key area 6 - structure and function of the heart

Continuous circulation of blood

Continuous circulation of blood is maintained by muscular pump, the heart

The heart is divided into

• four chambers

• Two atria

• To ventricles

Flow flow through the heart

• The right atrium receives deoxygenated blood from all parts of the body via the vena cava

• The oxygenated blood passes through the right ventricle before leaving the heart through the pulmonary artery

• The pulmonary artery divide into two branches each leading to a lung

• Oxygenated blood returns to the heart by the pulmonary vein

• It flows from the left atrium to the left ventricle before leaving the heart by the aorta

Ventricle wall thickness

• The wall of the left ventricle is more muscular and thicker than that of the right ventricle

• The left ventricle is required to pump blood all around the body

• The right ventricle only pumps blood to the lungs.

Valves

( atrio-ventricular valves &:Semi-lunar valves)

• valves prevent the backflow of blood

• The presence of valves ensure the blood flows in One Direction through the heart

Where are the Atrio-ventricular valves

Valves between the atria and Ventricles

where are the semilunar valves present?

their present at the origins of the pulmonary artery and the aorta

Role of the semilunar valves

• these valves open during ventricular contraction, Allow allowing flow into the arteries

• When arterial pressure exceeds ventricular pressure they close

what is cardiac output?

• at each contraction, the right ventricle pumps, the same volume of blood through the pulmonary artery as a left ventricle pumps through the Aorta

Cardiac output calculation

• cardiac output is calculated by the heart rate and the stroke volume (CO=HR/SV)

Heart rate (pulse)

• this is the number of heart contractions, per minute, which corresponds to the pulse rate

Stroke volume

• this is the volume expelled by each ventricle on contraction

• Cardiac output is the volume of blood pump out a ventricle per minute

Pulse, health indicator

• The quantity of cardiac muscle present in their heart wall is greater and more efficient than an unfit person

• A very fit person tends to have a lower pulse rate than an unfit person

• The person‘s heart is larger and stronger

• A fit person struck volume is greater

• A person’s heart does not need to contract as often to pump an equal volume of blood around the body

The cardiac cycle

• The term cardiac cycle refers to the pattern of contraction (systole) and relaxation (diastole) During one complete heartbeat

• Average length of time of one cardiac cycle 0.8 seconds

Arterial and ventricular diastole

• during diastole, The blood returning to the atria flows into the ventricles

• When arterial pressure exceeds the pressure in the ventricles, the AV valves are pushed open and the blood entrance of ventricles

• And distally, the high pressure of the blood in the arteries, leaving, the heart close the SL valves again

The cardiac cycle

arterial and ventricular diastole - arterial systole - Ventricular systole - Diastole

Atrial systole

• during arterial systole, The two atria contract simultaneously and sends the remainder of the blood into the ventricles through the atrial ventricular valves, which are still in a state of ventricular diastole

• Atrial Systole is followed about 0.1 seconds later by ventricular systole

Ventricular systole

-this stage involves a contraction of ventricles and the closure of the AV valve

-The pressure exerted on the ventricles causes the valves to be pushed open as the blood is pushed through the SL valves

-blood is then pumped out from the heart into the air, water and pulmonary arteries

Heart rate

• The medulla of the brain regulates heart rate

• It regulates the rate of the heart through the antagonistic action of the autonomic Nervous system

• The cardio accelerator center sends nerve impulses via the sympathetic nerve to the heart

Result of an increase in the number of nerve impulses arriving at the Pacemaker

an increase in the number of nerve impulses Arriving at the peacemaker via the sympathetic nerve results in an increase in heart rate

The cardio inhibitor center

The cardio inhibitor center in The medulla Since it’s information via a parasympathetic nerve to the heart

Result of an increase in the number of impulses arriving at the SAN

The result in an increase in the number of impulses, arriving at the SAN from the parasympathetic nerve results in a decrease in the heart rate

Parasympathetic and sympathetic pathways

• The two pathways are antagonistic to one another as they have opposite effects on the heart rate

Sympathetic hormonal control

• under certain circumstances, such as stress or exercise, the sympathetic nervous system acts on the adrenal glands, making them release the hormone Nora adrenaline

hormonal control in terms of a pacemaker

• on reaching the SAN, the hormone makes the pacemaker generate cardiac impulses at a higher rate bringing about an increase in the heart rate

Parasympathetic hormonal control

• The parasympathetic nerve releases Acetylcholine Which decreases heart rate

Electrocardiogram visual

An electrocardiogram

• electrical activity Of the heart generates tiny currents that can be picked up on the skin surface are detected by an electrocardiogram

• The electrical signals produce a pattern called an electrocardiogram

A normal ECG

A normal ECG consists of three distinct waves normally refer to as P, QRS and T

P corresponds to

P corresponds to the wave of electrical expectation spreading over the Atria from the pacemaker

QRS represents

QRS represents the wave of expectation through the ventricles

T corresponds to

T corresponds to the electrical recovery of the ventricles at the end of Ventricular systole

Interpretation of an ECG

The interpretation of an ECG should therefore always involve calculation of the heart rate and linking the waves to atrial systole, ventricular systole , and diastole

Blood pressure

• Blood pressure is generated by the contraction of ventricles of the heart and his highest in the large elastic arteries

• Blood pressure is the force exerted by blood against the walls of blood vessels

Blood pressure fluctuations

• blood pressure increases during ventricular systole

• Blood pressure decreases during Diastole

• The highest value is in the water and the lowest in the vena cava

• Dream ventricular diversity the blood pressure in the Aorta rises to 120mm hg Greater than we expect

• There is a progressive decrease in pressure as blood travels around the circulatory system almost 0 when it reaches the right atrium again

Sphygmomanometer

Measure systolic and diastolic pressure

Sphygmomanometer Step one

The cuff is inflated until the pressure exerts stops. The blood flow through the arm artery

Sphygmomanometer step 2

Cough allowed to gradually deflate until Pressure in artery, exceeds pressure in cuff

Blood can be heard Spurting through artery and pulse can be felt

The pressure at the stage is a measure of systolic pressure

Sphygmomanometer step 3

more air is released until spurting blood and pulse cannot be heard. This is a measure of the diastolic pressure.

Hypertension

• hypertension is prolonged elevation of the blood pressure when at rest

• A typical blood pressure reading for a young adult is 120/80 mmHg

• High blood pressure usually involves values > 140/> 90 mm Hg

• Hypertension is a major risk for coronary heart, disease, and strokes

Hypertension is most commonly found in people with unhealthy lifestyles

• overweight

• Not enough exercise

• Fatty diet

• Too much salt

• Excessive alcohol

• Continuous stress