Blood Flow and Blood Pressure Flashcards
Relationship Between Blood Pressure and Perfusion
Pressure is driving force of perfusion. Low pressure = low flow (organ failure). High pressure = high proliferation (damaged cells)
Relationship between pressure, tissue stretching, baroreceptor signalling and heart rate
Increased pressure = increased stretching = more barorecptor signalling = activated parasymplathetic (negative chronotopes) (increased ressistance)= slowed heart rate
Sensory Afferents Function
Baroreceptors activates sympathetic/parasympathetic nervous system
Central Relays Outline
Cardiovascular centres in brain stem and medulla oblongata
Effector efferents Outline
Innervates heart and blood vessels
Realtionship between Cardiac Output, total peripheral ressistance and Mean Arterial Blood Pressure
Increase CO + Increase TPR = Increase MABP
How baroreceptors can lead to chronic hypertension over time
Baroreceptor resets every few days. If blood pressure is high at all times receptor may accept high value as new standard
Hypertension Outline
Independently asymptomatic. Risk factor for cardiovascular and renal disease. Measured over span of 24 hrs
Vascular Tone Def.
Force holding blood vessel shape when not fully constricted or dialated. Changing radius shape effects ressistance and changes perfusion. This helps control where blood flows to. Effected by constant dialtion and condtriction messages
Vascular Tone Regulation Outline
Both intrinsic and extrinsic factors. Tissues have different responses
2 Intrinsic Levels
meachanical stimuli (stretch and shear) and endothelail metabolites and autocoids
Extrinsic level
systemic regulation (nerves and hormones)
Vascular Endothelium Outline
Intrinsic via release of paracrine factors. Can be dialators (eg NO) or vasoconstrictors (eg thromboxane)
NO case stisy
Free radiacal, vasodilator, stimulted by shear stress and histamine. Relaxes vascular smooth muscle. anti-thrombogenic and anti-atherogenic
Shear def.
Blood passing through artery causing pooling at endothelium
endothelial Dysfunction consequences
Aggregation of blood. Impedement of substances corolling tone
Metabolites Def
Vasoactive waste products of metabolism. Tend to act locally. Increased metabolites = increased relaxation
Vasodilating Metabolites
CO2, K+, H+ and adenosine
Sympathetic nervous system effects on circulatory
Maintains tone
Sympathetic Fibre Innervation Results
Noradrenaline acts at alpha1-adrenoreceptors. Increased sympathetic activity = increased vasoconstriction
Beta-adrenoreceptors innervation results
Activated by adrenaline. Leads to vasodialation
Coronary Circulation (Heart Blood Supply) Outline
Left and Right coronary arteries supply myocardium and drain to right atrium. Most are end arteries (blood has 1 pathway) leading to increased risk of ischemia
Heart O2 Consumption
5% cardiac ouyput. O2 extraction by perfusion is 65% at rest, increasing activity increases perfusion. Perfusion occurs in diastole (arteries are compressed at systole)
Relationship between heart rate and amount of blood perfused
Increasing heart rate = decreased time for blood perfusion
