cardiovascular physiology 2 Flashcards
what does the ECG look like when patient has premature ventricular contractions?
at some point instead of a P wave a new QRS and T wave appears
what causes for premature ventricular contraction?
abnormal site will dire an AP
the beat produced by the abnormally fired AP is called what?
ectopic beat
what may cause for an abnormal site to produce an AP?
-clot formation in Arterie
what happens if the patients then enters sinus tachycardia and heart beats 5x per second?
o Heart doesn’t have time to fill since time of contraction is too slow thus no blood is being pumped in/out
what is the cardiac output if no blood gets pumped in/out
zero
what happens if the cardiac output and pressure and sroke volume are = 0?
ventricular fibrillation
what do the ventricles look like during v fibrillation and why?
like a bag of worms become APs get fired from anywhere
what happens if treatment is not recieved within 5 minutes of V fibrillation?
death
what is used to treat v fibrillation?
defibrillation of the heart using AED
what portion of the heart gets observed during mapping of cardiac electrical activity?
apex of the heart
what does mapping of cardiac electrical activity involve?
o Insert catheters which open into the heart on the epicardial where electrons are deflected
in patients who have already had a heart attach what is being tested by electrical cardiac mapping? how is it tested?
circular path known as reentry. due to presence of scar tissue. induce of ventricle tachycardia in patient
what can be observed through electrical mapping when a patient goes from VT to Vfib?
refractory period due to difference of speed causes for different afferents to propagate
cardiac cells are full of what type of cells?
actin and myosin
what induces contraction in the heart?
calcium which diffuses from T tubules to the cytosol this allows for transition from electrical signal to contraction
in excitation-contraction coupling, what enters the cardiac cells when an AP is fired?
Ca2+
with the entry of calcium into the heart what is released and what does this cause?
more calcium gets released and this causes contraction of the heart
how is contraction of the heart induced?
binding of calcium to actin and myosin
is contraction evaluted in ECGs?
no
how does the heart cycle function?
cyclic process
what happens during systole
pressure in RA is quite small causing for the ventricles to begin to contract
Pv > Pa causing for AV valves to close and semilunar valves
pressure in ventricles increases until Pv > Paorta
opening of aortic valve and blood enters pulmonary trunk
what happens during diastole?
muscles relax as pressure falls
Paorta > Pav valve
P pulmonary trunk > P RV causes for the semilunar valves to close
pressure falls near 0
during this time the atrium has been filling with deoxigenated blood from SVC/IVC where Patrium > P ventricle
what is the name of the phase when Patrium > P ventricle
ventricular filling phase
what is the duration of ventricle contraction and relaxation?
1/3 s. contraction
2/3 s. relaxation
does autoregulation require presence of hormones?
no, its accomplished by the organs themselves
what is regulated via coronary regulation?
conorary flow
what happens to flow in the coronary A. if the pressure in the Arteries drops?
flow will drop but will quickly reestablish due to autoregulation
what are the autoregulation mechanisms that take place? do they occur at the same time or in a sequence?
metabolic and myogenic mechanisms they take place at the same time
what is the main function of the metabolic mechanism of autoregulation?
Decrease in arterial pressure in organ
Decrease blood flow to the organ
Decrease O2 and Increase metabolites
what is the main function of the myogenic mechanism of autoregulation?
Decrease in stretch of wall vessels of organs
Arteriolar dilation in organs
Restoration of blood flow towards normal in organ
what do the mechanisms of autoregulation share in common what is different?
overall they produce the same effect to increase blood flow to organs however the consequences differ due to local metabolites
what composes the autonomic NS?
parasympathetic NS
sympathetic NS
what branch(es) of the ANS innervate the SA node?
both Parasympathetic and sympathetic
how does the parasympatic NS innverate the SA node
- preganglionic neuron in spinal cord goes to axon via vagus N.
- synapses with the postganglioic axon to reach the SA node
What Neurotransmitter is involved in the parasympathetic NS (pre/postganglionic) and what’s its receptor?
preganglionic: achetylcholine & nicotinic receptor
postganglionic: achetylcholine & muscarinic receptor
what is the role of Ach in parasympathetic innervation of the SA node?
-allows to fire more AP to the postganglionic axons
what happens when ACH binds to muscarinic receptor in the parasympathetic innervation of the heart
, the rate of the sinus node slows down.
overall, an increase in the parasympathetic tone causes what in the heart?
slows down
who is the target group fro atropine? how does it function?
- used in patients with brachycardia
- prevents ACh from binding thus increasing heart rate, cardiac output and BP
what receptor is found in the sympathetic NS when the AP reaches the SA node
Noreepinephrine binds to B-adrenergic receptor
what happens to the heart rate when Noreepinephrine binds to B-adrenergic receptor? in what pathway of the ANS does this occurs?
increase in heart rate
-occurs in the sympathetic pathwat
in the case of low BP, what medication can be given to patients? what are its effects? it replicated the effects of what?
b-agonist
- activates receptors allowing for increased heart rate
- replicated effect of norepinephrine
in the case of high BP, what medication can be given to patients? what are its effects?
B-blocker as it doesn’t activate the B andregenic receptors causing for lac of binding to the SA node thus causing HR to drop
what is the effect of the sympathetic pathway on the contractility of the ventricles?
increases force of contraction of the ventricular muscle
what happens to the sympathetic contractility if B agonist is supplied?
increase in force of contraction
increase stoke volume
increase MAP
increase CO
what happens to the sympathetic contractility if B blocker is supplied?
force of contraction will no increase as much
drop in stoke volume and in CO
does increasing volume increase contractility?
no, contractility is not increased by volume
what happens when stimulating sympathetic nerve while keeping end diastolic volume constant?
leads to increased contractility
what vessels are not innervated by the sympathetic NS?
capillaries
for the neural control of vessels, what NT are involved?
ACh and NE
what is the receptor involved in neural control of the vessels for NE?
a-adrenergic receptor.
what does binding of NE lead to in the vessels?
constriction of the vessels
what happens to the vessels if a-adrenergic is supplied?
causes constriction
BP will increase
TPR increases
the adrenal gland is part of which nervous system?
sympathetic NS
What does the adrenals lack due to evolution?
lacks axons
what happens when ACh is released in the adrenals?
realeases
catecholamines; epinephrine and norepinephrine
what may happen to the baroreceptor reflex with age?
autonomic disfunction causes delay of the reflex causing for fainting when standung
are the time scales the same for different operations?
no, times scales differ in different opperations
what organ has the stongest reflex?
kidney
what does gain in force refer to?
Gain refers to the strength of the reflex; capacity to bring you back where you should be
systems work over different ranges of what?
of BP
in the baroreceptor reflex, where are the receptor located?
- common carotid A. at bifurcation
- aortic arch
where do the signals sent from the carotid sinus go to?
to the brain
what is found embedded within the aortic arch?
nerve terminals
how is signal from the aortic arch sent to the brain?
receptors and nerve terminals are embedded and stretch causes to signal AP up to the brain
how many archs does each reflex have? what are they?
2 archs
senory and motor archs
what is the other name given to the sensory reflex arch?
afferent arch of reflex
signal sent to the brain
what is the other name given to the motor reflex arch? where is the signal send?
efferent arch of reflex
signal sent into ANS
when does the baroreceptor fire APs?
then the BP increases
what happens to the baroreceptor reflex if HR increases?
increases in HR leads to increase CO and MAP leads to negative feedback; drop of BP
what happens to the baroreceptor reflex if contractility increases?
BP will fall; increases sympathetic output, increased contraction
increased stroke volume
increased CO and MAP
what happens in the baroreceptor reflex if arterioles constrict?
increases TPR (decrease in size thus resistance to blood increases) This causes for an increase in MAP
what is an increase in TRP known as?
arteriolar constriction
what happens if BP falls in baroreflex?
- squeeze down on veins
- increases venous return
- LV will be more filled thus greater contraction
what is an easy way to get rid of reflex?
cut nerves and get rid of afferent reflex
what type of tension was observed in dog at rest when afferent reflex is denervated?
labile hypertension
what is another name used to identify baroreceptor reflex?
buffer reflex
what must be done to control BP when there is an increase
- kidney’s extract H20
- Decrease of blood volume
- fall of venous pressure and venous return
- decrease stroke volume
- drop in CO
through what mechanisms can arterial pressure be restored?
negative feedback
what is the RAA system?
- drop BP in kidneys= increases renin produced
- liver produced angeotensin-
- Lungs: angeotensin 2 is then produced
what is the function of angeotension 2?
constriction of arteries
how many aa are found in angeotensin 1?
10
how many aa are found in angeotensin 2?
8
where are baroreceptors located?
in the aorta
what happens when there is a burst of AP to the brain?
arteries are bein stretched BP increases baroreceptor nerve terminal increases increase rate of firing
what happens if Arterial BP decreases?
decrease of arterial baroreceptors firing
increase of sympathetic outflow to the heart, arterioles and veins
increases HR, contractility, arteriolar constriction, venoconstriction
what happens during venial constriction?
the pressure of blood int he veins increases which drives blood back to the heart
what are some effects of venule constriction?
SV increases
what causes for SV increases in venule constriction?
B adrenergic receptor
vein constriction
what is pressure diaresis?
process that regulates water levels in urine, controlled by kidneys
what do the 3 paths of RAA involve?
- production of angiotensin 2
- secretion of vasopressin (ADH)
- production of aldosterone
what is the first step of RAA system
- drop of BP will stimulate renin secretion
- liver produces angiotensin
- renin will cleave angiotensin into angiotensin 1
- ACE produces angiotensin 2
- angiotensin causes for constriction of arterioles
where does angiotensin cause for the secretion of vasopressin?
in the brain
what happens with the release of ADH in the RAA system?
decreases renal sodium and water
-increases PV, blood volume, venous return, end diastolic volume, stroke volume, cardiac output, MAP
how do aldosterone-receptor agonist function in high blood pressure?
drop of blood pressure as it blocks aldosterone receptors thus doesn’t cause the kidneys to decrease sodium and h20
what is the 3rd process that takes place in the RAA system?
angiotensin binds to the adrenals and increase the production of aldosterone
stimulates kidneys to decrease Na+ and water excretion, thus decrease of MAP
how does AT-2 receptor blocker function in high blood pressure?
blocks angiotensin 2 receptor preventing AT2 from binding to it causing for BP to fall
how does ACE inhibitor function in high blood pressure?
prevents the conversion of angiotensin 1 into angiotensin 2 thus BP will fall
how does renin inhibitors function in high blood pressure?
inhibits the action of renin thus less angiotensin 1 is made, thus less angiotensin 2 is made thus drop in BP
what is orthostatis?
maintenance of upright standing position
generally in standard patient, what should happen to the MAP of a patient when standing?
it should be unchanged?
what should happens to diastolic and systolic BP when standing?
- diastolic should rise
- systolic should decrease
what reflex changes as we age?
baroreceptor reflex
what happens if the ventricles are fill less due to a drop in pressure?
the ventricles will be less stretched thus smaller force of contraction hence decreased SO
what happen to CO if SV decreases? why does it act different as expected?
due to baroreceptor reflex, CO will decrease, however not as much as expected due to increase HR
what causes for MAP to remain constant and not decrease due to CO decrease?
increase of TRP
how is the TRP increased in orthostatic decrease in central blood flow?
the flow of blood to certain organs can be compressed and sacrificed to ensure to get the blood pressure back ip
the contraction of what may prevent from faiting in lagging baroreceptor reflex?
contraction of calf muscle
what happens when standing to the water content?
loss of water
what happens when muscle pumps are activated?
lower of bp
how much fluid is lost daily?
~4L of water, provided by lymphe flow
