Lecture 2: Blood pressure Flashcards
What is a portal system?
When a capillary bed reassembles into a blood vessel that splits again into another capillary bed
Allows transport of chemicals from one tissue to another without being diluted by mixing with blood at the heart
What is the equation for mean pulse pressure?
Pmean = Pdiastolic + (Psystolic-Pdiastolic / 3)
What is normal SV?
70ml
What is normal HR?
70bpm
What is normal RR interval?
0.86s
What is normal CO?
4.9L/min
What is normal EDV?
120ml
What is normal ESV?
50ml
What is normal EF?
58% (55-70)
What is the effect of radius on flow?
Flow increases to the power of 4
What are the causes of dilation and constriction of individual blood vessels?
Central: CNS, autonomic, endocrine
Local: blood vessels have own control
Immune: flow of immune cells
Haemostasis
What controls systemic blood pressure?
Local: endothelial cells, NO
Neurological: SNS
Humoral: renal, pituitary, adrenal
What are the effects of increased SNS on blood vessels?
Increased PR, increased pressure, increased HR, increased CO
Where are baroreceptors located?
Transverse aortic arch and carotid sinuses of the left and right carotid arteries
Where are chemoreceptors located?
Carotid bodies and aortic bodies
What is volume overload?
When preload is too large and the heart is no longer able to respond appropriately
What factors increase preload?
Increased ventricular compliance
Increased atrial contractility
Decreased HR
Increased aortic pressure
Increased venous pressure (Increased blood volume and/or decreased venous compliance)
What causes increased after load?
Increased back pressure from aorta or pulmonary arteries
If the exit valve fails to open completely
What causes pressure overload?
When the after load is elevated
Describe the thoracic pump.
During inspiration, intrathoracic pressure is negative, abdominal pressure is positive (compression of the abdominal organs by diaphragm), creates pressure gradient that pulls blood to right atrium
Describe muscle pump.
Contraction of limb muscles, squeezes blood out of nearby veins, valves assure one way flow to heart
When does most blood flow occur?
Diastole
What conditions result fro hypertension?
Aneurysm Stroke MI Kidney failure Heart failure Cardiac hypertrophy
What is orthostatic hypertension?
Low BP on standing
(decreased venous return)
Dizziness/syncope
Causes: drugs, hypovolaemia, age
