Cardio 6 Flashcards
Describe the circulatory system.
-closed circuit
-blood returning to heart equals blood pumped by LV into aorta
-flow of blood around circuit depends on:
>number & strength of heart contractions
>total volume of blood
>characteristics of vessels
What are the 2 circulations in series in the cardiovascular system?
- Pulmonary circulation
- Systemic circulation
Describe pulmonary circulation.
-portion of CVS that carries deoxygenated blood away from heart, to the lungs, & returns oxygenated blood back to the heart
Describe systemic circulation.
-part of CVS that carries oxygenated blood away from the heart to the body & returns deoxygenated blood back to the heart
Describe the circulation 3 divisions.
- Distribution system
-ventricles, arteries, arterioles - Perfusion/exchange system
-capillaries - Collecting system
-venules, veins, atria
Describe arteries.
aorta is the largest artery in systemic circulation
-receive blood from heart
-strong vascular walls
-blood flows at high velocity
-elastic tissue
-smooth muscle
-CT
-transport blood under high pressure to tissues
>carry stressed volume
-deliver oxygen & other nutrients to organs
What are the two types of arteries?
- Elastic (high compliance)
-more elastin (increased distensibility)
-more capable to hold lg volume of blood
EX: aorta & carotid artery - Muscular (high resistance)
-more smooth muscle
-more capable to vasoconstriction & dilation
EX: femoral & mesenteric arteries
Describe compliance.
volume of blood the vessel can hold at a pressure
[C = V/P]
C = compliance (mL/mmHg)
V = volume (mL)
P = pressure (mmHg)
Describe vascular resistance.
-resistance that must be overcome to push blood through the circulatory system & create flow
Describe arterioles.
-last smallest branch of arterial system
-act as control conduits (blood released into capillaries)
-strong muscular walls = allow vasoconstriction/vasodilation
>innervated by sympathetic adrenergic nerve fibers
>alter blood flow in response
site of highest resistance to blood flow
Describe alpha 1 & 2 receptors.
-expressed in arterioles of most visceral organs
-alpha 1 = predominant & couple to Gq
-alpha 2 = couple to Gi
>present in nerve terminal to inhibit NE release (feedback)
-norepinephrine = primary endogenous agonist
>released from postganglionic neurons
-found in vascular smooth muscle
-causes vasoconstriction
smooth muscle contraction
Describe beta 2 adrenergic receptors.
-expressed in arterioles of coronaries, skeletal muscle, & liver
-GPCR = Gs
-epi is primary endogenous agonist
>released from adrenal gland
-found in vascular smooth muscle
-cause vasodilation
smooth muscle relaxation
Describe the tonic control of arteriolar diameter.
-arterioles = site of highest resistance & site where resistance can be changed by sympathetic activity
>by circulating cathecolamines & other vasoactive substances
Describe capillaries.
-exchange fluid, nutrients, electrolytes, hormones, & other substances between the blood & interstitial fluid
-thin walled
-single layer of endothelial cells surrounded by basal lamina
-lipid soluble substances cross capillary wall by dissolving in & diffusing across endothelial membrane
-water soluble (ex. Ions) cross capillary wall through:
1. Water filled clefts (spaces) between endothelial cells
2. Large pores in walls (ex. Fenestrated)
not all capillaries perfumed w blood always = depends on metabolic needs
Describe venules.
-collect blood from capillaries & coalesce into larger veins
-thin walled
-endothelial layer
-elastic
-smooth muscle
-CT
Describe veins.
-function as conduits to transport blood from the venules back to heart
-low pressure
-thin wall
-carry unstressed volume
-muscular (contract/expand)
-major controllable reservoir for extra blood
valves = prevent backflow of blood
Describe compliance VS capacitance.
-compliance or capacitance of veins higher than arteries
-capacitance = related w distensibilty
-higher compliance = more volume can hold at a pressure
-veins hold large volumes at low pressure
-arteries have low compliance bc hold less blood at higher pressure
What happens if there is a change in compliance/capacitance of veins?
-redistribution of blood between veins & arteries
-veins constrict = decrease in volume the veins can hold
-blood shifted from veins to arteries
-smooth muscle in walls of veins (arterioles) is innervated by sympathetic nerve fibers
-A1 adrenergic activation = contraction of veins & reduce capacitance & unstressed volume
Describe the velocity of blood flow.
-rate of displacement of blood per unit of time
vary in diameter & cross section area
[V = Q/A]
V = velocity of blood flow (cm/sec)
Q = flow (mL/sec)
A = cross sectional area (cm^3)
Describe the relationship between cross sectional area & velocity of flow.
-cross section area of veins are larger than arteries
>explains lg blood storage capacity of venous system
-as systemic arteries branch to form small arteries, arterioles & capillaries = the total cross sectional area of vessels increase
>forward velocity of blood flow decreases
-blood is collected into venules & veins = total cross sectional area is reduced
>velocity of blood flow increases
Describe the total cross sectional area & velocity.
-velocity of blood varies inversely with total cross sectional area of blood vessels
-TOTAL = all capillaries/arteries/veins together
-CROSS SECTIONAL AREA = area of circle
although capillaries have a smaller diameter, they are more numerous
>flow of blood slows down when there’s a bigger cross sectional area
What is blood flow through a blood vessel determined by?
- Pressure difference between 2 ends of vessel (inlet/outlet)
>driving force for blood flow - Resistance of vessel to blood flow
>impediment to flow
[Q = deltaP/R]
Q = flow (mL/min)
deltaP = pressure difference (mmHg)
R = resistance (mmHg/mL/min)
What is the direction of blood flow determines by?
-the direction of pressure gradient
-high to low pressure
Describe vascular resistance.
-resistance that must be overcome to push blood through circulatory system (creates flow)
-amount of blood flowing through circulation = inversely proportional to resistance
>increasing resistance = decreases flow
(EX: arteriolar vasoconstriction)
vice versa
