CSB520 Lecture Notes - Lecture 5: Vasoconstriction, Glycogenesis, Vasopressin
Week 5 Lecture - Haemodynamics
Thursday, 7 April 2016 3:17 PM
Circulatory SystemCirculatory System
•The liver (like the lungs) has a very large venous blood supply
○It also has a lot of arterial supply, since it's the body's
largest visceral organ
•Note: the diagram above only show the main vessels, but the
actual gas exchange happens within the capillaries
•These are the structures that the cancers are most likely to
break into
PressurePressure
•Hydrostatic pressure (lower leg) drops as it goes from arteries to
veins (through arteriole, capillaries, venule)
•In the systemic circuit:
•Arteries have a very high pressure
•As capillaries are very delicate, the pressure needs to be
lowered otherwise it may just burst
•In the pulmonary circuit, there is a similar gradient, but with a
much larger drop - it has to have a lower pressure, otherwise
the lungs may blow apart
Vessel StructureVessel Structure
•Arteries & veins have similar layers - just with different
proportions
•Tunica InternaTunica Interna
○Endothelium
○Subendothelial layer
○Internal elastic lamina
•None in veins
•Tunica MediaTunica Media
○External elastic lamina
•Very thick layer of muscles in arteries (to constrict &
dilate)
•Very thin in veins
•Tunica ExternaTunica Externa
•The thickest layer in veins
•Also called adventitia
•LumenLumen
○Very wide in veins
•The tunica media layer is thin in veins, and thus, veins need
external forces (musculoskeletal) to assist in pushing the blood
back up to the heart
•Capillary
○One cell layer thick
Where is the blood?Where is the blood?
•Veins don't just carry the blood - it actually stores a lot of it as
well
○Thin walls allow for dilation and storage of lots of blood
○This is good for when we're losing blood
○But if a person has congestive heart failure, when they lie
down it will put more pressure on the right side of the
heart
•Prop them up instead of lying down
Vasodilators and VasoconstrictorsVasodilators and Vasoconstrictors
•Vasodilators:
○Metabolic (intrinsic/auto regulation):
•Decrease O2; Increase CO2
•Increase H+; Increase K+
•Prostaglandins
•Adenosine
•Nitric Oxide
○Neuronal (extrinsic):
•Decrease in sympathetic tone
○Hormonal (extrinsic):
•Atrial natriuretic peptide
•Vasoconstrictors:
○Myogenic (intrinsic/auto regulation):
•Stretch
○Metabolic (intrinsic/auto regulation):
•Endothelins
○Neuronal (extrinsic):
•Increase sympathetic tone
○Hormonal (extrinsic):
•Angiotensin II
•Angio = blood vessels, tensin = to tense
•Antidiuretic hormone
•Epinephrine (adrenaline)
•Norepinephrine (noradrenaline)
RAASRAAS
•Renin-Aldosterone-Angiotensin System
•Activated by the kidney
○One of the key jobs on the kidney is to regulate BP
○Kidney usually receives 20-25% of the cardiac output
•So if it feels like it's receiving less blood, it can
activate the RAAS system
•Potentially life-saving if we're losing blood
○Very sensitive to drops in blood pressure
•Kidney releases renin (triggers an inevitable pathway)
○Stimulates release of/activates:
1. (Stimulates release of) Aldosterone
•This tells kidneys (looping pathway) to
increase Na+ and H2O
•Also, uptake in DCT
•Instead of urinating out the Na+ and
water, it will stay in the blood to
increase blood pressure
•Increases Blood VolumeIncreases Blood Volume
2. (Activates) Angiotensin
•Increases sympathetic tone
•Basically causes vasoconstriction
•Increases Vascular ResistanceIncreases Vascular Resistance
○Those two things lead to:
•Increase of Blood PressureIncrease of Blood Pressure
•Either normotension or hypertension
•This pathway will be activated if there is kidney disease
○Kidney will think whole body has disease
○Heart disease & kidney disease go hand-in-hand
•This pathway will be activated if there is atherosclerosis
○Kidney thinks it's losing more blood
○But hypertension can damage the arteries - and then the
kidney increases blood pressure again
•Vicious cycle
•This pathways also:
○Increases synthesis of RBCs
•If it is sensed by the kidney that there isn't enough
RBCs or enough oxygen being carried by them
•It will release EPO to act on bone marrow
Renal PhysiologyRenal Physiology
•Formation of urine - removal of wastes
•Regulates plasma ions (Na+, Cl-, PO43-, K+, Ca2+)
•Regulates pH (through H+, HCO3-)
•Endocrine function (vitamin D, RAAS, EPO)
•Regulation of blood volume
