Introduction to circulation Flashcards
what is the function of circulation
supply oxygen and nutrients to tissues and remove waste (co2 and heat)
homeostasis of extracellular fluid (via kidneys)
distribute hormones
regulate temperature
infection defence
how do circulatory pathologies arise
diminished oxygen and diminished perfusion (compelling symptoms derived from waste)
what is the function go the cardiovascular system
perfusion (flow) which requires a pressure difference (pressure and resistance are closely linked)
why must correct blood pressure be maintained
blood pressure too low then there’s insufficient delivery of blood and oxygen
what does hypertension cause
vessel damage, heart damage and other pathologies
what does hypotension cause
syncope (shock) via insufficient perfusion (common death in the critically ill)
what are the two sides of the heart
right - pulmonary
left - systemic
what are the principles of blood pressure and flow
determined by heart, blood volume and vessels
how can BP be calculated
BP = cardiac output x peripheral resistance
how can BP be measured
korotkoff sounds
via a blood pressure cuff
artery closed/ open = no sounds but at right pressure it opens and closes (systole then diastole) = sounds
what is the function of the aorta and arterioles
aorta - stretch and recoil, store energy
arteries - distribute and adjust volume
what is the function of the venules and veins
venules - collect blood, some exchange
veins - reservoir (2/3 blood in veins), muscle pump
what is the structure of blood vessels
intima (endothelium, basement membrane and lamina propria)
internal elastic membrane
media (smooth muscle and some elastic fibres)
adventitia
vasa vasorum (VAN)
how do arteries and arterioles compare
arteries - muscular and thick elastic walls
arterioles - muscular and little connective tissue
how do veins and venules compare
veins - thin walls, smooth muscle, flacid
venules - thin walls with some smooth muscles
how do systemic and pulmonary circulation compare
pulmonary - right ventricle, thin walled, crescent x section (lungs only, low pressure, high flow, low resistance)
Systemic - left ventricle, thick walled, circular x section (multiple organs, high pressure, variable flow, variable resistance)
what is the apex beat
at systole, the apex of the heart moves forward to strike the chest wall
what prevents valve prolapse
chordae tendinae attached to papillary muscles (2 mitral and 3 tricuspid)
what is the function of the mitral and tricuspid (AV) valves
papillary fibres close in systole (S1 1st heart sound, Lub)
What is the function of the aortic and pulmonary (semilunar) valves
close during diastole (longer than systole) (S2 2nd heart sound, dub)
how does the heart muscle (cardiomyocytes) contract
by a conducting system
myocyte is electrically activated (Action potential, extra cell (negative) to intracell (positive) as free intracellular calcium increases
muscle contracts
calcium removed and muscle relaxes
how is blood volume set
by the kidneys (water and sodium central to this as depends on water intake)
do formed elements have any effect on blood pressure
not unless blocking entire vessels
how is BP determined
balance between circulating blood volume and circulating capacity
what do the kidneys control
blood volume and the concentration of salts, ions, electrolytes
how is blood filtered in the kidney
small molecules (H20, glucose, ions) go through nephron (contains glomerulus)
blood cells and protein can’t pass
desirable small molecules reabsorbed
excess fluid and undesirables left in bladder and excreted
what controls filtration in the kidney
endocrine system and autonomic nervous system
how can the rate of filtration be changed
constrict afferent arteriole (decrease)
dilate afferent and constrict efferent arteriole (increase)
what is the renal portal system (filtration, reabsorption, secretion, excretion)
afferent arteriole glomerulus bowman's capsule urinary excretion or continue to efferent arteriole to peritubular capillaries to the renal vein
how many glomeruli are there
1 million in a kidney
one input via the afferent arteriole and two exits via bowman’s capsule or via efferent arterioles
what is the glomerular filtration rate
fluid entering all bowman’s capsules in ml/min
increasing GFR = fluid loss to urine
increasing renal blood flow = increases GFR
what is hypoxia/ anoxia/ hypoxaemia
insufficient O2 supply to region/ entire body
anoxia (complete deprivation)
what causes insufficient O2 in tissues
low haemoglobin (anaemia) tissue consumption to much for flow lung - failure of gas exchange/ breathing
what is ischaemia
insufficient blood flow to a region
what causes ischaemia
vessels clogged, constricted or closed
insufficient blood volume (eg haemorrhage)
heart generates insufficient pressure
What is angina pectoris
a symptom
chest pain (overexertion of (damaged) heart tissue)
with/without physical exertion
how can angina pectoris be treated
nitrates for immediate relief
long term as per CHD
what causes angina pectoris
ischaemia of the heart tissue due to obstruction/ spasm of coronary artery
ultimately may be caused by coronary artery disease/ embolism
what is myocardial infarction
death of one region of the heart
what are signs of MI
sudden crushing chest pain from occlusion of coronary artery
how can MI be treated
immediate reperfusion (morphine, nitrates, aspirin, oxygen)
what is heart failure
pumps out insufficient blood resulting from previous MIs
what are symptoms of heart failure
fatigue, dysponea, oedema
what is shock
critically low perfusion eg haemorrhagic shock
affects cerebral and renal function
what is syncope
loss of consciousness due to insufficient blood flow to the brain due to heart failure (shock, arrhythmia)
