GENERAL SOMATIC AFFERENT (GSA) PATHWAYS FROM THE BODY

Pain and Temperature

Pain and temperature information from general somatic receptors is conducted over small-diameter (type A delta and type C) GSA fibers of the spinal nerves into the posterior horn of the spinal cord gray matter .

Fast and Slow Pain

Fast pain, often called sharp or pricking pain, is usually conducted to the CNS over type A delta fibers.

Slow pain, often called burning pain, is conducted to the CNS over smaller-diameter type C fibers.

Touch and Pressure

Touch can be subjectively described as discriminating or crude.

Discriminating (epicritic) touch implies an awareness of an object's shape, texture, three-dimensional qualities, and other fine points. Ability to recognize familiar objects simply by tactile manipulation.

The conscious awareness of body position and movement is called the kinesthetic sens

Crude (protopathic) touch,  lacks the fine discrimination described above and doesn't generally give enough information to the brain to enable it to recognize a familiar object by touch alone.

Subconscious Proprioception

Most of the subconscious proprioceptive input is shunted to the cerebellum.

Posterior Funiculus Injury

Certain clinical signs are associated with injury to the dorsal columns.

 As might be expected, these are generally caused by impairment to the kinesthetic sense and discriminating touch and pressure pathways.

 They include

 (1) the inability to recognize limb position,

 (2) as­tereognosis,

 (3) loss of two-point discrimination,

 (4) loss of vibratory sense, and

 (5) a positive Romberg sign.

Astereognosis is the inability to recognize familiar objects by touch alone. When asked to stand erect with feet together and eyes closed, a person with dorsal column damage may sway and fall. This is a posi­tive Romberg sign.

Heart sounds

Heart sounds are a result of beating heart and resultant blood flow . that could be detected by a stethoscope during auscultation . Auscultation is a part of physical examination that doctors have to practice them perfectly.
Before discussion the origin and nature of the heart sounds we have to distinguish between the heart sounds and hurt murmurs. Heart murmurs are pathological noises that results from abnormal blood flow in the heart or blood vessels.
Physiologically , blood flow has a laminar pattern , which means that blood flows in form of layers , where the central layer is the most rapid . Laminar blood flow could be turned into turbulent one .

Turbulent blood flow is a result of stenotic ( narrowed ) valves or blood vessels , insufficient valves , roughened vessels` wall or endocardium ,  and many diseases . The turbulent blood flow causes noisy murmurs inside or outside the heart.

Heart sounds ( especially first and second sounds ) are mainly a result of closure of the valves of the heart . While the third sound is a result of vibration of ventricular wall and the leaflets of the opened AV valves after rapid inflow of blood from the atria to ventricles . 

Third heart sound is physiologic in children but pathological in adults.

The four heart sound is a result of the atrial systole and vibration of the AV valves , due to blood rush during atrial systole . It is inaudible neither in adults nor in children . It is just detectable by the phonocardiogram .

Characteristic of heart sounds :

1. First heart sound  (S1 , lub ) : a soft and low pitch sound, caused by closure of AV valves.Usually has two components ( M1( mitral ) and T1 ( tricuspid ). Normally M1 preceads T1.

2. Second heart sound ( S2 , dub) : sharp and high pitch sound . caused by closure of semilunar valves. It also has two components A2 ( aortic) and P2 ( pulmonary) . A2 preceads P2.

3. Third heart sound (S3) : low pitched sound.

4. Fourth heart sound ( S4) very low pitched sound.

As we notice : the first three sounds are related to ventricular activity , while the fourth heart sound is related to atrial activity.
Closure of valves is not the direct cause for heart sounds , but sharp blocking of blood of backward returning of blood by the closing valve is the direct cause.
 

Blood is a liquid tissue. Suspended in the watery plasma are seven types of cells and cell fragments.

• red blood cells (RBCs) or erythrocytes
• platelets or thrombocytes
• five kinds of white blood cells (WBCs) or leukocytes
  • Three kinds of granulocytes
    • neutrophils
    • eosinophils
    • basophils
  • Two kinds of leukocytes without granules in their cytoplasm
    • lymphocytes
    • monocytes

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

Cells, cytoplasm, and organelles:

• Cytoplasm consists of a gelatinous solution and contains microtubules (which serve as a cell's cytoskeleton) and organelles

• Cells also contain a nucleus within which is found DNA (deoxyribonucleic acid) in the form of chromosomes plus nucleoli (within which ribosomes are formed)

• Organelles include:

1. Endoplasmic reticulum : 2 forms: smooth and rough; the surface of rough ER is coated with ribosomes; the surface of smooth ER is not , Functions include: mechanical support, synthesis (especially proteins by rough ER), and transport
2. Golgi complex consists of a series of flattened sacs (or cisternae) functions include: synthesis (of substances likes phospholipids), packaging of materials for transport (in vesicles), and production of lysosomes
3. Lysosome : membrane-enclosed spheres that contain powerful digestive enzymes , functions include destruction of damaged cells & digestion of phagocytosed materials
4.  Mitochondria : have double-membrane: outer membrane & highly convoluted inner membrane
   1. inner membrane has folds or shelf-like structures called cristae that contain elementary particles; these particles contain enzymes important in ATP production
   2. primary function is production of adenosine triphosphate (ATP)
5. Ribosome-:composed of rRNA (ribosomal RNA) & protein , primary function is to produce proteins
6. Centrioles :paired cylindrical structures located near the nucleas , play an important role in cell division
7. Flagella & cilia - hair-like projections from some human cells
   1. cilia are relatively short & numerous (e.g., those lining trachea)
   2. a flagellum is relatively long and there's typically just one (e.g., sperm)

• • Villi  Projections of cell membrane that serve to increase surface area of a cell (which is important, for example, for cells that line the intestine)

The pancreas

The pancreas consists of clusters if endocrine cells (the islets of Langerhans) and exocrine cells whose secretions drain into the duodenum.

Pancreatic fluid contains:

• sodium bicarbonate (NaHCO₃). This neutralizes the acidity of the fluid arriving from the stomach raising its pH to about 8.
• pancreatic amylase. This enzyme hydrolyzes starch into a mixture of maltose and glucose.
• pancreatic lipase. The enzyme hydrolyzes ingested fats into a mixture of fatty acids and monoglycerides. Its action is enhanced by the detergent effect of bile.
• 4 zymogens— proteins that are precursors to active proteases. These are immediately converted into the active proteolytic enzymes:
  • trypsin. Trypsin cleaves peptide bonds on the C-terminal side of arginines and lysines.
  • chymotrypsin. Chymotrypsin cuts on the C-terminal side of tyrosine, phenylalanine, and tryptophan residues (the same bonds as pepsin, whose action ceases when the NaHCO₃ raises the pH of the intestinal contents).
  • elastase. Elastase cuts peptide bonds next to small, uncharged side chains such as those of alanine and serine.
  • carboxypeptidase. This enzyme removes, one by one, the amino acids at the C-terminal of peptides.
• nucleases. These hydrolyze ingested nucleic acids (RNA and DNA) into their component nucleotides.

The secretion of pancreatic fluid is controlled by two hormones:

• secretin, which mainly affects the release of sodium bicarbonate, and
• cholecystokinin (CCK), which stimulates the release of the digestive enzymes.