Wize High School Grade 11 Biology Textbook > Human Physiology: The Circulatory System
Cardiovascular Regulation
0:00 / 0:00
Regulation
Why do we need to regulate the CV system?
- as our activity level changes, our need for oxygen changes (we must regulate our blood flow)
- we can regulate the diameter of blood vessels to help with heat loss/retention
- sometimes we need to maintain some systems and temporarily shut others off by decreasing the blood flow to that area (ex. during a stressful time)
Myogenic Theory of regulation
- the idea that some organs control the capillary bed that feeds them by causing vasoconstriction or dilation of the blood vessels.
- vasoconstriction: smooth muscles in arterioles contract
- vasodilation: smooth muscles in arterioles relax
- this is done to maintain a constant blood flow. If the blood pressure gradient increases rapidly, the organs can decrease the blood flow by causing vasoconstriction (less blood will be able to get through - recall the blood flow equation and the effect of the vessels radius on blood flow)
- can be done by the brain, the heart and the kidneys
Metabolic Theory of regulation
- the idea that the more active we are, the more vasodilator metabolites (VDM) we produce.
- ex. if we are playing a game of soccer, we will produce lots of VDMs. These VDMs will cause arterioles to dilate, resulting in increased blood flow. We then get more O2 to the tissues that need it when we are running after the ball!
- some examples of VDMs:
- high CO2
- increased temperature
- increased acidity (hydrogen concentrations)
- decrease in O2
- if VDMs are present, it tells our body the alter vasoconstriction/vasodilation accordingly.
Humoral Regulation
- hormonal control of vasoconstriction and dilation
- hormones that cause vasoconstriction:
- vasopressin
- epinephrine
- angiotensin ll
- hormones that cause vasodilation
- kinins
- histamine
- ANF
- epinephrine
Neural Mechanisms
- neurons can cause direct vasoconstriction or vasodilation
- the ANS changes vessel diameters in order to change blood flow
- Sympathetic = vasoconstriction = decreased blood flow
- Parasympathetic = vasodilation = increased blood flow
0:00 / 0:00
Explain why you pass out when you hyperventilate using the metabolic theory of CV regulation. Why does using a paper bag help?
When we hyperventalate, we breathe in and out a lot. By doing this, we get rid of lots of CO2 and increase our O2 levels. Both of these are VDM signals to cause vasoCONSTRICTION. The blood flow to all tissues is decreased because we have too much O2 in our blood. The brain doesn't get enough blood, so eventually we just pass out.
The paper bag causes you to breath back in the same air you breathed out. By doing this, you take back in the CO2 that you breathed out already. This helps you're blood CO2 concentrations stay relatively stable, resulting in no vasoconstriction or dilation. Your brain still gets proper blood supply and you don't pass out.
Practice: Vasoconstriction & Dilation
Match the following terms with the correct definition
A.
The narrowing of blood vessels
B.
The expanding of blood vessels
C.
Molecules produced during metabolism that cause the dilation of blood vessels
D.
The degeneration of the blood vessel caused by the accumulation of fat deposits along the inner wall
E.
A network of neurons that can alter the diameter of blood vessels
Vasoconstriction
Vasodilation
Vasodilator metabolites
Atherosclerosis
Autonomic nervous system
Practice: Hormone Cardiovascular Regulation
Some allergic reactions involve the release of histamine. What happens to the blood vessels during this type of allergic reaction?