Weekend 2 lecture 7

Question 1

What happens when a normal person exercises

Answer 1

During exercise the CO can increase several fold. The increase in LV output must be matched by an increase in the LV input. The increase in LV output is accomplished by an increase in HR, a modest increase in SV, an increase in contractile force which increases LV systolic pressure and force of ejection

Question 2

How does the LV increase its input when the diastolic filling time is decreasing?

Answer 2

Increasing the HR shortens the duration of LV filling, thereby requiring that the diastolic filling rate during exercise must be increased out of proportion to the CO. An increase in flow rate across the mitral valve requires that the transmitral diastolic pressure gradient must be increased. The normal LV accomplishes the increase in the diastolic filling rate during exercise by rapidly and markedly decreasing the intra-LV pressure during early diastole. This early diastolic LV pressure decrease creates a relative LV “suction” effect. The mechanisms by which this occur are:

1) The increase in force of contraction during systole increase in early diastolic myocardial elastic recoil.
2) Acceleration of myocyte relaxation due to the increased rate of calcium reuptake by the sarcoplasmic reticulum.

Question 3

What changes in the exercise response of patients with heart failure?

Answer 3

The left ventricle loses the ability to augment diastolic filling in response to the exercise by the mechanisms described above (accentuated elastic recoil and early diastolic “suction” effect). Early diastolic filling is increased during exercise in CHF, but the mechanism by which this occurs in an increase in left atrial pressure. The increase in left atrial pressure creates a transmitral gradient, but at the expense of pulmonary congestion—this is the hallmark of CHF.

If ischemia develops during exercise, not only is the normal increase in the LV distensibility lost, but actually LV wall stiffness increasesincreased diastolic pressure further increases in pulmonary congestion.

***This is why it is important to monitor parameters which correlate well with MVO2 when exercising patients: RPP = HR x SBP (r = .9 with MVO2)

Question 4

ATP-CP System explain please

Answer 4

Occurs in the cytosol, splitting of the ~P from these compoundsenergy available for cellular reactions such as biosynthesis, active transport, and muscular contraction

Question 5

Rapid Glycolysis and Lactic Acid Formation whats happens in the aerobic phase vs the anaerobic phase

Answer 5

Aerobic glycolysis

• Six ATP are gained during the catabolism of glucose to pyruvate ( 2 in the cytosol by the Embden-Meyerhof pathway (aka glycolytic) pathway; and 4 in the mitochondrion during couple reoxidation of cytosolic NADH+H by the mitochondrion via the proton shuttle and the electron transport chain).
• Seven ATP are gained if glycogen is the original substrate
• Anaerobic glycolysis (sites of inadequate O2 flow to mitochondria)
• Serves to reoxidize NADH + H to NAD+ with a net increase in lactice acid production. Lactate will increase relative to pyruvate as NadH + H/NAD+ increases in the cytosol

Question 6

Krebs Cycle & Electron Transport System please explain this and how much each cycle produces of ATP made this high :).

Answer 6

-Formation of 2 Acetyl CoA from pyruvate its subsequent entry into the Krebs’s cycle yields a total of 30 ATP from these reactions. When added to the 2 ATP from glycolysis and the 4 others obtained from reoxidation of cytosolic NADH + H by the proton shuttle, the total gain in ATP from complete oxidation of glucose is 36. (When glycogen is the original carbohydrate source, an additional ~P is obtained with a net yield of 37 ATP.)

Question 7

Metabolic Respiratory Quotient

Answer 7

Metabolic Respiratory Quotient (RQ): RQ ~VCO2/VO2

Question 8

Remember Basic Principles in Cardiac Physiology

Factors affecting Cardiac Output ( Q = HR x SV)

Answer 8

Factors affecting Cardiac Output ( Q = HR x SV)

1. HR
2. Contractility
3. Preload
4. Afterload

Question 9

Alternative Methods for Measuring Blood Pressure

Answer 9

• Palpation using a blood pressure cuff, but without a stethoscope
  
  • Check patients radial pulse. Note the strength of the pulse the regularity at rest
• Inflate BP cuff while maintaining your hand on the patients radial pulse…inflate at least 20mm above the point where you no longer feel the radial pulse.
  
  • Slowly at a rate of 2-3 mm hg/sec deflate the cuff
  • The first point at which you feel the radial pulse is documented as the SBP
• Allow the cuff to continue to deflate slowly, the point at which the pulse feels as strong as it did at rest is considered the DBP. NOTE the the accuracy of the DBP will not be that great, but will at least allow you to estimate the DBP
• Forearm BP
  
  • Place cuff on forearm of patient
  • Place your stethoscope over the radial artery at the wrist
  • Measure Blood pressure in the same way that you would when using the brachial method.
  • Remember that the arm should be kept at heart level
• Calf BP
  
  • Place the cuff on the lower portion of the calf of the patient
  • Place your stethoscope over the posterior tibial artery at the ankle
  • Measure the blood pressure in the same way that you would when using the brachial method
• Remember that the leg should be kept at approximately heart level…this is easiest to do with the patient in supine; however if you had to perform this in sitting, support the leg with the knee in extension and document the position used.