Bronchitis = Irreversible Bronchioconstriction
 .    Causes - Infection, Air polution, cigarette smoke

a.    Primary Defect = Enlargement & Over Activity of Mucous Glands, Secretions very viscous
b.    Hypertrophy & hyperplasia, Narrows & Blocks bronchi, Lumen of airway, significantly narrow
c.    Impaired Clearance by mucocillary elevator
d.    Microorganism retension in lower airways,Prone to Infectious Bronchitis, Pneumonia
e.    Permanent Inflamatory Changes IN epithelium, Narrows walls, Symptoms, Excessive sputum, coughing
f.    CAN CAUSE EMPHYSEMA

The hepatic portal system

The capillary beds of most tissues drain into veins that lead directly back to the heart. But blood draining the intestines is an exception. The veins draining the intestine lead to a second set of capillary beds in the liver. Here the liver removes many of the materials that were absorbed by the intestine:

• Glucose is removed and converted into glycogen.
• Other monosaccharides are removed and converted into glucose.
• Excess amino acids are removed and deaminated.
  • The amino group is converted into urea.
  • The residue can then enter the pathways of cellular respiration and be oxidized for energy.
• Many nonnutritive molecules, such as ingested drugs, are removed by the liver and, often, detoxified.

The liver serves as a gatekeeper between the intestines and the general circulation. It screens blood reaching it in the hepatic portal system so that its composition when it leaves will be close to normal for the body.

Furthermore, this homeostatic mechanism works both ways. When, for example, the concentration of glucose in the blood drops between meals, the liver releases more to the blood by

• converting its glycogen stores to glucose (glycogenolysis)
• converting certain amino acids into glucose (gluconeogenesis).

The bulk of the pancreas is an exocrine gland secreting pancreatic fluid into the duodenum after a meal. However, scattered through the pancreas are several hundred thousand clusters of cells called islets of Langerhans. The islets are endocrine tissue containing four types of cells. In order of abundance, they are the:

• beta cells, which secrete insulin and amylin;
• alpha cells, which secrete glucagon;
• delta cells, which secrete somatostatin, and
• gamma cells, which secrete a polypeptide of unknown function.

Beta Cells

Beta cells secrete insulin in response to a rising level of blood sugar

Insulin affects many organs. It

• stimulates skeletal muscle fibers to
  • take up glucose and convert it into glycogen;
  • take up amino acids from the blood and convert them into protein.
• acts on liver cells
  • stimulating them to take up glucose from the blood and convert it into glycogen while
  • inhibiting production of the enzymes involved in breaking glycogen back down (glycogenolysis) and
  • inhibiting gluconeogenesis; that is, the conversion of fats and proteins into glucose.
• acts on fat (adipose) cells to stimulate the uptake of glucose and the synthesis of fat.
• acts on cells in the hypothalamus to reduce appetite.

Diabetes Mellitus

Diabetes mellitus is an endocrine disorder characterized by many signs and symptoms. Primary among these are:

• a failure of the kidney to retain glucose .
• a resulting increase in the volume of urine because of the osmotic effect of this glucose (it reduces the return of water to the blood).

There are three categories of diabetes mellitus:

• Insulin-Dependent Diabetes Mellitus (IDDM) (Type 1) and
• Non Insulin-Dependent Diabetes Mellitus (NIDDM)(Type 2)
• Inherited Forms of Diabetes Mellitus

Insulin-Dependent Diabetes Mellitus (IDDM)

IDDM ( Type 1 diabetes)

• is characterized by little or no circulating insulin;
• most commonly appears in childhood.
• It results from destruction of the beta cells of the islets.
• The destruction results from a cell-mediated autoimmune attack against the beta cells.
• What triggers this attack is still a mystery, although a prior viral infection may be the culprit.

Non Insulin-Dependent Diabetes Mellitus (NIDDM)

Many people develop diabetes mellitus without an accompanying drop in insulin levels In many cases, the problem appears to be a failure to express a sufficient number of glucose transporters in the plasma membrane (and T-system) of their skeletal muscles. Normally when insulin binds to its receptor on the cell surface, it initiates a chain of events that leads to the insertion in the plasma membrane of increased numbers of a transmembrane glucose transporter. This transporter forms a channel that permits the facilitated diffusion of glucose into the cell. Skeletal muscle is the major "sink" for removing excess glucose from the blood (and converting it into glycogen). In NIDDM, the patient's ability to remove glucose from the blood and convert it into glycogen is reduced. This is called insulin resistance. NIDDM (also called Type 2 diabetes mellitus) usually occurs in adults and, particularly often, in overweight people.

Alpha Cells

The alpha cells of the islets secrete glucagon, a polypeptide of 29 amino acids. Glucagon acts principally on the liver where it stimulates the conversion of glycogen into glucose (glycogenolysis) which is deposited in the blood.

Glucagon secretion is

• stimulated by low levels of glucose in the blood;
• inhibited by high levels, and
• inhibited by amylin.

The physiological significance of this is that glucagon functions to maintain a steady level of blood sugar level between meals.

Delta Cells

The delta cells secrete somatostatin. Somatostatin has a variety of functions. Taken together, they work to reduce the rate at which food is absorbed from the contents of the intestine. Somatostatin is also secreted by the hypothalamus and by the intestine.

Gamma Cells

The gamma cells of the islets secrete pancreatic polypeptide. No function has yet been found for this peptide of 36 amino acids.

Exchange of gases takes place in Lungs

• A person with an average ventilation rate of 7.5 L/min will breathe in and out 10,800 liters of gas each day
• From this gas the person will take in about 420 liters of oxygen (19 moles/day) and will give out about 340 liters of carbon dioxide (15 moles/day)
• The ratio of CO₂ expired/O₂ inspired is called the respiratory quotient (RQ)
  • RQ = CO₂ out/O₂ in = 340/420 = 0.81
  • In cellular respiration of glucose CO₂ out = O₂ in; RQ = 1
  • The overall RQ is less than 1 because our diet is a mixture of carbohydrates and fat; the RQ for metabolizing fat is only 0.7
• All of the exchange of gas takes place in the lungs
• The lungs also give off large amounts of heat and water vapor

1.Rhythmicity ( Chronotropism ) :  means the ability of heart to beat regularly ( due to repetitive and stable depolarization and repolarization )  . Rhythmicity of heart is a myogenic in origin , because cardiac muscles are automatically excited muscles and does not depend on the nervous stimulus to initiate excitation and then contraction . The role of nerves is limited to the regulation of the heart rate and not to initiate the beat.

There are many evidences that approve the myogenic and not neurogenic origin of the rhythmicity of cardiac muscle . For example :
-  transplanted heart continues to beat regularly without any nerve supply.
-  Embryologically the heart starts to beat before reaching any nerves to them.
-  Some drugs that paralyze the nerves ( such as cocaine ) do not stop the heart in given doses.

Spontaneous rhythmicity of the cardiac muscle due to the existence of excitatory - conductive system , which is composed of self- exciting non-contractile cardiac muscle cells . The SA node of the mentioned system excites in a rate , that is the most rapid among the other components of the system ( 110 beats /minute ) , which makes it the controller or ( the pacemaker ) of the cardiac rhythm of the entire heart.

Mechanism , responsible for self- excitation in the SA node and the excitatory conductive system  is due to the following properties of the cell membrane of theses cells :
1- Non-gated sodium channels
2- Decreased permeability to potassium
3- existence of slow and fast calcium channels.

These properties enable the cations ( sodium through the none-gated sodium voltage channels , calcium through calcium slow channels) to enter the cell and depolarize the cell membrane without need for external stimulus.

The resting membrane potential of non-contractile cardiac cell is -55 - -60 millivolts ( less than that of excitable nerve cells (-70) ) . 

The threshold is also less negative than that of nerve cells ( -40 millivolts ).

The decreased permeability to potassium from its side decrease the eflux  of potassium during the repolarization phase of the pacemaker potential . All of these factors give the pacemaker potential its characteristic shape

Repeating of the pacemaker potential between the action potentials of contractile muscle cells is the cause of spontaneous rhythmicity of cardiac muscle cells.

Factors , affecting the rhythmicity of the cardiac muscle :

I. Factors that increase the rate ( positive chronotropic factors) :
1. sympathetic stimulation : as its neurotransmitter norepinephrine increases the membrane permeability to sodium and calcium.
2. moderate warming : moderate warming increases temperature by 10 beats for each 1 Fahrenheit degree increase in body temperature, this due to decrease in permeability to potassium ions in pacemaker membrane by moderate increase in temperature.
3. Catecholaminic drugs have positive chronotropic effect.
4. Thyroid hormones : have positive chronotropic effect , due to the fact that these drugs increase the sensitivity of adrenergic receptors to adrenaline and noreadrenaline .
5. mild hypoxia.
6. mild alkalemia : mild alkalemia decreases the negativity of the resting potential.
7. hypocalcemia.
8. mild hypokalemia

II. Factors that decrease rhythmicity ( negative chronotropic):

1.Vagal stimulation : the basal level of vagal stimulation inhibits the sinus rhythm and decrease it from 110-75 beats/ minute. This effect due to increasing the permeability of the cardiac muscle cell to potassium , which causes rapid potassium eflux , which increases the negativity inside the cardiac cells (hyperpolarization ).
2. moderate cooling
3. severe warming : due to cardiac damage , as a result of intercellular protein denaturation. Excessive cooling on the other hand decrease metabolism and stops rhythmicity.
4. Cholenergic drugs ( such as methacholine , pilocarpine..etc) have negative chronotropic effect.
5. Digitalis : these drugs causes hyperpolarization . This effect is similar to that of vagal stimulation.
6. Hypercapnia ( excessive CO2 production )
7. Acidemia.
8. hyper- and hyponatremia .
9. hyperkalemia
10. hypercalcemia
11. Typhoid or diphteria toxins.

Neurons :

Types of neurons based on structure:

a multipolar neuron because it has many poles or processes, the dendrites and the axon. Multipolar neurons are found as motor neurons and interneurons. There are also bipolar neurons with two processes, a dendrite and an axon, and unipolar neurons, which have only one process, classified as an axon.. Unipolar neurons are found as most of the body's sensory neurons. Their dendrites are the exposed branches connected to receptors, the axon carries the action potential in to the central nervous system.

Types of neurons based on function:

• motor neurons - these carry a message to a muscle, gland, or other effector. They are said to be efferent, i.e. they carry the message away from the central nervous system.
• sensory neurons - these carry a message in to the CNS. They are afferent, i.e. going toward the brain or spinal cord.
• interneuron (ie. association neuron, connecting neuron) - these neurons connect one neuron with another. For example in many reflexes interneurons connect the sensory neurons with the motor neurons.