Biology: 6.2 The Heart

Electrocardiography

'P' wave: depolarisation of the atria in response to signalling from the sinoatrial node PR interval 'QRS' wave: depolarisation of the ventricles triggered by signals from the AV node ST interval 'T' wave: depolarisation of the ventricles and the completion of a standard heart beat

Describe the cardiac cycle.

1. Atrium contracts -- blood goes into ventricle 2. Atrium relaxes. 3. Ventricle contracts -- blood pressure from ventricular contraction causes the atria-ventricular valve to close and the bicuspid or tricuspid valve to open

How does blood transport help in cell respiration in body tissues?

1.brings oxygen from lungs to all tissues of the body 2. removes carbon dioxide from tissues to bring back to the lungs

How many chambers does the human heart have?

4

Systole

Blood returning to the heart flow into the atria and ventricles as the pressure in them is lower when ventricles are about 70% full, atria will contract (atrial systole) increasing pressure in the atria and forcing blood into ventricles as ventricles contract ventricular pressure exceeds atrial pressure and AV valves close to prevent back flow with both sets of heart valves closed pressure rapidly builds in contracting ventricles when ventricular pressure exceeds blood pressure in the aorta the aortic valve opens and blood is released into the aorta

How do capillaries allow the exchange of materials between cells in the tissues and blood in the capillaries?

Capillaries, which are one-cell thick, have permeable walls that allow these materials to diffuse through.

Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves.

Deoxygenated blood enters through the right atrium. The tricuspid valve opens when the atria pumps, and blood flows into the right ventricle. The tricuspid valve prevents back flow. The blood then pumps from the right atrium to the right ventricle through the semi-lunar valve. The semi-lunar valves between the ventricle and the pulmonary arteries prevents back flow. The pressure from the contraction of the right ventricle sends the blood to the lungs via the pulmonary arteries. Once the blood passes through the lungs it is oxygenated and goes back to the heart via the pulmonary veins. It enters the left atrium, and then is pumped through the bicuspid valve to the left ventricle. From the left ventricle blood is pumped through the semilunar valve to the aorta. The aorta branches into arteries, which then branch into arterioles, which then branch into capillaries. Gas exchange occurs at the capillary level. The oxygen diffuses from the blood to the cells. The carbon dioxide in the cells diffuses into the blood. The blood now travels from the capillaries, though the venues, thought the veins, through the vena cava, back to the right atrium.

Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart.

Image from www.ibguides.com

How does blood transport help in excretion?

It brings the wage product urea to the kidneys.

How does blood transport help in development and coordination?

It carries hormones from the endocrine glands to specific organs.

How does blood transport help in defense against disease?

It circulates antibodies.

How does blood transport help in temperature regulation?

It distributes heat.

How does the circulatory system help in hydration?

It transports water to all the tissues in the body.

Circulation according to William Harvey

Single circulatory system between organs/flesh, heart, and lungs

Why do we say that the human circulatory system is a double system?

There is one circulation to the lungs and another to the rest of the body

Why are the nerves that come from the brain that effect rate of heart beat called antagonistic?

They have opposite effects. One speeds up the beat; the other slows it down.

Why do arteries need muscle cells and the elastic fibers in their walls?

They move blood coming from the heart at high pressure. Additionally, they need to maintain blood pressure between cycles.

Systolic Blood Pressure

a higher value that represents the pressure in the vessel when the heart is contracting

Diastolic Blood Pressure

a lower value that represents the pressure in the vessel when the heart is relaxing

What is the pacemaker of the heart?

a structure found in the right atrium cell wall called the sino-atrial node.

How does the sino-atrial node work?

a.k.a., the pacemaker of the heart, it has muscle fibers that go to each atrium. Nerve impulse move along these muscles causing the atria to contract. Another muscle then picks up the impulse and causes the ventricles to contract. Between these contractions is a period when no impulse can travel.

What is the average heart beat?

about 50 beats/min

Diastole

as blood exits the ventricle and travels down the aorta, ventricular pressure falls when ventricular pressure drop below aortic pressure, the aortic valve closes to prevent back flow when the ventricular pressure drops below the atrial pressure, the AV valve opens and blood can flow from atria to ventricle throughout the cycle aortic pressure remains quite high as muscle and elastic fibres in the artery wall maintain blood pressure

What is the specific name of atria ventricular valve between the left atrium and the left ventricle?

bicuspid valve (also called mitral valve)

How can the heart rate be increased or decreased?

by impulses brought to the heart through two nerves from the medulla of the brain.

How does the sino-atrial node work?

by sending out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of the ventricles.

Vein

collect the blood form the tissues and convey it at low pressure to the atria of the heart structure: - very wide lumen to maximise blood flow - thin wall containing less muscle and elastic fibres as blood is flowing at very low pressure - valves prevent back flow and stop blood flow from pooling at the lowest extremities

Blood Components: Plasma

consists mainly of water which dissolves materials and functions as a transport medium contains electrolytes which are important for maintaining fluid balance and blood pH proteins in the blood plasma maintain osmotic potential, transport lipids, and help clot

Arteries

convey blood at high pressure from the heart ventricles to the tissues of the body and lungs structure: -narrow lumen - thick wall containing an outer layer of collagen to prevent rupturing - arterial wall contains and inner layer of muscle and elastic fibres to help maintain pulse flow

How does the heartbeat change?

depending on which nerve send the impulses from the medulla of the brain . One speeds up the beat, the other slows it down

Capillaries: Continuous

endothelial cells held together by tight junctions to limit permeability of large molecules

Capillaries

exchange materials between the cells in tissues and blood travelling at low pressure branches of capillaries ensure blood moving slowly structure: - very small in diameter --> allows passage of only a single red blood cell at a time - capillary wall made of a single layer of cells to minimise the diffusion distance for permeable materials -surrounded by a basement membrane which is permeable to necessary materials -contain pores to further aid in the transport of materials between tissue fluid and blood

Describe the blood pressure in arteries

high

The nervous control of the heart beat is by reflex action. What does that mean?

involuntary, not under the control of our conscious

State what is transported in the blood.

nutrients, oxygen, carbon dioxide, hormones, antibodies, urea, heat

Capillaries: Sinusoid

open spaces between cells and be permeable to large molecule and cells

State the components of the blood.

plasma, erythrocytes, leucocytes (lymphocytes and phagocytes), and platelets

Capillaries: Fenestrated

porous for tissues specialised for absorption

Blood Components: Red Blood Cells

red blood cells are responsible for transporting oxygen around the body oxygen is bound to haemoglobin at the lungs and released from the red blood cells at respiring body tissues

What is the name of the valve between the left ventricle and the aorta?

semilunar valve

What is the name of the valve between the right ventricle and the pulmonary artery?

semilunar valve

What are some other factors that could effect heart rate?

stress, emotion

Blood Components: Buffy Coat

the fraction of blood sample that contains white blood cells and platelets white blood cells are involved in the body's immune defence platelets are involved in blood clotting

What happens to the rate of the heart beat when the blood pressure in the arteries rises?

the heart rate slows down.

What happens to the rate of the heart beat when the blood pressure in the arteries lowers?

the heart rate speeds up

What does myogenic mean in terms of heart beat?

the origin of each beat in the heart is within the heart (heart controls its own beating)

What is the sino-atrial node?

the pacemaker of the heart.

How does blood flow to the tissues?

through the capillaries.

What is the purpose of the coronary arteries?

to supply the heart muscle with oxygen and nutrients

What are the main roles of blood circulation?

transport nutrients and oxygen throughout the cell, defense against disease, helps in cell respiration, keeps the body hydrated, helps in excretion, involved in development and coordination, helps in temperature regulation

What is the specific name of atria ventricular valve between the right atrium and the right ventricle?

tricuspid valve