part 8 Flashcards
Cardiac output =?
Venous return.
What determines vascular resistance of the body?
The size of peripheral vascular tubes which is a collective r^4.
So if delta-P (pressure difference) is set by cardiac output and cardiac output is set by venous return then what collective behavior will determine cardiac output?
Behavior of vascular tubes. Or the collective r^4.
What will determine the r^4 for the entire system?
Local factors from metabolizing tissues.
So after all of that what will determine the cardiac output?
Metabolizing tissues.
The heart is a permissive pump that responds to what?
Body tissue.
How will increasing metabolism increase cardiac output?
it will increase local metabolites which increase vasodilation and increase flow into the venous system which increases venous return which increase cardiac output.
What are the 2 outputs in the cardiovascular system?
- cardiac output. 2. tissue output (coupled with venous pump)
What are the 2 pumps for the systemic circulation of blood?
- Left ventricle. 2. Collective skeletal muscles.
If r^4 for a given area increases what happens to Q?
It should increase.
What keeps blood pressure from dropping off all the way when r^4 increases and so flow increases?
Delta-P must be maintained.
Blood pressure in the short-term is regulated how?
Regulated by the redistribution of blood.
How is mean systemic filling pressure made?
average of all arterieal and venous pressures.
What is the mean systemic filling pressure usually at?
10 mm Hg.
Why is the mean systemic filling pressure so low?
Because most blood is in the venous system and this is very low pressure.
What system can control the potential chaos that could result from excessive demands of tissues all crying out I want blood?
The sympathetic nervous system can modify the cardiac output and peripheral tissues.
Why do we need to warm down after exercising?
it is needed to prevent sudden post-exercise pooling of blood through venous pumping.
what is VO2?
the volume of o2 consumed per minute.
What is a typical VO2 at rest?
250 ml/min.
What is maxvo2?
Maximum aerobic limit.
What is A-V O2?
Arteriovenous oxygen difference. It is a measure of tissue metabolism.
With exercise Q or flow of blood is sent where?
To brain as a constant and sent to skin for sweating, also muscles and heart.
With exercise Q or Flow of blood is decreaes where?
gut, kidneys.
Mean arterial pressure divided by Resistance equals what?
Cardiac output.
What is the source of flow for pulmonary circulation?
Right ventricle.
What shape will the right ventricle be?
Crescentic or “c” shaped.
How much blood will the right ventricle pump compared to the left ventricle?
The same amount per unit time. Just not as far.
What is the normal or average pulmonary circulation blood pressure?
22/8
What is the pulse pressure for the pulmonary circulation?
14 mm Hg.
What is the mean blood pressure for pulmonary system?
13 mm Hg.
What will the blood pressure be in the capillaries of the pulmonary system?
around 7 mm Hg.
Why can pulmonary blood pressure be so low?
It doesn?t need to be high since it only travels short distances from the heart, and the lungs have a negative interpleural pressure.
What will low blood pressure do for the alveoli?
Allows them to ramain relatively dry.
How is blood distributed in lungs normally?
The lower 1/3 will have the most blood due to gravity and this area will be over-perfused, The upper 1/3 will not have much blood and it will be under-perfused, and the middle 1/3 of the lungs will be just right.
Pulmonary vasculature is compliant, but what is the size of the container here?
It is small.
Pulmonary blood vessels are like what?
veins.
How much blood can be in the pulmonary circuit at any time?
around 450 ml.
How much blood can be in the pulmonary capillaries at any given time?
only around 75 ml.
What is pulmonary edema?
A condition where the lungs accumulate too much blood.
What happens when there is too much blood in the lungs?
It ends up in plasma filtrate and goes into alveoli.
What happens to alveoli when they get blood on them?
This will greatly compromise the ventilation and gas exchange.
Is it possible to shift blood volume between the pulmonary and systemic systems?
yes.
What medical condition is associated with blood volume leaving the systemic system and entering the pulmonary system?
Congestive heart failure.
What controls the flow of blood through the pulmonary system?
The venous return. This can be metabolizing tissues in the systemic system.
Why will local factors not regulate blood flow through the pulmonary system?
decreased O2 in the pulmonary system will cause vasoconstriction.
Why will decreased O2 in the pulmonary system cause vasoconstriction?
So the blood can flow to better oxygenated areas.
Will nervous innervation go to the pulmonary system and will it help control flow of blood?
Yes it is innervated, but it will not help regulate flow.
What is circulatory shock?
inadequate blood flow to the extent the tissues become damaged.
What are the 3 basic types of circulatory shock?
- Hypovolemic shock. 2. low-resistance shock. 3. Cardiogenic shock.
What causes hypovolemic shock?
A hemorrhage (internal or external) that decreased blood volume. Or burns that remove lots of fluids.
Hypovolemic shock is aka?
Cold shock.
What causes low-resistance shock?
Due to loss of vasomotor tone.
Low-resistance shock is aka?
Warm shock.
What is anaophylaxis?
Widespread mast cell degranulation.
What type of shock is created from anaophylaxis?
Low-resistance shock.
What causes a cardiogenic shock?
Loss of pumping capacity.
Cardiogenic shock happens in what percentage of MI patients?
10% and is very deadly.
The warm or cold aspects relate to what?
The presence or lack of compensatory mechanisms at work.
What type of shock will blood pressure increase?
Hypovolemic shock.
What type of shock will blood pressure decrease?
low-resistance shock.
Why would you lay a patient down with head below trunk to treat shock?
to increase venous return.
What type of disorder is lymphedema?
A tissue swelling disorder.
Ultimately the only blood flow that matters is where?
In the tissues.
What is interstitium?
aka Extra cellular matrix or ECM.
Fluid/molecular movement is a function of what 5 basic factors?
- Solubility 2. Size 3. capillary permeability 4. concentration 5. pressure.
What are the different types of capillaries?
type I, Type II, Type III.
Of the different types of capillaries which one is most common?
Type I.
Of the 5 basic factors of fluid/molecular movement which one is a huge determinate of the net flux across an endothelium?
Permeability.
If a molecule can move across a capillary what will primarily drive the permeation ?
pressure dynamics between blood and interstitium.
What are the 4 forces that determine net fluid exchange between the blood and the interstitium?
- Capillary pressure 2. interstitial free fluid pressure 3. plasma colloidal osmotic pressure 4. interstitial fluid colloidal osmotic pressure.
What is capillary pressure?
An outward pushing force= Pc
What is interstitial free fluid pressure?
an inward pushing force= Pt
What is plasma colloidal osmotic pressure?
an inward pulling force= pi c
What is interstitial fluid colloidal osmotic pressure?
an outward pulling force= pi t
What do these 4 forces (that determine net fluid exchange between the blood and the interstitium) collectively produce?
A net driving force.
What are the actual forces of capillary pressure?
10-20 mmHg
What is the interstitial free fluid pressure?
around -6 mmHg
What is a negative pressure?
It is just below atmospheric pressure.
What is the plasma colloidal osmotic pressure?
around 28 mmHg
What is the interstitial fluid colloidal osmotic pressure?
Around 5 mm Hg
How can we determine the net driving force?
Add up all the pressures.
Of the 4 forces which is the only one that has an inward pressure?
Plasma colloidal osmotic pressure.
What will increased venous pressure do to capillary pressure?
Increase it.
What will increased capillary pressure do to arteriolar resistance?
Decrease it.
What will decreased arteriolar resistance do to capillary pressure?
Increase it.
Of the different forces on blood in the capillaries which one is variable?
Pc aka capillary pressure.
What will the net driving force be at for different parts of the capillary?
A net Out of around 7 at the arteriole end and a net in around -7 at the venule end.
What is the net filtration when the net driving force is greater than 0, and when it is less than 0?
Greater than 0 = out, less than 0= in
What is it called when the net fluid loss and net fluid resorption is 0?
Starling equilibrium.
Where is the starling equilibrum found at?
Roughly the midpoint of the capillary.
What is the net filtration pressure in the typical systemic capillary?
There is a slight net outward filtration pressure.
Will blood that leaves one capillary return only to the same capillary?
no it can go to other capillaries.
What is the slight net capillary out and what will it cause?
around 0.3 mmHg and it causes a flux from plasma to interstitium.
Since our capillaries lose more plasma than they resorbe how much plasma is lost from the capillary system per minute?
2-3 ml/min.
What is flux?
A net fluid movement.
A net flux can be more percisely determined by including what 2 factors?
- Kf= filtration coefficient 2. A= surface area.
What will pick up the lost plasma from the capillary system?
The lymphatic system.
Where are lymphatic capillaries found at?
Nearly everywhere in the body.
What is the pressure like in lymphatic vessels?
Very low.
Since lymphatic pressure is so low how will it flow?
It uses valves and action of skeletal muscle to move blood.
What is the use of valves and skeletal muscle to move lymph called?
The lymphatic pump.
What can increase the lymphatic fluid pressure?
If the interstitial free fluid pressure is increased.
What is the usual cause of increased interstitial free fluid pressure?
Increased capillary pressure.
Increased capillary pressure will do what to arteriolar resistance and venous resistance?
Arteriolar resistance will decrease, and venous resistance will increase
Of the 4 forces that determine net fluid exchange between the blood and the interstitium which one will go down if the interstitial free fluid pressure increases?
Plasma colloidal osmotic pressure.
What is interstitial free fluid pressure normally like?
It is stable due to natural turgor of tissues that tend to resist internal stretching.
How compliant are tissues generally?
Not very compliant.
What happens to most fluid that leaves the capillaries?
It is conducted into the lymphatic system.
What is the average amount of total body interstitium?
12 liters in average adult.
What is the normal pressure of the lymphatic system?
around -6 mmHg
At what lymphatic pressure will fluid go into the lymphatic system?
anywhere below zero.
What is the safety factor?
The large range for lymphatic pressure where fluid will still be taken in. Lymphatics take fluid in for a decent range on either side of -6 mm Hg.
What is the safety factor analogous to?
Blowing up a balloon it is hard to do until you reach a point and then it is easy to do.
What happens when the safety factor is exceeded?
Fluids pour into tissues.
What is edema?
fluid accumulation in tissues.
How is increased capillary permeability caused?
burns, histamine from mast cells, injury. This allows for increased seepage by way of vessel wall changes.
What can cause a high capillary pressure?
Venous obstruction, acute arteriolar dilation, cardiac failure
What happens with high capillary pressure?
it allows for increased Net driving force and the starling equilibrium shifts to the right.
What can cause a decrease in plasma protiens?
nephrosis (kidney disease), starvation, burns.
What will decreased plasma proteins cause?
It allows for increased seepage due to decreased colloidal osmotic pressure.
What causes lymphatic obstruction?
parasites, or surgery
What will a lymphatic obstruction cause?
Lymphedema because it blocks the drainage from the lymphatic system and increases the interstitial free fluid.
What is lymphedem due to?
accumulation of lymphatic fluid in interstitium.
What will lymphedema cause?
Swelling in tissues.
What is the pressure called that drives fluid out of the capillaries?
Capillary pressure.
What is the fluid that pushes fluid out of the interstitial space called?
Interstitial free fluid pressure.
What is the pressure that pulls fluid in from the interstitial area into the capillaries?
Plasma colloidal osmotic pressure.
What is the pressure that pulls fluid out of the capillaries into the interstitial area?
Interstitial fluid colloidal osmotic pressure.
