Cardiovascular Flashcards
(166 cards)
Where does excitation within the heart begin?
The pacemaker cells within the Sino-Atrial Node
Each pacemaker cell produces a SPP (__________ _________ __________) which trigger an _______ ________ when they combine and exceed a threshold.
Spontaneous Pacemaker Potential
Action Potential
What ions move Before/during and after pacemaker potential depolarizations?
Before- Na+ ion influx
During- Ca2+ influx through L-type channels
After- K+ efflux- repolarization
Through what junctions does excitation spread?
Gap junctions
What is unique about myocyte action potentials?
They exhibit a plateau phase which is maintained by Ca2+ channels.
What effect does vagal tone have on the heart rate?
The vagal tone slows the intrinsic heart rate (which is around 100bpm) to the normal resting heart rate (60bpm).
What effect does parasympathetic stimulation have on heart function?
negative chronotropic- slows heart rate and increases AV nodal delay
What receptors are involved in vagal stimulation of the heart?
Muscarinic M2 acetylcholine receptors
What effect does sympathetic stimulation have on the heart and what receptors do they use?
Positive chronotropic effect and positive inotropic effect- increases heart rate and decreases AV nodal delay Beta1 adrenoceptors (noradrenaline)
What do cardiac sympathetic nerves supply?
SA and AV nodes
myocardium
What drug is used to increase the heart rate during extreme bradycardia?
How does it act?
Atropine
Competitive inhibitor of muscarinic M2 receptors
why is Ca2+ necessary for muscle contraction?
It removes the troponin and tropomyosin from the myosin heads allowing crossbridge formation
Where is Ca2+ stored in myofibrils?
the sarcoplasmic reticulum
What is the purpose of transverse tubules?
They carry action potentials to the sarcoplasmic reticulum
What does the Frank-Starling curve show?
The greater the end diastolic volume the greater the stroke volume
What does one Cardiac cycle consist of?
The period from the beginning of one heart beat to the beginning of the next.
During contraction and relaxation the volume of the ventricles remains constant. What do you call these states?
Isovolumetric ventricular contraction and relaxation.
What causes the dicrotic notch?
Valve vibration
where would you place your stethoscope bell to listen to each of the four valves?
Aortic- 2nd intercostal space on right beside sternum
Pulmonary- 2nd intercostal space on left side of sternum
Tricuspid- 4th intercostal space on left side beside sternum
Mitral- 5th intercostal space mid-clavicular line
Where is most of the blood stored?
Peripheral venous pool
What name is given to the sounds heard when investigating the blood pressure?
Korotkoff sounds
Which blood vessels contribute most to systemic vascular resistance?
Arterioles
how do you investigate postural hypotension?
Ask patient to lie flat for 3 minutes then record change in blood pressure
systolic drop by 20mmHg or more
diastolic drop by 10mmHg or more
Where is Angiotensinogen produced?
the liver