Chapter 1

Question 1

Homeostasis

Answer 1

The maintenance of the near constant conditions of the internal environment.

Question 2

Negative feedback system

Answer 2

The feedback system that reduces the output of a given system. Ex, the hormonal secretion.

Question 3

Positive feedback system

Answer 3

The feedback system that increases the output of another system. For example, the clotting enzyme cascade theory.

Question 4

Physiology

Answer 4

The science that seeks to explain the physical and chemical mechanics that are responsible for the origin, development and progression of life. Each type of life has its own functional characteristics.

Question 5

Human Physiology

Answer 5

The science of human physiology attempts to explain the specific characteristics and mechanisms of the human body that makes it a living body.

Question 6

Cells

Answer 6

The basic living unit of the body is the cell. Each organ is an aggregate of different cells held together by intercellular supporting structures.

Question 7

First characteristic of cells

Answer 7

Each type of cell is specially adapted to perform one or a few particular functions.

Question 8

How many red blood cells are there in the body? How many cells are there in the body?

Answer 8

There are 25 trillion red blood cells in the body. There are 75 trillion other cells in the body. There are a total of 100 trillion cells in the body.

Question 9

Second characteristic of cells

Answer 9

Cells often differ markedly from one another, all of them have certain basic characteristics that are alike.

Question 10

Give an example of the second characteristic of cells

Answer 10

Oxygen reacts with carbohydrates, proteins and fat to release energy needed to function. All cells deliver the products of their chemical reactions into the surrounding fluids.

Question 11

Intracellular fluid

Answer 11

The fluid present inside the cells is called intracellular fluid. 2/3rds of the total fluid in body is present as intracellular fluid

Question 12

Extracellular fluid

Answer 12

Fluid present outside the cells is called extracellular fluid. This fluid contains the ions needed to maintain life. It is 1/3rd of the total body fluid.

Question 13

The diffusion of the extracellular fluid

Answer 13

The extracellular fluid is in constant motion throughout the body. It is transported rapidly in the circulating blood and then mixed between the blood and the tissue fluids by diffusion through the capillary walls.

Question 14

Who discovered the extracellular fluid?

Answer 14

A french physiologist Claude Bernard gave the term milieu intérieur, which means extracellular fluid which is also called internal environment.

Question 15

Difference between extracellular and intracellular fluid

Answer 15

Extracellular fluid contains more sodium, chloride and bicarbonate ions along with nutrients like oxygen, glucose, fatty acids and amino acids as well as carbon dioxide.

Intracellular fluid contains large amounts of potassium, magnesium and phosphate ions.

Question 16

Who invented the term Homeostasis?

Answer 16

In 1929, Walter Cannon invented the term Homestasis.

Question 17

Disease and homeostasis

Answer 17

Disease is considered to be a state of disrupted homeostasis. However homeostasis continues to operate and maintain vital functions through several compensations even during disease. Pathophysiology explains how various physiological processes are altered in injury or disease.

Question 18

Stages of ECF movement

Answer 18

The first stage is movement of blood through the body in the blood vessels and the second stage is movement of fluid between the blood capillaries and the intercellular spaces between tissue cells. As blood passes through the blood capillaries continual exchange of ECF also occurs between plasma portion of blood and the interstitial fluid.

Question 19

How long does it take for blood to traverse the body?

Answer 19

All blood circulates throughout the body in an average of 6 minutes. During active moments, it takes about 1 minute.

Question 20

Explain the kinetic flow of body fluid

Answer 20

The process of diffusion is caused by the kinetic movement of the molecules in both the plasma and the interstitial fluid. That is, the molecules of the fluid and plasma constantly moving and bouncing in all directions in the fluid and plasma within the intercellular spaces, as well as through the capillary pores. Few cells are located more than 50 micrometer from a capillary, which ensures diffusion of almost any substance from the capillary. Thus the fluid in the extracellular spaces and the fluid in the interstitial region constantly mixes together and maintains homogenity.

Question 21

Examples of how little changes in values can cause great adverse effects

Answer 21

An increase of even 7 degree celsius in the body can lead to a vicious cycle which leads to an increase in cellular metabolism causing cell death on large scale. If potassium ion concentration is reduced to less than one third of the normal then person is likey to get paralyzed as nerves cant carry signals. If that concentration increases two to three times then heart muscle will be severely depressed. If calcium falls below one half of the normal then sponataneous generation of excessive nerve impulses will happen causing tetani. When glucose concentration falls to less than one half of normal then this can lead to extreme mental irratibility and sometimes even convulsions.

Question 22

How does negative feedback relate to homeostasis? Give an example of negative feedback

Answer 22

If some factor in the body becomes excessive or deficient, a control of system initiates negative feedback which consists of a series of changes that return the factor toward a certain mean value, thus maintaining homeostasis. For example, in the arterial pressure- regulating mechanisms a high pressure causes a series of reactions that promote a lowered pressure.

Question 23

Gain of control system

Answer 23

Degree of effectiveness with which a control system maintains constant conditions is determined by gain of the negative feedback. Gain = correction/error. Correction = value to which something rises - value to which it would have risen without negative feedback. Error, the amount the thing rose after negative feedback. The more the absolute value of gain, the better the system. For example, the gain of temperature regulation system is -33 whereas for baroreceptor it is -2. So temperature regulation system is much more effecient.

Question 24

Positive feedback and its example.

Answer 24

Positive feedback is also known as ‘vicious cycle’ because it can increase a negative attribute further thus leading to a vicious cycle causing death of the person. For example, when a person loses blood, their heart weakens as less blood goes to the coronary vessels, this in turn leads to pumping of less blood. Thus at the end the heart becomes so weak that it cannot pump out any more blood anymore.

Question 25

How can positive feedback be overcome by negative feedback?

Answer 25

Sometimes positive feedback may be overcome by the negative feedback if it is mild and thus, the vicious cycle fails to develop. For example, if a person is bleeding about 1L instead of 2L then maybe the normal feedback mechanism for controlling cardiac output and arterial pressure can counterbalance the positive feedback and the person can recover.

Question 26

State an instance in which the positive feedback mechanism is useful.

Answer 26

Positive feedback mechanism can be useful sometimes, such as in the enzyme cascade theory. When blood vessels are ruptured and a clot begins to form, multiple enzymes called clotting factors are activated within the clot. Some of these enzymes act on other inactivated enzymesof the immediately adjacent blood, causing more clotting. Process continues till the hole is plugged. On occassion however this can cause formation of unwanted clots which causes acute heart attacks due to clot forming in the atherosclerotic plaque in the coronary artery and then blocking it. Childbirth is another instance where positive feedback is beneficial. When uterine contractions are strong enough for the baby’s head to start pushing through the cervix, it sends signals through the uterine muscles back to the body of the uterus, causing even more powerful contractions.

Question 27

How does positive feedback affect nerve signal generation

Answer 27

Stimulation of nerve fibres causes slight leakage of sodium ions through sodium channels in the nerve membrane to the fibre’s interior. The sodium ions entering the fibre then change the membrane potential, which in turn causes more opening of channels, more change of potential, still more opening of channels and so on.

Question 28

Give examples of positive feedback being a part of the negative feedback systems

Answer 28

In the case of blood clotting, the positive feedback is a part of the overall negative feedback process for the maintenence of normal blood volume. Positive feedback that causes nerve signals allows the nerves to participate in thousands of negative feedback in the nervous control system.

Question 29

Explain the feed forward control with an example

Answer 29

The brain uses a principle called feed forward system where it causes a required muscle to contract and the sensory nerve signals from the moving parts tell whether the part is moving correctly or not. If there is a problem, the brain sends signals for the corrected move in the subsequent movements. This is called adaptive control which is a form of delayed negative feedback system.

Question 30

Tell the NV, NR and ASNL for venous oxygen and carbon dioxide.

Answer 30

Oxygen. NV= 40 mmHg. NR = 35-45 mmHg. ASNL = 10-1000 mmHg. Carbon dioxide. NV = 45 mmHg. NR = 35-45 mmHg. ASNL = 5-80 mmHg.

Question 31

Tell the NV, NR, ASNL for the potassium, calcium, bicarbonate, chloride, sodium ion.

Answer 31

Sodium ion. NV = 142 mmol/L. NR = 138-146mmol/L. ASNL = 115-175 mmol/L. Potassium ion. NV = 4.2mmol/L. NR = 3.8-5.0mmol/L. ASNL = 1.5-9.0mmol/L. Calcium ion. NV = 1.2mmol/L. NR= 1.0-1.4mmol/L. ASNL = 0.5-2.0/L. Chloride ion. NV = 106mmol/L. NR = 103-112 mmol/L. ASNL = 70-130mmol/L. Bicarbonate ion. NV = 24 mmol/L. NR = 24-32 mmol/L. ASNL= 8-45mmol/L.