cardiac physiology

The following materials are needed per group:
Cotton balls and alcohol
17 Lancets
6 Filter papers
2 Sphygmomanometers
3 Capillary tubes
15 Microscope slides
3 Toothpicks

Pulse

It is a blood wave created by the left ventricle contracting.
It is the alternate constriction and dilation of an artery.

Pulse Rate/Heart Rate

It is the number of heartbeats per minute.
The pulse reflects the heartbeat in healthy people.
In a healthy person, the pulse rate is the same as the ventricular contraction rate.
Normal heart rate varies person to person.
The normal value is 60-100 beats per minute.
Tachycardia is an excessively faster rate (>100 bpm).
Bradycardia is <60 bpm.

Pulse Sites

Temporal
Carotid
Apical
Brachial
Radial (most commonly used)
Femoral
Popliteal
Posterior tibial
Dorsalis pedis
All arteries have pulse, but it is readily palpable at the wrist (radial).

Reasons for Using Specific Pulse Site

Radial site is readily accessible.
Temporal site is used when radial pulse is not available.
Carotid site is used in cases of cardiac arrest, used to determine circulation to the brain.
Cardiac site is routinely used for infants and children up to 3 years of age, and used to determine discrepancies with radial pulse.
Brachial site is used to measure blood pressure and during cardiac arrest for infants.
Femoral site is used in cases of cardiac arrest.
Popliteal site is used to determine circulation to the leg.
Posterior tibial/pedal site is used to determine circulation to the foot.

Getting Your Pulse Rate

Using your right index and middle fingers, count the number of beats in 60 seconds for the most accurate reading.
The rhythm should be regular, with equal intervals.
The ratio is about 4 heartbeats to every respiration.

Activities Affecting Pulse Rate

Sitting, standing for 15 minutes, running around the lab, immediately after eating, 5 minutes after eating, before an exam, and after an exam all affect the pulse rate.

Pulse Amplitude Scale

0 = Absent, not palpable
1 = Diminished, difficult to palpate, thready, weak
2 = Expected, easy to palpate
3 = Full, increased
4 = Bounding, strong

Factors Affecting Pulse Rate

As age increases, the pulse rate gradually decreases.
After puberty, the average male's pulse is slightly lower than the female's.
The pulse increases with activity; the rate of increase in professional athletes is often less than in the average person because of greater cardiac size, strength and efficiency.
With fever, pulse rate increases due to increased metabolic rate.
Some medications decrease the pulse rate, and others increase it.
Cardiotonics (digitalis prepation) decrease heart rate.
Epinephrine increases heart rate.
Loss of blood from the vascular system normally increases pulse rate.
In response to stress, sympathetic nervous system stimulation increases the overall normal activity of the heart.
Fear and anxiety as well as the perception is severe pain stimulate the sympathetic system.
When a person is sitting or standing, blood usually pools in dependent vessels of the venous system.
Pooling results in transient decrease in the venous blood return to the heart and a subsequent reduction in blood pressure and increase in heart rate.
Increased blood pressure and pulse rate after eating.
Certain diseases such as some heartbeat conditions or those that impair oxygenation can alter the resting pulse rate.

Blood Pressure

It is the pressure or the force exerted by the blood upon the walls of the containing vessel.
Measured in mmHg
Blood moves in waves, thus there are two blood pressure measures.
Systolic pressure is the pressure of blood as a result of contraction of the ventricles (ventricular systole) that is the pressure of the height of the blood wave.
Diastolic pressure is the pressure when the ventricles relax (ventricular diastole).

Pulse Pressure

It is the difference between systolic and diastolic pressures.
Normal value is 30-40 mm Hg

Blood Pressure Categories (American Heart Association)

Normal: less than 120 mmHg systolic and less than 80 mmHg diastolic
Prehypertension: 120-139 mmHg systolic or 80-89mmHg diastolic
Hypertension Stage 1: 140-159 mmHg systolic or 90-99 mmHg diastolic
Hypertension Stage 2: 160+ mmHg systolic or 100+ mmHg diastolic
Hypertensive Crisis (emergency care needed): Higher than 180 mmHg systolic or Higher than 110 mmHg diastolic

High Blood Pressure Diagnosis

Healthcare providers will get an accurate picture of blood pressure and chart what happens over time.
The American Heart Association recommends a blood pressure screening starting at age 20 at your regular healthcare visit or once every 2 years if your blood pressure is less than 120/80 mm Hg.
Blood pressure rises with each heartbeat and falls when the heart relaxes between beats.
BP can vary from minute to minute, but it should normally be less than 120/80 mm Hg (less than 120 systolic AND less than 80 diastolic) for an adult age 20 or over.
Doctors may take readings over time/have you monitor your blood pressure at home if your blood pressure reading is higher than normal.
A single high reading does not necessarily mean that you have high blood pressure.
However, if readings stay at 140/90 mm Hg or above (systolic 140 or above OR diastolic 90 or above) over time, your doctor will likely want you to begin a treatment program.
Seek immediate emergency medical treatment for a hypertensive crisis if a systolic reading of 180 mm Hg or higher OR a diastolic reading of 110 mm HG or higher occurs.

Factors Affecting Blood Pressure

Newborns have a mean systolic pressure of about 75 mmHg.
Blood pressure rises with age, reaching a peak at the onset of puberty, and tending to decline somewhat.
In older adults, arteries lose elasticity and become more rigid, resulting in an elevated systolic pressure.
Physical activity increases the cardiac output and blood pressure; resting 20-30 minutes after exercise is indicated before assessing resting BP.
Stress stimulates the sympathetic nervous system, which increases cardiac output and vasoconstriction of arterioles, increasing blood pressure.
African American males over 35 years of age have higher blood pressures than European American males of the same age.
After puberty, females usually have lower BP than males; this difference is thought to be due to hormonal variations although after menopause BP in women rises.
Higher pulse rate and blood pressure than people with normal weight for those who are obese/overweight.
Pressure is usually lowest early in the morning, when the metabolic rate is lowered, then rises throughout the day and peaks in the late afternoon or early evening.
Disease processes can affect BP.

Control Mechanisms Modifying Stroke Volume and Heart Rate

Intrinsic Regulation of the Heart
Extrinsic Regulation of the Heart
Nervous regulation
Chemical regulation

Intrinsic Regulation of the Heart

It refers to mechanisms contained within the heart itself.
The amount of blood in the ventricles at the ends of ventricular diastole determines the degree to which cardiac muscle fibers are stretched.
Venous return is the amount of blood that returns to the heart.
Preload is the degree to which the ventricular walls are stretched at the end of diastole, and the amount of blood that fills the ventricles during ventricular relaxation (end diastolic volume).
Afterload refers to the pressure against which ventricles must pump blood.
Conversely, if venous return decreases, the preload, stroke volume and cardiac output also decrease.
Starling's Law of the Heart is the relationship between preload and stroke volume.

Extrinsic Regulation of the Heart

It refers to the mechanisms external to the heart, such as either nervous or chemical regulation.
Nervous Regulation: Baroreceptor Reflex
Nervous influences are carried through the autonomic nervous system.
Sympathetic nerve fibers cause heart rate and stroke volume to increase, while parasympathetic nerve fibers cause heart rate to decrease.
The baroreceptor reflex is a mechanism of the nervous system that plays an important role in regulating heart function.
Baroreceptors are stretch receptors that monitor blood pressure in the aorta and in the wall of the internal carotid arteries.
Chemical Regulation: Chemoreceptor Reflex:
Epinephrine and small amounts of norepinephrine, released from the adrenal medulla in response to exercise, emotional excitement, or stress, influence the heart's function.
Epinephrine and norepinephrine bind to receptor proteins on cardiac muscle and cause increased heart rate and stroke volume.

Heart Sounds

Auscultation is the act of listening to sounds within the body, usually done with a stethoscope.
The sound of the heartbeat comes primarily from blood turbulence caused by the closing of the heart valves.
Smoothly flowing blood is silent.
Four heart sounds occur during each cardiac cycle, but in a normal heart, only the first and second heart sounds (S1 and S2) are loud enough to be heard through a stethoscope.

First Sound (S1) or Lubb Sound

Dull, louder and a bit longer than the second sound
Caused by blood turbulence associated with closure of the Atrioventricular (AV) valves soon after ventricular systole begins
Ventricular occurs between the first and second heart sounds.
AV valves are tricuspid and bicuspid (mitral) valve

Second Sound (S2) or Dupp Sound

Shorter and not as loud as the first sound
Caused by blood turbulence associated with closure of the Semilunar (SL) valves at the beginning of ventricular diastole.
Semilunar valves are aortic and pulmonic valves.

Additional Heart Sounds

S1 and S2 are due to blood turbulence associated with the closure of valves, and they are best heard at different surface locations on the chest than at the valve sites.
The sound is carried by the blood flow away from the valves.
Normally not heard due to faintness: S3- due to blood turbulence during rapid ventricular filling and S4- due to blood turbulence during atrial systole.