Setting the Heart’s Tempo

Setting the Hearts Tempo

Cardiac Muscle

The heart is Made up of A type of cardiac muscle known as myogenic muscle:

Cardiac Muscle: Striated muscle that is branched.

Myogenic muscle: Muscle that is able to contract without external nerve stimulation

Proof of Myogenic Muscle

• A heart will continue to beat after it is removed (usually only a few beats)

• A frog’s heart chopped in small pieces and sprinkled with salt = each piece beats

How does the heart keep its rythum

Sinoatrial (SA node): - A bundle of specialized nerve and muscle cells

located in the right atrium below the superior vena cava

How does the heart keep its rythm

Sinoatrial (SA node): - A bundle of specialized nerve and muscle cells

located in the right atrium below the superior vena cava

- Acts as a pace maker- From this group nerve impulses are

transported to other muscle cells by modified muscle tissue

How does the heart keep its rythm

Atrioventricular (AV node): - Acts as a conductor- Sends the impulse along a special nerve track

down the septum between the two ventricles

How does the heart keep its rythm

Atrioventricular (AV node): - Acts as a conductor- Sends the impulse along a special nerve track

down the septum between the two ventricles- This special tract is called the Purkinje fiber

and it continues up to the atrium

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Result of nerve impulses

Nerve impulse moving down Purkinje fibre:Contracts the heart muscles starting with the

atria then the ventricles.

Monitoring the heart

Electrocardiograph: Measures the electrical impulses traveling through the heart. This provides information about

Monitoring the heart

Electrocardiograph: Measures the electrical impulses traveling through the heart. This provides information about

- rate and regularity of heartbeats, - size and position of chambers,

Monitoring the heart

Electrocardiograph: Measures the electrical impulses traveling through the heart. This provides information about

- rate and regularity of heartbeats, - size and position of chambers, - presence of any damage (dead tissue does not

contract = abnormal wave)

Monitoring the heart

Electrocardiograph: Measures the electrical impulses traveling through the heart. This provides information about

- rate and regularity of heartbeats, - size and position of chambers, - presence of any damage (dead tissue does not

contract = abnormal wave)- effects of drugs or devices used to regulate

the heart (pacemaker) and stress tests

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Heart rate

• Increased need for oxygen during exercise = heart rate increases to get oxygenated blood to cells

Tachycardia:

Bradycardia:

Heart rate

• Increased need for oxygen during exercise = heart rate increases to get oxygenated blood to cells

Tachycardia: Heart rate over 100 beats per minute

Bradycardia: Heart rate under 60 beats per minute with other symptoms such as fainting

Heart Sounds

“Lubb-dubb” : They typical heart sound created by the closing of the heart valves

Lubb = av valves closeDubb = closing of the semilunar valveDiastole:

Systole:

Heart Sounds

“Lubb-dubb” : They typical heart sound created by the closing of the heart valves

Lubb = av valves closeDubb = closing of the semilunar valveDiastole: the relaxing of the heart between

contractions

Systole: The contracting of the heart muscles