# data[].attributes.headline
State that the sinoatrial node acts as a pacemaker.

# data[].attributes.subject
State that the sinoatrial node acts as a pacemaker.

# data[].attributes.body
The sinoatrial (SA) node acts as a pacemaker in the sense that it is a groups of specialized muscle cells that initiates each heartbeat and sets the heart rate.

# data[].attributes.headline
Identify blood vessels as arteries, capillaries or veins from the structure of their walls.

# data[].attributes.subject
Identify blood vessels as arteries, capillaries or veins from the structure of their walls.

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Arteries:

Their walls contain elastic fibers formed from elastin protein (thicker walls than capillaries and veins).

Muscle and elastic fibers present in walls of the artery assist in maintaining blood pressure between pump cycles.

Arterial muscles keep the arteries narrow enough to maintain high pressure.

Layers of the arterial wall

Tunica intima

tunica media

tunica adventitia

Arteries supply blood arterioles

Capillaries:

Thinner walls than arteries and capillaries.

Networks which connects arteries with veins.

They allow nutrients and 02 to reach every cell in the body.

Small (diameter: 3-4 micrometers) enough to fit between individual cells.

Their walls are only one cell thick.

No muscles fibers or other layers (leaky/porous)

Allows for exchange of materials (permeable walls).

Veins:

Thinner walls than arteries.

Transport blood to the heart from body tissues, returning it to the atrea.

Low blood pressure-->Do not need thick walls with lots of muscle fibers.

Valves are present inside the vein (stop blood backflow).

Skeletal muscles in the vein help with blood flow.

Blood pressure in the veins is lower than in arteries+gravity=danger of backflow.

Layers:

Tunica intima

Tunica media

Tunica adventitia

# data[].attributes.headline
Describe the application of William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.

# data[].attributes.subject
Describe the application of William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.

# data[].attributes.body
His discovery explained how nutrients, 02, C02, hormones, and blood cells can be transported to and from body tissues. Harvey's discovery on the circulatory system helped explain how body temperature and pH are stabilized in the process of homeostasis. His discovery is applied in the field of cardiology.

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Outline that there is a separate circulation for the lungs.

# data[].attributes.subject
Outline that there is a separate circulation for the lungs.

# data[].attributes.body
There are two kinds of circulation for the lungs: pulmonary and bronchial circulation.

# data[].attributes.headline
Explain how the sinoatrial node sends out an electrical signal that stimulates contractions as it is propagated through the walls of the atria and then the walls of the ventricles.

# data[].attributes.subject
Explain how the sinoatrial node sends out an electrical signal that stimulates contractions as it is propagated through the walls of the atria and then the walls of the ventricles.

# data[].attributes.body
The signal from the sinoatrial node travels along the walls of the atria to the atrioventricular (AV) node. From there, the signal leaves the atria and through the interatrial septum goes into the atrioventricular node. The signal then travels from atrioventricular node to the bundle of His, which then splits into both the right and left bundles. Finally, the signal reaches the end of the bundles in the bottom tip of the heart and then the signal is distributed through the Purkinje fibers along the walls of the ventricles.

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Process:

Blood enters the heart via the inferior and superior vena cava, with 02-poor blood from the body tissues flowing into the right atrium.

As the atrium contracts, blood flows from the right atrium into the right ventricle through the open tricuspid valve.

When the ventricle is full it contract, increasing blood pressure against the tricuspid valve, forcing it shut. This prevents backflow into the atrium.

As the ventricle contracts, blood leaves the heart via the pulmonary valve into the pulmonary artery and flows to the lungs where it's oxygenated.

# data[].attributes.headline
Explain how the heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.               Describe how epinephrine increases the heart rate to prepare for vigorous physical activity.

# data[].attributes.subject
Explain how the heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.               Describe how epinephrine increases the heart rate to prepare for vigorous physical activity.

# data[].attributes.body
There are two nerves in the cardiovascular center, which is in the medulla oblongata of the brain, which signal the sinoatrial node to change the heart rate. One increases the heart rate and is called the cardiac accelerator nerve, and the one that decreases the heart rate is called the vagus nerve. Blood pressure, pH and carbon dioxide concentration of the blood are monitored by the cardiovascular center to control the sinoatrial node accordingly. Exercise can cause those values to change and consequently signal the brain that the body needs more oxygen.

# data[].attributes.headline
Describe how epinephrine increases the heart rate to prepare for vigorous physical activity.

# data[].attributes.subject
Describe how epinephrine increases the heart rate to prepare for vigorous physical activity.

# data[].attributes.body
Epinephrine (also referred to as adrenaline) is a hormone that is secreted from the medulla of the adrenal glands. Strong emotions cause epinephrine to be released and carried to the heart, where it stimulates the sinoatrial and atrioventricular nodes to fire faster. Epinephrine also triggers muscle strength, blood pressure and sugar metabolism since it travels all around the body, and because of this it is also known as the fight or flight hormone.

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Recognize the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure.

# data[].attributes.subject
Recognize the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure.

# data[].attributes.body
The heart has two sides that pump blood through pulmonary circulation. Each side has two chambers; ventricle that pumps blood into arteries and atrium that collects blood from veins and passes it to the ventricle. Each side has two valves (arteriole ventricular valve) between atrium and ventricle and semi lunar valve between ventricle and arteries. Oxygenated blood flows into left side through pulmonary veins from lungs and out through aorta. De-oxygenated blood flows into left side through veena cava out into pulmonary arteries.

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State that veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.

# data[].attributes.subject
State that veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.

# data[].attributes.body
Unlike in capillaries, the pressure in veins, or venous pressure is low. Veins are less elastic than arteries and have thin walls. The features of thin walls and less elasticity in veins allow for a higher percentage of blood in circulation. Veins throughout the body, or the venous system can accommodate a large amount of blood at relatively low pressures, this function is referred to as high capacitance.

# data[].attributes.headline
Outline that the muscle and elastic fibres assist in maintaining blood pressure between pump cycles.

# data[].attributes.subject
Outline that the muscle and elastic fibres assist in maintaining blood pressure between pump cycles.

# data[].attributes.body
The blood entering an artery from the heart is at high pressure and  the muscle and elastic fiber assist in maintaining this pressure between pumps.

- muscle: assist to form a rigid arterial wall that is capable of withstanding the high blood pressure without rupturing.  They can also contract to decrease the size of the lumen, and this increases the pressure between pumps which helps to maintain blood pressure throughout the cardiac cycle/  between the pulses of high pressure blood traveling from the heart.

- elastic fibers stretch to increase the lumen with every pulse of blood. The pressure exerted on the arterial wall is returned to the blood when the artery returns to its normal size (elastic recoil). The elastic recoil helps to push the blood forward through the artery as well as maintain arterial pressure between pump cycles

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Explain how blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary.

# data[].attributes.subject
Explain how blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary.

# data[].attributes.body
Capillaries are the narrowest blood vessels with diameter of about
10 μm.

The function of capillaries is to exchange materials between the cells in tissues and blood traveling at low pressure (<10mmHg)

The capillary wall is very permeable and allows part of the plasma(the fluid in which the blood cells are suspended)  to leak out and form tissue fluid as it consists of one layer of very thin endothelium cells, coated by a filter-like protein gel, with pores between the cells. Tissue fluid has glucose, oxygen, and other substances in blood plasma excluding large protein molecules, which can pass through the capillary wall. The fluid flows between the cells in a tissue enables the cells to absorb useful substances and excrete waste products. The tissue fluid then re-enters the capillary network. The permeabilities of capillary walls differ between tissues, enabling particular proteins and other large particles to reach certain tissues but not others.

Note that permeabilities can change over time and additionally capillaries repair and remodel themselves continually depending on the needs of tissues that they perfuse.

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State that valves in veins ensure circulation of blood by preventing backflow.

# data[].attributes.subject
State that valves in veins ensure circulation of blood by preventing backflow.

# data[].attributes.body
When the muscles of limbs, like legs and arms are activated, meaning that they contract, the valves in the veins open which allows blood to flow back towards the heart. Each of the valves in the veins have two opposing flaps which act as gates, opening in one direction to prevent backflow, when the blood moves backwards away from the heart.

# data[].attributes.headline
Explain how the heartbeat is initiated by a group of specialised muscle cells in the right atrium, called the sinoatrial node.

# data[].attributes.subject
Explain how the heartbeat is initiated by a group of specialised muscle cells in the right atrium, called the sinoatrial node.

# data[].attributes.body
There is a group of specialised muscle cells in the wall of the right atrium called the sinoatrial (SA) node. This SA node initiates (starts) each heartbeat and it sets the heart rate, so it is often called the pacemaker. The SA node 'fires' (sends electrical signals) at regular intervals to cause the heart to beat with a rhythm of about 60 to 70 beats per minute for a healthy, resting heart.