Please enable JavaScript.
Coggle requires JavaScript to display documents.
Regulation of Blood Volume (Intrinsic Regulations (Arteriole controls…
Regulation of Blood Volume
Net Filtration Pressure in Capillary
Hydrostatic Pressure
17-37 in capillary
1 in blood
Osmotic colloidal pressure
25 in capillary
0 in interstitium
(HPc + OPi) - (HPi+OPc)
Oedema
Venous blockage
Increased BP
Leakage of proteins into IF
Myxedema
Low plasma proteins
Lympathic blockage
Regulation by Kidney
Filtration by Glomerulus
Modification across Nephron
Regulation by quantity reabsorbed
According to body needs
ADH
Released under low osmolarity (dehydration, salt intake)
Thirst
Promotes H20 reabsorption
Inhibited under high osmolality
Aldosterone and Angiotensin
Triggers RAAS
Causes vasoconstriction
Salt and water retention
Net effect: Increase
Blood pressure
Blood volume
Na+ concentration
ANP
Opposes Aldosterone action
CAuses salt and water excretion
Extrinsic Regulation
Sympathetic
Increases TPR
Increase CO
Vasodilation of arterioles near muscle
Increase blood flow
Shunting of blood from viscera to skeletal muscle
Parasympathetic
Vasodilative
Not so important, only innervate
GI
Saliva
Genitalia
ADH (High) and Angiotensin
Vasoconstriction
Increase blood pressure
Paracrine
Vasodilators
Bradykinin, prostacyclin
Nitric Oxide (important)
Sets resting tone of vessel, MOA of many drugs such as GTN, Viagra
Vasoconstrictors
Endothelin 1
Intrinsic Regulations
Myogenic control
Vessels contract when stretched and vice versa
i.e. arterial pressure decrease causes vasodilations
Blood flow matches local requirement
Vasodilation
Low 02, pH
High CO2, adenosine, K
Heart and Brain must always receive adequate supply of blood
All myocytes within 10 micron of capillary
Contain high amt of mitochodria and aerobic enzymes
Myoglobin supplies O2 during systole
Coronary artery occlusion
Arteriole controls blood flow and BP
Mainly in capillary
Capillary has low Pressure
downstream of high pressure arterioles
large surface area
High sympathetic activation
Arteriolar vasoconstriction and CO increase
Kidney - blood volume and stroke volume
Baroreceptor reflex
Located in aortic arch and carotid synapses
Stretch increases action potential firing to vasomotor and cardiac control centres in medulla
Most sensitive to sudden change and decrease in BP
Atrial stretch receptors
Activated by increases Venous return
Decrease BP
Stimulate reflex bradycardia
Decrease ADH, increase ANP
During Exercise
Initial
Sympathetic Innervation
Capillary near skeletal muscle dilates
Shunting of blood to skeletal muscle
Blood flow to brain is same
Chronic
Intrinsic regulation is major regulator
Increase in sympathetic innervation increase SV and CO
HR and EF increase TPR
Coronary Blood Flow via intrinsic regulation
Normal circumstances via sym
NE-vasoconstriction
Epi-vasodilation
At rest, flow to muscles is low due to tonic sympathetic activity
Contracted muscles decrease flow due to constriction
Blood flow to brain
Almost exclusively by intrinsic regulation
BP increase, cerebral arterioles constrict
Vice versa
Respond to CO2 levels
Sensitive to local neural metabolic activity
metabolically active parts of brain granted more oxygen
15% total resting CO
Held constant at all times (750mL/min)
Not influenced by sympa activity