Setting the Heart’s Tempo Setting the Heart’s 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 close Dubb = closing of the semilunar valve Diastole: Systole:

Heart Sounds “Lubb-dubb” : They typical heart sound created by the closing of the heart valves Lubb = av valves close Dubb = closing of the semilunar valve Diastole: the relaxing of the heart between contractions Systole: The contracting of the heart muscles