Chewing muscle electromyography a - left, b - right when chewing bread on the right side.

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Chewing muscle electromyography a - left, b - right when chewing bread on the right side.

Conclusion: to indicate the dependence of the EMG on various activities of the muscles.

Digestion 2

General Principles of Gastrointestinal Secretion and Absorbtion.

The goal of lesson is studying of secretion and absorbtion in the gastrointestinal tract.

Questions for discussion.

1. Secretion of saliva, regulation of secretion. The composition of the saliva of various salivary glands.

1. Digestion in the stomach, secretion. Regulation of this process.

2. Digestion in the small intestine and suction Its secretion, and suction. Regulation of secretion.

3. The role of the liver in digestion. Composition of bile, regulation of secretion and removing. Pancreatic function. Its external secretion, regulation of secretion.

4. Absorbtion function in various parts of the digestive tract.

Virtual work 1. Substrate specificity of salivary amylase.

The salivary amylase is glycolytic enzyme whose characteristic substrates are represented by starch and glycogen. The most active at a temperature of 37-38 degrees and a slightly alkaline environment, pH 7. 5 – 8. Saliva amylase is mixed with three carbohydrates of different structures. To detect monosaccharides, the Tromer reaction is used, it proves that only starch is broken down.

Table 1.

		monosaccharides
Starch	+ salivary amylase	+
Sucrose	+ salivary amylase
Cellulose	+ salivary amylase

Conclusion. Amylase acts only on starch.

Virtual work 2. The influence of pH on the action of pepsin

Pepsin is proteolytic enzyme which synthesized as inactive pepsinogen by the main cells of the gastric glands. Pepsinogen is turned into active pepsin when pH is lower then 5. These condition provides by hydrochloric acid in the gastric liquid. Pepsin belongs to the group of endopeptidases. It splits peptides into polipeptidicchains and it is most efficient at a pH about 2. Ovalbumin is only degraded by pepsin with HCl.

Table 2.

		Digestion
Ovalbumin	Pepsin + HCl	+
Ovalbumin	Pepsin + H2O
Ovalbumin	H2O + HCl

Conclusion. Pepsin is active in an acidic environment.

Practical work 3. Functional Power System

Draw the picture 1.

Picture 1.

Cortex behavior

ANS digestive empty concentration glucose in

tract stomach blood

LRC AR Depot

substances mechanoreceptors chemoreceptors

Endocrine Gl. (liver, fatty tissue)

AR - automatic regulation. LRC – limbic-reticular complex.

Work 4. Write down and remember the composition of digestive juices

1. The composition of saliva (pH between 6. 0 and 7. 0):

water, salts, mucin, enzyme: amylase (breaks down starch to maltose),

2. Composition of the gastric juice (pH 1. 8 to 5. 0):

water, salts, hydrochloric acid, internal factor and mucus, enzyme: pepsinogen (under the influence of hydrochloric acid it turns into pepsin and breaks down proteins into peptides)

3. Pancreatic juice (pH is 8, 0)

contains a large amount of bicarbonate ions, which play an important role in neutralizing the acidity of chyme from the stomach;

a)enzymes for digesting proteins: are trypsin, chymotrypsin and carboxypolypeptidase;

b) enzyme for digesting carbohydrates is amylase, which hydrolyzes starches, glycogen;

c) enzymes for fat digestion: (1) pancreatic lipase, which is capable of hydrolyzing neutral fat into fatty acids and monoglycerides; (2) cholesterol esterase, which causes hydrolysis of cholesterol esters; (3) phospholipase, which splits fatty acids from phospholipids.

4. Composition of bile ( pH 7. 3 - 8. 0):

bile acids, bilirubin, fatty acids, cholesterol, salts, bicarbonates. ). Functions: 1) emulsifies fats, 2) activates lipase, 3)enhances intestinal motility, 4) transports fatty acids, 5) bactericidal action.

5. Small intestinal juice (duodenum, jejunum and ileum, pH 7. 0-8. 6):

water, salts, mucus, urinary and lactic acid, more than 20 enzymes that complete the cleavage of nutrients on the membranes of the brush border - Membrane digestion.

6. Large Intestine juice (pH 8. 5-9. 0):

water, salts, the dense part of which consists of mucous lumps in which enzymes from the small intestine are found.

Component of the large intestine contains microflora, anaerobic bacteria predominate (90%), the remaining 10% are lactic acid bacteria and Escherichia coli; functions of microflora are as follows: synthesis of vitamins K, group B; production of BAS; Fiber splitting (up to 40%); cleavage of residues of nutrients, fermentation of carbohydrates to lactic and acetic acids, such an environment prevents decay. Also, the microflora is important in immunity: it does not allow to reproduce pathogenic microbes, promotes the production of antibodies.

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