Cardiovascular 7 Flashcards
MAP is the driving force
For blood flow
-balance between blood flow into and out of arteries
Mean arterial pressure is proportional to
Cardiac output x peripheral resistance
If cardiac output increases and peripheral resistance doesn’t, then blood is pumped
Into arteries faster than it is removed
Means ^ volume in arteries, ^ MAP
MAP influenced by: (4)
Blood volume
Cardiac Output
Resistance of system to blood flow
Relative distribution of blood between arterial and venous blood vessels
Arteries are:
Low volume vessels
-contain about 11% of total blood volume (of the 5L)
Veins are:
High volume vessels and hold around 60% of circulating blood volume (of the 5L)
-act as volume reservoir, can constrict if blood needs to shift
Small changes in volume occur from
Ingestion of food and liquids
-primarily resolved by kidneys
(Increased urination gets rid of excess fluids, lowers pressures)
Decreases in blood volume require what response
Integrated response fro kidneys, CV system (increased sympathetic output), and ingestion of fluid
Resistance of flow is highest in the
Arterioles
Total resistance depends on:
Radius of each vessel, length of each vessel, how they are arranged (series, parallel)
Local Control of Arteriolar resistance
Matches blood tissue blood flow to the metabolic needs of tissue
-heart and skeletal, these controls take power over reflex control from CNS
Arteriolar Resistance is influenced by both local and systemic control mechanisms that do what
They both alter the vascular smooth muscle, changing the radius of vessels, influencing resistance
Resistance is proportional to
1/ radius ^4
Sympathetic reflexes
Mediated by CNS
-maintain MAP
-govern blood distribution for homeostastic needs, like tempurature
Hormones
Regulate salt and water excretion by kidneys
-influence blood pressure by acting on articles
Myogenic Autoregulation
^ tension, ^ blood flow to other arteries
-contraction in response to stretch of vascular smooth muscle
Paracrines alter smooth muscle how
They are released from target tissue or endothelial cells that affect specific muscle nearby
Metabolism related paracrines
Decrease O2, increase CO2, NO, H+, lactate, adenosine
Non metabolism paracrines
Kinins, histamine, serotonin
Main determinant of resistance in the majority of arterioles is
The sympathetic nervous system -50% about
-innervate articles, topically control arterial diameter
Alpha 1 adrenergic receptors do what
Activated/ deactivated by norepinephrine
Activated: constrict vessels
Deactivated: Dialation of vessel
Secondary sympathetic control of vascular smooth muscle uses
Epinephrine from adrenal medulla
-low affinity for alpha1 for vasoconstriction, but a high affinity for B2 adrenergic receptors which lead to VASODILATION
Muscles have more kind of what receptor
More beta receptors than alpha
GI Tract has more of what kind of receptors
More alpha recceptors than beta
Norepinephrine to a alpha 1 receptor causes
The blood vessel to constrict
Factors Influencing Peripheral Blood Flow: (2)
Pressure gradient and Resistance to Flow
Skeletal muscle recieves what % of Q at rest
About 20%, but can increase to as high as 85% during strenuous exercise
At rest, regional amount of blood flow depends on:
The number and size of arteries feeding the organ
Total blood flow through all the arterioles equals
Cardiac Output
Flow (arteriole) is proportional to 1/ R (arteriole)
Blood is diverted away from high resistance arterioles to
Low resistance arterioles
-takes the path of least resistance
Main Integrating centre
Medullary Cardiovascular Control Centre
-ensures adequate blood flow to the brain and heart by maintaining sufficient MAP
CVVC recieves input from sensory receptors and other brain regions to:
Specifically alter function in some organs or tissues
