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3 years ago

Jonas Salk was awarded the Nobel Prize for discovering a way to vaccinate against

Biology

1 answer:

Bogdan [553]3 years ago

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Answer:

Jonas Salk was awarded the Nobel Prize for discovering a way to vaccinate against polio in the United States in the 1950's. This allowed millions of school-age children to avoid crippling disease, and to swim during summer again, as polio was often spread in public swimming areas before.

The statement that best describes how the polio vaccine works is:

It triggers the immune system to produce antobodies to fight the disease-causing agent.

Explanation:

There are two main reasons for this answer. The first one is that every vaccine is aimed to introduce a controlled amount of antigenes to be accepted by the organism. These antigens are made after some studies were conducted in a lab and were obtained from substances that the human body can accept to train the immune system to develop an effective defense for the virus or bacteria on the matter. In our case, the polio vaccine works the same way and allowed to save many lives.

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List all the electrical and mechanical events that occur within 1 heartbeat (in order). Also be able to state which are occurrin

eimsori [14]

Answer:

Phases of the Cardiac Cycle are Diastole and Systole

Explanation:

<h2>Cardiac Cycle Phases </h2>

(First Phase) Atrial contraction

This is the phase of atrial contraction.

In this fase, 80% of ventricular filling has been done passively even before the onset of atrial contraction, and the remaining 20% of ventricular filling is due to atrial contraction. The active filling of ventricles becomes valuable during physical activity.

When pressure in the atrium increases, blood rush into the ventricles through the opened mitral valve. During left atrium contraction, pressure and volume are transferred into left ventricle through opened mitral valve. Aortic valve is closed because pressure in aorta is greater than the pressure in left ventricle at this moment.

(Second Phase) Isovolumetric Contraction

The early phase of ventricular systole. When ventricles contract, there is a progressive increase in intraventricular pressure. This wil leads to closure of mitral valve. That produces first heart sound (S1) and little bulging of mitral valve into atrium causing the slight increase in the atrial pressure.

Intraventricular pressure progressively increases upto 80mmHg altought it is not competent enough to open the aortic valve.

At this moment ventricle is contracting with closed mitral and aortic valves. Meanwhile, intra atrium pressure is gradually increasing due to accumulation of blood returning from lungs into the left atrium. During the same phase, aorta pumps whatever blood it contains into more peripheral part of arterial tree due to its elastic nature.

This is the stage of ventricular contraction when backward valves are closed yet the forward valves are not opened. Ventricle is contracting as a closed chamber without any change in volume and size of the ventricle. We call it isovolumetric contraction of early part of ventricular systole.

(Third Phase) Rapid Ventricular Ejection

When pressure reaches to 81mmHg, aortic valve opens. This starts third phase of cardiac cycle. Ventricles keep on contracting, and there is a progressive increase in intraventricular pressure upto 120mmHg. During this phase, aortic valve opens and blood is ejected quickly into the aorta. At this point left ventricle and aorta behave as a single chamber.

The pressure changes occurred in the ventricles results in the transmission of pressure to aorta. Meanwhile left atrium continues receiving blood from the lungs.

(Fourth Phase) Slow Ventricular Ejection

In this phase atrium is still behaving as reservoir of blood and the pressure is keep on building. Mitral valve is closed. Ventricles are still contracting but intraventricular pressure starts falling, due to ejection of blood . Hence, pressure in aorta also starts falling, but intraventricular pressure is still more than aortic pressure.

Aortic valve remains open leading to slow ejection of blood into aorta. Elastic aorta keeps on squeezing the blood and pumps it into peripheral arterial tree.

(Fifth Phase) Isovolumetric Relaxation

In this phase ventricles start relaxing. Intraventricualr pressure falls quickly. In the beginning, as soon as the ventricular pressure becomes less than pressure in aorta, aortic valve closes.

Even though pressure in ventricle is falling, it is still high enough compared to pressure in atrium. Ventricle is relaxing with closed valves and it is known as isovolumetric relaxation. During this phase atrium is still behaving as reservoir of blood.

(Sixth Phase) Rapid Passive Ventricular Filling

When left ventricle start relaxing, pressure in left ventricle start dropping until it reaches the point where pressure in the ventricle becomes less than the pressure in atrium, leads to opening of mitral valve. Blood which was previously accumulated in atrium will rush into ventricle. This quick filling is done without atrial contraction.

(Seventh Phase) Slow Passive Ventricular Filling

As atrioventricular valve open, blood coming to atrium rushes into the ventricle. Here atrium is not acting as reservoir.

7 0

4 years ago

Fossil fuels deep in the earth act as a carbon reservoir, storing it for millions 1 point

Arada [10]

Answer: By burning fossil fuels, people are changing the carbon cycle with far-reaching ... The rest is in the ocean, atmosphere, plants, soil, and fossil fuels. ... Graph of oxygen isotope ratios in the deep ocean for the past 67 million years. ... The increased temperature results in higher evaporation rates and a wetter ...

Explanation:

3 0

3 years ago

A wilted house plant is watered explain how structure 1 and 3 is going to work together to cause a change in the plant

Ksivusya [100]

Answer:

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3 years ago

Observations of organisms include

g100num [7]

Observations of organisms include descriptions of the size, number, and arrangement of parts of the organism.

Hope that helped!

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3 years ago

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Imagine that you are managing a large wildlife preserve that was formerly a cattle ranch. You know from historical accounts that

zhuklara [117]

Being that they don’t have any natural predators by that 10th generation it should be back to normal capacity because of all the hunting. Sometimes humans do things out of convenience because they think that those animals are pests but,sheep aren’t predators and they are actually a very essential part of the animal kingdom in the farms and how they distribute food and kind of take care of each other, other animals and help farmers tremendously. and I mean they’re kind of amazing creatures and they provide a lot of resources for us that there’s it’s not necessary for us to hunt them. We won about 100 head of black Angus beef cattle and we only feed them organic however we won’t kill them unless maybe one has a bad leg or if there’s like an anomaly somewhere other than that he’s happy as most humane as possible and I appreciate your question and I hope it helped.

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3 years ago