Vascular chapter 21 Flashcards
systolic pressure
“Peak” arterial BP, during ventricular systole
diastolic pressure
“Minimum” arterial BP, at end of ventricular diastole
pulse pressure
difference between systolic and diastolic pressure
mean arterial pressure (MAP)
(mean arterial pressure) = diastolic pressure + (pulse pressure/3)
how to calculate pulse pressure
ex if BP = 120mmHG/ 80 mmHG then…
systolic BP- diastolic BP
120mmHG- 80 mmHG
=40 mmHG
how to calculate MAP
ex if BP = 120mmHG/ 80 mmHG then.. Diastolic BP + Pulse pressure/3 80mmHG + 40 mmHG/3 80mmHG + 13.3 mmHG = 93.3 mmHG
Describe how the following change from arteries through capillaries and veins:
-vessel diameter
- decreases from arteries to capillaries
- increases from capillaries to small vessels
Describe how the following change from arteries through capillaries and veins:
-total cross sectional area
- big vessels near the heart have a small cross sectional area
- capillaries have a large cross sectional area
- decreases again for small vessels
Describe how the following change from arteries through capillaries and veins:
-velocity (speed) of blood flow
- high velocity near aorta
- decreases in capillaries
- starts to increase slowly in veins
therefore blood flows slower through smaller vessels
Describe how the following change from arteries through capillaries and veins:
-blood pressure.
- blood pressure is highest near the heart (areteries)
- decreases in veins
therefore decrease in BP away from pump
its all about capillaries
each capillary is smaller in diameter to make it easier for diffusion to occur, we have huge numbers of them , BP is fairly low but higher at one end of the capillary bed, velocity and blood flow through capillaries are very slow making lots of time for efficient exchange
hydrostatic pressure
Fluid pressure
- Forces water out of a solution (“push”)
- Water is being “pushed” from an area of higher pressure to an area of lower pressure
ex: blood pressure, the force of hydrostatic pressure means that as blood moves along the capillary, fluid moves out through its pores.
Osmotic pressure
- Draws water into a solution (“pull”)
- Higher solute concentration = higher osmotic pressure
net hydrostatic pressure
CHP - IHP
net colloid osmotic pressure
BCOP - ICOP
Define/describe the following terms relating to capillary exchange: net filtration pressure.
(NFP) = net hydrostatic pressure – net colloid osmotic pressure -NFP = (CHP – IHP) - (BCOP - ICOP)
Describe how net filtration pressure is affected by net hydrostatic pressure and net colloid osmotic pressure, and how this adds up to filtration.
essentially asking you to describe “bulk flow” and exchange across the capillary wall, at the arteriole end
“Arteriole end” of capillary: blood pressure in capillary (CHP=35 mmHg out) is greater than osmotic pressure (BCOP=25 mmHg in)
-HP>OP so Net movement: out of capillary! (filtration)
Describe how net filtration pressure is affected by net hydrostatic pressure and net colloid osmotic pressure, and how this adds up to reabsorption.
essentially asking you to describe “bulk flow” and exchange across the capillary wall, at the venule end of a capillary.
“Venous end”: pressure in capillary (CHP=18 mmHg out) is less than osmotic pressure (BCOP=25 mmHg in)
-HP less than op therefore absorption and net movement in to the capillary
Describe how blood is moved through veins.
Valves in the veins prevent blood flow from moving backward
describe various factors that can help to increase venous return
-Pumping from skeletal muscles
-increasing sympathetic vasoconstrictor activity
-increasing blood volume
All increase venous pressure and venous gradient which increases venous return
Describe the local control of blood pressure and blood flow (autoregulation).
autoregulation is a very localized effect ( right at the tissues) when tissues regulate their own blood supply.
-with the help of vasodilators and vasoconstrictors
vasodilators
vasodilators : open pre-capillary sphinters to increase bloody supply .
Therefore more blood flow and decrease blood pressure
vasoconstrictors
vasoconstrictors : close pre-capillary sphinters to decrease blood supply and increase resistance
factors that trigger vasodilation in very active tissues
active cells may produce:
- lower oxgyen and higher CO2 levels cause vasodilation
- increased lactic acid causes vasodilation
- higher temperature causes vasodilation in the warm area
- increased histamine
- increased NO (nitric oxide)
Describe the relationship between blood flow and pressure and resistance.
-blood flow depends on pressure gradients (high to low)
-blood flow depends on peripheral(vascular) resistance
if resistance is increases then blood flow decreases
Describe how peripheral resistance can be affected by friction and vessel diameter
-the smaller the diameter the more resistance and friction because more contact with wall of the vessel.
Describe how peripheral resistance can be affected by blood viscosity
increased viscosity increases resistance
-the more thick the slower the flow
Describe how peripheral resistance can be affected by turbulence.
makes it harder for blood to flow through
how do changes in cardiac output change blood pressure
increasing cardiac output will increase blood pressure
by elevating heart rate or stroke volume which will increase blood pressure and blood flow
Describe how changes in total peripheral resistance can affect blood pressure.
increasing resistance will increase blood pressure (because area of blood to flow is reduced therefore increasing the blood pressure)
Describe, how changes in blood volume can affect blood pressure.
increasing blood volume will increase blood pressure (because the more volume of blood in blood vessels then there is a higher pressure on the walls of the vessels)
blood pressure must be regulated so that
High enough to ensure adequate blood flow to organs (especially the brain…)
Low enough to prevent excess strain on heart or damage to blood vessels
Briefly describe how chemoreceptor reflexes affect blood pressure.
1)chemoreceptors are stimulated when CO2 level increases and pH and O2 levels decrease
2)resulting in:
-respiratory centers stimulated (increases respiratory rate so that we breathe more and let out CO2)
-cardioacceleratory center stimulated and cardioinhibitory center inhibited (which increases cardiac output and blood pressure)
-vasomotor center is stimulated(causing vasoconstriction)
all of this increases pH and O2 levels and decrease CO2 levels
If BP too high:
will lead to wide-spread vasodilation + decrease cardiac output (to decrease BP)
If BP too low:
will lead to wide-spread vasoconstriction + increase cardiac output (to ↑ BP)
Briefly describe how the baroreceptor affect blood pressure.
1) if BP too high its detected by barorecepters which are then stimulated
2) they send info to the medulla obllogonta where:
- cardioinhibitory centers are stimulated
- cardioacceleratory center is inhibited
3) therefore cardiac output decreases
4) at the same time vasomotor center is inhibited therefore vasodilation occurs
5) vasodilation and decreased cardiac output reduces blood pressure
the opposite happens when BP is low( vasomotor center is stimuated, cardioinhibitory center is is inhibited and cardioaccelatory center is stimulated) causing vasoconstriction, increased cardiac output and increased BP
Describe how blood pressure can be regulated/influenced by hormones:
including the natriuretic peptides
- Released by cells in atrium in response to high volume (if you have high venous return will result in stretching of heart which releases natriuretic peptides)
- Reduce your thirst; stimulate vasodilation; block release of ADH and several other hormones; increase Na+ excretion and water loss in urine; all to reduce blood volume and BP
Describe how blood pressure can be regulated/influenced by hormones:
erythropoietin
- Released by cells in the kidney in response to low O2-carrying capacity of blood
- Stimulates production and maturation of RBCs, to increase blood volume and viscosity (& therefore increase BP)
Describe how blood pressure can be regulated/influenced by hormones:
antidiuretic hormone
- Released by posterior pituitary
-stimulated when increase in osmolarity or decrease in blood volume - Conserves water “loss” at kidneys; causes wide-spread vasoconstriction to increase blood volume (and therefore increase BP too)
Describe how blood pressure can be regulated/influenced by hormones:
aldosterone
- Released by cells of the adrenal cortex
- stimulated when increases K+ or decreases Na+
- Promotes Na+ retention at kidneys, therefore also increases water retention which increase blood volume and increase BP
Describe how blood pressure can be regulated/influenced by hormones:
angiotensin II
- Part of the renin-angiotensin-aldosterone system
- A potent vasoconstrictor, leads to increase in BP
Describe the effects of the sympathetic nervous system (and epinephrine) on heart rate
-opens Na+ channels,which increase rate of depolarization in pacemaker cells therefore increasing heart rate
Describe the effects of the sympathetic nervous system (and epinephrine) contractility and cardiac output
-Increase Ca2+ in contractile cells of heart Increased contractility of cardiac cells ↑ SV and ↑CO
Describe the effects of the sympathetic nervous system (and epinephrine) on blood pressure.
Vasoconstriction of arterioles which Increases peripheral resistance therefore increase BP
Describe the effects of light exercise on cardiovascular function
-Cardiac output increases (due to many factors, including ↑ venous return); blood flow to skeletal muscle and skin increases, but blood flow to most other organs decreases
Describe the effects of heavy exercise on cardiovascular function
higher CO, greater increases and decreases in blood flow to other organs
Describe how the hormone epinephrine affects blood flow to different tissues
- by binding to adrenergic receptors on target cells
- in Alpha receptors in smooth muscle of blood vessels in digestive tract :will make the smooth muscle of some blood vessels to contract(increasing BP)
- in Beta receptors in smooth muscle of blood vessels in cardiac and skeletal muscle: will make the smooth muscle of some blood vessels relax (increasing blood flow)
cardiovascular training
resting heart rate to be lower and stroke volume will go up
Filatration
Out of the blood and into the tissues
Reabsorption
Back into the blood from the tissues
Capillary hydrostatic pressure CHP
Blood pressure in capillaries is greater than fluid pressure at interstitial fluid (IHP) therefore pushes water( and soluble molecules )out of the blood and into the interstitial fluid
Blood colloid osmotic pressure
Pressure due to the osmolarity of blood
Higher than osmotic pressure of interstitial fluid (ICOP) therefore the net pull of water into the blood
