers…
Vasodilate (e.g. vessels to skeletal muscles, coronary muscles)
Two ways of maintaining MAP through cardiac output
- Intrinsic regulation
- Extrinsic regulation
Intrinsic regulation
Property of myocardium
Frank Starling Law of the Heart (blood pumps all of the blood that it receives)
-Dependednt on venous return
Extrinsic regulation
By ANS
How does the sympathetic nervous system increase CO?
Increases SV and HR
How does the sympathetic NS decrease CO?
Decreases HR
Frank Starling Law of the Heart
Increase in venous return -> Increase in end diastolic volume -> Increase in stroke volume
What underlies the Frank-Starling law?
Length-tension relationship in cardiac muscle
What does the parasympathetic nervous system use to decrease HR?
Acetylcholine (cholinergic / muscarinic receptors)
First way that Acetylcholine decreases HR
Increasing K+ currents
Hyper polarizes
-Pacemaker cells in SA node
-Conductive cells in AV node
Second way that acetylcholine decreases HR
Decreasing rate of Na+ leakage, slows the rate that the pacemaker cell reaches threshold
How much of an effect does the parasympathetic nervous system have on myocardial contractility (power of muscle contraction)?
Little
What does the sympathetic nervous system use to increase HR and force of contraction?
Norepinephrine
First way that norepinephrine increases HR
Decreasing / slowing outflow of K+ and depolarizing pacemaker cells in SA node
Second way that norepinephrine increases HR
Increases rate of Na+ leakage (speeds rate that pacemaker cells reach threshold)
How does norepinephrine increase strength in contraction of heart muscle?
Increasing Ca2+ currents in ventricular myocytes
Parasympathetic regulation of systemic vascular resistance
Acetylcholine decreases SVR
Vasodilation of systemic arterioles in organs that assist with resting and digesting
-Constriction in underutilized muscle is controlled locally
Effects of norepinephrine and epinephrine in sympathetic regulation of systemic vascular resistance depends on…
Target tissue
Acetylcholine receptors in sympathetic nervous system systemic vascular resistance regulation
In arterioles of skeletal, cardiac and pulmonary vascular smooth muscle causes vasodilation in these organs
Adrenergic receptors in sympathetic nervous system systemic vascular resistance regulation
Expressed just about everywhere else
- Alpha-adrenergic tend to be vaso-constrictive
- Beta adrenergic tend to be vasodilatory along with Ach
Net effect of sympathetic nervous system in systemic vascular resistance
Sympathetic division DECREASES SVR generally in areas of immediate need (muscles) but INCREASES SVR in areas that require lots of blood (liver)
