Cardiovascular Physiology and Complex CHD

Question 1

What does adenosine do to coronary artery flow

Answer 1

Causes coronary artery vasodilation

Question 2

Where is calcium stored in a mature myocyte and how is it released

Answer 2

• Sarcoplasmic reticulum
• Calcium enters through L type voltage gated channels when then activates the ryanodine receptor and causes calcium release from the sarcoplasmic reticulum

Question 3

How does renin get released from the kidney

Answer 3

• 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

Question 4

Most common abnormal coronary arrangement in TGA

Answer 4

Anoamlous circ from the RCA (16% of patients) but most have normal coronaries

Question 5

ANP effects on the kidney

Answer 5

• ANP is released in response to atrial stretch and leads to increased GFR
• Also decreases sodium resorption in the distal tubules

Question 6

What causes shifting to the right in the hemoglobin/oxygen dissociation curve

Answer 6

• Acidosis
• Increased temperature
• Increased 2, 3 DPG

Question 7

What is the systemic arterial response to decreased oxygen

Answer 7

• 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

Question 8

Least saturated blood in the fetus

Answer 8

Coronary sinus and SVC

Question 9

The dominant resting conductance of the myocyte is dependent on which ion

Answer 9

Potassium
- Keeps the myocyte negatively polarized until an action potential arrives to activate the cell into phase 0

Question 10

What happens in phase 0 of action potential

Answer 10

Rapid depolarization due to Na entry into the cell

Question 11

What happens in phase 1 of action potential

Answer 11

Early repolarization with K efflux from the cell

Question 12

What happens in phase 2 of action potential

Answer 12

Influx of calcium into the cell through L-type calcium channels

Question 13

What happens in phase 3 of action potential

Answer 13

Repolarization phase and is dominated by K efflux from the cell

Question 14

What happens in phase 4 of action potential

Answer 14

Return of the resting membrane potential and is maintained by Na/K ATPase channels

Question 15

What is the role of fibroblasts in the heart

Answer 15

• 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

Question 16

What is the function of intercalated discs

Answer 16

• Connect cardiac myocytes end to end
• Transmit electrical impulses
• Made of desmosomes, adherens junctions, gap junctions

Question 17

What is the process of calcium uptake during relaxation phase

Answer 17

80% done by Ca-ATPase SERCA pumps on the sarcoplasmic reticulum

Question 18

Fetal hemoglobin subunits and relative oxygen affinity compared to adult

Answer 18

• 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

Question 19

How does norepinephrine activate B1 adrenergic receptors

Answer 19

• 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

Question 20

Functions of troponin C

Answer 20

Binds to calcium and allows tropomyosin to change positions to allow actin and myosin to bind and lead to muscle cell contraction

Question 21

Baroreceptors location and response to arterial stretch

Answer 21

• Carotid sinus and aortic arch
• Send impulses to brain and decrease BP by decreasing HR and causing vasodilation

Question 22

How does troponin lead to cardiac contraction

Answer 22

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)