Cardiovascular Physiology Flashcards
What effect does the SNS system have on the heart and on what receptors
The SNS affects the automaticity of the heart and also the contractlity by binding to beta-1 receptors found on the nodal cells and also on the myocardium. Beta receptors on the nodal cells increases the L-type calcium channels expressed by phosphorylation more channels. Whereas in the myocardium there is an increased entry of calcium increase the number of cross links this increasing contractility.
Tachycardia
What effect does the PNS system have on the heart and what receptors are implicated?
The PNS system: Ach binds to the M2 receptors found only on the nodal cell reducing the rate of action potentials sent through so it is a negative chronotrope.
Bradycardia.
What is a chronotrope?
Chronotropic effects are those that change the heart rate. Chronotropic drugs may change the heart rate and rhythm by affecting the electrical conduction system of the heart and the nerves that influence it, such as by changing the rhythm produced by the sinoatrial node.
What is an ionotrope ?
Inotropic factors are factors that affect the amount of force that the cardiac fibers contract with
Cardiac output equation
CO= HR x SV
What area of the heart’s electrical conduction is known as the “pacemaker” of the heart?
?
a. SA node
b. AV node
c. Purkinje Fibers
d. Bundle of His
A
What area of the heart is responsible for the delay of
conduction between the atrium and ventricles?
a. AV node
b. Bundle of His
c. Bachmann’s Bundle
d. Right bundle branch
A
True or False: Depolarization of the heart muscle is
when the muscle contracts and repolarization is
when the heart muscle rests.
a. True
b. False
A
The SA node fires at a rate of?
a. 80-90 bpm
b. 40-60 bpm
c. 60-100 bpm
d. 60-80 bpm
d
On an EKG the P-wave represents what area of the
heart? (You may choose more than one)
a. Left bundle branch
b. AV node
c. Bachmann’s Bundle
d. SA node
e. Atrial myocardium
D/E
What is a consequence of hypokalemia?…
More [K+] will leave the cell to go to the concentration of low [K+] resulting in activation of Na+ channel more readily at nodal cell; this will lead to arrythmia that could be potentially fatal.
What is consequence of hyperkalemia ?
↑K+ ECF–> ↓ K+ leaving cell–> K+ accumulates in the cell–> cell +++–> Na+ voltage gated channels remain inactivated —> don’t return to resting state—> cardiac arrest.
What drugs cause hyperkalaemia
ACE-Inhibitors
Potassium supplements
Spironolactone, amiloride
Heparins
What drugs cause hypokalaemia
Diuretics
Beta agonist
Insulin
Corticosteroids
lithium
What drugs cause hypernatraemia
Corticosteroids
IV antibiotics with sodium
Oral contraceptive
Sodium bicarbonate
What drugs cause hyponatremia
Antidepressant
Desmopressin
Carbamazepine
Diuretics
Lithium
What drugs out of this list is not renally cleared?
A. Diuretics
B. Beta blocker
C. Calcium channel blocker
D. Ramipril
D. Ramipril excreted by the bile.
What happens to aldosterone during dehydration?
Aldosterone and ADH secretion increased following dehydration. It is suggested that the ADH. besides its water reabsorptive functions in the kidney, initiates aldosterone secretion. The aldosterone then works primarily on the distal and collecting ducts causing absorption of salt and water.
What is automaticity.
The heart’s intrinsic ability to depolarize and generate action potential free of autonomic innervation.
Describe ECG starting from P-wave all the way to T wave.
ECG: At the start of the P wave the sino-atrial node depolarizesà P-wave: Depolarization of the atriaà QRS-Complex: depolarization of the ventricular myocardiumà T-wave: Repolarization of the ventricular myocardium
Describe the conduction pathway.
Sino-atrial node —> AV node (0.1s wait before the bundle of His is innervated to allow for the atria to contract). —> Bundle of His —> Purkinje Fibers: Contraction of the ventricles
Describe briefly the channels involved in SA nodes depolarisation occurring
Funny Na+ channels are open at rest and there is a slow movement of Na+ making the cell positive moving it to -55 mV where T-type calcium channels are stimulated.
T-type calcium channels allow for more Ca2+ move into the cell and at -40 mV the L-type Ca2+ open.
L-type Ca2+ channels allow for explosion of Ca2+ influx causing the nodal cells to depolarise into adjacent contractile myocardial cells via intercalated discs.
Describe briefly the contraction of myocardium
L-type Ca2++ channels open allowing Ca2+ enter and rise in intracellular Ca2+ allows for myosin to bind actin forming cross bridges.
The more cross-bridges formed the stronger the …. Of the heart
Contraction
