Cardiovascular Physiology and Complex CHD Flashcards
What does adenosine do to coronary artery flow
Causes coronary artery vasodilation
Where is calcium stored in a mature myocyte and how is it released
- Sarcoplasmic reticulum
- Calcium enters through L type voltage gated channels when then activates the ryanodine receptor and causes calcium release from the sarcoplasmic reticulum
How does renin get released from the kidney
- In response to lower renal perfusion pressure from the juxtaglomerular apparatus
- Leads to cleavage of angiotensinogen to angiotensin I and then angiotensin II by ACE
- Angiotensin II then induces vasoconstriction and stimulates ADH (vasopressin) secretion
Most common abnormal coronary arrangement in TGA
Anoamlous circ from the RCA (16% of patients) but most have normal coronaries
ANP effects on the kidney
- ANP is released in response to atrial stretch and leads to increased GFR
- Also decreases sodium resorption in the distal tubules
What causes shifting to the right in the hemoglobin/oxygen dissociation curve
- Acidosis
- Increased temperature
- Increased 2, 3 DPG
What is the systemic arterial response to decreased oxygen
- Systemic vasodilation due to attempts to get more oxygen delivery through increased flow
- Local vasodilation is also caused by increasing pCO2, increasing acidosis or increasing K
Least saturated blood in the fetus
Coronary sinus and SVC
The dominant resting conductance of the myocyte is dependent on which ion
Potassium
- Keeps the myocyte negatively polarized until an action potential arrives to activate the cell into phase 0
What happens in phase 0 of action potential
Rapid depolarization due to Na entry into the cell
What happens in phase 1 of action potential
Early repolarization with K efflux from the cell
What happens in phase 2 of action potential
Influx of calcium into the cell through L-type calcium channels (voltage dependent)
What happens in phase 3 of action potential
Repolarization phase and is dominated by K efflux from the cell
What happens in phase 4 of action potential
Return of the resting membrane potential and is maintained by Na/K ATPase channels
What is the role of fibroblasts in the heart
- Structural integrity, remodeling, development
- Deposition of extracellular matrix
- Involved in secretion of cytokines and growth factors
- Most common non-myocyte cardiac cell in the heart
What is the function of intercalated discs
- Connect cardiac myocytes end to end
- Transmit electrical impulses
- Made of desmosomes, adherens junctions, gap junctions
What is the process of calcium uptake during relaxation phase
80% done by Ca-ATPase SERCA pumps on the sarcoplasmic reticulum
Fetal hemoglobin subunits and relative oxygen affinity compared to adult
- Fetal is alpha and gamma
- Adult is alpha and beta
- Fetal has higher affinity for oxygen and becomes adult by about 3 months of age
How does norepinephrine activate B1 adrenergic receptors
- Activates the Gs subunit of the G protein complex which activates adenylate cyclase to convert ATP to cAMP and activates protein kinase A
- PKA phosphorylates multiple proteins involved in muscle contraction and action potentials of the heart
Functions of troponin C
Binds to calcium and allows tropomyosin to change positions to allow actin and myosin to bind and lead to muscle cell contraction
Baroreceptors location and response to arterial stretch
- Carotid sinus and aortic arch
- Send impulses to brain and decrease BP by decreasing HR and causing vasodilation
How does troponin lead to cardiac contraction
In systole calcium binds to troponin C which binds to troponin I and moves it from the ATP site on actin. Troponin T binds to tropomyosin which changes the conformation and allows cross bridging of actin and myosin leading to ATP becoming hydrolyzed and myosin and actin pulling the filament inward (power stroke)
In diastole troponin inhibits binding of myosin to actin
Path of oxygen rich blood from mom in fetus
Placenta –> umbilical veins –> ductus venosus –> Eustachian valve across PFO –> L heart –> ascending aorta
Path of oxygen deplete blood in fetus
SVC –> R heart –> PA –> PDA (decreased SVR and high PVR) –> DAo and body