PROPERTIES OF SPECIAL CIRCULATION Flashcards
role of cardiac veins
carry blood with a poor level of oxygen from the myocardium to the right atrium
special requirements for heart
-needs high basal supply of oxygen -20 times skeletal muscle
-increase oxygen supply in proportion to increased demand
what are the special features of the heart
-high capillary density
-large surface area for oxygen transfer
-reduced diffusion distance to myocytes
What causes the Bohr shift
-coronary sinus blood returning to right atrium from myocardial tissue has greater carbon dioxide content due to high capillary density , surface area and small diffusion distance
-high co2 , low ph shifts curve to the right
-haemoglobin has less affinity for oxygen
-more oxygen given up to myocardial tissue
What happens during the normal activity of the heart
-high blood flow
-relative sparse sympathetic innervation
-high nitric oxide released leading to vasodilation
-high oxygen extraction
What happens during an increased demand of the heart
-coronary blood flow increases inproportion to the demand
-production of vasodilators outcompete relatively low sympathetic vasoconstrictors
-circulating adrenaline dilates coronary vessels due to abundance of beta two adrenoreceptors
On an oxygen dissociation curve what does the right and left shift mean
Right shift is decreased affinity
Left shift means increased affinity ( for oxygen )
Signs of thrombosis
-cell death ( necrosis )
-impaired contractibility
-arrhythmias
-sympathetic activation
Mechanical factors reducing coronary flow
-shortening diastole
-increase ventricular end diastolic pressure
-reduced diastolic ventricular pressure
What are the special structural features that affect blood flow In the skim
-atrio-venous anastomoses - direct connections of arterioles and venules expose blood to regions of high surface area
-sympathetic vasoconstrictor fibres
-sudomotor vasodilator fibres -Ach acting on endothelium to produce NO
the lewis triple response of skin to trauma
-redness, caused by capillary vasodilation
-flare, a redness in the surrounding area due to arteriolar dilation mediated by axon reflex
-wheal , exudation of extracellular fluid from capillaries and venules
when the heart experiences sudden obstruction what is it
acute thrombosis produce myocardial infarction
when the heart experiences slow obstruction what is it
atheroma , chronic narrowing of the lumen producing angina
when someone has an angina what problem arises with increased activity
-arterioles further dilate to reduce resistance
- total resistance is too high due to dominance of stenosis
- oxygen demand can not be met so angina develops
What activates metaboreceptors
-adenosine
-metabolites potassium ion s
-lactate
