Objectives of the Heart

Transcription

1

2 Objectives of the Heart Electrical activity of the heart Action potential EKG Cardiac cycle Heart sounds

3 Heart Rate The heart s beat separated into 2 phases Relaxed phase diastole (filling of the chambers) Contracted phase systole (pumps the blood out) Diastole Heart relaxes Semilunar valves shut bi- & tricuspid valves open Blood pumped from atria to ventricles dub (semilunar valves closes) Systole Heart muscle contracts Semilunar valves open while bi & tricuspid valves shut Blood pumped from ventricle à aorta & pulmonary arteries lub sound (bi & tricuspid valves shut)

4 Control of Heart beat Basic heart rate of heartbeat is controlled by electrical impulses Sinoatrial node (SA node) located in the wall of right atrium begins the beat. The impulse travels down to AV node by nerve fibers called bundle of His which produces impulses causing ventricles to contract.

5 Control of heartbeat - SA node is called the pacemaker - Regulates the heart s impulses - Makes the heart contract as an unit AV node - AV node or atrioventricular node - At border of right atrium and right ventricle - Receives the electrical impulse from SA node Bundle of His

6 The cycle 1. SA Node starts the cycle. Atrial contraction (diastole) forces blood to go into ventricles 2. Systole occurs when atria contracts ejected blood into the ventricles. Atrioventricular (cuspid) valves close (1 st sound) 3. Diastole occurs and ventricles relaxes. Semilunar valves close (2 nd sound) 4. Atria fills with blood, and forces back into ventricles and cycle is repeated.

7

8 Cardiac cycle M with Bruno Mars

9 Pumping the heart Electrical potential provides the pumping cycle of the heart. Review Action potential: Resting: Na+ outside (closed channels) then moves in Depolarization: K+ inside (closed channels) Repolarization: K+ moves out while Na+ closes

10

11 oi Cardiac Cycle ua

12 Electrical activity can be determined by EKG (electrocardiogra m) Electrodes placed on the surface of the body and attached to a recording device. Electrocardiogram

13 Electrocardiogram The cardiac cycle shown on ECG consists of a P, QRS complex and a T wave.

14 P wave electrical activity through upper heart QRS complex movement of electrical impulses through the lower heart chambers ST segment ventricles contract but no electricity is flowing T lower heart chambers are resetting and preparing for next contraction

15 Factors affecting heart rate Our hearts speed up and caused by Emotions (fear, excitement, shock and tension) Exercise Drugs (nicotine, caffeine, and alcohol) Hormones (adrenalin) Chemicals (carbon monoxide slows the heart)

16 Heart sounds Sounds by the heart is from the heart valves closing and opening. The first sound is produced when the tricuspid valves close and the semilunar valves open. This is the lub sound The second sound is produced by the closure of the semilunar valves and the opening of the valves between the chambers. The higher pressure entering the ventricles causes a higher pitch noise.

17 Abnormal heart sounds Murmurs faulty valves and blood leaks through the valves Narrow valves or stenosedcauses murmurs gqk

18 Blood pressure Measured with a sphygmomanometer Blood pressure is typically recorded as two numbers in a ratio systolic # / diastolic # Systolic # represents the pressure in the arteries when the heart is contracting Diastolic # is the pressure of the arteries between beats

19 Blood pressure readings

20 How sphyghmomanometers work? The cuff is pumped up and the blood is stopped from circulating. The reading of the pressure applied is recorded. The first reading is when a pulse is heard from a stethoscope at which the pressure is greatest. This is the maximum pressure exerted by the heart As the cuffs pressure is released, the pressure when there is no more sound is when the heart chamber is relaxed.

21 Relaxed low pressure High pressure

22 Blood pressure meanings High blood pressure means that blood is working too hard going through the arteries. Low blood pressure means not enough blood is pumped through (can faint easily)

23

24 End