Vascular Tone
What vessels are primarily involved in vascular tone?
What is arterioles?
Intrinsic control is also called what?
Local control
Veins serve as what type of reservoir?
Blood volume reservoir.
What is the primary function of capillaries?
Nutrient exchange.
What pressure pushes fluid out of capillaries?
Capillary hydrostatic pressure.
Vasoconstriction does what to resistance?
↑ Resistance
Intrinsic control is important for distributing what?
Cardiac output.
What do venous valves prevent?
Backward blood flow.
Where is blood velocity very slow?
Capillaries.
What pressure draws fluid into capillaries?
Plasma colloid osmotic pressure.
Vasodilation does what to blood flow?
↑ Blood flow.
Extrinsic control is important for regulating what?
Blood pressure
Faulty venous valves can cause what?
Varicose veins.
What regulates whether a capillary is open or closed?
Precapillary sphincter.
What is plasma colloid osmotic pressure?
25 mmHg.
What two things help cause normal vascular tone?
Low-level sympathetic stimulation + open Ca²⁺ channels
What neurotransmitter causes sympathetic vasoconstriction?
Norepinephrine.
What causes blood to pool in the lower extremities?
Gravity
O₂ and CO₂ cross endothelial cells by what process?
Diffusion through the membrane.
Interstitial hydrostatic pressure moves fluid in which direction?
Into the capillary.
↑ O₂ and ↓ CO₂ cause what response?
Vasoconstriction.
What receptors cause vasoconstriction vs. vasodilation?
α₁ = constriction; β₂ = dilation.
What two things does the venous pump use to move blood upward?
Muscle contraction + valves.
What passes through water-filled pores?
Na⁺, K⁺, glucose, and amino acids.
Interstitial colloid osmotic pressure moves fluid in which direction?
Out of the capillary.