Exam 2 - Cardio

Question 1

Define cardiac output (CO)

Answer 1

rate at which blood is pumped from the ventricles = Venous Return ( VR) rate at which blood is returned to the heart
Stroke volume x heart rate

Question 2

Describe pacemaker cells

Answer 2

automaticity
slow response cells - gNa is greater, gCa is greater, gK is lower than in fast response cells
unstable RMP

Question 3

What phase of the action potential sets the heart rate?

Answer 3

phase 4 of the pacemaker cell

slow depolarization

Question 4

What effect does acetylcholine have on the SA node?

Answer 4

hyperpolarizes max diastolic potential (makes more negative) by increasing gK
decreases gCa
parasympathetic
slows heart rate

Question 5

What effect does norepinephrine have on the SA node?

Answer 5

accelerates phase 3 repolarization -> shortens AP duration, increases frequency
increases slope of phase 4 (slow depolarization) -> increases gNa and gCa (T-type)
increases heart rate
sympathetic

Question 6

Define chronotropic effects

Answer 6

effects on ANS on heart rate

Question 7

Define dromotropic effects

Answer 7

effects on ANS on conduction velocity

Question 8

Define inotropic effects

Answer 8

effects of ANS on contractility

Question 9

Where does the vagus nerve innervate the heart?

Answer 9

SA node, AV node

NO innervation of ventricles unlike sympathetic system

Question 10

What are the differences between cardiac muscle and skeletal muscle?

Answer 10

1. Ca is released into cytoplasm from SR AND extracellular fluid in cardiac
2. cardiac cells can contract WITHOUT nerve stimulation as APs start in pacemaker cells
3. cardiac cells have gap junctions

Question 11

Describe preload

Answer 11

the resting length from which the muscle contracts
As volume increases, ventricular pressure increases
Increased preload increases sarcomere length toward the optimum actin-myosin overlap

Question 12

Describe afterload

Answer 12

the force against which cardiac muscle shortens = the load on the muscle during contraction
ex: for left ventricle the afterload is the aortic pressure

Question 13

Describe a positive inotropic effect and what drugs cause this

Answer 13

an increase in contractility -> increases in SV and CO for a given EDV
Dopamine, dobutamine, digoxin, amiodarone

Question 14

Describe a negative inotropic effect and what drugs cause this

Answer 14

a decrease in contractility -> decreases in SV and CO for a given EDV
Beta blockers, calcium, channel blockers

Question 15

What two factors determine overall force of ventricular contraction?

Answer 15

preload and contractility

Question 16

Describe the Frank-Starling relationship

Answer 16

the volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole –> ensures that the volume the heart ejects in systole equals the volume it receives in venous return

Question 17

Where is the largest pressure drop in the CV system?

Answer 17

arterioles

has the greatest resistance

Question 18

What blood vessels have the biggest cross sectional area?

Answer 18

capillaries

Question 19

What blood vessels contain the greatest amount of blood?

Answer 19

veins

Question 20

In what blood vessels is velocity the fastest? the slowest?

Answer 20

fastest - aorta

slowest- capillaries

Question 21

What factors increase turbulence?

Answer 21

decreased fluid viscosity, large-diameter tubes, increasing fluid velocity, vessel branching

Question 22

What two systems control blood pressure?

Answer 22

baroreceptor reflux - neurally mediated

renin-angiotensin-aldosterone system - hormonally mediated