The body fluid compartment

Concept of Steady-State Balance( in general):

The human body is an "open system," which means that substances are

added to the body each day and, similarly substances are lost from the body

each day.

The amounts added to or lost from the body can vary widely, depending on

the environment, access to food and water, disease processes, and even

cultural norms.

In such an open system, homeostasis occurs through the process of steady-

state balance.

To maintain homeostasis, inputs must be equal to outputs.

Concept of steady – state balance

To illustrate the concept of steady-state

balance, consider a river on which a

dam is built to create a synthetic lake.

Each day, water enters the lake from the

various streams and rivers that feed it.

In addition, water is added by

underground springs, rain, and snow.

At the same time, water is lost through the spillways of the dam and

by the process of evaporation.

For the level of the lake to remain constant (i.e., steady-state

balance), the rate at which water is added, regardless of source, must

be exactly matched by the amount of water lost, again regardless of

route.

Concept of steady – state balance :

To understand steady-state balance as it applies to the human body, the following

key concepts are important:

1. There must be a “set point" so that deviations from this baseline can be

monitored (e.g., the level of the lake in the preceding example, or setting the

temperature in a room by adjusting the thermostat).

There must be a “set point" so that deviations from this baseline can be

monitored (e.g., the level of the lake in the preceding example, or setting the

temperature in a room by adjusting the thermostat).

2. The sensor or sensors that monitor deviations from the set point must generate

“effector signals" that can lead to changes in either input or output, or both, to

maintain the desired set point (e.g., electrical signals to adjust the spillway in the

dam analogy, or electrical signals sent to either the furnace or air conditioner to

maintain the proper room temperature).

3. "Effector organs" must respond in an appropriate way to the effector signals

generated by the set point monitor (i.e., the spillway gates must operate, and the

furnace or air conditioner must turn on).

4. The sensitivity of the system (i.e., how much of a deviation from the set point

is tolerated) depends on several factors, including:

a) The nature of the sensor (i.e., how much of a deviation from the set point

is needed for the sensor to detect the deviation),

b) The time necessary for generation of the effector signals,

c) How rapidly the effector organs respond to the effector signals.

The amount of losses by respiration depend on humidity in

environment and rate of respiration, if respiratory rate increased

(during heavy exercise) the greater the amount of loss through

respiration.

cutaneous loss different from sweating loss.

oxygenation of

carbohydrate

insensible

water loss

insensible

water loss

To balance in steady – state we should have set point to variable (

water) and sensor which located in brain (hypothalamus).

We measure the body water through osmolality ( number of

milliosmoles in a kilogram of solution) , we measure the osmotically

active substance.

If the amount of water decreases through dehydration for example

This is mean decrease amount of solvent and increase concentration of

substances in solute

This leads to an increase osmolalrity.

To be effective the system should have effector signal and

effector .

organ( to back balance to normal).

If the number of osmolality became higher than the normal this

mean that there is a decrease in water.( negative balance)

In this situation the system response through effector signal and

effector organ in two direction.

a) The first one related to CNS (Central nervous system) which

increase the input , by feeling thirsty and drinking more water.

b) The other doing its job through endocrine system ( decrease

output), by making the kidneys excrete less amount of urine the

hormone responsible for this process is ) antidiuretic hormone =

ADH) which secreted from posterior pituitary gland.

inside the blood

vessels

The factor affected on proportion of body water fluid :

1- Age (The lower the age, the greater proportion of body water

fluid)

2- Sex ) The proportion of males is higher than that of females ) ,

Because the percentage of fat in females is more than males of the

same weight.

الايونات قد تكون

+Naموجبة زي

K+/Ca+/Mg+

ومنسميها

Cations

-clاو سالبة زي

/Hco3-/

ومنسميها

Anions

mainly in the plasma

component

Page | 8

If we take blood sample and put it in a centrifuge جهاز الطرد المركزيthis

apparatus will spin very fast for a certain controlled period of time then

the sample will be separated according to the weight into two parts red

part in the bottom (heavier) and yellow transparent part in the top.

The blood is a tissue fluid that’s move through the

cardiovascular system (closed system as it is isolated from

outside the body but allow to exchange materials between

other systems) that’s why it’s also called the intravascular

compartment.

The blood consist of:

A- The fluid part (plasma) 55 % - 60 % of the blood .

الطرد المركزي سوف يدور بسرعة كبيرة لفترة أذا وضعنا عينة من الدم في جهاز

معينة من الزمن يمكن التحكم فيها حتى يفصل مكونات الدم ،عند أخراج العينة من

شفاف في أصفرالجهاز سوف تكون مفصولة الى جزئين بناء على الوزن ، جزء

الأعلى لأنه أخف )البلازما( سائل يحتوي مكونات خلوية مثل البروتينات و جزء في

خلايا دم بيضاء. -3خلايا دم حمراء -2صفائح دموية -1القاع الأثقل يحتوي على

Page | 9

B- Cellular constituents orhematocrit value الخلوية المكونات 45% - 40% of

the blood which is divided into three parts:

1- Red blood cells الأكثر عددا فتعطي الدم اللون الأحمر

2- White blood cells

3- Platelets الصفائح الدموية

%40المكونات الخلوية % و60ملاحظة: في الكتاب البلازما

لنفرض أن hematocrit valueيكون عبارة عن مجموعة من الخلايا الدموية المتكدسة

% 45الدم يتكون من

نسبة زما بلكنها لا تكون مفصولة تماما عن البلازما حيث تحتوي على نسبة قليلة من البلا

hematocrit value% من كمية ال 4

% من الخلايا الدموية 40% من البلازما و 60الدم يتكون من المطلوب منا هو معرفة أن

% )يعني المادة 40% من البلازما من ضمن ال4مع كمية قليلة من البلازما حيث يوجد

% بلازما(4% خلايا دموية و 96% تحتوي على 40التي تكون بالقاع و نسبتها

%96 % ب40حتى تكون نسبة الخلايا الدموية صحيح تماما نضرب ال

Page | 10

Donnan effect or Donnan equilibrium

When an ion or charged particle on one side of a

membrane can’t diffuse through the membrane, the

distribution of other ions to which the membrane is

permeable is affected in a predictable way.

من الممكن أن تفسر هذه النظرية

The resting membrane potential as why a voltage difference

recorded between different sides of cell membrane.

If a charged substance or an ion is trapped on one side of the cell

membrane, the distribution of other ions will be affected e.g. if

the intercellular proteins is trapped inside the cell an ion

distribution of ions will occur.

مثلا في الصورة الشحنات تستطيع عبور غشاء الخلية و البروتين السالب لا

حنة فأن الشحنات الموجبة سوف يستطيع و لأن البروتين في اليسار سالب الش

تنتقل من الجانب الأيمن للجانب الأيسر من خلال غشاء الخلية و الشحنات

السالبة من الجزء الأيسر للجزء الأيمن حتى تحقق التوازن الكهربائي فتكون

اجمالي عدد الشحنات الموجبة و السالبة في كل جزء متساوي و حاصل

في كل جانب متساويضرب الشحنات الموجبة و السالبة

Page | 11

The Donnan effect justify the resting membrane

potential (why inside the cell is more negative than the

outside) .

Page | 12

Continuous process of exchanging substances expect the

proteins between the interstitial fluid and the blood is due to the

high permeability of the capillary walls.

The exchange between the blood and the interstitial fluid occurs

in the capillary.

That’s why there

is differences in

substances

concentration

between the

plasma and the

interstitial fluid

(the positively

charged

substances in the plasma is more than the interstitial fluid and

the negatively charged substances in the plasma is less than the

interstitial fluid) and that’s due to the Donnan equilibrium as

the plasma contains negatively charged proteins so the

concentration of positive ions is more in the plasma and the

negative ions is less.

Page | 13

In equilibrium the concentrations in booth side equal so

they are in static state (there is still a movement because the

kinetic energy of the dynamic equilibrium) but the static

means that the substances will stop moving through the cell

membrane.

That doesn’t happen really in human body what really

happen is the steady state.

Page | 14

In this photo there is no equilibrium, the concentration

of Na+ in the cell can’t increase because that will increase the osmatic loud on the cell and that’s may lead to the death of the

cell so the Na+ concentration should be contained constant and

the NA+ / K+ pump is responsible for the regulation of the Na+ concentration by the passive transport this state called the steady

state which means to maintain certain value concentration

constant within a compartment.

Steady state

يعني أن نحافظ على تركيز الصوديوم بقيمة معينة و لا يشترط أن تكون كمية الصوديوم داخل الخلية مساوي للخارج.

Equilibrium:

أن تكون كمية المادة داخل الخلية مساوي لخارجها.

Any equilibrium is steady state but not all the steady state is equilibrium .

Steady state versus Equilibrium When two compartments are in equilibrium, opposing forces are balanced, and there is no net transfer of a particular substance or energy from one compartment to the other. Equilibrium occurs if sufficient time for exchange has been allowed and if no physical or chemical driving force would favor net movement in one direction or the other.- A steady state is simply a condition that does not change with time. It indicates that the amount or concentration of a substance in a compartment is constant. -In a steady state, there is no net gain or net loss of a substance in a compartment. -Steady state and equilibrium both suggest stable conditions, but a steady state does not necessarily indicate an equilibrium condition, and energy expenditure may be required to maintain a steady state. There is a steady state for Na+ ions ; the amounts of Na+ entering and leaving cells per unit time are equal. But intracellular and extracellular Nat ion concentrations are far from equilibrium. Extracellular Nat is much higher than intracellular [Na+], and Na+ tends to move into cells down concentration and electrical gradients. The cell continuously uses metabolic energy to pump Na+ out of the cell to maintain the cell in a steady state with respect to Na+ ions. In living systems, conditions are often displaced from equilibrium by the constant expenditure of metabolic energy