Kim. Special Circulation Flashcards
The difference between basal flow and maximal flow for a specific organ is called the
Flow capacity or vasodilator reserve
Blood flow w/in coronary arteries _____ during cardiac systole and _______ during diastole
Decreases
Increases
Most of the blood flow to the myocardium occurs during ________
Diastole
Coronary blood flow is primarily regulated by ?
Changes in tissue metabolism
Unlike most other vascular bed, activation of sympathetic nerves to the heart causes
Transient vasoconstriction followed by vasodilation
When a person exercises, the increased CO primarily goes to the active skeletal muscles, heart and skin. Blood flow decreases to the __________
Gastrointestinal and renal circulation
Normally, coronary arteries dilate with increased heart rate and metabolism, if the coronaries are diseased and their vasodilator reserve is limited, increases in HR can _____
Limit coronary flow, lead to myocardial ischemia, and anginal pain
The ______ of coronary flow overrides the direct coronary nervous effects w/in seconds.
Metabolic control
This explains the transient vasoconstriction from sympathetics that is followed by vasodilation
What does ICP do to cerebral blood flow?
Collapses veins
Decrease effective CPP
Reduces blood flow
Cerebral blood flow is highly related to metabolism of the tissue. _______ is the main factor regulating cerebral blood flow
Arterial PCO2
Substances that increase the acidity of the brain tissue will __________ cerebral blood flow
Increase
As long as arterial PO2 is normal, cerebral blood flow is regulated by PCO2. However, a _________ in arterial PO2 will cause and increase in cerebral blood flow
Large decrease in arterial PO2
Neuropeptides originating in the brain;
Vasoactive intestinal polypeptide
Calcitonin gene-related peptide
Substance P
Cause
Vasodilation
Neuropeptide Y, a brain neuropeptide, causes
Vasoconstriction
Activation of sympathetic nerves that innervate the larger cerebral vessels has relatively little influence on cerebral blood flow because of?
The strong autoregulation mechanism in the brain
When skeletal muscle is not contracting, little oxygen is required and only about _____ of the capillaries are perfused
One-forth
In contraction, and active hyperemia, all anatomical capillaries may be perfused
W/ rhythmic or phasic contractions, mean blood flow increases _________
During the contractions
If measured w/o avg the blood flow is phasic, but averaged, it is increasing during
Why does blood flow decrease during contraction and increase during relaxation of muscle?
Because the muscles mechanically compress the vessels
A sustained muscle contraction does what to blood flow ?
Decreases the blood flow during the duration of the contraction, but increases the blood flow after due to a reflexive hyperemia
Decreased oxygen in muscle greatly _ ____ blood flow ?
Enhances
During activity, the blood flow in muscles increases. Why ?
- Decreased O2 causes increase
- Vasodilator substances are released during contraction: adenosine, potassium
Increased lactic acid, CO2 and H ions.
Under resting conditions, a significant portion of the vascular tone is generated by _________ therefore, in resting skeletal muscle, nervous control is dominant
Sympathetic activity
Splanchnic circulation includes blood flow to the _ _ _ _
GI tract
Spleen
Liver
Pancreas
All splanchnic ciruclation blood is supplied by which three arteries?
Celiac
Superior mesenteric
Inferior mesenteric
All blood that courses through the gut, spleen, and pancreas flow immediately into the?
Liver, via the portal vein
Hepatic blood flow is derived from which two source?
The hepatic artery
The portal vein
(About 3/4 use by liver is derived from hepatic arterial blood)
During active absorption of nutrients, blood flow in the villi and adjacent regions of the submucosa and the muscle layers of the intestinal walls is
Increased
Possible causes of increased blood flow during GI activity?
Several vasodilator substances released from mucosa during digestion (cholecystokinin, vasoactive intestinal peptide, gastrin, secretin)
GI glands release bradykinin
Decrease O2 conc in gut wall
What does sympathetic stimulation do to GI tract?
Causes intense vasoconstriction of the arterioles w/ greatly decreased blood flow
(Symp = fight or flight Parasymp = rest and digest)
_______ causes a decrease in volume in the large-vol intestinal and mesenteric veins. Displacing large amounts of blood to other parts of the circulation that actively need them.
Sympathetic stimulation
Splanchnic circulation functions as a venous reservoir
