Lesson 32. BIOCHEMISTRY OF MUSCULAR AND NERVOUS TISSUE

Task

Guidelines for performing the task

Study chemical composition of muscle tissue

1. Write down main classes of substances in muscle tissue.

2. Write down the classification and characterize muscle proteins.

3. Describe distinctive features of the structure of myofibrillar proteins - myosin, actin, actomyosin, tropomyosin, and troponin.

4. List sarcoplasmic proteins. Characterize the structure and significance of myoglobin. What is biological significance of higher affinity of myoglobin to oxygen compared to hemoglobin?

5. Write down main non-protein (extractive) substances of muscle tissue

#

Task

Guidelines for performing the task

2

Study the biochemical mechanism of muscle contraction and relaxation

1. Describe the role of Ca²⁺ in contraction and relaxation of muscles. What are the mechanisms of Ca²⁺ accumulation in the sarcoplasmic reticulum?

2. Describe the role of Na⁺ and K⁺ transmembrane gradient in the regulation of muscle contraction.

3. Make a schematic drawing of muscle contraction.

4. Describe the process of muscle relaxation

3

Consider the features of energy metabolism in muscle tissue

1. Describe the role of aerobic glucose oxidation, oxidation of fatty acids and oxidation of ketone bodies in energy supply to resting muscle.

2. Describe the role of glycolysis in energy supply to intensively contracting muscles.

3. Describe the mechanisms of rapid regeneration of ATP by intensively working muscles.

4. Write a scheme for synthesis of creatine and creatine phosphate, formation and excretion of creatinine from the body

4

Recall the main types of nervous tissue cells

1. Describe the features of the structure of neurons and glial cells.

2. Characterize the morphological structure of the blood-brain barrier

5

Study the features of chemical composition of nervous tissue

1. Writedown the percentage of main groups of brain proteins (neuroalbumins, neuroglobulins, cationic proteins, and neurosclero-proteins).

2. Describe the features of structure and functions of conjugated proteins in nervous tissue - lipoproteins and proteolipids, phos-phoproteins, glycoproteins, specific proteins of the nervous tissue (neurophysins, protein S-100, etc.).

3. Name the features of chemical composition of nervous tissue. Answer the questions:

• What is the ratio between lipids and proteins in myelin membranes?

• What is the ratio of different classes of complex lipids in brain myelin and peripheral nerves?

• Name the proteins of the myelin shell.

4. Compare the content of glycogen (mg/g of tissue) in the brain to other tissues (muscle, liver, etc.).

5. Describe the features of lipid composition of white and gray cerebral matter.

6. Write down the percentage of individual lipids to their total content in the gray and white cerebral matter:

#

Task

Guidelines for performing the task

Lipids Gray matter White matter

cholesterol

phospholipids

plasmalogens

sphingomyelin

cerebrosides

gangliosides

7. Compare the content (mmol/kg or g/l) of principal minerals in brain tissue, cerebrospinal fluid (CSF), and plasma; enter them into the table:

Substance

Brain tissue

CSF

Blood plasma

Na⁺ K⁺ Ca²⁺ CI^-

HCO₃^-

6

Study the features of chemical composition of cerebrospi-nal fluid

1. Write down the level of the following components in the cerebrospi-nal fluid:

• albumin and globulins;

• residual nitrogen;

• glucose;

• lactic acid;

• cholesterol;

• triacylglycerols;

• lecithin;

• Na⁺;

• K⁺;

• Ca²⁺;

• Cl^- ;

• HCO₃^-.

2. Compare the concentration of these components in the cerebrospinal fluid and blood.

3. Describe the changes in chemical composition of CSF in meningitis, encephalitis, stroke, brain tumor, cerebral trauma, and diabetes mellitus

#

Task

Guidelines for performing the task

7

Study the features of nervous tissue metabolism

1. Write down facts that prove that nervous tissue is characterized by constantly high levels of oxygen consumption.

2. Explain why coma develops rapidly in hypoglycemia.

3. How can you explain the extremely high dependence of the brain on glucose?

4. Write down a scheme of the principal ways of glucose utilization in neurons.

5. Write down the structure of principal high-energy compounds of the nervous tissue.

6. What is the cause of the high rate of protein metabolism in neuronal

synapses?

7. Characterize the features of amino acid metabolism in the brain tissue.

9. Make a schematic representation of the ways of ammonia formation in the nerve cells and the ways of its detoxification

8

Consider the mechanisms of nerve impulse formation and its transduction

1. Explain the mechanism of appearance of resting potential on the nerve cell membrane. What is the role of Na⁺,K⁺-ATPase in this process?

2. Consider the sequence of processes which are induced in the nerve by a stimulus. How can you explain the development of:

• polarization of the membrane (resting potential formation);

• membrane depolarization and the role of Na+ channels;

• inversion of membrane potential (action potential formation);

• hyperpolarization of the membrane

9

Study the molecular mechanisms of synaptic transmission

1. Write down all known neuromediators.

2. Write down reactions of biosynthesis and breakdown of acetylcho-line.

3. Make a schematic drawing of acetylcholine output from presynaptic vesicles and their entry into the synaptic cleft.

4. Write down reactions of synthesis of norepinephrine from tyrosine.

5. Describe the catabolism of neurotransmitters in the synapse.

6. Describe the disorders in metabolism of biogenic amines in mental diseases. Give examples of precursors of catecholamine and monoami-nooxidase (MAO) inhibitors used in treatment of depressive disorders.

7. Consider the biochemical mechanisms of short-term and long-term neurological memory.

8. What is the biological role of brain peptides? Give examples