Lecture 2: Blood Pressure Flashcards
what do portal systems allow
transport of chemicals from one tissue to another without being diluted by mixing with blood at the heart
what is a portal system
2 capillary beds in series
what is a healthy blood pressure
120 / 75
what is the reciprocal of heart rate
RR interval, 60 / heart rate
what is stroke volume and average value for an adult
- volume of blood pumped out of a ventricle during one beat of the heart
- 70ml
what is cardiac output and average value for an adult
- volume of blood pumped out of a ventricle per minute
- 4.9 L/min
what is end diastolic volume and average value
- volume of blood in ventricle at the end of diastole
- 120ml
what is end systolic volume and average value
- volume of blood remaining in ventricle at the end of systole
- 50ml
what is ejection fraction (Ef) and average value
- percentage of filled ventricular volume pumped out during a heart beat
- 55-70%
how does vasoconstriction affect resistance and flow rate
- higher resistance
- lower flow rate
by what power does flow increase as radius increases
power of 4
what causes vasoconstriction and dilation
- CNS autonomic and endocrine systems
- local regulation of pressure
- immune system
- haemostasis
where does exercise cause vasodilation and vasoconstriction
- vasodilation in muscle and skin
- vasoconstriction in splanchnic (digestive) circulation
how is heart rate, systolic pressure and diastolic pressure affected when standing up
- heart rate increases
- systolic unchanged
- diastolic increases
how is systemic blood pressure controlled
- endothelial cells make NO, causing relaxation of muscle tissue
- symapthetic system releases noradrenaline
- hormones released by renal pituitary and adrenal systems
where are baroreceptors located
- transverse aortic arch
- left and right internal carotid arteries
what do chemoreceptors detect and where are they located
- detect when O2 levels are low and feed back to the brain
- aortic and carotid bodies
what is venous return
rate of blood flowing back to heart through the veins
what is preload
- initial stretching of cardiac myocytes during diastole, before contraction
- ventricular filling
what is volume overload
pathological state when preload is too large for the heart to pump out
how does heart rate affect preload
decreased heart rate increases preload, as there is more time for the ventricles to fill
what is afterload
resistance during systole
what factors increase afterload
- increased back pressure from aorta or pulmonary arteries
- if the exit valve fails to open completely
what results from elevated afterload
pressure overload
features of the pulmonary circulation
- high capillary density
- low vascular resistance
- act as blood reservoir and filter
- endocrine control of blood pressure by ACE
how does low O2 affect pulmonary circulation
- constriction of arterioles
- minimises amount of blood that is poorly oxygenated
what is hypertension caused by
- mismatch between blood volume and circulatory capacity
- mostly idiopathic, hormones or brain medulla
- secondary to kidney diseases
what can chronic hypertension lead to
- aneurysm or stroke
- myocardial infarct
- kidney failure
- heart failure
- cardiac hypertrophy
what is orthostatic hypotension and what is it caused by
- low blood pressure on standing
- drugs, hypovolaemia and age
signs and symptoms of cardiogenic shock
- tachycardia and tachypnoea are compensatory mechanisms
- low urine output
- hypotension
- confusion
- syncope
- acidosis
