L09: Special Circulations Flashcards
Where does coronary arteries lie
On the pericardium
Which atrium does the coronary veins empty into
Right atrium
Which organ has the highest a-vo2 difference
Heart
Which organs have the smallest a-vo2 difference
Kidney
Skin
Where does the coronary artery originate from
Aorta (just after the aortic valve)
Are cardiac muscles highly or low perfused
Highly perfused
What adaptation of the cardiac myocytes allow it to have a reduced diffusion distance
High capillary density
In the coronary circulation what does haemoglobin hand the oxygen to
Myoglobulin
What is the affinity of oxygen to myoglobulin compared to haemoglobin
Higher affinity for oxygen
What does myglobulin do to the speed of oxygen transport inside the myocytes
Increase the speed of oxygen transport
What mechanism controls the blood flow in coronary circulation
Auto regulation via a myogenic response
What other things control the blood flow
Sympathetic innervation
Local factors
Endothelial factors
What are local factors
Factors from metabolism
List the substances from metabolism
Carbon dioxide
Potassium
Hydrogen ions
Adenosine
Which endothelial factors released from blood vessel result in vasodilation
Prostaglandins
Nitric oxide
Endothelial derives hyper-polarisation factors
What happens to blood flow in the coronary arteries when they are blocked
Blood flow decreases
What happens to the endothelial factors if the blood vessel walls are damaged due to the blockage
Decrease
What does reduced blood flow to the coronary circulation result in
Angina (chest pain).
Which type of angina is the most serious
Unstable angina (thrombus)
What vessels take blood to the brain
2 vertebral arteries
2 carotid arteries
What is the circle of Willis
The circle of blood vessel formed when vertebral arteries join to carotid arteries
What is the density of the capillaries like in the grey matter
High density
What does the high density of capillaries allow in the grey matter
Short diffusion distance for exchange
What type of junction does the blood brain barrier have
Tight junctions
What controls the blood flow to the brain
Auto regulation via myogenic response
What happens to the blood flow to other organs if the brain does not have enough blood flow
Other organs undergo peripheral vasoconstriction to main ABP and cerebral flow
What is hypercapnia
High carbon dioxide
What is hypocapnia
Vasoconstriction
What does hypercapnia do to the blood flow in the cerebral vessel
Increase it by vasodilation
What does hypocapnia do to the blood flow in the cerebral vessels
Decrease it via vasoconstriction
Are cerebral vessels responsive to levels of arterial oxygen as much as carbon dioxide
No they are less responsive
When does cerebral blood flow react to oxygen levels
When there is severe hypoxia
What substances does functional hyperaemia result in
Potassium
Adenosine
Carbon dioxide
Hydrogen ions
What causes a raised intracranial pressure
Bleeding
Cerebral oedema
Tumour
What happens to cerebral blood flow in postural syncope when you stand up
Cerebral blood flow decreases
What are the 2 main functions of the cutaneous circulation
Provide spine with modest metabolic requirements
Regulate body temperature
What is the network of cutaneous circulation like
Arteries give rise to arteriole that penetrate dermis to give capillaries
Blood flows into the venous plexus
Blood from arteries also give blood to venous plexus
How does he venous receive blood from the arteries
By arteriovenous anastomoses
What is the skin vessel mostly under the influence of
Sympathetic NS
What happens to the skin vessel when there is an increased temperature
1) arterioles dilate due to withdrawal of the SNS
2) AVA also dilates and increases blood flow straight into the venous plexus
3) increase in blood to the venous plexus provide a large area of heat exchange between the blood and skin and environment
What is the hypothalamic stimulation of the sympathetic fibres innervating the sweat glands
1) sweat glands receive innervation by the sympathetic fibres
2) sweat glands release bradykinin which causes the production of NO
3) this cause vasodilation to the cutaneous vessels and therefore heat loss
What happens to the TPR when there is an increase in temperature and vasodilation occurs as a result
TPR decreases
What happens to the ABP when TPR decreases
ABP decreases
When the ABP falls which reflex detects the change in pressure
The baroreceptor reflex
How does the baroreceptor reflex affect the heart
- decreases vagal activity (PNS) and increases SNS activity to the heart to increase HR
As a result in an increase HR what happens to the CO
Increase
If the CO output increases what happens to the ABP
Increases to normal
Therefore as a result of increased temperature how does it affect the heart overall
Tachycardia due to an increased heart rate
Describe what happens when there is a drop in temperature
1) SNS activity to the arterioles increase
2) vasoconstriction occurs
3) in addition AVA constricts so there is less blood flow into the venous plexus
4) this minimises heat loss by keeping blood away from the surface
In a decreased temperature when skin vessels vasoconstrict where is blood diverted to
Deep vessels that lye beneath insulating fat (interior vessels)
What happens to the cutaneous circulation when there is a prolonged exposure to cold
Cold induced vasoconstriction changes to a paradoxical cold vasodilation
What does a paradoxical cold vasodilation result in the skin
Red appearance
Why do we get a paradoxical cold vasodilation
Paralyses of NA transmission in response to cold
How do we transfer heat to the blood returning from the cold periphery
Via a countercurrent exchange
What is a Raynaud’s disease
When the skin vessels are overactive due to extreme vasoconstriction when exposed to cold
What does the pressure have to be like for blood to flow in a VESSEL
- flow depends on perfusion pressure
- artrial pressure is greater than venous pressure and theses 2 pressures have to be greater than the pressure outside (pressure in the ventricles)
What does the pressure inside represent
Pressure in aorta
What is the pressure outside
Pressure in the ventricles
What happens to the flow in the left coronary artery when there is systole of the ventricles
Decrease
Why does the coronary artery flow decrease in systole
The pressure outside i.e the ventricles is greater than the pressure in the aorta i.e the coronary artery (pressure inside the VESSELS)
What happens when the pressure outside the vessels i.e the ventricles exceed the pressure inside the VESSELS
Extravascular compression in the left ventricular wall
What happens to the blood flow during extra vascular compression the left ventricular wall
Coronary blood flow reverse as the myocytes squeeze the coronary vessels
What happens to the blood flow in the RIGHT coronary vessels when there is right ventricular contraction
Blood flow will increase
Why does the blood flow increase in systole in the RIGHT coronary vessel
The pressure inside the vessel i.e the aorta and therefore the coronary vessel increases greater than the pressure outside the vessel i.e the ventricular pressure
By how much does the aortic pressure increase in systole
40 mmhg
How much pressure increase is there in the right ventricular pressure in systole
25 mmHG
Why does the right ventricular pressure not increase as much as the left ventricular pressure
The right ventricular pressure doesn’t need a lot of pressure to overcome the pulmonary resistance whereas the left ventricular pressure needs a bigger pressure to overcome the systemic resistance
At what phase is the left coronary flow the highest
During diastole
At what phase is the right coronary artery the highest
During systole
