Structural Divisions of the nervous system:

1) Central Nervous System (CNS) - the brain and spinal cord.

2) Peripheral Nervous System (PNS) - the nerves, ganglia, receptors, etc

Lipids:

• about 40% of the dry mass of a typical cell
• composed largely of carbon & hydrogen
• generally insoluble in water
• involved mainly with long-term energy storage; other functions are as structural components (as in the case of phospholipids that are the major building block in cell membranes) and as "messengers" (hormones) that play roles in communications within and between cells
• Subclasses include:
  • Triglycerides - consist of one glycerol molecule + 3 fatty acids (e.g., stearic acid in the diagram below). Fatty acids typically consist of chains of 16 or 18 carbons (plus lots of hydrogens).
  • phospholipids - Composed of 2 fatty acids, glycerol, phosphate and polar groups , phosphate group (-PO⁴) substitutes for one fatty acid & these lipids are an important component of cell membranes

steroids - have 4 rings- cholesterol, some hormones, found in membranes include testosterone, estrogen, & cholesterol

Chemical Controls of Respiration

A.    Chemoreceptors (CO2, O2, H+)

1.    central chemoreceptors - located in the medulla
2.    peripheral chemoreceptors - large vessels of neck

B.    Carbon Dioxide Effects

1.    a powerful chemical regulator of breathing by increasing H+ (lowering pH)
    
a. hypercapnia            Carbon Dioxide increases -> 
                        Carbonic Acid increases ->
                        pH of CSF decreases (higher H+)- >
                        
DEPTH & RATE increase (hyperventilation)

b. hypocapnia - abnormally low Carbon Dioxide levels which can be produced by excessive hyperventilation; breathing into paper bag increases blood Carbon Dioxide levels

C.     Oxygen Effects

1.    aortic and carotid bodies - oxygen chemoreceptors

2.    slight Ox decrease - modulate Carb Diox receptors
3.    large Ox decrease - stimulate increase ventilation
4.    hypoxic drive - chronic elevation of Carb Diox (due to disease) causes Oxygen levels to have greater effect on regulation of breathing

D.    pH Effects (H+ ion)

1.    acidosis - acid buildup (H+) in blood, leads to increased RATE and DEPTH (lactic acid)

E.    Overview of Chemical Effects

 Chemical                             Breathing Effect

increased Carbon Dioxide (more H+)     increase
decreased Carbon Dioxide (less H+)     decrease

slight decrease in Oxygen             effect CO2 system
large decrease in Oxygen             increase ventilation

decreased pH (more H+)                 increase
increased pH (less H+)                 decrease

Vital Capacity: The vital capacity (VC) is the maximum volume which can be ventilated in a single breath. VC= IRV+TV+ERV. VC varies with gender, age, and body build. Measuring VC gives a device for diagnosis of respiratory disorder, and a benchmark for judging the effectiveness of treatment. (4600 ml)

Vital Capacity is reduced in restrictive disorders, but not in disorders which are purely obstructive.

The FEV₁ is the % of the vital capacity which is expelled in the first second. It should be at least 75%. The FEV₁ is reduced in obstructive disorders.

Both VC and the FEV₁ are reduced in disorders which are both restrictive and obstructive

Oxygen is present at nearly 21% of ambient air. Multiplying .21 times 760 mmHg (standard pressure at sea level) yields a pO₂ of about 160. Carbon dioxide is .04% of air and its partial pressure, pCO₂, is .3.

With alveolar air having a pO₂ of 104 and a pCO₂ of 40. So oxygen diffuses into the alveoli from inspired air and carbon dioxide diffuses from the alveoli into air which will be expired. This causes the levels of oxygen and carbon dioxide to be intermediate in expired air when compared to inspired air and alveolar air. Some oxygen has been lost to the alveolus, lowering its level to 120, carbon dioxide has been gained from the alveolus raising its level to 27.

Likewise a concentration gradient causes oxygen to diffuse into the blood from the alveoli and carbon dioxide to leave the blood. This produces the levels seen in oxygenated blood in the body. When this blood reaches the systemic tissues the reverse process occurs restoring levels seen in deoxygenated blood.

Control of processes in the stomach:

The stomach, like the rest of the GI tract, receives input from the autonomic nervous system. Positive stimuli come from the parasympathetic division through the vagus nerve. This stimulates normal secretion and motility of the stomach. Control occurs in several phases:

Cephalic phase stimulates secretion in anticipation of eating to prepare the stomach for reception of food. The secretions from cephalic stimulation are watery and contain little enzyme or acid.

Gastric phase of control begins with a direct response to the contact of food in the stomach and is due to stimulation of pressoreceptors in the stomach lining which result in ACh and histamine release triggered by the vagus nerve. The secretion and motility which result begin to churn and liquefy the chyme and build up pressure in the stomach. Chyme surges forward as a result of muscle contraction but is blocked from entering the duodenum by the pyloric sphincter. A phenomenon call retropulsion occurs in which the chyme surges backward only to be pushed forward once again into the pylorus. The presence of this acid chyme in the pylorus causes the release of a hormone called gastrin into the bloodstream. Gastrin has a positive feedback effect on the motility and acid secretion of the stomach. This causes more churning, more pressure, and eventually some chyme enters the duodenum.

Intestinal phase of stomach control occurs. At first this involves more gastrin secretion from duodenal cells which acts as a "go" signal to enhance the stomach action already occurring. But as more acid chyme enters the duodenum the decreasing pH inhibits gastrin secretion and causes the release of negative or "stop" signals from the duodenum.

These take the form of chemicals called enterogastrones which include GIP (gastric inhibitory peptide). GIP inhibits stomach secretion and motility and allows time for the digestive process to proceed in the duodenum before it receives more chyme. The enterogastric reflex also reduces motility and forcefully closes the pyloric sphincter. Eventually as the chyme is removed, the pH increases and gastrin and the "go" signal resumes and the process occurs all over again. This series of "go" and "stop" signals continues until stomach emptying is complete.

White Blood Cells (leukocytes)

White blood cells

• are much less numerous than red (the ratio between the two is around 1:700),
• have nuclei,
• participate in protecting the body from infection,
• consist of lymphocytes and monocytes with relatively clear cytoplasm, and three types of granulocytes, whose cytoplasm is filled with granules.

Lymphocytes: There are several kinds of lymphocytes, each with different functions to perform , 25% of wbc The most common types of lymphocytes are

• B lymphocytes ("B cells"). These are responsible for making antibodies.
• T lymphocytes ("T cells"). There are several subsets of these:
  • inflammatory T cells that recruit macrophages and neutrophils to the site of infection or other tissue damage
  • cytotoxic T lymphocytes (CTLs) that kill virus-infected and, perhaps, tumor cells
  • helper T cells that enhance the production of antibodies by B cells

Although bone marrow is the ultimate source of lymphocytes, the lymphocytes that will become T cells migrate from the bone marrow to the thymus where they mature. Both B cells and T cells also take up residence in lymph nodes, the spleen and other tissues where they

• encounter antigens;
• continue to divide by mitosis;
• mature into fully functional cells.

Monocytes : also originate in marrow, spend up to 20 days in the circulation, then travel to the tissues where they become macrophages. Macrophages are the most important phagocyte outside the circulation. Monocytes are about 9% of normal wbc count

Macrophages are large, phagocytic cells that engulf

• foreign material (antigens) that enter the body
• dead and dying cells of the body.

Neutrophils

The most abundant of the WBCs. about 65% of normal white count  These cells spend 8 to 10 days in the circulation making their way to sites of infection etc  Neutrophils squeeze through the capillary walls and into infected tissue where they kill the invaders (e.g., bacteria) and then engulf the remnants by phagocytosis. They have two types of granules: the most numerous are specific granules which contain bactericidal agents such as lysozyme; the azurophilic granules are lysosomes containing peroxidase and other enzymes

Eosinophils : The number of eosinophils in the blood is normally quite low (0–450/µl). However, their numbers increase sharply in certain diseases, especially infections by parasitic worms. Eosinophils are cytotoxic, releasing the contents of their granules on the invader.

Basophils : rare except during infections where these cells mediate inflammation by secreting histamine and heparan sulfate (related to the anticoagulant heparin). Histamine makes blood vessels permeable and heparin inhibits blood clotting. Basophils are functionally related to mast cells.  . The mediators released by basophils also play an important part in some allergic responses such as hay fever and an anaphylactic response to insect stings.

Thrombocytes (platelets):

Thrombocytes are cellular derivatives from megakaryocytes which contain factors responsible for the intrinsic clotting mechanism. They represent fragmented cells  which contain residual organelles including rough endoplasmic reticulum and Golgi apparati. They are only 2-microns in diameter, are seen in peripheral blood either singly or, often, in clusters, and have a lifespan of 10 days.