Cardiovascular physiology Flashcards
What happens once the arterial baroreceptors start firing?
the medullary cardiovascular center receive it and decrease sympathetic outflow to heart, arterioles and veins; and increase parasympathetic outflow to heart
What do arterial baroreceptors do?
respond to changes in pressure when walls of vessel stretch/relax, increase in MAP increases rate of firing of baroreceptors
What stage does pulse pressure disappear? (aorta, arterioles, capillaries etc.)
arterioles
What is hypotension?
abnormally low blood pressure (think: hypO- lOw) resulting in fainting, dizziness and shock
What is hypertension?
chronically increased arterial blood pressure resulting in heart attack, stroke or kidney damage
How is blood pressure measured?
systole/diastole
What does compliance mean?
the ability of a vessel to stretch/inflate and increase in pressure due to greater pressure inside the vessel than outside
What do lymph nodes do?
function in immune response
What are lymph vessels?
one-way valves that ensure lymph flows just to the right atrium and empty into the venous system
What are lymphatic capillaries?
a single layer of endothelial cells that have water-filled channels permeable to interstitial fluid components including proteins that enter by bulk flow
What are varicose veins?
when the vein walls are weak and so its valves do not function properly causing blood to pool and vessels swell
How many valves/fold/leaflets do veins have?
2 that project inwards to prevent backflow of blood to capillaries , blood travels in one direction only (compartmentalize)
What are veins?
high capacitance vessels or vessels that are able to store large volumes of blood
Which hold more blood veins or arteries?
veins because walls thicker
Where does the transition point between filtration and reabsorption lie?
closer to venous end of capillary
What are the 4 forces called the Starling forces?
interstitial fluid, capillary, hydrostatic pressure and colloid osmotic pressure
What is it called when fluid is favored to move out of the capillaries in interstitial fluid colloid osmotic pressure?
negligible
What is interstitial fluid colloid osmotic pressure?
small amount of plasma proteins may leak out of the capillaries and return to the lymphatic system
What is blood colloid osmotic pressure?
because plasma proteins in the capillaries are too large they cannot easily cross through the capillary walls and will pull water into the capillaries
When fluid moves into capillary by way of interstitial fluid hydrostatic pressure it is said to be what?
negligible (will not contribute significantly to bulk flow)
What is interstitial fluid hydrostatic pressure? what direction does it favor movement of fluid?
fluid pressure exerted on the outside of the capillary wall by interstitial fluid (think: interstitial fluid is on the outside so they will exert pressure outside), favors movement into capillary (H–>L, high pressure in interstitial fluid more than capillary)
What is capillary hydrostatic pressure? what direction does it favor fluid to move?
pressure exerted on inside of capillary walls by blood, it favors fluid to move out of capillary( H–>L)
What is hydrostatic pressure?
pressures that drive fluid movement (bulk flow) into and out of the capillary
What is reabsorption in capillary exchange?
movement of protein-free plasma from interstitial fluid into the capillary
What is filtration in capillary exchange?
the movement of protein-free plasma from the capillary out to the interstitial fluid
What is the function of bulk flow?
to distribute extracellular fluid (plasma and interstitial fluid) volume NOT the exchange of nutrients and metabolic end products across capillary walls
What is bulk flow?
the movement of protein-free plasma across the capillary wall
What is transcytosis?
use of vesicles (e.g. fused vesicle channel that forms a water-filled channel across the cell) to cross endothelial cells
How is blood altered to tissues according to needs (e.g. at rest vs during strenuous exercise)?
through capillary beds
What is a metarteriole (takes part in microcirculation)?
not true capillary that is made of smooth muscle cells and connects arterioles to venules. they change diameter to regulate flow
What are precapillary sphincters (take part in microcirculation)
have rings of smooth muscle and are at the entrance to a capillary. they alter blood flow but have no innervation just respond to local factors (e.g. oxygen and carbon dioxide levels)
What is microcirculation?
circulation of blood through smallest vessels
What are sinusoidal capillaries?
discontinuous capillaries that are flattened and irregularly shaped having large fenestrae with gaps between cells. The basement membrane is thin or absent. They exchange water and large solutes.
What are fenestrated capillaries?
capillaries that have fenestrate (pores) that penetrate endothelial lining and either have a diaphragm connecting different fenestra or not. They are also surrounded by basement membrane. They rapidly exchange water and solutes(small peptides)
What are continuous capillaries?
when endothelial cells form an uninterrupted tube, surrounded by complete basement membrane. They exchange water, small solutes, lipid-soluble material but do not exchange blood and plasma proteins
What are intercellular clefts? (in capillaries)
a narrow water-filled space at the junctions between cells
What is the function of capillaries?
to exchange material between blood and interstitial fluid
What are capillaries?
a thin walled vessel that are one endothelial cell thick. They have no smooth muscle or elastic tissue allowing for more rapid exchange of material
Steps of active hyperemia
an increase in metabolic activity of organ (e.g. exercise), decrease in oxygen, increase in metabolites in organ interstitial fluid, arteriolar dilation in organ, increased blood flow to organ
What are local controls/ active hyperemia?
mechanisms by which an organ can alter its own arteriolar resistance and as a result regulate its own blood flow without the use of nerves or hormones
What does epinephrine from the adrenal medulla do vasoconstrict or vasodilate the arterioles?
both
What does nitric oxide do to arterioles vasoconstrict or vasodilate?
vasodilate
What does norepinephrine do vasoconstrict or vasodilate arterioles?
vasoconstrict
What is vasoconstriction of arterioles?
contraction of arteriolar smooth muscle that decreases blood flow to organs
What is vasodilation of arterioles?
relaxation of arteriolar smooth muscle that will increase blood flow to organs
Structure of arterioles?
have an abundance of smooth muscle cells that regulate blood flow to organs, and determine MAP (blood pressure)
Rank from greatest pressure to least: arteries, capillaries, veins, venules, arterioles
arteries, arterioles, capillaries, venules, veins
What is the difference in appearance between the large vein and large artery?
large vein (inferior vena cava) have few layers of smooth muscle and connective while the large artery (aorta) they have many layers of smooth muscle and connective tissue
What is afterload?
any increase in arterial pressure will decrease stroke volume, because this is a “load” that the contracting ventricles have to work against. How hard the heart must work to eject blood in this situation is afterload
What is the relationship between the heart filling and the cardiac muscle fibers?
as the fibers stretches more (decreasing space between thick and thin filaments, allowing more cross bridges and increases the attraction of troponin for calcium and release of calcium by sarcoplasmic reticulum) the heart fills more
What is the Frank-starling mechanism?
the relationship between EDV and SV, increasing diastolic filling will increase EDV which will increase cardiac fiber length and create a greater force during contraction and greater SV
Heart rate during parasympathetic activity?
decreased
Heart rate during increase sympathetic activity?
increased
What is cardiac output?
the amount of blood pumped by each ventricle in one minute
Heart rate X Stroke volume (blood pumped out during systole)
units: L/min
What structures are involved in parasympathetic innervation of the heart?
atria, SA node, AV node
* not the ventricles
What structures are involved in sympathetic innervation of the heart?
atria, ventricles, SA node and AV node
When blood is flowing normally through valves does it make a sound?
No, it is laminar
What does the dub sound mean?
that diastole is about to start
How is the dub sound made?
by the closure of the semilunar valves
What is the second heart sound?
dub
What does the lub sound mean?
that systole is starting
How is the lub sound created?
with the closure of the AV valves
What is the first heart sound?
Lub
How does the right ventricle differ from the left in systole?
right ventricle develops lower pressures than left, because the myocardium at right ventricle is not as thick as left and does not generate as much pressure when it contracts
In what situation does stroke volume decrease and increase?
decrease during rest and increase during exercise
How is stroke volume how is it measured?
EDV- ESV
What is the end-systolic volume (ESV)?
amount of blood in each ventricle at the end of ventricular systole (in mL)
What is the end-diastolic volume (EDV)?
the amount of blood in each ventricle at the end of ventricular diastole (in mL)
Blood flows from a region of (higher/lower) __ pressure to a region of _ (higher/lower) pressure?
higher to lower
What is the atrial kick?
at the end of diastole/ ventricular filling when the atria contract