Cardiovascular Physiology - Lecture 6 Flashcards
Arteries
Main transporters of oxygenated blood
Huge lumen with lots of elastic tissue and some smooth muscle
Blood moves faster in these
Arterioles
Aka resistance vessels
Diameter is adjusted to regulate blood flow
There is a huge layer of smooth muscle to help regulate diameter
Capillaries
Diffusion occurs across the thin walls
Endothelium is a single cell layer so we can have that exchange
What are the functions of the endothelium in the blood vessels?
Serve as a physical lining that blood cells do not normally adhere to in the heart and blood vessels
Serve as a permeability barrier for the exchange of nutrients, meatbolic end products, and fluid between plasma and interstitial fluid; regulate the transport of macromolecules and other substances
Secrete paracrine agents that act of adjacent vascular smooth muscle cells, including vasodilators and vasoconstrictors
How does the amplitude of pressure pulses change as blood moves through the vasculature? Why?
The farther from the heart, the lower the pressure and the smaller the amplitude of the pulses
This is probably because of resistance vessels
Pulse pressure
Systolic pressure - diastolic pressure
What is blood pressure determined by?
Stroke volume (increase vol = increase pressure) Speed of the ejection of the stroke volume (increase speed = increased pressure) Arterial compliance
What is arterial compliance
Compliance = /\volume / /\pressure
If somethign is compliant, we can add a lot of volume without changing the pressure
What is the equation for mean arterial pressure?
MAP = DP + 1/3(SP-DP)
When we regulate blood pressure, what are we really regulating?
Mean arterial pressure
How can the blood move constantly, but the heart only pump intermittently?
The blood moved in a single heart contraction stretches out the arteries, so that the recoil continues to push on the blood, keeping it moving during diastole
Mean arterial presure
Pressure driving blood into the tissues arranged over the cardiac cycle
What determines the relative blood flow to an organ?
Arterioles
What is the equation for flow to an organ?
F(organ) = MAP / R(organ)
What happens when the smooth muscles in the arterioles relax? Constrict?
Relax = vasodilation Constrict = vasoconstriction
Dynamic adjustments in the blood distribution to the organs is accomplished by what?
Relaxation and contraction of circular smooth muscles in the arterioles
What is the intrinsic tone of arterioles controlled by?
Local controls
Extrinsic controls
What are local controls for intrinsic tone of arterioles controlled by?
Active hyperemia = accumulation of CO2, H, eiconsinoids, adenosine, bradykinin, and nitric oxide
Flow autoregulation = myogenic responses (some arteriole smooth muscle respond to increased stretch cause by increased pressure) and reactive hyperemia (respond to cessation of bloodflow)
What are the extrinsic controls for the intrinsic tone of arterioles?
Sympathetic nerves
Parasympathetic nerves
Noncholinic, noradrenergic autonomic neurons
Hormones
What does sympathetic stimulation of alpha-adrenergic receptors result in?
Causes vasoconstriction to decrease blood flow to that location
What does sympathetic stimulation of beta-adrenergic receptors result in?
Vasodilation to cause an increase in blood flow to that location
What are the paracrine vasodilators of arterioles?
Endothelium derived relaxing factor (EDRF) = NO2
Prostacyclin
What are the paracrine vasoconstrictors for arterioles?
Endothelin-1
Diversity among signals that influence contraction/relaxation in vascular smooth muscles implies what?
Diversity of receptors and transduction mechanisms
Capillary anatomy
Walls are a single endothelial cell in thickness
Primary point exchange between the blood and interstitial fluid - the intercellular clefts assist in this exchange
If capillaries lack smooth muscle, how is flow regulated through them?
Contraction/Relaxation of circular smooth muscle in upstream metarterioles and precapillary sphincters determine the volume of blood each capillary receives
What is an advantage of having blood move slowly through the capillaries?
It allows adequate time and surface area for exchange between the capillary blood and ISF
Filtration
Movement of fluid and solutes out of the blood
Absorption
Movement of fluid and solutes into the blood
Crystalloids
Low molecular weight, penetrating solutes
Colloids
Non-penetrating plasma proteins
Pc
Capillary hydrostatic pressure (favoring fluid movement out of the capillary)
Pif
Interstitial hydrostatic pressure (favoring fluid movement into the capillary)
TTc
Osmotic force due to plasma protein concentration (favoring movement into the capillary)
TTif
Osmotic force due to interstitial fluid protein concentration (favoring movement out of the capillary)
What is the equation for net filtration pressure?
Pc + TTif - Pif - TTc
At rest, how much blood is in the veins? Can that be changed?
60%
Sympathetically mediated venoconstriction can substantially increase venous return to the heart
What assists venous flow?
Skeletal muscle pump mechanism working in combination with one-way valves
What do alterations in venous return alter?
Alterations in venous return alter end-diastolic volume (EDV)
What does an increase in EDV result in?
It directly increases stroke volume and cardiac output
What is lymphatic fluid formed by?
The slight mismatch between filtration and absorption in the capillaries
What is the purpose of the lymphatic system?
Return blood to the veins
What can cause abnormalities of the lymphatic system?
Congenital, traumatic, or infections etiologies
