Hemodynamics Flashcards
This refers to the mechanisms which we deliver the right amount of blood to the right location at the right time
Hemodynamics
What is the driving factor of blood flow?
Pressure gradients
What two factors does blood flow rely on?
- Cardiac output
- Blood flow resistance
This describes how much blood the heart is pumping out
Cardiac output
This refers to the tendency for vascular to push blood back to the heart
Bloodflow resistance
What is the equation to find cardiac output?
Cardiac output = stroke volume (SV) x heart rate (HR)
How do you calculate stroke volume?
SV = EDV - ESV
What does EDV stand for
End diastolic volume
What does ESV stand for
End systolic volume
How to calculate ejection fraction
Ejection fraction = SV / EDV
What are the two variables to change that can influence cardiac output
- Heart rate
- Stroke volume
What organ determines the sympathetic and parasympathetic stimulation needed to adjust heart rate (+ maintain bp)
Medulla oblongata
How does a positive chronotrope affect heart rate?
Increases heart rate
How does a negative chronotrope affect the heart?
Decreases heart rate
What three factors does stroke volume depend on?
- Venous return
- Resistance
- Contractility
Greater venous return does what?
Increases end diastolic volume (EDV)
How does greater resistance affect the heart?
Decreases stroke volume
What are the two types of contractility factors?
- Intrinsic
- Extrinsic
What are the two types of contractility factors?
- Intrinsic
- Extrinsic
What are two intrinsic contractility factors?
- Frank-starling Law of the Heart
- Rate-induced regulation (treppe)
What are the extrinsic factors that affect contractility?
Epinephrine and norepinephrine
How do epi and norepinephrine increase contractility?
Increase Ca²+ availability
Changes in what affect the force of contraction?
Peak Ca²+ concentrations; sarcomere length
According to the Frank-Starling Law, larger heart volume results in what?
Stronger contraction
According to Frank-Starling Law, a smaller heart volume results in what?
Weaker contraction
The sarcomere stretch is determined by what?
End diastolic volume
Why does a larger heart volume result in a larger heart contraction?
Heart needs to get to the same end volume (requires more force)
What’s a potential downside to the frank-starling law
Rise in blood pressure
How is contractility augmented by the sympathetic system? (3)
- Increase in systole duration
- More depolarizations/min
- Higher diastolic Ca²+ concentrations
What 3 hormones influence the macroscopic blood volume
- Aldosterone
- Antidiuretic hormones
- Atrial natriuretic hormone
Where is atrial natriuretic hormone produced? What is the response to it?
Right atrium; increased H2O/Na+ excretion from kidneys
What is the response to aldosterone?
Retention of Na+ and H2O
How do fluids move at the microscopic level?
Constantly through interstitial, intracellular, and vascular components
About how many total liters of fluid are present in the intracellular and extracellular levels?
~50 Liters
Whats the arteriolar fluid movement pressure for the capillaries
10 mmHg out
What’s the venous fluid movement pressure at the capillary level?
7 mmHg in
What is driven by selective permeabilty?
Oncotic pressure
About what percent of water that leaves the plasma is recaputure?
90%
About what percent of water is indirectly returned to the plasma via the lymphatics?
10%
What is Poiseuille’s Law used for?
Resistance prediction for cylindrical tubes and newtonian fluids
Blood flow varies directly with the fourth power of what?
vessel radius
vasoconstriction is caused by..?
sympathetic nervous system
vasodilation is caused by…?
withdrawal of sympathetic tone
Vaso constriction does what to downstream circulation?
restricts
vasodilation does what to downstream circulation?
opens
The most blood resistance change occurs at what vessels?
arterioles
In regards to blood flow, organ systems are ordered in what?
parallel
What are 3 advantages of a parallel arrangement of organ systems?
- constant O2 supply
- can divert blood flow
- pressure gradient maintenance
What are the 3 cardiovascular responses to exercise (or increased metabolic demand)
- increased cardiac output
- decreased total peripheral resistance
- diversion of blood
During exercise, most blood diverts where? about what percentage is this?
skeletal muscles; 80-85%
At rest, most blood diverts where?
GI tract, kidneys, brain, skeletal muscles
What are two types of extrinsic controls of vasoconstriction/dilation?
- autonomic innervation
- paracrine controls
In fight or flight responses, what will cholinergic fibers do to vessels?
cause vasodilation
in fight or flight responses, adrenergic fibers will do what (regarding blood flow)?
close sphincters (gut and skin) to divert blood flow
The parasympathetic nervous system is ALWAYS what?
cholinergic and vasodilatory
What are 2 types of intrinsic controls regarding vasoconstriction/dilation?
- myogenic
- metabolic
This type of intrinsic control maintains constant flow in organs.
myogenic
This type of intrinsic control responds to local conditions to trigger vasodilation
metabolic
when blood pressure is high, myogenic control will do what to vascular smooth muscle?
constricts to prevent vessel rupture
when blood pressure is low, myogenic control will do what to vascular smooth muscle?
dilates to maintain flow
What three metabolic conditions will trigger vasodilation?
- decreased O2
- increased CO2
- low pH
What can happen (metabolically) when a tourniquet is applied?
increased CO2 and acidity
When a tourniquet is released, this can cause what?
hyperemia
What are 3 keys to regulating blood pressure?
- blood volume
- cardiac output
- peripheral resistance
The homeostasis of blood pressure is primarily regulated by what?
medulla oblongata
The medulla oblongata receives input from what (in regards to blood pressure)?
- baroreceptors
- chemoreceptors
- ischemia
These receptors in the aorta and carotid are responsible for sending input about pressure to the medulla oblongata
baroreceptors
These receptors in the aorta and carotid are responsible for sending input about O2 and CO2 to the medulla oblongata
chemoreceptors
these receptors that sense low O2 are found within the medulla oblongata itself
ischemia receptors
The AP of baroreceptors increases regarding what conditions?
elevated blood pressure
the system in place to stop bleeding response to injury
coagulation system
Cells will naturally secrete what 3 things when experiencing no injury?
- prostaglandin I2
- nitric oxide
- CD39
What is the purpose of CD39
breaks down ADP into AMP and Pi
What prevents clotting (not secretions)?
intact endothelium
this describes the stopping of bleeding
hemostasis
what two things recruits more platelets?
- ADP
- Thromboxane A2
Platelets will initially bind to
exposed collagen
What factor holds aggregating platelets together?
Von Willebrand Factor
Activated plasma clotting factors, leads to the development of what?
fibrin
polymerized fibrin fragments do what?
“glue” platelets, WBCs, and RBCs
A thickening of the tunica intima due to deposition of lipid, connective tissue, and inflammatory cells
Atheromatous plaques
What is the #1 killer in North America?
Artherosclerosis
Excess LDLs will likely become responsible for the formation of what?
Atheromatous plaques
What is the primary job of LDLs
transport cholesterol to tissues
What is the primary job of HDLs?
returns excess cholesterol back to the liver
The attempted phagocytosis of LDLs via macrophages produces what?
Foam Cells
