Cell Physiology Body fluids Cell membrane potential Respiratory system

2. Physiology of cell
• Plasma, membrane
• Cytoplasm (cytosol + organelles)
• Nucleus
The chemical composition of the cell:
• Water  70-85%
• Electrolytes
• Carbohydrates  1%
• Lipids  2%
• Proteins  10-20%
Cell membrane (plasma membrane):
• Lipids  40% (phospholipids + cholesterol)  lipid-soluble substances cross cell membranes easily because they can
dissolve in the lipid bilayer
• Protein  60%
Functions of cell membrane:
• The maintenance of cell shape and structure
• A selective transport function
• Intercellular adhesion
• Intercellular communication
• Directed cell movement

3. The membrane proteins:
[A] Integral proteins
• Ion channels proteins
• Pumps
• Transport proteins (carriers)
• Receptors
• Cell adhesion molecules
• Antigens and recognition proteins (identifiers)
• Enzymes
[B] Peripheral (associated) proteins:
• Cytoskeletal proteins
• Enzymes
• The extracellular matrix proteins
The general characteristics of trans-membrane ion channel
proteins:
[1] Specificity
[2] Opened channels
[3] Gated channels that are closed by gates
• Voltage Voltage gating (voltage-gated channel)
• Chemical or ligand gating (chemical or ligand-gated channel)
• Physical gating (physical-gated channel)

4. The receptors
Glycocalyx
• Repels other negative objects
• Attaching the cells to each other
• Receptor
• Enter into immune reactions
Figure 3: The glycocalyx.

5. The cytoplasm and its organelles
[A] Mitochondria
[B] The endoplasmic Reticulum
• Granular endoplasmic reticulum on which
granules called ribosomes
• Agranular endoplasmic reticulum
[C] Golgi apparatus
[D] Lysosomes
[E] Peroxisomes
[F] Cytoskeleton

6. [G] Cilia and flagella
[H] Microvilli

7. Body fluids:
60% in young males and about 50% in young women of the total
body weight (TBW) (lower level in fat, upper level in thin, 80% in
infants).
Extracellular fluid (ECF)  20% of TBW,
• The interstitial fluid  15%
• Plasma 4%
• Transcellular fluids 1% (fluid in the gastrointestinal, biliary,
and urinary tracts, the intraocular and cerebrospinal fluids, and
fluid in the serosal spaces, such as the pleural, peritoneal, and
pericardial fluid)
Intracellular fluid (ICF)  40% of the TBW.

8. Ions distribution between body fluid compartments:
Difference between interstitial fluid and plasma is the larger
concentration of proteins in the plasma
The composition differences between ICF and ECF is attributed
mainly to presence of the Na+-K+ ATPase pump in cell membranes
which actively transports three sodium ions out of cell in an
exchange with two potassium ion enter the cell, thereby
accounting for the high sodium ion and low potassium ion
concentrations in ECF and the opposite picture inside ICF.
In spite of the differences in ion concentrations and the total
concentration of the similar charges, osmolarity and electrical
neutrality is maintained within and in between compartments

9. Osmosis
is the diffusion or flow of water (solvent) molecules across a semipermeable membrane (through
channel proteins called aquaporins) into a region in which there is a high concentration of a solute to
which the membrane is impermeable
is the diffusion or flow of water molecules from region of high concentration of water molecules
across a semipermeable membrane (through channel proteins called aquaporins) into a region of low
concentration of water molecules

10. The number of the solute particles determines the magnitude of the osmotic pressure of the solution in which it is
dissolved. The Osmolality of the plasma and ECF is mainly due to Na ions, Cl ions, HCO3 ions, and to less extent due to other
ions (urea, glucose, and proteins).
The Osmolality of the ICF is mainly due to K ions, Mg ions, organic phosphates, proteins and other nitrogen containing
solutes. In spite of the differences in composition, these fluids have essentially identical total osmolality.
In spite of the differences in composition of the body fluids, they have essentially identical total osmolalities of about of
about 290-300 mOsmol/ kg H2O. Why?.......
This is because the capillary endothelium and cell membranes are freely permeable to water, allowing the plasma, interstitial
fluid, and ICF to be isomostic (iso-osmotic).
EXCEPTIONS: Urine, Peritubular interstitial fluid of the renal medulla
Tonicity is used to describe the effective osmotic pressure of a solution relative to plasma in which the normal body cells can
be placed without causing either swelling or shrinking.
• Isotonic
• Hypertonic
• Hypotonic

11. Resting membrane potential (RMP):
The genesis and the magnitude of
resting membrane potential (RMP):
• Passive outward diffusion of K+ ions
(diffusion potential)
• Electrogenic pump (Na+-K+ pump

12. The action potential of the nerve and skeletal
muscle fiber:
[1] Resting stage
[2] Initiation of an action potential (generation of
graded potential)
[3] Depolarization stage
[4] Repolarization stage

13. Table 4.3: Differences of graded potential versus action potential.
Graded potentials Action potentials
Graded potentials can be depolarizing or hyperpolarizing. Action potentials always lead to depolarization of membrane.
Amplitude is small (a few mV to tens of mV) & proportional to the strength of
the stimulus.
Amplitude is large (of ~100 mV) & and it is all-or-none.
The channels responsible for graded potentials may be chemical-, mechanical-
, or electrical –gated channels
The channels responsible for action potential are electrical –gated channels
(i.e. Voltage-gated Na+, orCa++ or K+ channels are responsible for the action
potential.
The ions involved are usually Na+, K+, or Cl−. The ions involved are Na+, K+ and Ca++ (for action potentials).
No refractory period is associated with graded potentials.
Absolute and relative refractory periods are important aspects of action
potentials.
Can be summed over time (temporal summation) and across space (spatial
summation).
Summation is not possible with action potentials (due to the all-or-none
nature, and the presence of refractory periods).
Graded potentials travel by passive spread (electrotonic spread) to
neighboring membrane regions.
Action potentials travel by active spread to neighboring membrane regions by
regeneration of a new action potential at every point along the way.
Amplitude diminishes as graded potentials travel away from the initial site
(decremental).
Amplitude does not diminish as action potentials propagate along neuronal
projections (non- decremental).
In principle, graded potentials can occur in any region of the cell plasma
membrane
Occur in plasma membrane regions where voltage-gated Na+ and K+ channels
are highly concentrated.

14. The action potential of the cardiac
and smooth muscle fibers
NOTES: In smooth muscle fibers such
as intestinal smooth muscle, the spike
potential and the plateau are both
due to voltage-gated Ca2+ channels
rather than sodium conductance.
Consequently, the rates of rise of
smooth action potentials are slow,
and the durations are long relative to
most neural action potentials
Re-establishment of the normal resting membrane potential:
• Na+-K+ pump
• Ca2+ pump

15. Propagation of the action potential:

16. The Refractory Period:
[1] Absolute refractory period
[2] Relative refractory period

17. The nerve, synapses, and neuromuscular junction

18. Respiratory system
The functions of the respiratory system are:
•Gas exchange
•Acid-base balance
•Phonation
•Pulmonary defense and metabolism
•Handling of bioactive materials
Anatomically the respiratory system consists of:
Upper respiratory tract which consists of nose and pharynx.
Lower respiratory tract which consists of larynx, trachea, bronchi (decrease in diameter and length with each successive
branching but the sum of their cross-sectional areas actually increases), bronchioles (about 1 mm in diameter), terminal
bronchioles (about 0.5 mm in diameter), respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli (figure 6.1).
Physiologically, the respiratory system can be divided into:
1. Conducting zone: Starts from the nasal cavity and ends with terminal bronchioles (16 generations).
2. Respiratory zone: Starts with respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli (7 generations).

21. The Pleura:
1. Lubrication
2. Holding the lungs and rib cage together
3. Prevents lung collapse (creation of pressure gradient):
4. Compartmentalization.

22. Respiratory functions of the nose:
[1] Warming the air by the extensive surfaces of the
conchae and septum.
[2] The air is almost completely humidified.
[3] The air is filtered.
Pulmonary ventilation:
[A] Inspiration
[1] Downward movement of the diaphragm
[2] Raising the rib cage.
[B] Expiration:
[1] Relaxation of diaphragm and the inspiratory muscles
[2] Elastic recoil tendency of the lung.
[A] The presence of elastic fibers (elastin)  1/3
[B] The surface tension of the fluid lining the alveoli  2/3

23. The Surface tension & the Surfactant
Laplace's law in Equation: P = 2T/r.

24. Pressure changes during respiration:

25. General classification of lung disorders:
• Obstructive lung diseases  Difficult to get air out of the lungs
• Restrictive lung diseases  Difficult to get air in to the lungs
 Pulmonary fibrosis (as in asbestosis, silicosis, and tuberculosis),
 Neuromuscular diseases (as in paralysis of respiratory muscles).
 Skeletal abnormalities (such as Kyphosis, Scoliosis).
• Gas diffusion diseases  Inability of the tissue of the alveoli to move oxygen into a person's blood through the respiratory
membrane

26. Expansibility of the lungs and thorax (Compliance): The volume
increase in the lungs for each unit increase in alveolar pressure or for
each unit decrease in pleural pressure.
Compliance = [V2-V1] / [P2-P1] = 120-130 ml / cm H2O
Compliance = 1/ elastance
Low compliance  Restrictive lung diseases
[1] Lack of surfactant.
[2] Pulmonary fibrosis, pulmonary edema.
[3] Pleural fibrosis.
[4] Decrease in the amount of ventilated lung tissue, such as removal
of one lung (pneumonectomy).
[5] Diseases of the thoracic cage muscles such as paralyzed and
fibrotic muscles.
[6] Diseases that reduces the expansibility of the thoracic cage such
as deformities of the chest cage (as kyphosis, sever scoliosis).
High compliance  emphysema & aging process

27. The work of breathing: Only 2-3% of the total energy is required or ~ 3 mL O2/min.
• Compliance work  It is the majority of the work
• Tissue resistance work  Few %
• Airway resistance work  Few %

28. Lung volumes & capacities
“Spirometer”
 SPIROMETER: An instrument which measure the volume of air moved into or out of
the lungs.

29. 1. Prevents sudden changes in
blood O2 & CO2 concentration
(harmful).
2. Measured indirectly by
Helium dilution technique.

30. Residual volume measurement:

31. Factors affecting lung volumes
& capacities
• AGE :
decrease in older age groups.
• SEX :
25% greater in males.
• Body build :
tall thin subject had greater values than short obese one .
• Athletics
had greater values.
• Body position :
is maximum in standing, less in sitting and least in lying position because:
– Abdominal contents press on the diaphragm.
– About 500 ml of blood shifted to the pulmonary circulation.

33. Peak expiratory flow (PEF): It is the
maximum airflow obtained during maximum
expiratory effort after maximum inspiration.
Normally 400-600 L/minute.
Reduced in obstructive& restrictive lung
disease.
Affected by
• Lung volume
• Airway resistance

35. Forced vital capacity (FVC), is the maximum volume of air expired forcefully following maximum inspiration. In normal
subject, the FVC is the person’s vital capacity (VC).
Forced expiratory volume (FEV) measures how much air a person can exhale during a forced breath.
FEV1 is the volume of air expired during the first second of forced vital capacity. Normally it is about 80% of the total FVC
Percent vital capacity (FEV1%): It is equal to [FEV1/VC] x 100. In normal subject, the FEV1% is at least 80%. However, in
obstructive lung diseases like asthma, FEV1% is markedly reduced while normal in restrictive lung diseases.

36. Table 6.1: PEF, VC, FEV1, and FEV1% in restrictive and obstructive lung diseases.
Condition
Peak expiratory
flow
Vital capacity FEV1 [FEV1/VC] x 100
Restrictive lung
diseases
Decrease Decrease Decrease Normal
Obstructive lung
diseases
Decrease May be normal Decrease Decrease

37. Flow-Volume Curves: Flow-volume curves or loops are graphic representations of the relationship between maximal flow
rates and volume of gas during a forced maneuver.
The flow volume curves can be used to measure the following:
1. Flow rates during expiration
2. Peak expiratory flow rate (PEFR)
3. Forced vital capacity (FVC)
4. Forced Expiratory Flow 25%–75% (FEF 25%–75%): The FEF 25%–75% is the average flow rate that occurs during the middle 50
percent of an FVC measurement . The FEF 25%–75% measurement reflects the condition of medium- to small-sized airways.

39. Dead space (wasted ventilation)
It is the space in which the gas exchange is
not taking place
• Anatomical: Respiratory passages where no gas exchange takes place (from nose to
terminal bronchioles).
– Normally = 150 ml.
– Increased with age & deep breathing.
• Physiological: Volume of gas not equilibrated with blood (presence of non or poorly
perfused alveoli).
– Normally = 0 ml

40. As we go down the trachiobronchial tree…….
• Airways decrease in size but increase in number
• Decreased cartilage (which completely gone in the
bronchioles) and increased smooth muscle in the
wall of airways. Very few muscle fibers in the wall
of respiratory bronchioles.
• The chief site of airway resistance in the airway
passages is at the medium-sized bronchi, where
the radius of the individual bronchi is decreased
and their cross-sectional area is small. The least
resistance to air flow is in the very small
bronchioles and terminal bronchioles because of
their large cross-sectional area

41. The factors that affect resistance to air flow:
1. Airway diameter  (R∝/r4)
Types:
• Fixed resistance  nose, pharynx, larynx, and trachea
• Variable resistance  bronchi and bronchioles
• Dynamic resistance (also called dynamic airway compression  bronchioles and distal to them
2. Lung volume
3. Turbulent gas flow
• Approximately one-half of the resistance to airflow occurs in the upper respiratory tract (nose and pharynx) when
breathing through the nose.
• The other one-half of the resistance lies within the lower respiratory tract . The chief site of airway resistance in the
airway passages is at the medium-sized bronchi.

42. The respiratory unit : The part of the respiratory system at which gas exchange between the pulmonary blood and the
alveolar air is taking place through its membrane which is called respiratory membrane.
Respiratory membrane: It is composed of a
respiratory bronchiole, alveolar ducts, alveolar
sacs, and alveoli (about 300 million in the two
lungs).
[1] A layer of fluid lining the alveolus and
containing surfactant.
[2] The alveolar epithelium.
[3] The epithelial basement membrane.
[4] A very thin interstitial space.
[5] A capillary basement membrane that in many
places fuses with the epithelial basement
membrane and obliterating the interstitial space.
[6] The capillary endothelial membrane.

43. Factors that affect rate of gas diffusion through the respiratory membrane:
[1] The thickness of the membrane
[2] The surface area of respiratory membrane
[4] The pressure difference
[3] The diffusion coefficient of the gas in the substance of the membrane, which is the water of the membrane
Fick’s law of diffusion, Diffusion = (Pressure gradient × Surface area × Solubility) / (Distance × MW½). (MW = Mol;ecular
weight of the diffused gas).
Lung diffusing capacity: The volume of a gas that diffuses through the membrane each minute for a pressure difference of
1 mm Hg.
Transport of O2 in the blood:
• In chemical combination with Hb in RBC  97%
• In the dissolved state in the water of the plasma  3%
Transport of CO2 in the blood:
In dissolved state in the blood  7%
In form carbonic acid mainly in RBC and to much less extent in plasma  70%
In form of carbaminohaemoglobin (HbCO2)  23%

44. The control of respiration  Respiratory center
Regulation of respiratory center activity: The
respiratory centers and consequently the ventilation
can be regulated by the following factors:
[1] Chemical regulation of respiration mediated
through changes in PCO2, [H+], and PO2.
[2] Peripheral receptors and proprioceptors regulation
of respiration.
[3] Brain centers regulation of respiration.
[4] Motor cortex regulation of respiration.
[5] Vasomotor center regulation of respiration.
[6] Body temperature regulation of respiration.