CARDIO

Question 1

What ion initiates spontaneous depolarization in SA node cells?

Answer 1

HCN (If) channels → slow Na⁺ influx

Question 2

What ion causes depolarization (Phase 0) in SA node cells?

Answer 2

Ca²⁺ influx via L-type (Cav1.2) channels

Question 3

What ion causes depolarization (Phase 0) in ventricular myocytes?

Answer 3

Na⁺ influx via fast voltage-gated Na⁺ channels (Nav1.5)

Question 4

What ion current is responsible for the plateau phase (Phase 2)?

Answer 4

Ca²⁺ influx (L-type) balanced by K⁺ efflux

Question 5

Which channel is mutated in Long QT syndrome that leads to delayed repolarization?

Answer 5

IKr (hERG) – delayed rectifier K⁺ channel

Question 6

What does the ST segment of the ECG represent?

Answer 6

Ventricular plateau phase → Ca²⁺ influx via L-type channels

Question 7

What receptors does epinephrine bind to in the heart?

Answer 7

β1-adrenergic receptors

Question 8

β1 stimulation pathway and effect?

Answer 8

β1 → Gs → ↑ cAMP → ↑ PKA → ↑ Ca²⁺ → ↑ HR and contractility

Question 9

β2 receptor location and effect?

Answer 9

Smooth muscle (e.g., vessels in skeletal muscle) → vasodilation via Gs → cAMP

Question 10

Does β2 stimulation increase heart contractility?

Answer 10

No – β2 has minimal direct effect on the heart

Question 11

Why does coronary perfusion occur mainly in diastole?

Answer 11

Systole compresses coronary arteries → blood flows when heart relaxes

Question 12

What is the baroreceptor response to ↑ BP?

Answer 12

↑ Stretch → ↑ CN IX & X firing → Medulla → ↓ Sympathetic, ↑ Parasympathetic → ↓ HR & contractility

Question 13

What is the Starling equation for capillary fluid exchange?

Answer 13

Net filtration = (Pc – Pi) – (πc – πi)

Question 14

Why does nephrotic syndrome cause edema?

Answer 14

↓ albumin → ↓ πc (oncotic pressure) → ↓ reabsorption → fluid leaks into tissues

Question 15

What ion causes depolarization in SA node pacemaker cells?

Answer 15

Ca²⁺ influx via L-type calcium channels

Question 16

What ion causes depolarization in ventricular myocytes?

Answer 16

Na⁺ influx via Nav1.5 fast sodium channels

Question 17

What is the resting membrane potential of ventricular myocytes?

Answer 17

Stable at approximately –90 mV

Question 18

Does the SA node have a stable resting membrane potential?

Answer 18

No, it has a slow rise due to spontaneous depolarization

Question 19

What initiates SA node action potentials?

Answer 19

Spontaneous depolarization via HCN (“funny current”) channels

Question 20

What initiates ventricular myocyte action potentials?

Answer 20

External stimulus

Question 21

Is there a plateau phase in SA node action potentials?

Answer 21

No

Question 22

What causes the plateau phase in ventricular myocyte action potentials?

Answer 22

Ca²⁺ influx balancing K⁺ efflux

Question 23

What ion is responsible for repolarization in both SA node and ventricular myocytes?

Answer 23

K⁺ efflux

Question 24

Which adrenergic receptor increases heart rate and contractility?

Answer 24

β1

Question 25

Where are β1 receptors located?

Answer 25

SA node, AV node, ventricles

Question 26

What is the signaling pathway of β1 receptors?

Answer 26

Gs → ↑ cAMP → ↑ PKA

Question 27

What is the effect of β2 receptor activation?

Answer 27

Vasodilation of vascular and airway smooth muscle

Question 28

Do β2 receptors directly affect heart rate?

Answer 28

No, they affect vascular tone, not heart rate

Question 29

Which receptor causes vasoconstriction and uses IP3 signaling?

Answer 29

α1 adrenergic receptor

Question 30

When is coronary blood flow highest?

Answer 30

Diastole

Question 31

Why is coronary blood flow reduced during systole?

Answer 31

The left ventricular muscle compresses coronary vessels

Question 32

What nerves are involved in the baroreceptor reflex?

Answer 32

Carotid sinus → CN IX, Aortic arch → CN X

Question 33

What is the brain region that receives baroreceptor input?

Answer 33

Nucleus tractus solitarius (NTS) in the medulla

Question 34

What happens to autonomic tone when blood pressure increases?

Answer 34

↑ Baroreceptor firing → ↓ sympathetic, ↑ vagus → ↓ HR, ↓ contractility

Question 35

What happens when blood pressure drops?

Answer 35

↓ Baroreceptor firing → ↑ sympathetic → ↑ HR, vasoconstriction, ↑ contractility

Question 36

What is the Starling equation for net filtration?

Answer 36

Net Filtration = (Pc − Pi) − (πc − πi)

Question 37

What does a drop in plasma oncotic pressure (πc) cause?

Answer 37

Edema due to reduced reabsorption of fluid

Question 38

What conditions reduce plasma oncotic pressure?

Answer 38

Nephrotic syndrome, liver failure

Question 39

What is preload?

Answer 39

Volume of blood in ventricles at end of diastole (EDV)

Question 40

What increases preload?

Answer 40

Hypervolemia, valve regurgitation, heart failure

Question 41

What is afterload?

Answer 41

Resistance the heart must overcome to eject blood

Question 42

What increases afterload?

Answer 42

Hypertension, vasoconstriction

Question 43

How does increased preload affect stroke volume?

Answer 43

↑ Preload → ↑ Stroke Volume

Question 44

How does increased afterload affect stroke volume?

Answer 44

↑ Afterload → ↑ workload → ↓ Stroke Volume

Question 45

Compare wall thickness of right vs left ventricles.

Answer 45

Right: thin; Left: thick

Question 46

What is the shape of the right ventricle?

Answer 46

Crescent

Question 47

What is the shape of the left ventricle?

Answer 47

Circular

Question 48

Which ventricle pumps blood to the lungs?

Answer 48

Right ventricle

Question 49

Which ventricle generates higher pressure?

Answer 49

Left ventricle

Question 50

Which has higher resistance: pulmonary or systemic circulation?

Answer 50

Systemic

Question 51

What ion triggers action potentials in most cardiac muscle cells?

Answer 51

Na⁺ (not Ca²⁺)

Question 52

What is the Frank-Starling Law?

Answer 52

↑ EDV → More stretch → Stronger contraction

Question 53

What factors increase venous return?

Answer 53

Sympathetic activity, skeletal muscle pump, respiratory pump

Question 54

How does sympathetic activation affect veins?

Answer 54

Constriction (↑ venous return)

Question 55

What regulates total peripheral resistance (TPR)?

Answer 55

Arteriolar constriction/dilation

Question 56

What receptor causes vasoconstriction?

Answer 56

α1 adrenergic receptor (via NE)

Question 57

What receptor causes vasodilation in skeletal muscle?

Answer 57

β2 adrenergic receptor (via Epi)

Question 58

What is the renin-angiotensin-aldosterone (RAA) system’s function?

Answer 58

Regulate blood pressure and fluid balance

Question 59

When is the RAA system activated?

Answer 59

Low blood pressure or volume

Question 60

What effect does aldosterone have?

Answer 60

↑ Na⁺ and water reabsorption (↑ blood volume and BP)

Question 61

What happens to AP excitability in the AV node?

Answer 61

Rebound excitation due to Ca²⁺-dependent excitability

Question 62

What is the sequence of EKG waves?

Answer 62

P wave → QRS complex → T wave

Question 63

What does the P wave represent?

Answer 63

Atrial depolarization

Question 64

What does the QRS complex represent?

Answer 64

Ventricular depolarization

Question 65

What does the T wave represent?

Answer 65

Ventricular repolarization

Question 66

What autonomic input decreases heart rate?

Answer 66

Parasympathetic (vagus nerve, ACh release)

Question 67

What modulates heart rate variability?

Answer 67

Age, fitness, autonomic tone

Question 68

What always precedes a heartbeat?

Answer 68

Action potential

Question 69

What contributes to blood return to the heart during exercise?

Answer 69

Sympathetic tone, muscle pump, breathing