Cardiology Flashcards
Blood pressure
hydrostatic force exerted against blood vessel walls by blood
Systolic arterial pressure
force exerted on aorta and systemic arteries by blood when the heart contracts
Diastolic arterial blood pressure
force exerted on walls of the aorta and systemic arteries by blood when the heart relaxes
Pulse pressure
difference between systolic and diastolic blood pressure
Mean arterial blood pressure
average arterial blood pressure during a single cardiac cycle
When calculating MAP, which value is doubled and why
Diastolic blood pressure
As the diastolic portion of the cycle is twice as long as the systolic portion
Average systolic value (resting)
90-120
Average resting diastolic blood pressure (resting)
60-80
Average pulse pressure
30-50
Average (resting) map
70-105
What are baroreceptors used for
relaying information derived from blood pressure within the autonomic nervous system
What happens when blood pressure increases (3)
walls of blood vessels stretch more
Baroreceptors are activated
Signals are sent to the medulla
what does the brain do in response to increased baroreceptor firing (2)
Parasympathetic activity increases
Sympathetic activity decreases
What is the result of the brain’s response to increased baroreceptor firing (3)
Decreased cardiac output
Decreased vascular resistance
Decreased blood pressure
What happens when blood pressure decreases (3)
walls of the blood vessels stretch less
Baroreceptors detect less stretch
Signalling to the brain decreases
what is the brain’s response to decreased baroreceptor signalling (2)
increased sympathetic activity
Decreased parasympathetic activity
What is mean arterial blood pressure a product of (2)
Cardiac output and systemic vascular resistance
what is cardiac output the product of (2)
heart rate and stroke volume
What is cardiac output
Volume of blood pumped by each ventricle per minute
How does the sympathetic nervous system increases heart rate
releasing noradrenaline
How does the parasympathetic nervous system decrease heart rate
Releasing acetylcholine
What is stroke volume
volume of blood pumped by each ventricle per heart beat
What happens if sympathetic nerves innervate ventricular myocardium (2)
increases force of contraction
Which increases stroke volume
What is systemic vascular resistance
sum of resistance in all vasculature of the systemic circulation
What regulates systemic vascular resistance
Contraction and relaxation vascular smooth muscles
What is meant by vasomotor tone
Vascular smooth muscles are partially contracted even at rest
What is vasomotor tone caused by
tonic discharge of sympathetic nerves
What does tonic discharge of sympathetic nerves result in
Continuous release of noradrenaline
Describe autorhythmicity
the heart is capable of beating in the absence of stimuli
Where does excitation of the heart originate
Pacemaker cells in the sino-atrial node
Sinus rhythm meaning
when the heart is driven by the sino-atrial node
What exists in place of a stable resting membrane potential in pacemaker cells of the sino-atrial node
Generation of regular and spontaneous pacemaker potentials
Describe the pacemaker potential
Slow depolarisation of the pacemaker membrane to a threshold
What causes the pacemaker potential (3)
funny current
Decreased potassium ion efflux
Calcium ion influx
What is the funny current
depolarising cation current caused by influx of sodium ions through HCN channels
Once a threshold is reached for pacemaker cells, what happens(2)
rising phase
Falling phase
Describe the rising phase of an action potential in a pacemaker cell (2)
caused by opening of L-type calcium ion channels
Calcium ion influx occurs
Describe the falling phase of the action potential in pacemaker cells (2)
Caused by inactivation of L-type calcium ion channels and activation of potassium ion channels
Potassium ion efflux occurs
How does cell to cell spread of excitation occur
via gap junctions
What is the result of the slow conduction velocity within the atrioventricular node (2)
Conduction is delayed
So atrial systole precedes ventricular systole
What allows rapid spread of action potentials to the ventricles (2)
bundle of HIs
Purkinje fibres
What is the sole point of electrical contact between t he atria and ventricles
atrioventricular node
What is the resting membrane potential of contractile cardiac muscle cells
-90mV
Describe phase 0 of action potentials in contractile cardiac muscle cells (2)
there is rapid sodium ion influx
The membrane potential is reversed to +20mV
Describe phase 1 of action potentials in contractile cardiac muscle cells (2)
sodium ion channels close
There is transient potassium ion efflux
Describe phase 2 of action potentials in contractile cardiac muscle cells
there is influx of calcium ions via L-type calcium ion channels
Describe phase 3 of action potentials in contractile cardiac muscle cells (2)
L-type calcium ion channels close
Potassium ion efflux occurs
What is phase 4 of action potentials in contractile cardiac muscle cells
The resting membrane potential is restored
Describe the plateau phase
When the membrane potential do contractile myocytes is maintained near the peak of the action potential for a few hundred milliseconds
What is the main cause of the plateau phase in contractile myocytes
Influx of calcium ions via L-type calcium channels (phase 2)
What are the ECG waves (3) and what events cause them
P wave caused by atrial depolarisation
QRS wave caused by ventricular depolarisation
T wave caused by ventricular repolarisation
Is the vagus nerve part of the sympathetic or parasympathetic nervous system
Parasympathetic nervous system
What dominates under normal resting conditions
Vagal tone caused by continuous influence of the vagus nerve on the sino-atrial node
What is the importance of vagal tone
it slows intrinsic heart rate from roughly 100 bpm to a normal resting heart rate
What is supplied by the vagus nerve (2)
sino-atrial node
Atrioventricular node
What is the effect of vagal stimulation (3)
slower rate of firing of the sino-atrial node
Increased atrioventricular node delay
Decreased heart rate
Describe the neurotransmitter action involved in vagal stimulation (2)
acetylcholine
Acting at muscarinic M2 receptors (G-protein coupled)
What is supplied by cardiac sympathetic nerves (3)
sino-atrial node
Atrioventricular node
Myocardium
What is the effect of cardiac sympathetic nerve stimulation (3)
Increased rate of firing of the sino-atrial node
Decreased atrioventricular node delay
Increased force of contraction
Describe the neurotransmitter action involved in cardiac sympathetic nerve stimulation (2)
noradrenaline
Acting at β1 adrenoceptors (g protein coupled)
Summarise RAAS effect (2)
increases systematic vascular resistance
Increases plasma volume
Summarise Natriuretic peptides (3)
opposes RAAS system
Reduces blood volume
Reduces blood pressure
Summarise ADH (3)
Increase systemic vascular resistance
Increases blood pressure
Regulates extracellular fluid volume and osmolality to manage fluid load/deficit
What is renin
an enzyme found in plasma
When is renin released (3)
Due to sympathy stimulation of renal nerves
Due to decreased blood flow to the kidneys
Dye to reduced salt delivery to the kidneys
what is the sequence of events that occurs in the renin angiotensin aldosterone system (4)
Renin is released from kidneys
Angiotensinogen is converted to angiotensin 1
ACE converts angiontensin I to angiotensin II
Angiotensin II causes vasoconstriction and stimulates the release of aldosterone from the adrenal cortex
What is the effect of aldosterone (2)
increases renal absorption of plasma and water
Increases plasma volume
When are natriuretic peptides release (2)
in response to cardiac distension
In response to neurohormonal stimuli
What is the effect of natriuretic peptides (6)
decrease renin release
Vasodilation
Excretion of salt and water in kidneys
Reduce blood volume
Decrease blood pressure
Decrease SVR
What are the two types of natriuretic peptides
atrial natriuretic peptides
Brain-type natriuretic peptides
Where is ADH made and stored (2)
a peptide hormone made by the hypothalamus
Stored in the posterior pituitary
What stimulates secretion of ADH (2)
reduced extracellular fluid volume
Increased plasma osmolarity
Effects of ADH (6)
increase reabsorption of water in kidney tubules
Vasoconstriction
Increases plasma volume
Increases cardiac output
Increases blood pressure
Increases SVR