Unit 6 Asma Metabolism, Thermoregulation And Homeostasis

Front 1

Define homeostasis

Back 1

Essentially all of the organs and tissues of the body perform functions that help maintain the constituents of the extracellular fluid relatively constant, a condition called homeostasis.

Front 2

List examples of extracellular fluid

Back 2

Interstitial fluid and blood plasma.

Front 3

Describe the mechanisms by which nutrients are supplied to and waste products are removed from extracellular fluid.

Back 3

Extra-cellular fluid is transported throughout the body in two stages. The first stage is movement of blood around the circulatory system, and the second stage is movement of fluid between the blood capillaries and cells. The circulatory system keeps the fluids of the internal environment continuously mixed by pumping blood through the vascular system. As blood passes through the capillaries, a large portion of its fluid diffuses back and forth in to the interstitial fluid that lies between the cells, allowing continuous exchange of substances between the cells and the interstitial fluid and between the interstitial fluid and the blood.

Front 4

What is the nervous system action that it controls?

Back 4

The nervous system directs the activity of the muscular system, thereby providing locomotion. It also controls the function of many internal organs through the autonomi nervous system, and it allows us to sense our external and internal environment and to be intelligent beings so we can obtain the most advantageous conditions for survival.

Front 5

What is the endocrine system action that it controls?

Back 5

The endocrine glands secrete hormones that control many of the metabolic functions of the cells, such as growth, rate of metabolism, and special activities associated with reproduction. Hormones are secreted into the bloodstream and are carried to tissues throughout the body to help regulate cell function.

Front 6

What is the immune system action that it controls?

Back 6

The immune system also acts as a regulatory system by providing the body with a defense mechanism that protects against foreign invaders, such as bacteria and viruses, to which the body is exposed daily.

Front 7

What is the integumentary system action that it controls?

Back 7

The integumentary system, which is composed mainly of skin provides protection against injury and defense against foreign invaders as well as protection of underlying tissues against dehydration. The skin also serves to regulate body temperature.

Front 8

Describe the features of a negative feedback control system.

Back 8

Most control systems of the body operate by negative feedback. For regulation of CO2 concentration as discussed, a high concentration of CO2 in the extracellular fluid increases pulmonary ventilation, which decreases the CO2 concentration toward normal levels. This is an example of negative feedback; any stimulus that attempts to change the CO2 concentration is counteracted by a response that is negative to the initiating stimulus.

Front 9

Describe the features of a feed-forward control system.

Back 9

Feed-forward control systems anticipate changes. Because of the many interconnections between control systems, the total control of a particular body function may be more complex than can be accounted for by simple negative feedback. I.e. some movements of the body occur so rapidly that there is not sufficient time for nerve signals to travel from some of the peripheral body parts to the brain and then back to the periphery in time to control the movements. Therefore, the brain uses feed-forward control to cause the required muscle contractions. Sensory nerve signals from the moving parts apprise the brain in retrospect of whether the appropriate movement, as envisaged by the brain corrects the feed-forward signals it sends to the muscles the next time the movement is required.

Front 10

Feed-forward control system is also called what?

Back 10

This is also called adaptive control, which is in sense, delayed negative feedback.

Front 11

Describe the differences in composition of intra and extracellular fluid.

Back 11

The intracellular fluid and extracellular fluid is separated by a highly selective cell membrane that is permeable to water but not to most electrolytes found in the body. For this reason, the concentration of water and the osmolarity of intra/extra fluids are equal under steady-state conditions, although the concentrations of these carrier cells are different.

Front 12

Describe the differences between channel proteins and carrier proteins.

Back 12

Channel proteins provide watery pathways for molecules to move through membranes.
Carrier proteins bind with specific molecules and then undergo conformational changes that move molecules through the system.

Front 13

Describe the differences between simple and facilitated diffusion.

Back 13

Simple diffusion means that molecules move through a membrane without binding with carrier proteins. Simple diffusion can occur viat two pathways
Facilitated diffusion requires a carrier protein. The carrier protein aids in passage of molecules through the membrane, probably by binding chemically with them and shuttling them trough the membrane in this form.

Front 14

What are the 2 pathways simple diffusion can occur?

Back 14

1 through the interstices of the lipid bilayer and 2 through watery channels in transport proteins.

Front 15

The carrier protein in facilitated diffusion aids in what?

Back 15

The carrier protein aids in passage of molecules through the membrane, probably by binding chemically with them and shuttling them trough the membrane in this form.

Front 16

Describe the features of protein channels.

Back 16

Protein channels have selective permeability for transport of One or more specific molecules. This permeability results from the characteristics of the channel itself, such as its diameter, its shape, and the nature of the electrical charges along its inside surfaces.

Front 17

Describe voltage gating

Back 17

Voltage gating. In this instance, the molecular conformation of the gate responds to the electrical potential across the cell membrane. For example, a strong negative charge on the inside of the cell membrane causes the sodium gates to remain tightly closed. When the inside of the membrane loses its negative charge these gates open suddenly, allowing sodium to pass inward through the sodium pores. The opening of sodium gates is the basic cause of action potentials in nerves.

Front 18

Descirbe chemical gating

Back 18

Chemical gating: Some protein channel gates are opened by the binding of another molecule with the protein; this causes a conformational change in the protein molecule that opens or closes the gate. This is called chemical gating. One of the most important instances of chemical gating is the effect of acetylcholine on the “acetylcholine channel.”

Front 19

Describe the steps involved in facilitated diffusion.

Back 19

Facilitated diffusion is also called carrier-mediated diffusion. A substance transported in this manner usually cannot pass through the membrane without the assistance of a specific carrier protein:
1:the molecule to be transported enters a blind-ended channel and binds to a specific receptor.
2: a conformational change occurs in the carrier protein, so the channel now opens to the opposite side of the membrane.

Front 20

Describe how permeability effects the rate of diffusion across a membrane.

Back 20

Permeability: The permeability of a membrane for a given substance is expressed as the net rate of diffusion of the substance through each unit area of the membrane for a unit concentration difference between the two sides of the membrane(when there are no electrical or pressure differences).

Front 21

Describe how concentration effects the rate of diffusion across a membrane.

Back 21

Concentration difference: The rate of net diffusion through a cell membrane is proportional to the difference in concentration of the diffusing substance on the two sides of the membrane.

Front 22

Describe how electric potential effects the rate of diffusion across a membrane.

Back 22

Electrical potential: If an electrical potential is applied across a membrane, the ions move through the membrane b/c of their electrical charges. When large amounts of ions have moved through the membrane, a concentration difference of the same ions develops in the direction opposite to the electrical potential difference. When the concentration difference rises to a sufficiently high level, the two effects balance each other. The electrical difference that balances a given concentration difference can be determined with the Nernst equation.

Front 23

Describe osmosis

Back 23

Osmosis is the process of net movement of water caused by a concentration difference of water. Water is the most abundant substance to diffuse through the cell membrane. However, the amount that diffuses in each direction is so precisely balanced under normal conditions that not even the slightest net movement of water occurs. Therefore, the volume of a cell remains constant.
Osmosis is the net diffusion of water across a selectively permeable membrane from a region of high water concentration to one of lower water concentration. The addition of a solute to pure water reduces the water concentration and causes water to move toward the region of high solute concentration. The concentration term used to measure the total number of solute particles in solution is the osmole: 1 osmole is equal to 1 mole (6.02 x 10(23)). Of solute particles. For biological solutions, the term milliosmole (mOsm), which equals 1/1000 osmole, is commonly employed.

Front 24

Describe osmotic pressure

Back 24

A concentration difference for water can develop across a membrane. When this happens, net movement of water occurs across the cell membrane, causing the cell to either swell or shrink, depending on the direction of the net movement. The precise amount of pressure required to prevent osmosis of water through a semipermeable membrane is called the osmotic pressure.

Front 25

Describe osmality

Back 25

The osmolor concentration of a solution is called its osmolality when the concentration is expressed as osmoles per kilogram of water and osmolarity when it is expressed as osmoles per kilogram liter of solution.

Front 26

Describe the processes of active transport

Back 26

Active transport means movement of substances across the membrane in combination with a carrier protein but also against an electrochemical gradient. This process requires a source of energy in addition to kinetic energy. When a cell membrane moves molecules or ions uphill against a concentration gradient , the process is called “active transport.”

Front 27

The process of active transport requires what 2 things?

Back 27

A source of energy in addition to kinetic energy

Front 28

Active transport can move a substance against what?

Back 28

An electromagnetic gradient.

Front 29

What is electromagnetic gradient?

Back 29

An electrochemical gradient is the sum of all the diffusion forces acting at the membrane-the forces casued by a concentration difference, an electrical difference, and a pressure difference. That is, substances cannot diffuse “uphill.”

Front 30

Describe the mechanism of the sodium/potassium pump.

Back 30

The soldium-potassium (Na+ - K+) Pump transports sodium ions out of cells and potassium ions into cells. This pump is present in all cells of the body, and it is responsible for maintaining the sodium and potassium concentration differences across the cell membrane as well as for establishing a negative electrical potential inside the cells.

Front 31

Describe how the pump operates.

Back 31

Three sodium ions bind to a carrier protein on the inside of the cell, and two potassium ions bind to the carrier protein on the outside of the cell. The carrier protein has ATPase activity, and the binding of ions causes the ATPase function of the protein to become activated. This then cleaves one molecule of ATP, splitting it to form adenosine diphosphate and liberating a high-energy phosphate bond of energy. This energy is then believed to cause a conformational change in the protein carrier molecule, extruding the sodium ions to the outside and the potassium ions to the inside.

Front 32

Describe the differences between co-transport and counter-transport

Back 32

Co-transport and counter-transport are two forms of secondary active transport. When sodium ions are transported out of cells by primary active transport, a large concentration gradient of sodium can develop. This gradient represents a storehouse of energy because the excess sodium outside the cell membrane is always attempting to diffuse to the interior.

Front 33

Define co-transport

Back 33

Co-transport: The diffusion energy of sodium can pull other substances along with the sodium (in the same direction) through the cell membrane using a special carrier protein.

Front 34

Define counter-transport

Back 34

Counter-transport: The sodium ion and substance to be counter-transpoted move to opposite sides of the membrane, with sodium always moving to the cell interior. Here again, a protein carrier is required.

Front 35

Define edema

Back 35

Edema: excess fluid in the tissues.

Front 36

What are the 2 conditions most likely to cause intracellular edema?

Back 36

Two conditions especially likely to cause intracellular swelling are 1: depression of the metabolic systems of the tissues and 2: lack of adequate nutrition to the cells.

Front 37

When the coniditons for intrcellular edema occur what happens?

Back 37

When these conditions occur, sodium ions that normally leak into the interior of the cells can no longer be pumped out of the cells, and the excess sodium ions cause osmosis of water into the cells. Intracellular edema can also occur in inflamed tissues. Inflammation usually has a direct effect on the cell membranes to increase their permeability, allowing sodium and other ions to diffuse into the interior of the cells with subsequent osmosis of water into the cells.

Front 38

State the fluid volumes of intracellular and extracellular fluid compartments.

Back 38

Chemical Intracel Fluid Xtracel Fluid
Na+ (mmol/L) 10 142
K+(mmol/L) 140 4
CL-(mmol/L) 4 108
HCO3-(mmol/L) 1 24
Ca2+(mmol/L) .0001 2.4
Mg2+ (mmol/L) 58 1.2
SO4 2-(mmol/L) 2 1
Phosphates (mmol/L) 75 4
Glucose (mg/dl) 0-20 90
Amino acids (mg/dl) 200 30
Protein (g/dl) 16 2

Front 39

What are the 2 general causes of extracellular edema?

Back 39

The two general causes of extracellular edema are 1: abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries and 2 failure of the lymphatics to return fluid from the intersitium to the blood.

Front 40

Renal blood flow constitutes about ___% of the cardiac output.

Back 40

22%

Front 41

Describe the physiologic anatomy of the kidney

Back 41

Blood flows to each kidney through a renal artery, which branches progressively to form the interlobar arteries, arcuate arteries, interlobular arteries, and afferent arterioles, which lead to the glomerular capillaries, where filtration of fluid nad solutes begins. The capillaries of each glomerulus coalesce to form an efferent arteriole, which leads to a second capillary network, the peritubular capillaries, which surround the tubules. The pertubular capillaries empty into the vessels of the venous system, which run parallel to the arteriolar vessels, and progressively form the interlobular vein, arcuate vein, interlobar vein, and renal vein, which leaves the kidney along the renal artery and ureter. The vasa recta are specialized peritubular capillaries that dip into the renal medulla and run parallel to the loops of Henle.

Front 42

What receives most of the blood flow to the kidney?

Back 42

The outer portion of the kidney, the renal cortex

Front 43

What % of total renal blood flow passes through the vasa recta?

Back 43

Only 1 to 2 % of the total renal blood flow passes through the vasa recta

Front 44

Blood flow in the vasa recta supplies what part of the kidney?

Back 44

The renal medulla.

Front 45

Describe the overall mechanism for blood volume control by the renal system.

Back 45

Renal blood flow is determined according to the pressure gradient across the renal vasculature and the total renal vascular resistance, as expressed by the following relation:
Renal blood flow= (renal artery pressure – renal vein pressure)/Total Renal Vascular Resistance

Front 46

The total renal vascular resistance is the sum of what?

Back 46

The total renal vascular resistance is the sum of the resistances of the individual vascular segments, including the arteries, arterioles, capillaries, and veins.

Front 47

Where does most of the renal vascular resistance reside?

Back 47

In three major segments: interlobular arteries, afferent arterioles, and efferent arterioles.

Front 48

Describe the renal system’s role in the control of extracellular fluid volume.

Back 48

Although multiple mechanisms control the amount of sodium and water excreted by the kidneys, two primary systems are particularly involved in regulating the concentration of sodium and the osmolarity of extracellular fluid: 1 the osmoreceptor-ADH feedback system and 2: the thirst mechanism.

Front 49

State the normal skin and core body temperatures

Back 49

The temperature of the deep tissues of the body remains constant within + or - 1F despite large fluctuations in the environmental temperature. The average normal body temperature is generally thought to be between 98.0 and 98.6 F when measured orally and about 1 F higher rectally.

Front 50

Temperature is controlled by a balance between what?

Back 50

Heat production and heat loss.

Front 51

Heat production is a by-product of what?

Back 51

Metabolism

Front 52

State the factors that determine the rate of metabolic heat production.

Back 52

Temperature is controlled by the balance between heat production and heat loss. Heat production is a by-product of metabolism. Extra heat can be generated by muscle contraction (shivering) in the short term or by an increase in thyroxine in the long term. Most of the heat produced in the body is generated in the deep tissues. The rate of heat loss is determined by the rate of heat conduction to the skin and the rate of heat conduction from the skin to the surroundings.

Front 53

Where is most of the heat produced in the body generate from?

Back 53

The deep tissues

Front 54

The rate of heat loss is determined by what?

Back 54

The rate of heat conduction to the skin and the rate of heat conduction from the skin to the surroundings.

Front 55

Describe the insulatory effects of the skin

Back 55

Blood vessels are distributed profusely immediately underneath the skin. An increase in blood flow to these vessels can cause more heat loss, and a decrease in blood flow to these vessels can cause less heat loss. The rate of flow to these vessels can vary from 0-30% of the cardiac output. The skin is a highly effective “heat radiator” system for transferring heat from the body core to the skin.

Front 56

Describe the effect of the circulatory system on body cooling

Back 56

Vasodilation: of the blood vessels of the skin can increase the amount of heat transfer to the skin by as much as eightfold.

Front 57

What does sweating do in regard to heat loss?

Back 57

Sweating increases the rate of evaporative heat loss. A 1 C increase in body temperature induces sufficient sweating to remove 10 times the basal rate of heat production.

Front 58

Name two strong inhibition of mechanisms that increase heat production

Back 58

Shivering and chemical thermogenesis.

Front 59

Name the ways heat loss from the skin to the surroundings occur.

Back 59

Radiation, conduction, convection, and evaporation.

Front 60

Describe how radiation effects thermoregulation with regards to the skin.

Back 60

Radiation causes loss of heat in the form of infrared rays.

Front 61

Describe how conduction effects thermoregulation with regards to the skin.

Back 61

Conductive heat loss occurs by direct contact with an object

Front 62

Describe how convection effects thermoregulation with regards to the skin.

Back 62

Convective heat loss results from air movement.

Front 63

Describe how evaporation effects thermoregulation with regards to the skin.

Back 63

Evaporation is a necessary mechanism of heat loss at very high temperatures.

Front 64

Describe the physiological mechanism involved in the production of sweat.

Back 64

Sweat glands contain a deep, coiled glandular portion and a straight ductal portion that exits on the surface on the skin. A primary secretion similar to plasma but without plasma proteins is formed by the glandular portion of the sweat gland. As the solution moves up the duct toward the surface of the skin, most of the electrolytes are reabsorbed, leaving a dilute, watery secretion.

Front 65

What are sweat glands innervated by?

Back 65

Sweat glands are innervated by sympathetic cholinergic fibers.

Front 66

What happens when sweat glands are stimulated

Back 66

The rate of precursor solution secretion is increased.

Front 67

The reabsortion of electrolytes occurs at a ____ rate.

Back 67

Constant

Front 68

Describe the role of the hypothalmus in the regulation of body temperature

Back 68

The anterior hypothalamic-preoptic area contains large numbers of heat-sensitive neurons; the septum and reticular substance of the midbrain contain large numbers of cold-sensitive neurons. When the temperature centers detect that the body is either too hot or too cold, these areas institute appropriate and familiar temperature increasing or temperature decreasing procedures.

Front 69

Describe the physiological mechanism that produces fever.

Back 69

When bacterial or viral particles are present in the body, they are phagocytized. These cells release interleukin-1 in response to the phagocytized particles. Interleukin-1 induces the formation of protablandin E2, which acts on the hypothalamus to elicit the fever reaction. When prostaglandin formation is blocked by drugs, the fever is completely abrogated or at least reduced. This is the proposed mechanism of action for aspirin etc, to reduce the level of fever.

Front 70

State the symptoms of heat stroke

Back 70

Nausea, weakness, headache, profuse sweating, confusion, dizziness, collapse, and unconsciousness..

Front 71

State the “normal” pH of arterial blood, venous blood, interstitial fluid.

Back 71

Arterial blood has a normal pH of 7.4, whereas the pH of venous blood and interstitial fluids is about 7.35.

Front 72

When is a person considered to have acidosis?

Back 72

When the arterial pH falls below 7.4

Front 73

When is a person considered to have alkalosis?

Back 73

When the arterial pH rises above 7.4

Front 74

Describe the physiological effects of exposure to extreme cold.

Back 74

When the body is too cold, the temperature control systems initiate mechanisms to reduce heat loss and increase heat production.
Vasocontriction: of the blood vessels of the skin, this decreases transfer of heat from the core of the body.
Piloerection, which raises the hair to trap air next to the skin and create a layer of warm air that acts as an insulator.
Greater heat production by metabolic systems such as sympathetic excitation of heat production, increased thyroxine secretion, and shivering. Shivering can increase the rate of heat production by 4 to 5 fold.

Front 75

What are the lower and upper limits that a person can live for more than a few hours for pH?

Back 75

The lower limit of pH at which a person can live for more than a few hours is about 6.8 and the upper limit is about 8.0.

Front 76

What is the bicarbonate buffer system composed of?

Back 76

The bicarbonate buffer system consists of a water solution that has two main ingredients: a weak acid, and a bicarbonate salt, which is formed in the body through the reaction of CO2 with H2O.
The second component of the system, bicarbonate salt, occurs mainly as a sodium bicarbonate, in the extracellular fluid.

Front 77

What is a buffer?

Back 77

A buffer is any substance that can reversibly bind H+.

Front 78

What is the general form of a buffering reaction?

Back 78

Buffer + H+ ------H BufferIn this example, free H+ combines with the buffer to form a weak acid (H buffer). when the H+ concentration increases, the reaction is forced to the right and ore H+ binds to the buffer for as long as available buffer is present. When the H+ concentration decreases, the reaction shifts toward the left, and H+ is released from the buffer.

Front 79

What are amongst the most important buffer systems in the body?

Back 79

Among the most important buffer systems in the body are proteins in the cells, and to a lesser extent, proteins in the plasma and interstitial fluids.

Front 80

The phosphate buffer system (HPO4 2-/H2PO4-) is not a major buffer in the ____ ____ but is important as what 2 things?

Back 80

Is not a major buffer in the extracellular fluid but is important as an intracellular buffer and as a buffer in renal tubular fluid.

Front 81

Describe the protein buffer system

Back 81

The most important extracellular fluid buffer is the bicarbonate buffer system (HCO3-/PCO2), primarily because the components of the system, CO2 and HCO3-, are closely regulated by the lungs and kidneys, respectively.

Front 82

Describe the function of the respiratory system in the regulation of acid-base balance

Back 82

Because the lungs expel CO2 from the body, rapid ventilation by the lungs decreases the concentration of CO2 in the blood, which in turn decreases the carbonic acid (H2CO3) and H+ concentrations in the blood. Conversely, a decrease in pulmonary ventilation increases CO2 and H+ concentration in the blood. Increased hydrogen ion concentration stimulates pulmonary ventilation. Not only does the pulmonary ventilation rate influence the H+ concentration by changing the PCO2 of the body fluids, increased H+ concentrations markedly stimulate pulmonary ventilation. As pH decreases from the normal value of 7.4 to the acidic value of 7.0 pulmonary ventilation increases to 4 or 5 times the normal rate. This in turn reduces the PCO2 of blood and returns the H+ concentration back toward normal. Conversely, if the pH increases above normal, the respiration becomes depressed, and the H+ concentration increases toward normal. The respiratory system can return the H+ concentration and pH to about two thirds of normal within a few minutes after a sudden disturbance of acid-base balance.

Front 83

Describe the function of the renal system in the regulation of acid-base balance.

Back 83

The kidneys control the acid-base balance by excreting either acidic urine, which reduces the amount of acid in extracellular fluid, or basic urine, which removes base from the extracellular fluid. The kidneys regulate extracellular fluid H+ concentrations through three basic mechanisms: 1: secretion of H+, 2: reabsorption of filtered HC)3- and 3: production of new HCO3-.

Front 84

When disturbances of acid-base balance result from primary changes in extracellular HCO3-, they are referred to as what?

Back 84

Metabolic acid-base disorders.

Front 85

Describe the causes of metabolic acidosis and alkalosis

Back 85

Acidosis caused by a primary decrease in HCO3-, concentration is termed metabolic acidosis, whereas alkalosis caused by a primary increase in HCO3- concentration is called metabolic alkalosis.

Front 86

Acidosis caused by an increase in PCO2 is called what?

Back 86

Respiratory acidosis

Front 87

Alkalosis caused by a decrease in PCO2 is called what?

Back 87

Respiratory alkalosis

Front 88

Describe the effects of acidosis on the body

Back 88

With alkalosis, there is an excess of bicarbonate ions over hydrogen ions in the urine. Because the HCO2- cannot be reabsorbed unless it reacts with H+, the excess HCO3- is left in the urine and is eventually excreted, which helps correct the alkalosis.

Front 89

Describe the effects of alkalosis on the body

Back 89

With acidosis, there is an excess of hydrogen ions over bicarbonate ions in the urine. This causes complete re-absorption of the filtered HCO3-, and the excess H+ passes into the urine after combining with buffers in the tubules such as phosphate and ammonia. Thus, the basic mechanism by which the kidneys correct for acidosis or alkalosis is incomplete titration of H+ against HCO3-, leaving one to pass into the urine and therefore to be removed from the extracellular fluid.