Lesson 15 and 16 - Heart Function

Lesson Objectives

A. Content Objective: The heart moves deoxygenated and oxygenated blood around the body. The process of a "heartbeat" requires a careful coordination of nerves, cardiac muscle and pressure to effectively transport blood around.

B. Language Objective: Describe the processes involved in a heartbeat.

C. Syllabus Statements:

Structure of the heart

There is a separate circulation for the lungs.
The heartbeat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node
The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain
Normal heart sounds are caused by the atrioventricular valves and semilunar valves closing causing changes in blood flow.
~~Structure of cardiac muscle cells allows propagation of stimuli through the heart wall.~~
~~Conducting fibres ensure coordinated contraction of the entire ventricle wall.~~
Application: William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.

Pressure changes in the heart

Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle

Propagation of electrical impulse

The sinoatrial node acts as a pacemaker.
The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of the ventricles
The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
Epinephrine increases the heart rate to prepare for vigorous physical activity.
~~Signals from the sinoatrial node that cause contraction cannot pass directly from atria to ventricles.~~
~~There is a delay between the arrival and passing on of a stimulus at the atrioventricular node.~~
~~This delay allows time for atrial systole before the atrioventricular valves close.~~