ObjectivesObjectives:: -Cell structure.

-Cell membrane.

-Transport mechanism through cell membrane.

-Homeostasis.

• Lipid bilayer

• diffusion : - Constant motion. Through cell membrane

#. Simple diffusion & #. facilitated.

I. Passive:

• Simple: -Lipid soluble substances O2, N2 , CO2 , -Lipid insoluble small H2O, urea 20% less

• Through protein channels (charge) , (size) selective, gated (voltage, ligand)

II. Facilitated diff. : Carrier-mediated , Vmax • Rate of diff. :permeability, thickness,

soluble, s.a, t , Mw, gradients.

II.Active :

Primary : - Secondary

Na-K pump Co- & counter-tr.

Ca - pump Na - Gl Na -aa

H - pump Na -H Na - Ca

-Basic principles of osmosis water diffuses from high [water] to region of lower [HO] . (Kinetics).

Osmosis across selectively permeable membranes

Cell:Cell: Basic living unit performs one or a few particular functions. 100 trillion cells.

Basic characteristics of cellBasic characteristics of cell : :

• In all O + nutrients produces energy for function.

• Mechanism of energy prod. in all cells the same.

• All produce end product into surrounding fluids.

• Most cell able to reproduce.

HomeostasisHomeostasis

Maintenance of static or constant conditions in the internal environment. Control systems regulate the functional systems to operate in harmony with one another.

Circulatory system :Plasma intravascular _ interstatial.

Enternal Environment:-Enternal Environment:-

ECF 1/3 of B.F and it is in constant motion throughout the body.

• All cells live in ECF • If [ ] of O2, Glu, ions. a.a, f.a, others is constant cells live, grow, perform their functions. • most control systems act by negative feedback

• Automaticity , gain theory .

• Gain = Correction Error

1.1.Origin of nutrientsOrigin of nutrients::

- Respir. system blood takes O2 .

- G.I.T. blood takes nutrients. - Liver metabolic function more usable forms. - muscular skeletal s. move to appropriate

place & time to obtains food.

2. Removal of metabolic end products :

- Resp. S. - Kidneys- G.I.T

3. Regulation of body functions3. Regulation of body functions::

1. Nervous system :

a. Sensory input : detects the state of the body and surroundings . (Receptors, eyes, ears).

b. C.N.S : brain stores information generates thoughts, creates ambition & determines rxns.

c. Motor output carry out the ones desires. d. Autonomic N.S operates at a subconscious

level.

2. 2. Hormonal system:

8 glands __ hormones which regulate cell function.

Thyroid hormone __ rate of rxns.

Insulin __ controls glucose.

Corticosteroids __ Na , K , protein, metabolism.

4. Reproductive system : maintains static conditions by generating new beings to take the place of those that are dying.

- Genetic control systems _ control intracell function & extracelluler function. - Other control systems operate w/in the organs. - Other control systems operate throughout body.

Examples of control mechanisms

- Reg. of O2 and CO2 - Reg. of blood pressure.

Characteristics of control systemCharacteristics of control system

1. Negative feedback nature: Series of changes that return the factor toward and certain mean value.

Gain of a control S.

Degree of effectiveness with which a control system. maintains constant conditions. [gain of the (-) feedback] .

Blood transfusion __ BP from 100 to 175 mmHg Blood transfusion w/control ___ BP from 100 to

125mmHg .“Correction - 50 Error + 25 Gain = Correction = -50 = - 2

Error 25 1 if 3 units ___ only one unit appears.

2. Positive feedback: Vicious circles and death. Initiating stimulus causes more of the same.

Example of useful (+) feedback:

- Blood clotting

- Childbirth

- Generation of nerve signal

3. Adoptive control system: Feed-forward control: Movements of the body occur so rapidly, where time is not enough for nerve signal to travel from peripheral parts of the body to brain then back. If the feed-forward movement was not appropriate then the brain corrects the feed-forward signals (delay negative feedback).

Body fluidBody fluid

1-The maintenance of a relatively constant volume and a stable composition of the body fluids are essential for homeostasis.

[Most important problems in clinical medicine arise because of abnormalities in the control systems that maintain this constancy of the body fluids] .

2- During steady-state conditions intake and output must be balanced, despite the continuous exchange of fluid and solutes with the external environment as well as within the different compartments of the body

Intake 2.3 L/day : Output 2.3 L/day :

-Ingested water 2.1 L/d - Insensible loss 700 ml/d

-Synthesis 200 ml/d - Sweat 100 ml/d

- Feces 100 ml/d

- Urine 1.4 L/d

3- Body fluid compartments 60% of body weight

Intravascular Extravascular

a.Plasmaa. Extracellular 20% b.Interstatial

c.Transcellular b. Intracellular 40%

4-Measurement of fluid volumes :

- Indicator-dilution principle Vi Ci = Vf Cf

a. Total body water: tritium H2O, deuterium H2O, Antipyrine

b. ECF : Labeled Na , Cl, thiosolfate, and inuline

c. ICF = TBW - ECF (calculated)

d. Plasma : I - serum albumin, Evans blue dye

e. Interstitial = ECF - plasma (calculated)

f. Blood vol. = plasma vol. 1 - Htct

Regulation of fluid exchangeRegulation of fluid exchange

b/w intra-and extracellular fluidb/w intra-and extracellular fluid

-Frequent problem in the treatment of seriously inpatients is the difficulty of maintaining adequate fluids in one or both of the intra- and extracellular compartments.

-Balance of hydrostatic and colloid osmotic forces across the capillary membrane determines the distribution of ECF b/w plasma and interstitial fluids.

(starling cap. circulation)

- Osmotic effect of electrolytes (NaCl) determines the distribution of fluids b/w intra- and extracell. comp.

(because membrane permeable for H2O but not for Na and Cl)

- moles and osmoles 1 osmole = 1 mole of solute particles (6.02 x10). 1 mole glucose = 1 osm. 1 mole NaCl = 2 osm. 1 mole Na2SO3 = 3 osm.

- Osmolality and osmolarity in human fluids they are equal.

-Osmotic pressure : pressure that prevents the osmosis . The higher the osmotic pressure of a solution, the lower its [HO] but the higher its [solute]. 1 osm/L = 19300 mmHg.

Osmotic equilibriumOsmotic equilibrium

Small changes in concentration of impermeant solutes in the ECF can cause tremendous changes in cell volume .

Isotonic Hypertonic Hypotic Isosmotic Hyperosmoti Hypoosmotic

Osmotic equal. principles :

1. Osmolarity of ECF and ICF remain almost exactly equal.

2. Cell membrane almost impermeable to many solutes so # of osmoles is constant.

1. Calculation of H2O deficit in dehydration

- 70 Kg pt. dehydrated unconscious. Plasma osm. 320 mOsm. - How much water needed to restore plasma osmolarity to 280 mOsm/L .

First step: assuming ECF 20% of body wt. ICF 40% ____

Vol. ECF 14 L ICF 28 L Total 42 L Osm. # 4480 896 13440

(because osm. = 320)

Second step: determine the volume needed to reduce osmol. to 280 mOsm/L. Knowing that # of mosmoles is constant then volume = # mosmoles

osmolarity

ECF ICF Total Vol. 16 32 48 L Osm. 280 280 280# osm. 4480 8960 13440

Third step : Calculate the fluid volume needed.

48 L - 42 L = 6 L water

2- Hyponatremia:

(a). Water excess in ECF : (hypoosmotic over hydration) - secretion of ADH

(b). Loss of Na Cl (hypoosmotic dehydr.)

-Excessive sweating, diarrhea, vomiting - Overuse of diuretics - Addison’s disease aldosterone Na reabs. in kidneys

3. Hypernatremia:

a. Loss of water from ECF (hyperosmotic dehydration)

- Lack of ADH diabetes insipidus - Sweating

b. Excessive NaCl added to ECF (hyperosmotic overhydration)

Starling capillary circulation

- 3 mmHg - 3 mmHg 8 mmHg 1 8 mmHg

____________________________

1 30 mmHg 1 28 mmHg

1 10 mmHg ______________________________

Mean capillary pr. 17.3 mmHg Negative interstitial pr. 03.0 mmHg Osmotic interstitial pr. 08.0 mmHgPlasma colloid pr. 28.0 mmHg

____

Net filtration 0.3 mmHg

EdemaEdema

A-A- IntracellularIntracellular: causes 1.depression of the metabolic system

of the tissues.

2. Lack of adequate nutrition to the cell. Ischemia - edema,

inflammation -edema.

Na-K pump stopped - Na lacks inside H O follows.

B- ExtracellularB- Extracellular: Two major causes (1). Abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries.

(2). Failure of the lymphatic to return fluid from the interstitium back into the blood. filaria nematodes, surgery, cancer. Filtration = K x (P -P - T + T )

Causes of extracellular edemaCauses of extracellular edema

1.Increased capillary pressure :

A. Excessive kidney retention of salt and water 1. Acute or chronic kidney failure 2. Mineral corticoid excess

B. High venous pressure :

1. Heart failure 2. venous obstruction 3. Failure of venous pumps:

a. muscle paralysis b. Immobilized part c. V. valve failure

C. Decreased arteriolar resistance:1. Heat 2. Insufficiency of symp. S. 3. vasodilators

2. Decreased plasma proteins:

A. Nephrotic syndrome

B. Protein loss : Wounds , burns

C. Failure to produce proteins: 1.Liver disease 2. Malnutrition

3.Increased capillary permeability:

A. Immune rxns. ___ histamine B. Bacterial inf. C. Toxins D. Vit. C deficiency E. Burns F. Prolong ischemia

4.Blockage of lymph Return:

A. Cancer B.Infections (filari) C.Surgery D. Congenital abnormality of

lymphatic vessels

C-Safety factors that prevent C-Safety factors that prevent edemaedema:1.Low tissue compliance of the interstitium when pres. is (-). 3mmHg

2.Ability of lymphatic flow to increase 10-50 times. 7mmHg

3.Washout proteins from interstitium. 7mmHG