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20 Cards in this Set

  • Front
  • Back
What is alpha methyldopa and clonidine used for?
Decrease blood pressure by passive vasodilation of resistance arteriole and supression of cardiac output.

alpha 2 agonists
Name two determinants of pulse pressure
Stroke volume
Arterial compliance
What determines DBP?
TPR which is determined by resistance arterioles.

Name the determinants of SBP.
Stroke volume
Arterial compliance
Describe the relationship between CO and HR.
In Adult:
HR is a minor determinant. Primarily determined by SV. This is because as long as VR remains constant, CO remains constant.

In Children:
Increase in HR will increase CO because the left ventricle is a lot smaller. Therefore, the time for the ventricle to fill completely is very short.
Describe the relationship between CO and the following:
preload, cardiac contractility and afterload.
Increase in preload - Inc CO
Inc contractility - Inc CO
Inc afterload - Dec CO
How can you increase CO maximally?
Inc preload, Inc contractility and dec afterload.
Describe the carotid baroreflex response to a decrease in BP.
Decrease Stretch - decrease inhibitory signal to brain - release "brake" on sym - inc sym and dec vagal activity

Overall result:
1. arterial constriction (Inc DBP)
2. Venoconstriction (Inc VR & CO)
3. Cardiac inotropism & HR ( Inc CO)
Describe the consequence of suppression of sympathetic outflow.
1. Dec stimulation of B-1 receptors - Dec HR, atrial conduction, atrial and ventricular contractility therefore CO falls.

2. Dec stimulation of alpha-1 in resistance arterioles. Passiva vasodilation therefore DBP falls

3. Dec stimulation in capacitance vessels causing passive VD. Dec VR and CO
Describe the consequence of increased vagal nerve activity.
1. Decrease HR and AV conduction

2. Direct suppression of atrial contractility

3. slight decrease in ventricular contractility.
What happens in the alpha-2 stimulation in RVLM?
Prevents normal homeostasis regulated by the baroreflexly-mediated increase in sympathetic.

THerefore, fall in BP with clonidine and alpha-methyldopa does not result in cardiac stimulation. Slight bradycardia.
What does yohimbine do?
Blocks alpha 2 receptors in RVLM.

Increase in efferent sympathetic nerve activity.
Therefore, you get hypertension and tachycardia.
Describe the relationship between parasympathetic nerve activity and BP.
Decrease in BP = Decrease in parasym. and Increase in sym.
B agonist

Increases HR by direct stimulation of SA node.
Describe the 2 mechanisms that drugs can either cause tachycardia or bradycardia.
1. Direct stimulation of the SA node

2. Indirectly via arterial baroreflex.
Arterial VD

RElaxes smooth muscle to lower BP
Increases HR via arterial baroreflex.
cholinergic agonist

Decrease heart rate by direct action on SA node.
Decrease HR via arterial baroreflex
Describe 2 mech to induce bradycardia
1. Activation of muscarinic receptor

2. Carotid sinus massage
What are the clinical significance of carotid baroreflex?
1. Fall in BP - tachycardia
2. From lying/seated to standing - tachycardia
3. increase in BP - bradycardia
4. carotid sinus massage and vestigial reflex - bradycardia