Flashcards in Physiology Deck (74)
What is the equation for MABP?
((2 x diastolic pressure) + systolic pressure)/3
What is a different equation for MABP?
diastolic pressure + 1/3 (systolic - diastolic)
What is the normal range of MABP?
What is the minimum MABP required for perfusion of coronary arteries, brain and kidneys?
What effect does sympathetic stimulation have on the arterioles and veins?
Which system controls the short term regulation of mean arterial blood pressure?
The baroreceptor reflex
Where are the baroreceptors?
Which nerves do the baroreceptor signals travel in to reach the brain and where in the brain do they go?
CN IX and CN X
How do the baroreceptors respond to a decrease in blood pressure?
Decrease firing from baroreceptors
Decrease vagal activity, so sympathetic activity increases
Heart rate and stroke volume increase ergo cardiac output increases
Vasocontriction occurs, so TPR increases
Venoconstriction occurs, so venous return increases and SV increases
How do the baroreceptors respond to an increase in blood pressure?
Increase firing from baroreceptors
Increase vagal activity
HR decreases, SV decreases, CO decreases
Vasodilatation occurs, so TPR decreases
Venodilatation occurs, so venous return decreases and SV decreases
Which receptor regulates the contraction of vascular smooth muscle?
L-type Ca2+ channels
What molecule does the calcium-calmodulin compound activate?
Myosin light chain kinase
What does myosin light chain kinase do that allows contraction?
Phosphorylates, and thus activates, myosin light chain
What effect does phosphorylation of MLCK have on it?
Which enzyme dephosphorylates phosphorylated MLC?
What molecule activates myosin-LC-phosphatase and this stimulates relaxation?
Where are the electrical signals of the heart generated?
Within the heart itself - pacemaker cells of the sinal atrial node
Where is the SA node located?
In the upper right atrium close to where the SVC enters the right atrium
What is the term given to the state where the heart is controlled by the sinal atrial node?
What is the pacemaker potential?
The potential that must be taken to threshold potential to generate an action potential in the SA node
What generates the pacemaker potential?
It is slow depolarisation caused by a decrease in potassium efflux and a slow sodium influx
What is the "funny current"?
The slow sodium influx of the pacemaker potential
What causes the rising phase of the action potential?
Activation of voltage gated Ca2+ channels
Rapid influx of Ca2+
What is the falling phase of the action potential caused by?
Which junctions spread electrical excitation from cell to cell?
Where is the AV node located?
At the base of the right atrium, just above the junction between atria and ventricles
What is the only point of electrical contact between atria and ventricles?
What structures allow the spread of the action potential to the ventricles?
The bundle of His
What is the resting potential of the ventricular muscle cell?