Download Cardio I

Human Physiology 11/10/08
Jeff Weiner
Cardio I Objectives- Dr. Brand
1. List four factors that determine the rate of diffusion of a solute across a membrane.
a. Concentration gradient
b. Permeability/surface area of the capillary wall
c. Molecular Weight (bigger molecules diffuse more slowly)
d. Distance (greater the distance the longer it takes to diffuse)
2. Identify which of these factors are adjusted to meet changing metabolic needs and
explain how this occurs.
a. Concentration gradient can be effected by the rate of metabolism in the tissues
(linear relationship between cardiac output and oxygen consumption)
b. Distance can be affected by pathological states. Edema, for example will increase
diffusion distance due to a an excess in interstitial fluid
3. Explain how cardiac output is measured by the Fick principle (using oxygen
consumption) and by thermodilution.
a. Consumption = flow x extraction
i. VO2 = (Flow)((ml O2/ml arterial blood) - (ml O2/ml venous blood))
ii. The amount of oxygen consumed by any organ or tissue equals the amount in
the arterial blood minus the amount in the venous blood draining that organ or
tissue.
4. Describe the two physiological responses that allow oxygen consumption by a tissue
or organ to increase when metabolism increases.
a. Active tissue will require more oxygen, it achieves this by increasing flow,
extraction, or both.
b. Physiologically, this means increasing the number of muscle capillaries or
increasing the number of mitochondria
5. Write the equation relating flow to pressure gradient and resistance.
a. Flow = ΔP/F. Can be rearranged several helpful ways:
i. R = ΔP/F
ii. Conductance = F/ΔP (inverse of resistance)
6. Describe the effects of length, viscosity and radius on resistance to flow of blood
through a blood vessel.
a. R = (8Lη)/(πr4)
b. R = Resistance, L = Length, η = Viscosity, r = Radius
7. Be able to describe and recognize on a diagram, the phases of the cardiac cycle as
presented in lecture. Know when in relation to these phases the 4 heart valves are
open and closed and when the two normal heart sounds occur. Also be able to
describe or recognize on a diagram the changes in the electrocardiogram, the
pressures in the aorta, left ventricle and left atrium, and the changes in volume of the
ventricle, that occur during a cardiac cycle.
a. Phases of the cardiac cycle
i. Atrial contraction
ii. Isovolumetric ventricular contraction
iii.
Rapid Ejection
iv.
Slow Ejection
v. Isovolumetric ventricular relaxation
Human Physiology 11/10/08
Jeff Weiner
vi. Rapid ventricular filling
vii.
Slow ventricular filling
b. Four Valves (Left and Right)
i. AV valve: Open during diastole, forced closed by the ventricular pressure in
the onset of systole.
ii. Aortic valve: Closed during diastole and in the onset of systole. Once
ventricular pressure rises above aortic pressure, the aortic valve is open and
blood is ejected from the ventricle
c. Heart Sounds
i. First sound (low pitched ‘lub’) is associated with closure of the AV valves
ii. Second sound (louder ‘dup’) is associated with closure of the pulmonary and
aortic valves
8. Define systolic, diastolic, mean, and pulse pressures.
a. Systolic: Looking at an arterial pressure wave, the systolic pressure is the peak
b. Diastolic: Lowest pressure on the wave
c. Mean: Average value of the wave
d. Pulse: Difference between systolic and diastolic pressures
9. Explain the ionic basis of the resting membrane potential in a cardiac muscle cell.
a. In a resting cardiac myocyte, potassium channels are open (permeable to K+).
The Na/K pump will pump potassium into the cell (2 in, 3 Na out). This net
movement, along with the diffusion OUT of the cell will cause a net NEGATIVE
intracellular potential
10.
Name the four phases of a ventricular myocyte action potential, and explain the
ionic basis for each phase.
a. Phase 0: “Upstroke” = rapid depolarization caused by the influx of sodium through
open fast Na channels
b. Phase 1: Partial repolarization. This is due to transient increase in Potassium
permeability
c. Phase 2: Plateau. L-type (“Long acting) calcium channels remain open, some
potassium channels remain open
d. Phase 3: Repolarization. Calcium channels close, potassium channels open
e. Phase 4: Return to resting potential (see #9)
11.
Define relative and absolute refractory period as applied to a cardiac myocyte.
a. Relative refractory period:
b. Absolute refractory period: Due to the prolonged depolarized plateau in the
cardiac muscle action potential, there is a long period where and excitable
membrane can not be re-excited
12.
Identify the ionic basis for the pacemaker potential and the action potential in a
sino-atrial node cell.
a. Pacemaker: Due to a “funny” Na current, because it opens as the cell membrane
repolarizes past -50 mV. This is spontaneous depoloarization
b. Upshoot: This is due to opening of L-type calcium channels (no fast-acting Na
channels in the SA node cells). Repolarization is due to opening of potassium
channels.
13.
Name the components of the normal pathway for excitation of the heart.
Human Physiology 11/10/08
Jeff Weiner
a. SA node---atrial myocytes---AV node---Bundle of His--- R&L bundle branches--Purkinje fibers---Ventricular myocytes
14.
List the electrophysiological events in the heart muscle that correspond to P,
QRS, and T waves and the PR, QT, and ST intervals of the electrocardiogram.
a. P: Atrial depolarization
b. QRS: Ventricular depolarization & atrial repolarization
i. More depolarization than atria because ventricles are bigger
c. T: Ventricular repolarization
d. PR: Atrial depolarization & conduction through AV node
e. QT: Ventricular depolarization & atrial repolarization
f. ST: Corresponds to plateaus of the action potentials