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Physiology Lecture 25 Control of Blood Pressure
Terms in this set (45)
What are cells surrounded by?
extracellular fluids (ECF)
What separates the cell from the ECF?
What type of fluid does the cell contain?
intracellular fluid (ICF)
What makes up the blood?
blood is made up of plasma and cells
What makes up plasma?
extracellular fluid with proteins
What ions does the extracellular fluid?
All the extracellular fluid has high levels of Na+ and Cl- and low levels of K+
What is the difference between the plasma and interstitial fluid?
Plasma (the liquid part of blood) has proteins that are not found in
interstitial fluid, the extracellular fluid that lies outside the blood vessel between cells
Where is blood plasma found?
the extracellular fluid found inside the blood vessel
Where is interstitial fluid found?
surrounds most cells
What separates the two compartments of the extracellular fluid (plasma and interstitial fluid)?
the capillary wall
two compartments of the extracellular fluid?
1. plasma (blood)
2. interstitial fluid
What does the cell membrane separate?
The cell membrane separates the intracellular fluid from the extracellular fluid.
What type of cells comprise the capillaries walls?
a single layer of endothelial cells
What happens in the capillary?
Capillaries are the only blood vessels where blood contents enter and leave the circulation; exchange of nutrients and water between the blood and tissues
characteristics of capillaries that makes exchange possible
1. thin walls for easy diffusion
2. short diffusion distances
3. flows slowly
Why is having short diffusion distance beneficial for the exchange that occurs in the capillaries?
The radius of the capillary is small, so the blood is close to the wall. Therefore, dissolved substances don't diffuse very far to get out.
Why is slow blood flow beneficial for exchange?
allows time for nutrients and wastes to diffuse into and out of the capillary
a layer of fibers that holds the endothelial cells in place but does not slow diffusion
How do hydrophobic molecules diffuse across the endothelial cells?
Hydrophobic molecules diffuse directly across the endothelial cells.
How do water soluble molecules (glucose, ions, H2O) diffuse across the endothelial cells?
Water and dissolved solutes pass between endothelial cells through endothelial cell junctions (cell attachments).
How do solutes diffuse across the endothelial cells?
solutes diffuse down concentration gradients
function of tight junctions
Tight Junctions between endothelial cells control what can pass through
Is the leakliness of a capillary the same in all capillaries?
the leakliness of capillaries is different in different organs
protects the brain by regulating what enters the brain. In the brain, junctions are very tight. What moves in and out of capillaries is determined by transport proteins
When compared to tight junctions in the brain, how would you describe the tight junctions in muscles and tissues?
In muscle and most tissues, endothelial cell junctions allow small molecules to pass but block proteins.
large gaps in the endothelial cells of capillaries; have "windows"
Why did the water move across the capillary wall?
1. blood pressure pushes fluid out
2. osmotic pressure pulls water into the capillary
What happens to blood pressure as it moves along the capillary?
blood pressure gets lower as blood moves along the capillary
How does osmotic pressure pulls water into the capillary?
Because of proteins in the blood, the blood has more dissolved solute than the extracellular fluid. So the blood has higher osmotic pressure pulling water into it.
When does fluid move out the capillary?
Fluid moves out of the capillary where blood pressure is higher than the osmotic pressure (near the arteriole)
When does fluid move into the capillary?
Fluid moves into the capillary where blood pressure is lower than the osmotic pressure (near the venule)
a condition characterized by an excess of watery fluid collecting in the cavities or tissues of the body due to excess interstitial fluid
function of lymph vessels
filter and transport fluid away from tissues before returning it to the blood. This helps to maintain normal blood volume and pressure
two types of blood pressure changes
1. short term (a few seconds): match the pumping of the ventricle into the arteries with flow out of the arteries through the capillaries
2. longer term (hours, days): make sure the body fluid volume in the arteries and veins is correct
short term fix to blood pressure change
match the pumping of the ventricle into the arteries with flow out of the arteries through the capillaries
long term fix to blood pressure change
make sure the body fluid volume in the arteries and veins is correct.
reflex that maintains the arterial blood pressure
steps of the arterial baroreflex to maintain arterial blood pressure
1. measure pressure in the arteries
2. decide if it's too high or too low
3. adjust the cardiac output
mechanoreceptors that measure blood pressure in the arteries
where are baroreceptor nerve endings located?
1. the wall of the carotid artery in the carotid sinus
2. in the wall of the aorta in the aortic arch
What do the nerves of the artery wall respond to?
The nerves respond to stretch of the artery wall
What happens to the number of action potentials fired when there is lower blood pressure?
Lower pressure, the baroreceptor nerves fire fewer action potentials.
What happens to the number of action potentials fired when there is higher blood pressure?
Higher pressure, the baroreceptor nerves fire more action potentials
Where do baroreceptor nerves send their action potentials?
Baroreceptor nerves go to the cardiovascular centers in the medulla (brainstem)
How can arterial mean pressure be changed?
by acting of the cardiac output and adjusting the resistance of the arterioles
Recommended textbook explanations
John R. Taylor
Introduction to Electrodynamics
David J. Griffiths
Engineering Electromagnetics (Irwin Electronics & Computer Enginering)
John Buck, William Hayt
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