Homeostasis

Question 1

Discuss type 1 diabetes

Answer 1

In type 1 diabetes, the blood glucose homeostat ceases to function because the beta cells of the pancreas are destroyed, most often by the body’s own immune system. Without beta cells, the body’s blood glucose sensors are absent and insulin is not produced in response to high blood concentrations of glucose. Without insulin, cells are not stimulated to take up glucose from the blood, the liver does not convert glucose to glycogen for storage, and the conversion of amino acids and glycerol into glucose is not inhibited. As a result, the concentration of glucose in the blood may rise to dangerously high levels

Question 2

What happens when the high glucose levels of type 1 diabetes are not controlled>

Answer 2

If the high blood glucose concentrations of type 1 diabetes are not controlled, they may lead to further homeostatic imbalances by damaging tissues and organs throughout the body. For example, high blood glucose concentrations may damage blood vessels in the kidneys and cause kidney disease and even kidney failure

Question 3

What is a disease?

Answer 3

The term disease can be broadly defined as a condition that is associated with the impairment of normal body functioning. Disease states can cause — as well as be caused by — the failure of homeostats to maintain homeostasis.

Question 4

Keeping all of the body’s internal variables within normal ranges is the function of physiological mechanisms called what?

Answer 4

Homeostasis

Question 5

What happens when homeostasis fails?

Answer 5

Sometimes homeostasis fail to perform properly. This can cause homeostatic imbalance, a condition in which variables in the internal environment are no longer maintained within normal ranges. As a result, cells may not get everything they need, or toxic wastes may accumulate in cells. Eventually, homeostatic imbalance may lead to disease.

Question 6

What are pathogens?

Answer 6

Pathogens are agents — usually microorganisms — that cause disease. Diseases caused by pathogens are called infectious, or communicable diseases because pathogens can spread the diseases by moving from host to host. Types of pathogens that commonly cause human diseases include bacteria, viruses, fungi, and protozoa (like the Plasmodium species). Examples of infectious diseases include the common cold, influenza, chickenpox, cholera, and malaria. Some infectious diseases are spread only or mainly through sexual contact. These diseases are called sexually transmitted infections (STIs) a

Question 7

What is meant by chronic disease?

Answer 7

Chronic disease is a long-term or even lifelong disease. For example, people who develop type 1 diabetes have the disease for life as do most people who develop cardiovascular diseases. Some non-infectious diseases, such as cancer, may be cured or they may be kept under control as chronic diseases with medications. Certain infectious diseases are also chronic rather than acute diseases because they are caused by pathogens that the body cannot eliminate. Examples are the viruses that cause herpes and AIDS.

Question 8

What is meant by acute disease?

Answer 8

Most infectious diseases are also acute diseases. An acute disease is a short-term disease. After a person gets sick, an acute disease either runs its course (with or without medical intervention) until the person gets better, or the disease leads to the death of the infected individual. Many non-infectious diseases are chronic diseases.

Question 9

Describe a pandemic

Answer 9

A pandemic is an epidemic that spreads across multiple populations, often across continents or even worldwide. Throughout human history, there have been many pandemics of infectious diseases. One of the most devastating pandemics was the Black Death (bubonic plague) pandemic that spread throughout Europe and much of Asia in the mid-1300s. In this pandemic, an estimated 75 million people died. Its impact on England is memorialized. More recent pandemics include influenza pandemics that occurred in 1918 and 2009

Question 10

What is an epidemic?

Answer 10

Some infectious diseases spread through a population from time to time as large-scale disease outbreaks called epidemics, but are not always present in the population, at least not at high levels. Such diseases are called epidemic diseases. An example is the flu (influenza). In the United States, flu spreads through the population at a certain time each year (generally, from November through April), but is not commonly found at other times of the year. Some epidemic diseases lead to pandemics.

Question 11

Define epidemiology.

Answer 11

epidemiology is the science that focuses on the patterns, causes, and effects of diseases in human populations. It is the cornerstone of public health. It shapes health policy decisions and medical practice by identifying risk factors for disease and targets for preventive healthcare. The term epidemiology was first applied to the study of epidemics, but it is now widely applied to the study of disease in general and even to the study of many non-disease conditions, such as high blood pressure and obesity.

Question 12

Hydrostatic pressure is due to?

Answer 12

Action of the heart.

Question 13

Osmotic pressure is due to?

Answer 13

Action by concentration of solute particles.

Question 14

Discuss the movement of water across membranes due to concentration.

Answer 14

• Water moves from dilute to concentrated solutions [from where there is more water to where there is less water]
• The more solutes {conc.} the greater the pull on the water molecules.
• More solutes mean less water and so the water will be drawn to that place.

Question 15

Define tonicity.

Answer 15

effect of a solution on a cell.

Question 16

What is meant by

impermeant solute

Answer 16

the impermeant solute is one that cannot cross a cell membrane.

Question 17

Isotonic solution

Answer 17

= 282 mOsm solution. cell of 282 mOsm/L put into 282mOsm/L solution. Nothing happens. the cells will not swell or shrink. the concentration in and outside of the cell is equal.

Question 18

Hypotonic solution

Answer 18

= Cell swells.

the concentration of the solution <282 mOsm/L - so the cell is more concentrated. solution has more water, so water moves from the solution into the cell, it swells and bursts.

[the moving in of water will continue diluting the icf and concentrating the ecf until equilibrium is reached]

Question 19

Hypertonic solution

Answer 19

= Cell shrinks
Concentration of the solution is >282mOsm/L - so the cell is less concentrated. cell has more water [or fewer solutes] than the solution, water leaves the cell, and the cell shrinks and dies. NaCl solutions 0.9 % are hypertonic.

Question 20

Homeostasis summary

Answer 20

• Homeostasis is dynamic not static process.

- Physiological variables can change but the system still be in overall balance

Question 21

Physiology vs Pathophysiology

Answer 21

• Homeostasis maintained = Physiology

- Homeostasis NOT maintained = Pathophysiology

Question 22

Dynamic constancy.

Answer 22

E.g glucose levels increase after eating. Levels return to set point via homeostasis

Question 23

An example of Thermoregulation

Answer 23

When temperature levels in a room decrease, the heat loss from the body increases. the body temperature starts to drop. Body response to decreased temperature is:

1. Constriction of skin blood vessels–> decreases in heat loss then the body temperature return to normal.
2. Curling up of the body –>decrease heat loss from the body and return to normal temperature.
3. Shivering, this increases heat production and returns body temperature to normal.

Question 24

Systems controls are positive and negative feedback differentiate between them.

Answer 24

• Positive feedback = enhances the production of the product.
• Negative feedback = shuts the system off once the set point has been reached.

Question 25

A strategy for exploring homeostasis

Answer 25

• Identify the internal environmental variable.
• Establish the “set point” value for that variable.
• Identify the inputs and outputs affecting the variable.
• Examine the balance between the inputs and outputs.
• Determine how the body monitors/senses the variable.
• Identify effectors that restore the variable to its set point.

Question 26

What is a reflex? give example

Answer 26

A reflex is a specific involuntary, unpremeditated, unlearned “built-in” response to a particular stimulus.

• Example: pulling your hand away from a hot object or shutting your eyes as an object rapidly approaches your face.

Question 27

What is a reflex arc?

Answer 27

• The pathway mediating a reflex is known as the reflex arc.

Question 28

What are the components of an arc? Discuss the components.

Answer 28

An arc has several components: stimulus, receptor, afferent (incoming)
pathway, integration center, efferent (outgoing) pathway, and effector.

Question 29

What is meant by Non-nerve reflexes?

Answer 29

Almost all body cells can act as effectors in homeostatic
reflexes.
• There are, however, two specialized classes of tissues—muscle
and gland—that are the major effectors of biological control
systems.
• In the case of glands, the effector may be a hormone secreted
into the blood.
• A hormone is a type of chemical messenger secreted into the
blood by cells of the endocrine system (see Table 1–1).
Hormones may act on many different cells simultaneously
because they circulate throughout the body.

Question 30

What are the different types of signals? 2 and define each

Answer 30

1. Hormones
2. Neurotransmitters
   • Hormones are produced in and secreted
   from endocrine glands or in scattered cells
   that are distributed throughout another
   organ.
   • Neurotransmitters are chemical messengers
   that are released from the endings of
   neurons onto other neurons, muscle cells, or
   gland cells.

Question 31

List the communication signals in three categories

Answer 31

Endocrine: signal reaches often-distant targets after
transport in the blood.
Paracrine: signal reaches neighboring cells via the ISF.
Autocrine: signal affects the cell that synthesized the signal.

Question 32

Point to note on Chemical messengers.

Answer 32

neuron, endocrine gland cell, and other cell types may all secrete the same chemical messenger. AND In some cases, a particular messenger may function as a neurotransmitter, as a hormone, or as a paracrine/autocrine. e.g NE is a neurotransmitter in brain, its also produced as a hormone by cells of the the adrenal glands.

Question 33

A given signal can fit all 3 categories: of being endocrine, paracrine, and autocrine. Give an example

Answer 33

[e.g., the steroid hormone cortisol affects the very cells in which it is made, the nearby cells that produce other hormones, and many distant targets, including muscles and liver.] This multi-factorial control of signal release adds more complexity.

Question 34

Describe the reflex arc.

Answer 34

• A stimulus is defined as a detectable change in the internal or external environment.
• A receptor detects the change.
• The pathway the signal travels between the receptor and the integrating center is known as the afferent pathway.
• The pathway along which information travels away from the integration center to the effector is known as the efferent pathway
• An integrating center often receives signals from many receptors, some of which may respond to quite different types of stimuli.
• Thus, the output of an integrating center reflects the net effect of the total afferent input; that is, it represents an integration of numerous bits of information.

Question 35

The two types of chemical communication between cells that do not require secretion of a chemical messenger are?

Answer 35

Gap junctions and Juxtacrine signaling.

Question 36

Gap junctions

Answer 36

Physical linkages connecting the cytosol between two cells and allow molecules to move from one cell to an adjacent cell without entering the extracellular fluid.

Question 37

Juxtacrine signaling

Answer 37

Is the chemical messenger not actually being released from the cell producing it, but rather is located in the plasma membrane of that cell. When the cell encounters another cell type capable of responding to the message, the two cells link up via the membrane-bound messenger.

Question 38

Differentiate between Adaptation and Acclimatization.

Answer 38

The term adaptation denotes a characteristic that favors survival in specific environments.

• Acclimatization refers to the improved functioning of an already existing homeostatic system based on an environmental stress.
• In an individual, acclimatization is reversible; adaptations are not

Question 39

Biological Rhythms. - Circadian rhythm [24h] what processes in the body undergo circadian variation?

Answer 39

Many body functions are rhythmical changes such as the sleep-wake cycle, hormone secretion, cardiovascular health, glucose homeostasis, and body temperature regulation.

Question 40

What have biological rhythms to do with homeostasis?

Answer 40

They add an anticipatory component to homeostatic control systems and in effect are a feed-forward system operating without detectors.

• The negative feedback homeostatic responses are corrective responses. They are initiated after the steady-state of the individual has been perturbed.
• Biological rhythms enable homeostatic mechanisms to be utilized immediately and automatically by activating them at times when a challenge is likely to occur but before it actually does occur.

Question 41

Describe the balance in the Homeostasis of Chemical Substances in the Body.

Answer 41

Many homeostatic systems regulate the balance between the addition and removal of a chemical substance from the body.

• Two important generalizations concerning the balance
concept:
(1) During any period of time, the total-body balance depends upon the relative rates of net gain and net loss to the body; and

(2) the pool concentration depends not only upon the total amount of the substance in the body but also upon exchanges of the substance within the body.

Question 42

Sodium homeostasis

Answer 42

Consuming greater amounts of dietary sodium initiates a set of dynamic responses that include greater excretion of sodium in the urine. The amount excreted would likely exceed the amount ingested until the “set point” is restored.