CV 3 Flashcards
At each level, arteries have (compared to veins): (3)
thicker walls
more elastic tissue
more smooth muscle
Vascular Tone
= Level of
Vascular Smooth Muscle Contraction
Vascular Tone (4)
Determines radius of vessel lumen
increase Tone increase vasoconstriction and decrease lumen diameter
decrease Tone increase vasodilation and increase lumen diameter
Δ vascular tone > ΔR > Δ Blood Flow through vessel
Q=
R=
ΔP/R
8Ln/Πr^4
Vascular Tone is Modified by: (2)
- Paracrines from Endothelial Cells
2. Autonomic NS
- Paracrines from Endothelial Cells (2)
NO and Prostacyclin (decreases tone; relaxes smooth
muscle)
Enothelin-1 (increases tone; contracts smooth muscle)
- Autonomic NS (2)
Sympathetic NS (influence depends on NT rec., typically increase)
*Parasympathetic NS (Decreases tone)
Arteries/Arterioles (2)
Basal Tone
Vasodilate or Vasoconstrict from rest
Veins/Venules (2)
No Basal Tone
Only vasoconstrict from rest
Artery Basal Tone
Mediated by: (2)
Paracrines secreted by endothelial cells
Tonic activity of sympathetic motor neurons
Abnormal Arterial Tone =
hypertension
Compliance =
how easily a structure stretches
= ΔVolume/ΔPressure
High compliance vessels can have large changes in volume with little
change in pressure; —
Veins
Low compliance vessels will have large changes in pressure with
small changes in volume; —
Arteries
The pressure gradient throughout the circulatory system is the
driving force for
blood flow
Pressure in the arterial vessels is —, producing (2)
pulsatile
systolic and diastolic pressures.
Damping α (R)(Compliance)
Pulsation disappears by the capillaries smoothing out due to
decreasing elastic/collagen tissue and increasing R as you move through arteries to capillaries
Mean Arterial Pressure (MAP)
Average driving pressure in systemic arteries
= Diastolic P + 1/3(Systolic P – Diastolic P)
= 80 + 1/3(120-80) = 93 mmHg
Elastic recoil prevents
arteriole diastolic pressure from dropping to ventricular diastole pressure
Elastic recoil is essential to maintain
driving pressure in systemic circulation
Pulse Pressure (PP) Felt as a
pulsation or throb in the arteries of the wrist or neck with
each heartbeat.