The Regulation of Blood Pressure Flashcards
How do the kidneys play a role in the regulation of blood pressure?
They are largely responsible for sodium and water transport and we use fluid dynamics to increase or decrease blood volumes
What is blood pressure?
the force placed on the walls of blood vessels as blood flows through it
What are changes in blood flow controlled by?
changes in the diameter of arteries and cardiac output
What is the minimum pressure needed for capillary exchange?
capillary hydrostatic blood pressure
what is capillary exchange?
When fluids and substances are exchanged across a capillary network
How do you work out blood pressure?
cardiac output x total peripheral resistance
How do you work out cardiac output?
heart rate x stroke volume
What is the total peripheral resistance dependent upon
changes in the arteriolar radius
What are the three processes that control blood vessel tone (changes in arteriolar radius)?
- automatic/ intrinsic
- short-term
- long-term
Why may homeostasis of blood flow be disturbed?
- Physical stress (trauma)
- Chemical Changes
- Increased tissue activity
What will homeostasis being disturbed lead to?
inadequate local blood pressure and blood flow
What does autoregulation do?
- Allows blood vessels to alter their diameters as a consequence of their environment around them
- Leads to a local decrease in resistance and increase in blood flow (in response to a low blood pressure)
What is the intrinsic control mechanism driven by?
vasodilatory metabolites
Why are vasodilatory metabolites produced?
- as a consequence of active tissue metabolism
- A inactive constricted vessel becomes active as a consequence of metabolism and produces vasodilatory metabolites
What are some examples of vasodilatory metabolites?
- H+
- CO2
- K+
- adenosine
- lactate
What do vasodilatory mechanisms do?
- Can act by themselves on the blood vessels in order to bring about a change in shape
- they will work on different systems in order to bring about vasodilation
- if vasodilation takes place more blood will be supplied to the tissue and that is exactly what you need when there is a low blood flow
Summarise the autoregulatory process
It is an intrinsic one in which healthy blood pressure can be restored to a tissue as a consequence of disturbance of homeostasis. The chemical mediators responsible for the intrinsic control are classified as Vasodilatory Metabolites
However what happens in pulmonary circulation?
A decrease in O2 and increase in CO2 causes vasoconstriction
What happens in the short-term regulation of blood flow?
- Stimulation of receptors (chemoreceptors and baroreceptors) sensitive to changes in blood pressure and blood chemistry. The receptors send signals send signals
- These signals activate cardiovascular centres in the CNS
- These centres bring about short-term elevation of BP by SNS stimulation of the heart rate and peripheral vasoconstriction
- Leads to homeostasis: healthy blood pressure and blood volume
What are baroreceptors?
pressure detectors that can respond to changes in blood pressure by generating electrical responses that can be relayed to the central nervous system – sensory cells that detect pressure changes
What are chemoreceptors?
chemical sensors
Where are chemoreceptors found?
- in the carotid body
- inside the blood vessels of the CNS
What do chemoreceptors do?
send signals to the cardio regulatory centres in the medulla oblongata
How do baroreceptors work in response to low blood pressure?
- If there is an inadequate blood supply or fall in blood pressure baroreceptors become inhibited (they are no longer stretched)
- This is then detected by the CNS through afferent fibres
- CNS responds to fall in blood pressure/ inadequate blood supply by increasing cardiac output, heart rate and bringing about vasoconstriction
What are the centres in the CNS that receive signals from the baroreceptors and are they activated or inhibited in response to the inhibition of baroreceptors (low blood pressure)?
- Cardioacceloratory centre (activated due to inhibition of baroreceptors)
- Vasomotor centres (activated due to inhibition of baroreceptors)
- Cardioinhibitory centre (inhibited due to inhibition of baroreceptors)