L27 Pathophysiology and Treatment of Hypertension Flashcards
what ensures fluid balance within the body?
cardiovascular and renal system
what causes hypertension?
high blood pressure
what is a determinant in blood pressure and haemodynamics?
resistance to blood flow
where is there high resistance to blood flow?
in small vessels like capillaries
what vessel is the most resistant to blood flow?
arterioles
what is systolic pressure?
the highest blood pressure when ventricles are contracting
what is diastolic pressure?
the lowest blood pressure in cardiac cycle when ventricles are relaxing
why does pressure not reach 0 in arteries?
because they have thick elastic walls and ability to recoil
explain pressure through circulatory system from highest to lowest in reference to areas
arterioles, arteries, capillaries, venules, veins
what is blood flow equal to?
pressure gradient/ resistance
what is the resistance of flow proportionate to?
length of tube x viscosity/radius
what explains the factors that cause resistance to flow?
Poiseulle’s Law
what factors cause resistance to blood flow?
vasodialation and vasoconstriction
what is the ‘rest state’?
partial contraction - allows restriction or dialation
what determines blood flow?
blood pressure and degree of vasconstriction and vasdialation
what induces vasodilation and reduced blood pressure? (increased blood flow)
nitric oxide and endothelin from endothelial cells
what hormone causes vasodialation?
histamine
what hormone causes vasoconstriction?
ADH
what metabolistic features cause dialation?
decreased oxygen availability and temperature increase
what metabolistic feature causes constriction?
nervousness/ anxiousness
what gives a false blood pressure reading?
arm raised above heart due to gravity interference
what is ideal blood pressure?
120mmHg at systole and 70mmHg at diastole
what is venous return?
the return of blood - flowing the wrong way
what is Total Peripheral Restriction (TPR)?
The sum of vasodialation and vasconstriction in an entire system
what determines mean arterial pressure/ blood pressure?
heart rate, stroke volume and TPR (sum of dialation and constriction)
what is involved in short term regulation of BP?
baroreceptor reflex
what is involved in long term regulation of BP?
regulation of blood vol via kidney, hormonal control
how is blood pressure decreased?
1) mechanoreceptors: baroreceptors of aortic arch and carotid sinus activate
2) nerve endings respond to stretch of vessel wall
3) dialation of blood vessel
what nerves connect to baroreceptors that allow change of BP?
A and C fibres
what are A fibres?
myelinated, detect low pressures of around 30.90mmHg
what are C fibres?
unmyleniated, detect high pressure of 70-140mmHg
what happens in relation to autonomic system when lowering blood pressure?
promote parasympathetic stimulation and lower sympathetic stimulation
what do baroreceptors do?
they detect the pressure and input into CNS medulla which activates either the parasympathetic or sympathetic nervous system
what does the renin-angiotensin aldotesterone system do?
it regulates sodium and water balance
how does renin-angiotensin aldosterone system influence blood pressure?
1) when blood pressure drops this pathway occurs via secretion of renin in kidneys
2) angiotensinogen proteins cleaved by renin to form angiotensin 1
3) angiotensin 1 forms angiotensin 2 when flowing through lungs
4) it produces aldosterone in kidneys to increase sodium reabsorption (conserves water)
what does angiotensin 2 stimulate?
thirst response and secretion of ADH (which increases water reabsorption)
what happens renal arteries during hypertension?
left and right arteries narrow
how is angiotension1 converted to angiotensin 2?
ace enzyme
how do we diagnose hypertension?
systolic pressure above 140 and diastolic pressure below 90
how to treat hypertension
decrease in alcohol, dietary, exercise, thiazide diuretics, ace inhibitors (inhibit alderstone formation)
what happens when renal arteries narrow?
less blood flow - kidney thinks this is low blood pressure but it is not which leads to secretion of aldersterone which increases blood pressure by reabsorption of salts
what does aldosterone corticoid do?
increases sodium reabsorption which increases blood pressure
what relieves hypertension in renal arteries?
stents
