Control of Blood Pressure Flashcards
which vessels are muscular and elastic?
arteries
describe arterioles
thinner than main arteries but muscular
which vessels are thinned walled, burst under high pressure because they can not change diameter?
capillary
what do veins and venules act as?
conduits and reservoirs
where is approx 70% of blood volume within circulation?
in venous circulation - they act as drainage and have large diameter vessels and can enter active circulation whenever
what are conduits?
channel for conveying water/ fluid
define heart rate
number of times the heart beats in a minute
what is a normal heart rate?
60-100 bpm
define stroke volume
volume of blood ejected from the heart in one beat
what is the stroke volume at rest usually?
70ml per beat
what is cardiac output?
the volume of blood ejected from the heart per minute
what is usual cardiac output?
5l of blood pumped in a minute
what is classed as bradycardic?
less than 60bpm
what bpm starts to show signs of bradycardia?
50 or less
what is tachycardia?
heart rate greater than 100 bpm
what is the calculation to get Cardiac output?
SV x Hr
define mean arterial blood pressure
average pressure exerted by the blood on the walls of major arteries
what is an average MABP at rest?
107mmHg
why is peripheral resistance hard to measure?
invasive procedure - aortic catherization
what three factors affect arterial blood pressure?
- circulatory volume (stroke vol)
- force of ventricular contraction
- elasticity of arteries
can stroke volume be altered?
yes - endurance exercises
what happens to arterial elasticity with age?
arterial stretch declines with age. Gradual thickening and changes in wall content - less elastin, advanced glycation, more inflammation, build up of ROS
what is the pressure of MABP as it reaches RA?
0 - end of journey
what three factors affect resistance?
- viscosity of blood
- length of vessels
- radius of vessels
for every pound you put on, how much more vessels are made?
5 miles
which vessels have the largest role to play within vascular resistance?
arterioles, capillaries and venules
when does the blood have the fastest velocity?
through aorta and arteries but it fluctuates with each beat
which nerve slows the heart rate down?
vagus nerve
how does the vagus nerve slow heart rate?
cardioinhibitory works via parasympathetic systems. The activity of the vagus nerve results in Ach being released
which cranial nerve is the vagus nerve?
X
what increases the heart rate? (system)
cardio-accelarator via sympathetic NS where noradrenaline is released
where does the glossopharyngeal nerve do?
provides sensory information from baroreceptor to medulla.
which cranial nerve is the glossopharyngeal?
cranial nerve IX
where are the baroreceptors within the heart
arch of aorta and carotid sinus of the brachiocephalic artery
what are sensory neurones known as and where do they go?
afferent - go back to the brain
what are motor neurones and where do they go?
efferent and go to organs/ muscles
during rest what are the sympathetic and parasympathetic NS doing to the heart?
providing slight stimulation contributing to autonomic tone
what is the role of baroreceptors?
detect change in pressue
How do baroreceptors detect change in blood pressure?
by atrial stretch - the more they are stretched the higher the blood pressure and the more they fire signals
what do atrial myocytes releae?
atrial natriuretic peptides
what do ANP do?
vasodilate
promotes Na+ secretion (water follows)
inhibits secretion of ADH (vasopressin)
only mechanism to lower BP
what is the NICE definition of hypertension?
having high blood pressure measurement that is consistently above 140/90 mmHg
how many people worldwide are affected by hypertension?
16 million people
what primary hypertension is also known as?
essential hypertension
is primary hypertension common?
yes -97% of hypertension cases
what does primary hypertension mean?
no clear cause - many factors involved
what can cause primary hypertension?
- haemodynamic factors
- physiological factors
- lifestyle
what are haemodynamic and physiological factors contributing to hypertension
- total circulating fluid volume
- vascular resistance
- plasma renin activity
- malfunctioning ion channels/ pumps in peripheral vasculature can lead to chronic increased stroke volume
what can contribute to lifestyle factors contributing to hypertension?
diet, stress, sodium intake, alcohol use, medications, drug use, oral contraceptives, corticosteriods
define secondary hypertension
another underlying disease eg CKD, atherosclerosis
can hypertension fluctuate?
yes - during normal daily activities eg sleeping (lower)
define polycythaemia and what is another name for it?
increased red blood cells - erthyocytosis
where are baroreceptors within the kidney?
juxtaglomerular cells
where is adrenaline released from?
adrenal medulla in response to lowered BP
what are the functions of adrenaline?
- speeds up Hr
- increases force of ventricular contraction
- dilate skeletal muscle and constricts splanchnic vascular beds
- diverts blood to other places that needs eg shifts to muscles in fight or flight response is triggered
what is splanchnic ciruclation?
goes to organs within abdo cavity
what is antidiuretic hormone is also known as?
vasopressin
where is ADH released from?
released from posterior part of pituitary in response to decreased blood pressure and increased plasma osmolarity
how does alcohol effect ADH?
slows down the release of ADH
how does ADH work?
- promotes reabsorption of water in the kidney
- constricts blood vessels
where is renin released from?
juxtaglomerular cells in the wall of the afferent arterioles of kidney glomeruli
when is renin released in response to?
to lower kidney perfusion caused by lowered BP
what does ACE do?
convert angiotensin I to angiotensin II
what does angiotensin lead to the secretion of?
aldosterone
what does aldosterone do?
reabsorb NaCl2 and H20
what is the medical terms of extreme thirst?
dipsogenic/ polydipsia
what is hyperplasmia?
enlargement of organ/ tissues by cell proliferation
what is polyuria?
constant need to wee
Does ANP affect renin?
can slow the release of renin
where is ACE produced?
in the lungs
where is ACE released from?
kidneys
what is conn’s disease?
primary aldosteronism
how does conn’s present as?
symptoms - polydipsia, polyuria, persistent hypokalaemia
what is the pathology of conns disease?
high levels of plasma aldosterone
what causes primary aldosteronism?
tumours/ hyperplasia of the cortex
how is conns managed?
laproscopic removal of adrenal gland
spironoactone
what can cause hypotension?
dehydration
heart failure
heart attack
shock
orthostatic hypotension
