Cardiology-Pharmacology Flashcards
How many liters of blood are in the body and where is the majority of it located?
5 liters of blood and the majority is in the venous system
What are the properties of cardiac muscle?
Contractility (Inotropic) Extensibility Rhythmicity (Chronotropic) Automaticity Conductivity (Dromotropic) Irritiability
Define Phase 0
Depolarization occurs because sodium is rushing into the cell and forcing potassium out. This shows up as the P-Wave and QRS Complex on an ECG.
Define Phase 1
Repolarization begins as sodium starts exiting the cell and calcium starts entering the cell. On an ECG this shows up as the T-Wave.
Define Phase 2
Repolarization is continuing and the voltage plateau’s and maintains itself for a bit. Calcium is entering the cell and helping it to maintain its energy. Sodium is being pushed out and potassium is being pulled in.
Define Phase 3
Phase 3 begins when enough Calcium has entered the cell to change the normal balance of electrical charges to a point which deactivates the Calcium channel gates. Ca++ flow into the cell stops. At this point the sodium/potassium pumps and Calcium pumps move enough Na+ and Ca++ out of the cell and begin the cells return to phase 4.
Define Phase 4
This is the resting phase of the cell. Sodium is under a great deal of pressure to enter the cell to balance electrostatic and concentration gradients while potassium concentration has balanced itself. Calcium is also waiting/trying to balance it’s concentration. The cell is waiting for something (electricity) to pull the trigger.
What does Calcium do to muscles?
Calcium causes all muscles, including cardiac to contract. It also has a positive charge.
What is the difference between a fast acting and slow acting miocyte (cell?)?
The difference is how fast the calcium is leaking into the cell. And in turn causes the cell to build up to threshold.
Example: SA/AV Node is fast.
Purkinje fibers and Bundle of His is slow.
What is the absolute refractory period?
This is the area above the threshold. In this area the cell cannot accept another charge until the voltage drops below the threshold.
What is the relative refractory period?
This is the area below the threshold. In the area the cell can accept a charge, even though it is not completely through the cycle yet.
What are the stages of blood vessel contraction?
1) Calcium enters the cell from SR and extracellular region
2) Calcium binds with a protein (Calmodulin)
3) Calmodulin then activates kinase enzyme
4) Kinase enzyme phosphoralates (ATP) to myosin filaments causing contraction
What is the formula for Mean Arterial Pressure (MAP)?
Systolic Blood Pressure + 2(Diastolic Blood Pressure)/3=MAP
What is the formula for Cardiac Output?
CO= Heart Rate x Stroke Volume
What is Stroke Volume?
The amount of blood ejected with one pump
Define pre-load.
The amount of tension (stretch) applied to the cardiac muscle prior to contraction. Also known as end diastolic volume.
What is Starlings Law?
The force of ventricular contraction is proportional to muscle fiber length (up to a point). As the fiber length increase there is a corresponding increase in contractile force.
- If you want more contractile force then increase the fluid (pre-load)
Define afterload
The pressure the heart must overcome to eject blood from the heart. Also called SVR (systemic vascular resistance).
What are the key points of Heart Rate?
The sum of the pacemaker rate, Autonomic Nervous system, slow cardiac action potential.
Balanced by the Autonomic nervous system
HR increased by the beta-1 receptor, the SA node
HR decreased by the parasympathetic nervous system through muscarinic receptors in the SA and AV node, via the Vagus nerve
How does the body maintain MAP?
Baroreceptors are feedback mechanisms which help maintain MAP in response to quick postural movements of the body. Baroreceptors are located in the Aortic arch and the Carotid sinus. Also the body maintains MAP through ADH release and RAAS (Renin Angiotensin Aldosterone System).
How does Anti-Diuretic Hormone (ADH) help maintain MAP?
ADH is released by the posterior pituitary gland when the body is markedly hypotensive. ADH causes some vasoconstriction, but mainly causes fluid retention in the body.
What are the key points to remember for RAAS?
Aldosterone causes the kidney to hold onto Na and H2O increasing fluid retention
Renin is a chemical released by the kidney
A negative feedback loop occurs in response to a decreased renal perfusion
What causes renin to be released?
Beta-1 stimulation A decrease in renal perfusion factors Decreased blood pressure Decreased volume Hyponatremia
What happens when renin is released?
Renin binds with angiotensinogin (protein) and converts to angiotensin 1
