Vascular physiology II Flashcards
When does Venous return increase?
- Increase in blood volume
- Decrease in arteriolar pressure (resistance)
- Supine position or with elevated legs
When does Venous return decrease?
Increase in right atrium pressure (It diminishes the pressure gradient)
Where does the main function of circulation take place? (important)
The main function of the circulation takes place within the microcirculation
= transport of nutrients to tissue and removal of cellular waste products
Whats the non-nutritional role?
important
Formation of glomerular filtrate
✓ Regulation of temperature
✓ Immune response
✓ Transport of hormones
Where exactly does the microcirculation happen?
important
End portion of arterioles, metarterioles, capillaries and post capillary venules.
From where does the blood flow from?
Blood flows from arterioles into capillaries into venules.
By what is the blood flow regulated?
Blood flow through the capillary bed is regulated by vasoconstriction and vasodilation of smooth muscle within metarterioles and venules
How are these spincters called?
precapillary sphincters
What tissue does the sphincter have?
ring of contractile smooth muscle
What movements do they do?
important
Relax and constrict
What are capillaries?
important
Join arterioles and venules Very narrow: allow exchange of substances with interstitial fluid.
Where can we find the arterioles in the tree?
important
In the last division of the arterial tree
Where do we find the venues of the tree?
important
First part or the venous system
Does a single capillary has a high or a low resistance?
Has a high resistance to blood flow due to its small diameter
Does the capillary network have a high or low resistance?
If we consider it as a whole, it has a very low resistance
How is the speed of blood in the capillary network?
its very low
How is the pressure in inside the capillary network?
Blood pressure is very low
Where does the optimal condition for exchange of nutrients and waste (gases, fluids) between plasma occur?
Optimal conditions for exchange of nutrients and waste (gases, fluids) between plasma and interstitial fluid occur in capillaries.
Whats the exchange mechanism between capillaries and interstitial fluid (IF)?
- simple diffusion
- facilitated diffusion
- filtration
- absorption
What`s simple diffusion?
important
Fick’s Laws of diffusion
related to the concentration
What`s facilitated diffusion?
imposant
Pinocytosis or Vesicular transport, endo/exocytosis
thanks to something without energy
What`s the ficks law?
important
Fick’s law
Diffusion speed of a substance through a membrane is directly proportional to the concentration gradient of such a substance across that membrane.
What`s simple diffusion in better words?
important
Process by which molecules spontaneously move from a high concentration area towards an area with lower concentration (following concentration gradient)
(ex. gases)
Regarding simple diffusion, how do lipidic substances travel?
(important)
Directly through the endothelial membrane: OXYGEN AND CARBON
DIOXIDE.
What are HIDROSOLUBLE SUBSTANCES?
important
Through “membrane pores”: WATER, IONS, GLUCOSE.
What is net filtration?
important
the difference between the gradient between hydrostatic pressure (pressure of the blood that pushes the liquid through the pores in capillaries) and osmotic pressure (pressure exerted by proteins)
What`s reabsorption?
important
If net fluid movement goes towards the capillary
What`s filtration?
important
If net fluid movement goes towards the outside of the capillary
Who is responsible for the capillary interstitial fluid transfer?
The starling law
What`s hydrostatic capillary pressue?
important
Hydrostatic pressure exerted by blood on the walls of a blood vessel.
IT depends on:
- Cardiac Output (CO).
- Blood volume.
- Vascular resistance
What`s interstitial hydrostatic pressure?
Opposes to the filtration towards the capillary.
Most physiologists refer to a negative value (-3) mmHg (close to 0).
Whats the force that governs filtration?
important
The hydrostatic force that governs FILTRATION is normally HCP
Whats blood colloid osmotic pressure?
Due to the presence of plasma proteins.
• Normal BCOP 28 mmHg (70% due to proteins)
• Albumin (globulins, fibrinogen)
What do osmotic forces have?
Blood colloid osmotic pressure
Interstitial fluid osmotic pressure
What`s Interstitial fluid osmotic pressure?
Small as Albumin concentration is low in interstitial fluid
8mmHg
What does an increase in HCP (hydrostatic colloid pressure) do?
An ↑ in HCP favours the movement of fluid towards the interstitial space.
What does an increase in BCOP (blood colloid osmotic pressure) do?
An ↑ in BCOP favours the movement of liquid towards the capillaries from the interstitial space.
What does the blood colloid osmotic pressure avoid?
The blood colloid osmotic pressure avoids the loss of intravascular volume
What does the microcirculation control?
- The pressure gradient between the arterial and venous ends of a capillary network.
- Vasoconstriction-vasodilation of arterioles, metarterioles and precapillary sphincters (VASOMOTION)
What`s vasomotion?
Vasoconstriction-vasodilation of arterioles, metarterioles and precapillary sphincters
What`s proportional to the metabolic needs in the most tissues?
In most tissues, the local flow is proportional to the metabolic needs of those tissues.
Arterial pressure depends on:
- Cardiac Output (CO) = SV x HR
- Systemic Vascular Resistance (SVR)
- Volume
On what does F (cardiac output) depends on?
F depends on cardiac output = SV x HR
On what does R (resistance) depend on?
R depends on viscosity, length of blood vessel and size of lumen (radius)
Arterial pressure regulation due to:
- neural mechanisms
- humoral mechanisms
- slow action mechanisms
What are neural mechanisms?
Immediate control
What are humeral mechanisms?
Intermediate control
- adrenal/noradrenaline
- vasopressin
- renin-angiotension
- aldosterone
What is slow action mechanism?
long term control
- renal function
- liquid intake
Body response to an increase in arterial pressure:
blood pressure increase, blood vessel stretch and activate baroreceptor, increased potential activity
We have an increased potential activity due to:
Cardiovascular center
Vasomotor center
What does the cardiovascular center do by an increase in arterial pressure?
- decreased sympathetic activity of to heart
- decreased heart rate and force if contraction
- decreased cardiac output
What does the vasomotor center do by an increase in arterial pressure?
- blood vessel dilate
- decreased total peripheral resistance
- blood pressure decreases to normal
What do mechanoreceptors do?
Detect changes in volume (Mechanoreceptors located in the atria and major veins). Sympathetic response. Increase in urine production
What do Baroreceptors do?
Modify the peripheral resistance, the cardiac frequency, and cardiac output in response to changes in blood pressure (Baroreceptors in the carotid sinus and the arch of the aorta)
What do chemoreceptors do?
Detect changes in pressure of oxygen and carbon dioxide, changes in pH and arterial pressure (Chemoreceptors in the aortic and carotid bodies). Low O2: hypoxia; high CO2: hypercapnia; high H+: acidosis. All increase SANS
Does the Baroreflex include the brain?
No, without any connection to the brain
just:
first: aortic arch baroreceptor
second: glossopharyngeal nerve
third: vagus nerve
fourth: Sympathetic nerves
fifth: blood vessels
