Question

1. How does the heart rate from the subject at rest, immediately after exercise, and at 1 min, and 2 min after exercise compare? Explain the physiology reasons for any differences.

2.What is occurring during the P-Q interval? How do the average P-Q intervals from rest and each time interval compare? How does the average at rest value compare to the "normal" value?

3. How does the average pulse-wave amplitude from rest and each time interval compare? Explain any variations.

Answer 1

1.Heart rateis the number of contractions of heart per minute . Normal value of HR is 72 beats per minute.

Case 1 : When person is resting .

When an individual is reating his HR is between 60 and 90 heart beats per minute .

Heart rate is rythmically generated by SA nodes.It is also influenced by parasympathetic and sympathetic factors .

Sympathetic stimulatiom causes the release of neurotransmitter nordrenaline at NMJ .This shortens the repolarization period and increase depolarisation whixh in turn increase theheart rate .

Parasympathetic stimulation originates from the cardioinhibitory region with impulses travelling via vagus nerve .

It produces the neurotransmitter acetylcholine .thereby depressing the heart rate .

The continous balance between these 2 helps in maintaing the heart rate in normal resting person .

Case 2 : When the patient is exercising .

Physiology : During exercise the force of contraction and cardiac output increases substantially and therby the heart rate increases .

Reasons : Activation of proprioreceptors

Increased production of noradrnaline

Chemoreceptors gets activated due to increase in CO2 and lactic acid accumulation.

To calculate your maximal heart rate is 208 - ( 0.7 * Age ) gives the HR max

The more intense workout more it take the heart to return to normal state .

In an average it will take atleast 10 mins to recover.

Qn 2 :

In electrocardiography ,the PQ interavl is the time between the beginning of P wave and beginning of QRS wave .

Mostly R is considered over Q .

It is mostly between 120- 220 ms .

PR represents the conduction time from the onset of atrial activation through purkinjee fibres during a normal cardiac cycle .

Conclusion in interval variation during exercise :

It is therby concluded that during exercuse there is a decrease in PR interval .

PR interval changes corresponding to heart rate increments were linearly decreased .

Qn 3 :

Pulse wave amplitude is the signal obtained from finger plethysmography directly and positively correlated to finger blood flow .

Pulse wave amplitude of each interavl during exercuse:

1. Q wave amplitude .

Normal value : 0.1mV ( 0..03 mV - 0.20 mV )

In pretest condition of exercising ,it is decreaced by 0.15mV

As exercise progressed heart rate to 150 or more bpm

2. R wave amplitude

Normal value : Largest resting amplitude : 3 mV

And also the greatest decrese in amplitude during exercise .

3.S wave amplitude

Pretest amplitude is -0.3mV and it becomes more negative with exercise .

4. T wave amplitude

Value ranges from 0.5- 0.9 mV .

T wave intially decreses during exercise and progressively increases after a period.