NEET MDS Lessons
Physiology
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
Plasma: is the straw-colored liquid in which the blood cells are suspended.
|
Composition of blood plasma |
|
|
Component |
Percent |
|
Water |
~92 |
|
Proteins |
6–8 |
|
Salts |
0.8 |
|
Lipids |
0.6 |
|
Glucose (blood sugar) |
0.1 |
Plasma transports materials needed by cells and materials that must be removed from cells:
- various ions (Na+, Ca2+, HCO3−, etc.
- glucose and traces of other sugars
- amino acids
- other organic acids
- cholesterol and other lipids
- hormones
- urea and other wastes
Most of these materials are in transit from a place where they are added to the blood
- exchange organs like the intestine
- depots of materials like the liver
to places where they will be removed from the blood.
- every cell
- exchange organs like the kidney, and skin.
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
- it's the individual pressure exerted independently by a particular gas within a mixture of gasses. The air we breath is a mixture of gasses: primarily nitrogen, oxygen, & carbon dioxide. So, the air you blow into a balloon creates pressure that causes the balloon to expand (& this pressure is generated as all the molecules of nitrogen, oxygen, & carbon dioxide move about & collide with the walls of the balloon). However, the total pressure generated by the air is due in part to nitrogen, in part to oxygen, & in part to carbon dioxide. That part of the total pressure generated by oxygen is the 'partial pressure' of oxygen, while that generated by carbon dioxide is the 'partial pressure' of carbon dioxide. A gas's partial pressure, therefore, is a measure of how much of that gas is present (e.g., in the blood or alveoli).
- the partial pressure exerted by each gas in a mixture equals the total pressure times the fractional composition of the gas in the mixture. So, given that total atmospheric pressure (at sea level) is about 760 mm Hg and, further, that air is about 21% oxygen, then the partial pressure of oxygen in the air is 0.21 times 760 mm Hg or 160 mm Hg.
Functions
Manufacture - blood proteins - albumen, clotting proteins , urea - nitrogenous waste from amino acid metabolism , bile - excretory for the bile pigments, emulsification of fats by bile salts
Storage - glycogen , iron - as hemosiderin and ferritin , fat soluble vitamins A, D, E, K
Detoxification -alcohol , drugs and medicines , environmental toxins
Protein metabolism -
- transamination - removing the amine from one amino acid and using it to produce a different amino acid. The body can produce all but the essential amino acids; these must be included in the diet.
- deamination - removal of the amine group in order to catabolize the remaining keto acid. The amine group enters the blood as urea which is excreted through the kidneys.
Glycemic Regulation - the management of blood glucose.
- glycogenesis - the conversion of glucose into glycogen.
- glycogenolysis - the breakdown of glycogen into glucose.
gluconeogenesis - the manufacture of glucose from non carbohydrate sources, mostly protein
CNS PROTECTION
- Bones of the Skull Frontal, Temporal, Parietal, Sphenoid, Occipital
- Cranial Meninges Dura mater, Arachnoid Space, Pia mater
- Cerebrospinal Fluid
Secreted by Chroid Plexi in Ventricles
Circulation through ventricles and central canal
Lateral and Median apertures from the 4th ventricle into the subarachnoid space
Arachnoid villi of the superior sagittal sinus return CSF to the venous circulation
Hydrocephalic Condition, blockage of the mesencephalic aqueduct, backup of CSF, Insertion of a shunt to drain the excess CSF
Hyperventilation
- Treatments :Rebreath air, hold breath (Increase CO2)
Give oxygen for Hypoxemia